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17 Centralised Lubrication Systems Design
395
17
CENTRALISED LUBRICATION SYSTEMS DESIGN
J.G.MERRETT,
17.1
Managing D i r e c t o r , E n g i n e e r i n g and General Equipment L t d .
INTRODUCTION
W h i l s t we a r e k e p t c o m p a r a t i v e l y w e l l informed o f t h e l a t e s t developments i n o i l and grease technology and t h e v i t a l r o l e i t p l a y s i n i n d u s t r i a l and commerc i a l applications,
v e r y l i t t l e has been w r i t t e n about t h e e q u a l l y v i t a l "Centra-
I i s e d L u b r i c a t i o n Systems" and some o f t h e methods a v a i l a b l e t o Engineers by which grease and o i l may be t r a n s m i t t e d t o t h e p o i n t o f l u b r i c a t i o n . I n our s o c i e t y where energy, machinery and l a b o u r a r e now (1981) expensive commodities,
i t i s c l e a r t h a t i n t h e p a s t i n s u f f i c i e n t a t t e n t i o n has been p a i d
t o the d i r e c t and i n d i r e c t losses o f energy, occasioned by wear and f r i c t i o n and t o t h e savings o f m a t e r i a l s .
However,
i n 1977 a government f i n a n c e d Ameri-
can Report suggested t h a t $16.25 b i l l i o n p.a.
( a t 1976 v a l u e s ) c o u l d be saved
by a "Strategy f o r Energy Conservation through T r i b o l o g y "
U.K.
[l].
Converted i n t o
(1980) v a l u e s , t h i s i n d i c a t e s an e q u i v a l e n t s a v i n g o f energy through t r i -
bology i n excess o f €1;
b i l l i o n p.a.
I n s h o r t , c o r r e c t l y s e l e c t e d l u b r i c a n t s and t h e i r methods o f a p p l i c a t i o n by C e n t r a l i s e d Systems can e f f e c t s i g n i f i c a n t savings, e.g. machine t o o l s , conveyors, cranes, r o l l i n g m i l l s , b l a s t furnaces, b a l l m i l l s , sugar machinery, paper m i l l s , heavy m o b i l e p l a n t , e t c . t o v a r y i n g degrees, a l l r e q u i r e t h e a p p l i c a t i o n o f lubricants.
A c o r r e c t l y designed and i n s t a l l e d C e n t r a l i s e d L u b r i c a t i o n
System i s t h e e n g i n e e r ' s insurance a g a i n s t some o f t h e severe t r i b o l o g i c a l problems, i . e .
f r i c t i o n and wear, which would o t h e r w i s e occur i f t h e p l a n t and
machinery were i n a d e q u a t e l y l u b r i c a t e d . U n f o r t u n a t e l y , a l l t o o o f t e n i n t h e supply of p l a n t and machinery t h e s e l e c t i o n o f t h e l u b r i c a n t and C e n t r a l i s e d L u b r i c a t i o n equipment a r e considered a t a l a t e stage i n t h e manufacture o f t h e p l a n t which, coupled w i t h t h e c o n f l i c t i n g i n t e r e s t s o f machinery b u i l d e r s , can r e s u l t i n u n s u i t a b l e l u b r i c a t i o n equipment being s e l e c t e d .
L i k e w i s e , t h e l u b r i c a t i o n equipment supply companies have a
r e s p o n s i b i l i t y , n o t o n l y t o know t h e i r own p r o d u c t , b u t a l s o t o a p p r e c i a t e t h e t r i b o l o g i c a l requirements o f t h e p l a n t and machinery which r e q u i r e s t o be
396 lubricated.
F a i l u r e i n t h i s area i n v a r i a b l y r e s u l t s i n the p l a n t user being
p l a c e d i n t h e u n e n v i a b l e p o s i t i o n o f h a v i n g t o a p p l y , a t an e a r l y stage, f o r a d d i t i o n a l c a p i t a l t o r e c t i f y new p l a n t o r , more o f t e n t h a n n o t , t o l i v e w i t h t h e problems and r e c t i f y as and when t h r o u g h a maintenance budget
-
both o f
which the p l a n t u s e r would be t h e f i r s t t o agree i s e n t i r e l y u n s a t i s f a c t o r y . T h i s paper endeavours t o deal w i t h some o f these f a c t o r s a f f e c t i n g t h e c h o i c e o f l u b r i c a n t and l u b r i c a t i n g equipment, t h e b a s i c elements o f t h e machinery t o be l u b r i c a t e d , and t h e c o n d i t i o n s under which i t o p e r a t e s . 17.2
POINTS OF LUBRICATION
Bearings, t h e e s s e n t i a l components o f p l a n t and machinery, may be g e n e r a l l y grouped i n t o j o u r n a l , t h r u s t , conveyor c h a i n p i n and l i n k , a n t i - f r i c t i o n , ways and crane r a i l s .
slide-
Each wear s u r f a c e must be t r e a t e d s e p a r a t e l y w i t h r e g a r d
t o l u b r i c a n t and l u b r i c a t i o n t e c h n i q u e . The l u b r i c a t i o n requirement o f a p l a i n j o u r n a l b e a r i n g i s t h e p r o v i s i o n o f an adequate and c o n s t a n t f l o w o f l u b r i c a n t o f s p e c i f i e d v i s c o s i t y t o g i v e a f l u i d f i l m o f high-load bearing capacity.
The j o u r n a l b e a r i n g has i n h e r e n t l y a
convergence between t h e s h a f t and t h e b e a r i n g .
When r e l a t i v e m o t i o n takes p l a c e
a f i l m o f l u b r i c a n t i s induced between t h e s u r f a c e s , e f f e c t i v e l y s e p a r a t i n g them. Bearings employed t o absorb t h r u s t and p r e v e n t misalignment of s h a f t s v a r y g r e a t l y i n t y p e and l u b r i c a t i o n requirement, w h i l s t a n t i - f r i c t i o n b e a r i n g s r e q u i r e l e s s l u b r i c a n t than p l a i n b e a r i n g s .
Most a v a i l a b l e formulae d e a l i n g
w i t h t h e a p p l i c a t i o n o f grease t o these b e a r i n g s t r e a t speed as an i m p o r t a n t factor.
For small a n t i - f r i c t i o n b e a r i n g s such as those employed i n l i g h t l y
loaded f r a c t i o n a l horse-power motors, t o o much grease can be damaging. I n such cases, recommended l u b r i c a t i o n i n t e r v a l s o f up t o s e v e r a l years have been e s t a blished.
Chain p i n s and l i n k s p r e s e n t m a j o r c r i t i c a l wear p o i n s on f l o o r and
overhead ( i n c l u d i n g Power and Free) conveyors.
I n t h e automobi e i n d u s t r y ,
c h a i n l e n g t h s o f s e v e r a l hundred metres, h a v i n g thousands o f
PO
nts requiring
l u b r i c a t i o n , a r e commonplace ( F i g . 1 ) . Slideway and crane r a i l l u b r i c a t i o n r e q u i r e s t h e r i g h t l u b r i c a n t and t h e r i g h t a p p l i c a t o r (see Fig.10,
S e c t i o n 17.6.1).
Too l i t t l e l u b r i c a n t r e s u l t s i n
r a p i d wear; e x c e s s i v e l u b r i c a n t can be a hazard t o l i f e o r l i m b . Every case i s d i f f e r e n t , y e t i n e v e r y case i t i s c r i t i c a l t h a t t h e l u b r i c a n t i s a p p l i e d i n l i n e w i t h the requirements o f t h a t component,
b o t h w i t h r e g a r d t o mechanical
wear and t o energy conservancy.
17.3
SELECTING THE LUBRICANT
-
O I L OR GREASE?
I n modern machinery l u b r i c a t i o n ,
l u b r i c a n t s and t h e means o f t h e app i c a t i o n
must be considered t o g e t h e r . The b e s t l u b r i c a n t w i l l s e r v e no u s e f u l purpose i f i t i s n o t a p p l i e d a t t h e
397
Fig.1
Excessive p i n and l i n k wear i n a conveyor c h a i n . A 3mm p i n wear p e r p i n on a 732111 conveyor increases t h e c h a i n l e n g t h by 23 metres.
r i g h t t i m e , a t t h e r i g h t p l a c e , and i n t h e c o r r e c t q u a n t i t y .
Conversely, t h e
best l u b r i c a t i o n equipment, a p p l y i n g l u b r i c a n t q u i t e c o r r e c t l y , w i l l be o f l i t t l e use i f t h e l u b r i c a n t i t feeds i s u n s u i t a b l e f o r t h e d u t y i t has t o perform. L u b r i c a n t s g e n e r a l l y , e i t h e r o i l s o r greases, a r e s u p p l i e d by o i l companies supported by s p e c i a l i s t o i l and grease m a n u f a c t u r i n g companies, who w i l l p r o v i d e advice on any p a r t i c u l a r l u b r i c a n t and a p p l i c a t i o n as w e l l as on t h e c h o i c e o f lubricants i n general.
The s u p p l i e r o f t h e l u b r i c a t i o n equipment w i l l a l s o
o f t e n be a b l e t o a d v i s e , e s p e c i a l l y on l u b r i c a t i o n d e s i g n problems, o r a c t as an intermediary
.
The s u b j e c t o f l u b r i c a n t s i s t r e a t e d h e r e o n l y i n i t s v e r y broadest terms under t h r e e headings:"OIL"
o r GREASE";
when t o use one and when t h e o t h e r .
LUBRICATING GREASE;
t h e types and how t o s e l e c t them.
LUBRICATING OILS; types and how t o s e l e c t them.
17.3.1
O i l o r Grease? When t o Use One and When t h e Other
Movement between two d r y s u r f a c e s causes heat and wear.
The purpose o f
i n t r o d u c i n g a l u b r i c a n t between t h e two s u r f a c e s i s t o reduce f r i c t i o n , heat, and wear.
O i l has t h e f o l l o w i n g advantages: and i t scavenges.
A t t h e same t i m e ,
i t flows,
i t penetrates,
i t removes heat,
i t has l i m i t e d s e a l i n g q u a l i t i e s and poor
' s t a y i n g ' power, t h e r e f o r e r e q u i r e s more f r e q u e n t r e p l e n i s h i n g than grease.
398 L u b r i c a t i n g grease, a s e m i - s o l i d p l a s t i c - l i k e m a t e r i a l , has e x c e l l e n t s e a l ing characteristics,
possesses good ' s t a y i n g ' power,
i.e.
i t adheres t o surfaces
more r e a d i l y and l o n g e r t h a n o i l and i t can be an e x c e l l e n t c o r r o s i o n p r e v e n t a tive.
Unlike o i l ,
i t i s a poor conductor o f heat and a poor scavenger;
n o t f l o w o r spread e a s i y where c o n t a m i n a t i o n by
-
i t does
t h e l a t t e r p r o p e r t y can, however, be an advantage
u b r i c a n t s must be avoided such as i n f o o d and b o t t l i n g
and t h e t e x t i l e i n d u s t r es and where t h e l u b r i c a n t i s used as a s e a l i n g medium. Where an a p p l i c a t i o n e n t a i l s HEAT REMOVAL, o i l i s t h e r e f o r e g e n e r a l l y t h e choice.
I t can be appl ed i n t h e f o r m o f a l i q u i d o r as an o i l m i s t ,
m i c r o - f o g comprising an o i l - a i r m i x t u r e .
i.e.
I n severe cases o f h e a t removal, o i l
can be r e c i r c u l a t e d and, d u r i n g t h e c i r c u l a t i o n ,
i t can be c o o l e d and cleaned.
Large t u r b i n e b e a r i n g s and f a s t gear t r a i n s a r e t y p i c a l examples where o i l c i r c u l a t i n g systems a r e used and l a r g e amounts o f o i l a r e c i r c u l a t e d . For a p p l i c a t i o n s where heat removal i s n o t a p r o b l e m , b u t LUBRICATION o r t h e PREVENTION OF INGRESS OF DIRT, WATER, DUST and OTHER EXTRANEOUS MATTER i s l u b r i c a t i n g grease can be used.
-
I t s a p p l i c a t i o n ranges from heavy m i l l b e a r i n g s
and s l i d e s t o t e x t i l e machinery, e t c .
I t i s a l s o t h e most s u i t a b l e where a p p l i -
c a t i o n o f t h e l u b r i c a n t i s r e q u i r e d a t LONG INTERVALS. N e a r l y a l l B a l l and R o l l e r Bearings, except those i n r e s p e c t o f which heat removal i s e s s e n t i a l , a r e g e n e r a l l y grease l u b r i c a t e d .
Where DIRTY/DUSTY and
WET CONDITIONS e x i s t , grease
s generally preferable.
The convenience o f grease
l u b r i c a t i o n makes grease t h e
p r e f e r r e d ' l u b r i c a n t f o r the vast m a j o r i t y o f
r o l l i n g bearings. G e n e r a l l y , o i l l u b r i c a t i o n i s employed i n t h e r e l a t i v e l y few cases where i t i s n o t p o s s i b l e t o t a k e advan age o f t h e m e r i t s o f grease as a r o l l i n g b e a r i n g
1u b r i c a n t . Where motion i s INTERMITTENT o r OSCILLATING, grease i s o f t e n t h e more s u i t able lubricant. Summarising, where heat conveyance away f r o m r u b b i n g s u r f a c e s o r p e n e t r a t i o n o f t h e l u b r i c a n t i s o f importance, o r t h e scavenging f u n c t i o n i s necessary, o i l i s p r e f e r a b l e , w h i l s t l u b r i c a t i n g grease can and,
i n most cases, should be
considered as t h e p r e f e r r e d l u b r i c a n t f o r slow moving machinery,
long l i f e
l u b r i c a t i o n , and where d i r t and d u s t has t o he kept o u t o f t h e b e a r i n g s , s l i d i n g surfaces, etc.
17.3.2
L u b r i c a t i n g Grease
-
The Types and How t o S e l e c t Them
Greases designed f o r l u b r i c a t i o n a r e e s s e n t i a l l y a m i x t u r e o f m i n e r a l o i l and t h i c k e n e r , a c c o r d i n g to t h e a p p l i c a t i o n requirement.
I n t h e most w i d e l y
used modern grease t h e t h i c k e n e r i s a m e t a l l i c soap, u s u a l l y o f l i t h i u m o r calcium, w i t h t h e q u a n t i t y o f o i l a d j u s t e d t o g i v e a s o l i d , s e m i - s o l i d o r semi f 1u i d consistency.
399 The soap f i b r e s form a s t r u c t u r e t h a t r e t a i n s t h e o i l , t h e dimensions and arrangement o f t h e f i b r e s v a r y i n g a c c o r d i n g t o t h e metal and t h e f a t t y a c i d from which t h e soap was made.
The q u a n t i t y , dimensions and d i s t r i b u t i o n o f t h e
f i b r e s a r e t h e main parameters c o n t r o l l i n g t h e s t a b i l i t y and f l o w p r o p e r t i e s o f this lubricating material. One o f t h e most i m p o r t a n t p h y s i c a l f e a t u r e s o f grease i s s t i f f n e s s ( f o r s i s t e n c y ) which i s i n d i c a t e d by a t e s t t h a t measures t h e d e p t h t h a t t h e cone s i n k s i n t o a sample o f grease.
The d e p t h measured i s a t e n t h o f a m i l l i m e t r e ,
and r e f e r r e d t o as t h e degree o f p e n e t r a t i o n .
F i g u r e 2 shows one c l a s s i f i c a -
t i o n system f o r greases. Grade Number. 000 OD 0 1 2 3
445
-
355
-
400 310 265 220
4 5 6
Fig.2
Worked p e n e t r a t i o n a t 25'C
175
130
85
-
-
-
475
430 385 340 295 250 205 160 115
Description Very f l u i d Fluid Semi - f 1 u i d Very s o f t Soft Semi-firm Firm Very f i r m Hard
NLGl c l a s s i f i c a t i o n o f t h e c o n s i s t e n c y o f greases.
Although lithium-based greases today s a t i s f y a v a s t number o f l u b r i c a t i o n requirements f o r cranes, conveyors, f o r g i n g presses, continuous c a s t i n g p l a n t s , r o l l i n g mills, etc.,
t h e r e a r e a number o f s i t u a t i o n s r e q u i r i n g l u b r i c a n t s w i t h
s p e c i a l p r o p e r t i e s , f o r example, t h e a b i l i t y t o w i t h s t a n d h i g h temperatures such as those encountered i n power s t a t i o n t u r b i n e s , bakery oven conveyors, e t c . These l a t t e r greases i n c l u d e t h e c l a y - t h i c k e n e d and o t h e r s o l i d - t h i c k e n e d compounds which w i t h s t a n d c o n s i d e r a b l y h i g h e r temperatures, e s p e c i a l l y when employed w i t h h i g h temperature s y n t h e t i c l u b r i c a n t s , e.g.
polyglycol, s y n t h e t i c esters,
and s i l i c o n e s . The upper temperature l i m i t a t which any grease may be used i s dependent p a r t l y on t h e t y p e o f t h i c k e n e r , p a r t l y on t h e f l u i d and i t s r e q u i r e d s e r v i c e life.
Higher o p e r a t i n g temperatures have t h e e f f e c t o f s h o r t e n i n g t h e l u b r i -
c a n t ' s s e r v i c e l i f e and r e d u c i n g p e r m i s s i b l e o p e r a t i n g speeds.
I t i s therefore
convenient t o express t h e working l i m i t s o f a grease i n terms o f b e a r i n g speeds and temperatures, as shown i n Fig.3.
T h i s diagram shows t h a t l i t h i u m , sodium
and calcium-based greases have upper temperature l i m i t s o f 130, 110 and 7OoC r e s p e c t i v e l y , and t h a t clay-based and calcium-complex greases can be used a t up t o 150°C.
400
Fig.3
17.3.3
Lubricating 011s
Working l i m i t s o f m i n e r a l o i l greases
-
Types and How t o S e l e c t Them
Vegetable and animal o i l s a r e e x c e l l e n t l u b r i c a n t s , b u t have s h o r t l i f e as they o x i d i s e and tend t o go r a n c i d ; as a r e s u l t , t h e i r main use i s f o r 'one s h o t ' a p p l i c a t i o n s such as f o r f o r g i n g o r as a d d i t i v e s f o r m i n e r a l o i l s . G e n e r a l l y , t h e o r i g i n o f t h e o i l determines i t s use ( F i g . 4 ) O i l Origin
ADD1
ication
Mineral O i l
e.g. p e t r o l e u m base f o r general l u b r i c a t i o n o f mechanical p a r t s such as engines, gears and g e n e r a l e n g i n e e r i n g p l a n t .
Vegetable O i l
e.g. c a s t o r , palm, and rape seed o i l s f o r s p e c i a l a p p l i c a t i o n s where h i g h l u b r i c i t y i s d e s i r a b l e such as k i l n s , bakery ovens.
Animal O i l
e.g. sperm o r o t h e r f i s h o i l s from sheep wool f o r a p p l i c a t i o n s such as k i l n s , bakery ovens.
Synthetic O i l
e.g. glycol d e r i v a t i v e s and d i e s t e r f o r extreme h i g h temperature. Fig.4
Origin of Oils
401 F i g u r e 5 i l l u s t r a t e s how v i s c o s i t y o f o i l s change w i t h temperature, becoming t h i n n e r when they a r e heated, b u t they do n o t change v i s c o s i t y a t t h e same r a t e . The r a t e o f v i s c o s i t y change w i t h temperature i s r e f e r r e d t o as the ' v i s c o s i t y index'.
-40-30-20 -10 0 10 20 30 $0 50 60 70 80 90XX)11O1201X)14015MM)710
degrees fahrenheit
Fig.5
17.3.3.1
V i s c o s i t y vs Temperature f o r two o i l s h a v i n g v i s c o s i t y indexes o f 0 and 100 r e s p e c t i v e l y .
The p r o p e r t i e s o f t h e o i l must be c a r e f u l l y considered when d e s i g n i n g
a l u b r i c a t i o n system, e.g.
conveyor chains passing through a p r e - t r e a t m e n t oven
may reach a temperature o f 180/200°C.
O i l s w i t h s p e c i a l i n c l u s i o n s such as
g r a p h i t e o r molybdenum d i s u l p h i d e i n g l y c o l as used i n bakery ovens must have p r o v i s i o n f o r a g i t a t i o n o r r e c i r c u l a t i o n w i t h i n t h e l u b r i c a t o r s t o r a g e tank t o prevent s e t t l i n g o u t o f t h e g r a p h i t e o r molybdenum. Bakery ovens g e n e r a l l y use molybdenum d i s u l p h i d e i n g l y c o l w h i l s t f o r extreme p r e s s u r e l o a d i n g c o n d i t i o n s on Power and Free t r o l l e y s , as i n the c a r i n d u s t r y , chains and t r o l l e y wheels r e q u i r e s p e c i a l l u b r i c a n t s , h a v i n g a h i g h adhesion c h a r a c t e r i s t i c - a s w e l l as i m p a r t i n g r u s t - p r o o f i n g and w a t e r - p r o o f i n g .
402
17.3.3.2
A f u r t h e r s p e c i a l i s t l u b r i c a n t i s rape seed o i l ;
f a t t y vegetable o i l .
t h i s i s a low a c i d
Because o f i t s r e l a t i v e l y h i g h f l a s h - p o i n t
i t i s suitable
f o r h i g h temperature work when r e f i n e d and g i v e n a g r a p h i t e i n c l u s i o n . uses a r e f o r continuous c a s t i n g moulds, f o r g i n g , metals.
Typical
and as a c u t t i n g o i l f o r harder
Here a g a i n , i t s s p e c i a l p r o p e r t i e s must be considered when p r o v i d i n g
t h e l u b r i c a t i n g means.
17.3.4
Summarising L u b r i c a n t S e l e c t i o n
For t h e f i n a l s a t i s f a c t o r y s e l e c t i o n o f l u b r i c a n t t h e f o l l o w i n g f a c t o r s must t h e r e f o r e be determined.
The c o n s t r u c t i o n and m a t e r i a l s employed i n t h e compon-
e n t s t o be l u b r i c a t e d , o p e r a t i n g speeds and l o a d i n g , l i f e requirement o f l u b r i c a n t and machine, o p e r a t i n g environment, e.g.
t h e presence o f w a t e r , steam,
chemicals o r a b r a s i v e m a t e r i a l s i n t h e atmosphere; and l a s t , b u t n o t l e a s t , t h e method o f a p p l i c a t i o n , t h e t y p e o f system t o be employed, t h e diameter of p i p e runs, e t c .
17.4
PIPE DIAMETER vs
FLOW CHARACTERISTICS
To determine t h e l u b r i c a n t f l o w r a t e and volume,
t h e l e n g t h and diameter o f
t h e p i p e l i n e s should be c a r e f u l l y c a l c u l a t e d t o ensure t h a t t h e l u b r i c a n t can s a t i s f a c t o r i l y reach t h e wear p o i n t s a t t h e extreme ends o f t h e p i p e l i n e s .
The
f o l l o w i n g t a b l e summarises some p r a c t i c a l r e s u l t s f r o m t e s t s t o prove optimum measurements and e n d - o f - l i n e p r e s s u r e , u s i n g a l i t h i u m - b a s e d grease o f No.2 consistency a t
15OoC. Nominal bore (mm)
50 38 25 19 17.5
Applied pressure (kPa)
P r e s s u r e drop (kPa/m)
1100
36.1 61.5 144.7 210.3
1 a75
4410 6410
LUBRICATION REQUIREMENTS FOR PLAIN BEARINGS
For normal w o r k i n g c o n d i t i o n s i t has been found t h a t t h e amount o f grease required f o r p l a i n bearings i s equivalent t o a layer o f O . l m m b e a r i n g area (0.1 x d x L) p e r hour o f b e a r i n g o p e r a t i o n .
on t h e developed
Figure
6 illustrates
a c h a r t f o r c a l c u l a t i n g t h e grease requirements f o r p l a i n b e a r i n g s . p l e t o c a l c u l a t e t h e grease r e q u i r e d f o r a b e a r i n g o f long,
i n t e r s e c t diameter and l e n g t h a s a t
*
As an exam-
75mm diameter by 250mm
f o l l o w l i n e o f a r r o w and where i t
i n t e r s e c t s t h e t o p s c a l e , t h i s i n d i c a t e s t h e amount o f grease r e q u i r e d , b e i n g i n t h i s example 6 g m o r 0.21 oz p e r hour.
403
D
LENGTH OF BEARING L
Fig.6
17.6
Grease requirements f o r a p l a i n b e a r i n g .
SELECTING THE RIGHT TYPE OF LUBRICATION SYSTEM
L u b r i c a t i o n systems f o r p l a n t and equipment, whatever t h e a p p l i c a t i o n , i n d i v i d u a l design.
t h e b e a r i n g requirements and t h e d e s i g n e r s ' a p p l i c a t i o n s p e c i f i c a t i o n . regard t o t h e human element, chapter deal w i t h : 17.6.1
require
They must be f u n c t i o n a l and c o r r e c t l y engineered t o s a t i s f y they must be f o o l - p r o o f .
With
Systems i n c l u d e d i n t h i s
Grease, O i l and Micro-Fog.
Grease L u b r i c a t i o n Systems
A l l C e n t r a l i s e d Grease L u b r i c a t i o n Systems a r e o f t h e n o n - r e c i r c u l a t i n g t y p e and o p e r a t e on t h e t o t a l loss p r i n c i p l e .
They a r e b a s i c a l l y d i v i d e d i n t o D i r e c t
Feeding systems and I n d i r e c t Feeding systems, o t h e r w i s e r e f e r r e d t o as L i n e systems, as i l l u s t r a t e d i n F i g . 7 .
17.6.1.1
D i r e c t Feeding Systems a r e those where t h e volume o u t p u t o f t h e D i r -
e c t Feeding l u b r i c a t i n g pump i s p o s i t i v e ;
t h e pumping p l u n g e r s and means o f
m e t e r i n g t h e o u t p u t t o i n d i v i d u a l wear p o i n t s b e i n g i n c o r p o r a t e d i n t h e l u b r i c a t i n g pump.
T h e r e f o r e D i r e c t Feeding systems o p e r a t e on a P o s i t i v e Volume P r i n -
ciple,
t h e y i n t r o d u c e a metered volume o f l u b r i c a n t i n t o t h e pipes, and
i.e.
s i n c e t h i s volume i s n o t a f f e c t e d by p r e s s u r e i n t h e p i p e s , t h e pumps can work c o n t i n u o u s l y a g a i n s t h i g h back pressures.
- -I
I
GREASE SYSTEMS TOTAL LOSS SYSTEMS
DIRECT FEEDSYSTEMS
INDIRECT FEED M T E M S
I
PR0GRESSI:E MSTEMS
I
I
Y DUAL L I N E
FIG.7
FUNDAMENTAL LUBRICATION
DIVISION OF C E N T R A L I S E D GREASE SYSTEMS.
PARALLEL SVSTEMS
405 D i r e c t Feeding systems can be d i v i d e d i n t o those where each o u t l e t has i t s own m e t e r i n g p l u n g e r (F i g . 8 )
and t ho se where a s i n g l e moving plunger d i s t r i b u t e s
p r o g r e s s i v e l y t h e metered amounts o f grease i n t o t h e v a r i o u s o u t l e t s ( F i g . 9 ) . N o r m a lly , d i r e c t f e e d i n g l u b r i c a t o r s o b t a i n t h e i r pumping a c t i o n e i t h e r by means o f moving p l u n g e r s , combined w i t h a system o f p o r t i n g , o r by the use o f p l u n g e r s i n c o n n ect i on w i t h s p r i n g - l o a d e d b a l l v a l v e s .
The l a t t e r type should
be a v o id e d i n t h e case o f d i r t y o r d u s t y c o n d i t i o n s as any i n g r e s s o f e x t r a n eous m a t t e r may l o dg e i n t h e s e a t i n g o f t h e b a l l v a l v e and render t h e l u b r i c a t o r inoperative. I t f o l l o w t h a t where a l u b r i c a t o r i s d r i v e n by a moving p a r t o f a machine, an amount o f l u b r i c a n t r e q u i r e d r e l a t i v e t o t h e movement o f t h e s h a f t i n t h e bearing be in g l u b r i c a t e d , a d i r e c t f e e d i n g l u b r i c a t o r should be used (Fig.10) l u b r i c a t o r d r i v e n v i a t h e d i r e c t d r i v i n g elements, e.g.
w i t h the
E c c e n t r i c D r i v e s , Throw
Plates, o r O f f s e t P i n Drives. 17.6.1.2
I n d i r e c t o r L i n e Systems have t h e pumping and m e t e r i n g elements geo-
g r a p h i c a l l y separated;
t he y a r e connected by means o f one o r s e v e r a l p i p e l i n e s .
The a c t i o n i s h y d r a u l i c ,
t h e pump s e r v i n g as a p r e s s u r e c r e a t i n g u n i t f o r pumping
grease i n t o a p i p e l i n e whi ch i s t h e r e b y s e t under pressure.
As t h e pressure
i nc r e a s e s , so t h e v a r i o u s m e t e r i n g elements e j e c t t h e i r charges e i t h e r progressi v e l y , o r a c c o r d i n g t o t h e back pre ssure s a g a i n s t which t h e y operate. D u r in g normal o p e r a t i o n s each element, ha ving g i v e n up i t s metered amount,
blocks i t s e l f and w i l l n o t pass any f u r t h e r l u b r i c a n t t o t h e p o i n t s o f a p p l i c a tion.
When a l l elements have g i v e n up t h e i r metered charge, a r a p i d r i s e i n
pre s s u r e o c c u r s i n t h e main l i n e .
U t i l i z i n g e i t h e r t h i s i n c r e a s e i n pressure a t
t h e pump o r a t t h e end o f t h e l i n e , a s i g n a l i s g i v e n i n d i c a t i n g t h a t t h e l u b r i c a t i n g phase i s completed. Thereupon t h e main l i n e has t o be d ep ressurized, w hich i s u s u a l l y e f f e c t e d by opening i t t o t h e grease sup pl y u n i t , e.g.
the reservoir.
Depending on the
t y p e o r make o f system, t h e p l u n g e r s o f t h e m e t e r i n g v a l v e s a r e then r e s e t t o p e r m i t t h e i r f u r t h e r o p e r a t i o n , o r t h e y a r e a l r e a d y s e t f o r another a p p l i c a t i o n phase wh ic h moves them back i n t o t h e i r o r i g i n a l p o s i t i o n , thereby completing a system c y c l e .
The method and mechanics o f r e s e t t i n g depend on t h e p a r t i c u l a r
ty p e o f system; a l s o whether one complete c y c l e o f t h e system i n v o l v e s one o r two a p p l i c a t i o n ( l u b r i c a t i o n ) phases. The fundamental d i v i s i o n o f ' l i n e systems' p a r a l l e l t y p e s o f systems.
i s t h a t between p r o g r e s s i v e and
I n t h e p r o g r e s s i v e system t h e l u b r i c a n t must pass
thro u g h t h e m e t e r i n g elements o r v a l v e s p r o g r e s s i v e l y ,
i.e.
o n l y a f t e r having
a c t u a t e d t h e f i r s t element t o f ee d l u b r i c a n t t o t h e p o i n t o f a p p l i c a t i o n w i l l t h e l u b r i c a n t be passed t o t h e second element, and so f o r t h .
T h i s i s i n con-
t r a s t t o t h e o p e r a t i o n o f t h e p a r a l l e l system, on w hich t h e m e t e r i n g u n i t s a r e
YOl>INNO> OlNW
m
YOU3NN03 a 3 a ~ 33 1 1 ~ 1 s
SNOIWINNOJ L l l A n O
YJMOllOJON 3AVH Sl3aOW (110)V l
*I
:S)ltlOM 1 1 MOH
NOllV3l11!fll 01Slll11lN33 311VWOlflV 11Oj 1102V3111!111 0334 1331110 90P
407
408
Application: Lubiicat/onoluplo I W p ~ ) i n l ~ . ~ l l h g ~ e a l e o r o s . pafl(IcUlar1yon presses. machine lools, packagmg machinery
Introducingcentral lubrication in stages:
Design:
A m a n pipe l m m a simple fillinp 01 lubricalion pump loads lo the dislrtbulor; the quantities of lubricant delivered are diitiibuled by the. d w i b u l o r 10the outlels in a parlicular pie. arranged sequence If required. the Iubricanl lrom the distributor can be led lo other distrtbulors lor lurlhet redislribulion
11 . .tg.: L u b r m i c o nof not more lhan 20 points by means 01 a grease nipple screwed into the dislributor andsgreasegun whichisoperaled untiltheflow indjcatoc shows tihat the lubr#calionoperation has been compleletl.
2nd .lago: A hand pump and dlslrlbUIorSin Series. WhlCh distribute the lubr~csnllo the lubrication point6 in a specified manner.
Fig. 11.
Examples o f Progressive Systems.
Fig. 12.
Progressive Lubrication on a plate shear.
409 a c t u a t e d as p r e s s u r e i n c r e a s e s i n t h e main l i n e . Each group i s f u r t h e r d i v i d e d i n t o systems u t i l i z i n g one l i n e o n l y and systems u t i l i z i n g two l i n e s , t h e f o r m e r b e i n g c a l l e d s i n g l e - l i n e systems, t h e l a t t e r d u a l - l i n e systems.
The most p o p u l a r t y p e s o f systems used a r e :
P r o g r e s s i v e Systems, o p e r a t e o n p r e s s u r e / v o lu m e c y c l e s ;
i n t h e i r case t h e
i n c r e a s i n g p r e s s u r e c r e a t e d by t h e pump a c t u a t e s a m e t e r i n g v a l v e w h ic h , h a v i n g g i v e n up i t s s e t amount o f l u b r i c a n t . a l l o w s t h e g r e a s e t o pass i n t o t h e main l i n e leading t o the next metering valve.
When s u f f i c i e n t p r e s s u r e has been
b u i l t up, t h e v a l v e i s a c t u a t e d and l u b r i c a n t a l l o w e d t o f l o w t o t h e n e x t m e te r i n g v a l v e , and so o n p r o g r e s s i v e l y , u n t i l i t r e t u r n s t o t h e l u b r i c a t o r o r where, when s u f f i c i e n t p r e s s u r e has been b u i l t up, a r e v e r s i n g v a l v e i s a c t u a t e d w h ic h reverses t h e f l o w o f t h e grease.
The s e l e c t i o n o f p r o g r e s s i v e systems i s depen-
dent upon t h e number o f p o i n t s t o be l u b r i c a t e d .
F i g u r e 1 1 i l l u s t r a t e s some
o p t i o n s a v a i l a b l e , and F i g . 1 2 shows a t y p i c a l i n s t a l l a t i o n o f a p r o g r e s s i v e l u b r i c a t i o n system on a P l a t e Shear. Dual L i n e Systems ( P a r a l l e l ) , o p e r a t e o n t h e same b a s i c p r i n c i p l e , v i z : t h e m o t o r i z e d l u b r i c a t i n g pump ( F i g . 1 3 )
f o r c e s g r e a s e i n t o one o f two main f e e d
l i n e s i n w hi ch a r e p l a c e d a number o f d u a l - l i n e m e t e r i n g e le m e n ts , each o u t l e t
M U orised BS-A h
p
SC-A Diffaeraial R c Un
MODE L BSA
Fig.13
Dual l i n e system.
410
I
Line 1 weuurising
2oo
I_
I_
Line 2 pressurising
I
Fig.14
Interval
end of line 1 b 2
Dual l i n e system p r e s s u r e .
66
Main Line 2
Fig.15
2
Dual l i n e m e t e r i n g element.
D u a l - l i n e m e t e r i n g elements o p e r a t e h y d r a u l i c a l l y w i t h o u t t h e use o f b a l l s and s p r i n g s o r check v a l v e s .
A c o n t r o l p i s t o n d i r e c t s t h e supply o f grease t o
e i t h e r s i d e of a m e t e r i n g p i s t o n which i s f i t t e d w i t h an i n d i c a t o r p i n , e n a b l i n g easy i n s p e c t i o n o f o p e r a t i o n a t each p o i n t on t h e system.
R e g u l a t i n g screws
f i t t e d t o each i n d i c a t o r housing p e r m i t adjustment down t o 20% o f maximum o u t p u t . The p o s i t i o n o f t h e c o n t r o l p i s t o n ( 2 ) and t h e feed p i s t o n (6) a r e shown i n ' A ' a f t e r the f i r s t p a r t o f the d u a l - l i n e cycle.
P r e s s u r i s e d l u b r i c a n t f r o m main
411 l i n e 1 has moved o v e r c o n t r o l p i s t o n ( 2 ) and then a t t h e upper s i d e o f t h e feed
( 6 ) , d i s p l a c i n g i t and d i s c h a r g i n g a measured q u a n t i t y o f l u b r i c a n t v i a c ros s p o r t i n g (7) and a cross spool (1) t o o u t l e t ( 8 ) . P o s i t i o n ' B ' i s t h e second
piston
p a r t o f t h e d u a l - l i n e c y c l e and p r e s s u r i s e d l u b r i c a n t from main l i n e 2 has moved c o n t r o l p i s t o n ( 2 ) and d i s p l a c e d t h e m e t e r i n g p i s t o n (6) thus d i s c h a r g i n g a measured s h o t o f l u b r i c a n t v i a cro ss p o r t (5) and across spool ( 3 ) t o o u t l e t ( 4 ) . For e x t r e m e ly d i r t y and a b r a s i v e environments such as those found i n a B l a s t Furnace, P i g Caster o r Coal P r e p a r a t i o n and Washery P l a n t , i t i s a d v i s a b l e t o have t h e d u a l l i n e m e t e r i n g elements housed i n toughened g l a s s - f r o n t e d p r o t e c t i o n boxes, s i m i l a r t o t h a t shown i n F i g. 16 .
F i g. 16
P r o t e c t i o n box.
412 17.6.1.3
Comparison o f P a r a l l e l Systems - S i n g l e l i n e and D u a l - l i n e .
B o th systems d e p r e s s u r i z e t h e l i n e , b u t i n t h e case o f t h e S i n g l e L i n e System the r e s e t t i n g o f t h e p l u n g e r s i n t h e m e t e r i n g elements i s u s u a l l y e f f e c t e d by s p r i n g p r e s s u r e , whereas i n t h e Dual L i n e system. when main feed l i n e No.2 i s p r e s s u r i s e d , a second s e r i e s o f dual l i n e m e t e r i n g elements d i s c h a r g e l u b r i c a n t t o the points o f application.
I n d o i n g s o , t hey r e s e t t h e dual l i n e m e t e r i n g
elements i n main l i n e No.1, w i t h which t h ey f orm an i n t e g r a l u n i t . 17.6.1.4
S e l e c t i n g Grease L u b r i c a t i o n Systems.
Wherever p o s s i b l e , l u b r i c a t i o n systems sh ould be avoided w hich use equipment i n c o r p o r a t i n g s p r i n g s and v a l v e s , p a r t i c u l a r l y where t h e l u b r i c a t i o n systems a r e r e q u i r e d t o o p e r a t e i n arduous and a b r a s i v e environments. I n g e n e r a l p r a c t i c e , t h e m a j o r i t y o f C e n t r a l i s e d L u b r i c a t i o n Systems used a r e e i t h e r o f t h e ' D i r e c t Feed' o r ' P a r a l l e l - D u a l be in g o p e r a t e d ' m a n u a l l y ' o r ' a u t o m a t i c a l l y ' .
L i n e ' type;
b o t h a r e capable o f
The c h o i c e o f Grease L u b r i c a t i o n
Systems i s u s u a l l y d i c t a t e d by t h e number o f p o i n t s o f a p p l i c a t i o n and t h e i r l o c a t i o n , always b e a r i n g i n mind t h a t f o r utmost r e l i a b i l i t y and minimal maintenance D i r e c t Feed Systems sh ou l d be s e l e c t e d wherever i t i s p r a c t i c a l . o f explanation,
By way
a P a r a l l e l - D u a l L i n e system can c y c l e and y e t f a i l t o d e l i v e r
l u b r i c a n t t o some of t h e p o i n t s o f a p p l i c a t i o n w hich i s o n l y e v i d e n t i f t h e o p e r a t o r v i s u a l l y examines t h e p o s i t i o n o f e very dual l i n e element i n d i c a t o r pin. Q u i t e o f t e n t h i s i s i m p r a c t i c a l because o f elements b e i n g l o c a t e d i n hazardous areas
o n l y b e in g a c c e s s i b l e when t h e p l a n t and machinery a r e shut down.
T h i s cannot o c c ur w i t h D i r e c t Feed pumps, f o r t h e y w i l l o n l y o p e r a t e e f f e c t i v e l y providing
the points o f application are receiving lubricant;
course, broken f ee d-p i pe s
barring, o f
(which can a p p l y t o b o t h types o f system).
I n prac-
t i c e , a D i r e c t Feed pump can u s u a l l y c a t e r f o r up t o 40 p o i n t s o f a p p l i c a t i o n . 17.6.1.5
L u b r i c a t i o n o f P l a i n o r Sleeve Bearings.
These b e a r i n g s , p a r t i c u l a r l y t h ose o v e r 4" diameter, r e q u i r e as near c o n t i n uous l u b r i c a t i o n as i s p o s s i b l e .
I t i s n o r m a l l y recommended t h a t b e a r i n g s of
t h i s t y p e be f e d by D i r e c t Feeding l u b r i c a t o r s d r i v e n from t h e moving s h a f t . T h i s ensures l u b r i c a n t i s f e d t o t h e b e a r i n g s when t h e s h a f t i s i n o p e r a t i o n and no l u b r i c a n t i s f e d t o t h e b e a r i n g when t h e s h a f t i s i n o p e r a t i v e . 17.6.1.6
Lubrication o f Anti-Friction
( B a l l and R o l l e r ) Bearings.
A n t i - f r i c t i o n be ari n gs r e q u i r e c o n s i d e r a b l y s m a l l e r q u a n t i t i e s o f l u b r i c a n t tha n p l a i n b e a r ings.
Except i n t h e case o f l a r g e a n t i - f r i c t i o n b e a r i n g s , they
w i l l n o t n o r m a l l y be l u b r i c a t e d c o n t i n u o u s l y . Where a n t i - f r i c t i o n b ea ri ng s a r e c l o s e t o g e t h e r , a hand-operated o r t i m e c l o c k c o n t r o l l e d d i r e c t f e e d i n g pump may be used.
Where they a r e spaced over
413 some d i s t a n c e , a l i n e system, e i t h e r hand-operated o r t i m e c l o c k c o n t r o l l e d ,
is
preferred. For l a r g e a n t i - f r i c t i o n b e a r i n g s and t h ose i n s t a l l a t i o n s where t h e g r e a t e s t r e l i a b i l i t y o f D i r e c t Feeding systems i s d e s i r a b l e
b u t t h e number o f p i p e s
should be k e p t low, d i r e c t f e e d i n g pumps w i t h P o s i t i v e D i v i d e r s may be used, s p l i t t i n g v o l u m e t r i c a l l y metered amounts o f l u b r i c a n t independent o f v a r y i n g back p r e s s u r e s . Very f a s t o p e r a t i n g a n t i - f r i c t i o n b e a r i n g s such as those running a t 1400 rpm should n o t be f e d c o n t i n u o u s l y .
However, o v e r - g r e a s i n g w i l l do no harm t o l a r g e
s l o w - r u n n in g a n t i - f r i c t i o n b e a r i n g s where q u i t e o f t e n t h e grease i s used as a s e a l a n t , p r e v e n t i n g d i r t and o t h e r f o r e i g n m a t t e r a n t i - f r i c t i o n bearings
-
t o e n t e r t h e b ea ri ng .
-
the greatest destroyer o f
Therefore i t i s essential t h a t
t h e grease i s k e pt c l e a n a t a l l t i mes, w i t h t h e l u b r i c a t i n g pump c o n t a i n e r o r r e s e r v o i r b o t to m f i l l e d v i a a grease keg o r b u l k grease s t o r a g e system.
17.6.2
O i l L u b r i c a t i o n Systems
O i l L u b r i c a t i o n Systems s e r v e two purposes:
t o l u b r i c a t e and/or c o o l .
On
many a p p l i c a t i o n s . p a r t i c u l a r l y i n t h e absence o f h i g h ambient temperature o r where t h e h e a t g ene rat ed i n t h e b e a r i n g s o r t h e gears i s n o t g r e a t . t h e removal o f h e a t by t h e o i l need n o t f e a t u r e as a se parate c o n s i d e r a t i o n i n t h e s e l e c t i o n o f t h e o i l c i r c u l a t i o n system.
T h i s can be arranged on t h e b a s i s o f l u b r i c a t i o n
c o n s i d e r a t i o n s a l o ne .
i n t h e case o f many o t h e r a p p l i c a t i o n s , the
However,
c o o l i n g p r o p e r t i e s o f t h e o i l a r e o f g r e a t importance. O i l systems may t h e r e f o r e be grouped under t h r e e main headings:Group 1
Systems designed f o r l u b r i c a t i o n on a t o t a l loss basis.
Group 2
Systems designed f o r l u b r i c a t i o n and w i t h a small amount o f heat removal.
Group
3
Systems designed f o r l u b r i c a t i o n where an a p p r e c i a b l e degree o f c o o l i n g i s a l s o r e q u i r e d because o f operating conditions.
Group 1 and 2 systems v a r y a c c o r d i n g t o t h e t y p e o f machine and i t s l u b r i c a t i o n requirements.
Systems o f t h e t o t a l l o s s t y p e may be operated e i t h e r manually,
m e c h a n ic a lly , o r mo t o ri sed , whereas systems o f t h e t y p e which c o l l e c t t h e used o i l and r e c i r c u l a t e i t must be a u t o m a t i c .
V arious combinations o f these systems
can be employed, and t h e f o l l o w i n g a r e some t y p i c a l examples: 17.6.2.1
Group 1
- Total
loss systems designed f o r l u b r i c a t i o n purposes o n l y .
I n t h i s t y p e o f system t h e l u b r i c a n t , a f t e r l u b r i c a t i n g t h e b e a r i n g s o r gears, i s n o t used a g a in. pumps.
The group c o n s i s t s o f manual, mechanical o r motor operated
The fo r m er g e n e r a l l y a p p l i e s on sma l l items o f p l a n t , e.g.
machine t o o l s ,
414 mechanical h a n d l i n g equipment, j i g s and f i x t u r e s , presses, e t c .
These systems
may be f u r t h e r s u b - d i v i d e d i n t o D i r e c t P o s i t i v e Systems or P o s i t i v e S p l i t Systems. D i r e c t P o s i t i v e Systems u s u a l l y comprise one o r more d i f f e r e n t i a l p l u n g e r ty p e o i l l u b r i c a t o r s , e.g.
Se ct i o ns 6.1.1
(F ig.9)
shows t h e o p e r a t i o n o f a man-
u a l l y o p e r a te d 8 - o u t l e t g rea se pump whi ch i s a l s o a d a p t a b l e f o r o i l , w i t h Fig.17 i l l u s t r a t i n g a t y p i c a l a p p l i c a t i o n on a pre ss l u b r i c a t i n g t h e slidew ays and crosshead.
For a p p l i c a t i o n s where a ut oma t i c l u b r i c a t i o n i s r e q u i r e d , mechanical
l u b r i c a t o r s h a v ing u s u a l l y 28 t o 32 pumping u n i t s may be f i t t e d ( F i g . 1 8 ) .
These
l u b r i c a t o r s may be d r i v e n e i t h e r m e c h a n i c a l l y t h r o u g h a r a t c h e t from t h e machine be in g l u b r i c a t e d o r by geared e l e c t r i c motor.
Each pump u n i t can be r e g u l a t e d
fro m z e r o t o maximum, t o f e e d m i n u t e p r e c i s e q u a n t i t i e s o f o i l t o t h e p o i n t s o f lubrication application.
F i g. 17
D i r e c t p o s i t i v e system.
415
Fig.18 P o s i t i v e S p l i t System.
D i r e c t p o s i t i v e system.
T h i s t y p e o f system i s used where q u a n t i t i e s o f o i l
per a p p l i c a t i o n p o i n t a r e g r e a t e r t h a n can be s u p p l i e d by t h e p r e v i o u s l y described d i r e c t f e e d i n g p l u n g e r system.
I t comprises o f one o r more small h i g h
p r e s s u r e pumps f i t t e d w i t h i n t e g r a l r e l i e f v a l v e s , and s u p p l i e s l u b r i c a n t t o t h e b e a r i n g s through volume d i v i d e r s .
The d i v i d e r s may be used e i t h e r t o i n -
crease t h e number o f p o i n t s o r t o m o d i f y t h e q u a n t i t i e s f e d t o t h e l u b r i c a t i o n points.
416
Fig.19
17.6.2.2
P o s i t i v e s p l i t system.
Group 2 - Systems designed f o r l u b r i c a t i o n w i t h s m a l l amount o f
heat removal.
T h i s t y p e o f system s u p p l i e s t h e l u b r i c a n t t o t h e b e a r i n g s and
r e t u r n s i t under g r a v i t y through t h e r e t u r n p i p e s and/or drainways t o t h e s u p p l y tank f o r r e c i r c u l a t i o n .
T h i s group can a l s o be s u b - d i v i d e d i n t o D i r e c t P o s i t i v e
Systems o r P o s i t i v e S p l i t Systems.
The former c o n s i s t s o f t h e m e c h a n i c a l l y
operated d i f f e r e n t i a l p l u n g e r t y p e o i l l u b r i c a t o r as d e s c r i b e d i n Group 1.
417 T y p i c a l a p p l i c a t i o n s i n c l u d e paper machines, l a r g e k i l n s , o r g e n e r a l l y where a l a r g e number o f b ea ri ng s a r e t o be f e d p o s i t i v e l y w i t h an a d j u s t a b l e feed. Systems o f t h i s t y p e r e q u i r e a minimum amount o f maintenance and a t t e n t i o n .
The
l u b r i c a t i o n r e s e r v o i r s o f c o n t a i n e r s can be kept f i l l e d e i t h e r by a header t a n k s u p p l y i n g s e v e r a l l u b r i c a t o r s , o r each l u b r i c a t o r can be f i t t e d w i t h s p e c i a l b u i l t - i n s u c t i o n pumps wh i ch sup pl y t h e c o n t a i n e r w i t h l u b r i c a n t from t h e main s u p p ly tank.
Each l u b r i c a t o r pump u n i t ( o u t l e t ) can be connected d i r e c t t o t h e
l u b r i c a t i o n p o i n t s o r t o a p o s i t i v e volume d i v i d e r , depending on t h e number o f feeds and t h e l u b r i c a t i o n req ui re men t s o f t h e p o i n t s . The l u b r i c a n t i s r e t u r n e d under g r a v i t y t o t h e main supply tank through d r a i n ways o r r e t u r n p i p e s (which can be a rran ge d w i t h b e a r i n g sump l e v e l c o n t r o l dev ic e s ) f o r r e c i r c u l a t i n g t o t h e l u b r i c a t o r c o n t a i n e r s o r header t a n k by means of s u c t i o n pumps, as d escri b ed , o r t o t h e t a n k by a f l o a t - c o n t r o l l e d gear pump (Fig.20).
-
Discharge f i l t e r
I
I
b
d
L
&
6
6
b
d
b
b
b
b
1
b b b
b b d
\ l b
/
b
O
b
l
d
b
b b
Reservoir
F ig . 20
System w i t h smal l amount o f heat removal
As i n t h e case o f t h e p r e v i o u s group,
t h e l u b r i c a t o r can be d r i v e n e i t h e r
d i r e c t f r o m t h e machine b e i n g l u b r i c a t e d o r f i t t e d w i t h i t s own motor,
Each
pump can be f e d e i t h e r f ro m t h e machine sump o r from a separate d r a i n and supply tank.
The system i s u s u a l l y i n s t a l l e d on machine t o o l s , sugar machinery, gear
boxes, p r i n t i n g machines, and sp eci a l -pu rpo se machinery.
17.6.2.3
Group
3
-
Systems designed f o r l u b r i c a t i o n c o o l i n g .
Where t h e r e i s c o n s i d e r a b l e ambient h ea t o r where t h e power t r a n s m i t t e d by t h e p a r t b e in g l u b r i c a t e d c r e a t e s a h i g h degree o f h e a t , t h e c o o l i n g f u n c t i o n o f t h e l u b r i c a n t assumes g r e a t importance.
I t i s necessary i n such cases t o
ap p ly s u f f i c i e n t l u b r i c a n t t o e x t r a c t t h e he at and t o m a i n t a i n t h e bearings o r gears a t an optimum t e mpe rat ure .
Arrangements must a l s o be made f o r r e t u r n i n g
t h e l u b r i c a n t t o a su pp l y t a n k f o r c o o l i n g , f i l t r a t i o n , and r e c i r c u l a t i o n , between t h e l u b r i c a t i o n equipment man uf act urer, t h e p l a n t designers, and t h e operators. Such a system u s u a l l y comprises a l a r g e o i l r e s e r v o i r o r s t o r a g e tank; motor d r i v e n pump ( n o r m a l l y a gear t y p e pump a d j a c e n t t o o r on t h e s t o r a g e t a n k ) ; coolers;
f i l t e r s ; p r e s s u r e gauges; a l a r m and f l o w c o n t r o l equipment; t o g e t h e r
w i t h t h e necessary v a l v e s and i n t e r c o n n e c t i n g pipework. and s e l f - c o n t a i n e d w i t h a c a p a c i t y o f 3 8 c c / s e c
The system may be simple
t o 750cc/sec
complex system c a pa bl e o f d e l i v e r i n g s e v e r a l l i t r e s / s e c .
p e r minute, o r a
These systems can be
p r o v i d e d w i t h s i m p l e o r e l a b o r a t e f l o w c o n t r o l , w arning d e v i c e s , and o t h e r i n s t r u m e n t a t i o n a c c o r d i n g t o t h e needs o f t h e i n s t a l l a t i o n (Fig.21).
Fig.21
T y p i c a l example o f l u b r i c a t i n g and c o o l i n g system packaged u n i t f o r t h e l u b r i c a t i o n o f rubber machinery.
419 17.6.3
Micro-Fog L u b r i c a t i o n Systems
Aerosol l u b r i c a t i o n i s t h e g e n e r i c term f o r o i l m i s t o r M i c r o - f o g systems which have been used s u c c e s s f u l l y f o r o v e r t w e n t y y e a r s .
Compared w i t h Centra-
l i s t e d Grease o r O i l l u b r i c a t i o n , a M i c r o - f o g system, t o p e r f o r m t h e same t a s k , r e q u i r e s l e s s l u b r i c a n t and energy and t h e i n i t i a l c o s t i s r e l a t i v e l y low. i s a l s o a h i g h l y f l e x i b l e system,
It
r e a d i l y i n s t a l l e d o n t o e x i s t i n g p l a n t as w e l l
as a t t h e new machine stage.
17.6.3.1
Working P r i n c i p l e s (Fig.22) o u t 1 i n e s t h e e s s e n t i a l and a u x i 1 i a r y
elements o f t h e M i c r o - f o g system and p r o v i d e s a g u i d e t o some o f t h e more common areas o f a p p l i c a t i o n .
During operation,
t h e system produces c o n t i n u o u s l y a dense
c o n c e n t r a t i o n of m i c r o p a r t i c l e s o f o i l which a r e conveyed i n a ' d r y ' f o g i n a low p r e s s u r e d i s t r i b u t i o n system.
On r e a c h i n g t h e p o i n t of a p p l i c a t i o n t h e
' d r y ' f o g i s passed t h r o u g h r e c l a s s i f i e r s , which a r e r e a l l y m e t e r i n g and condens i n g o r i f i c e s , so as t o a c c u r a t e l y f e e d an e x a c t q u a n t i t y o f l u b r i c a n t t o s u i t the operating conditions.
M i cro-foq
1u b r i c a t i o n
lubrication 1u b r i c a t i o n
Fig.22
M i c r o - f o g system.
420 To ensure t h a t t h e f o g reaches t h e r e c l a s s i f i e r d r y ,
the d i s t r i b u t i o n piping
i s sized t o allow o i l p a r t i c l e s t o travel along the piping a t a v e l o c i t y less tha n 7.3 metres/sec,
which i s sl o w enough t o p r e v e n t condensation.
l enc e i n t h e r e c l a s s i f i e r s causes t h e o i l p a r t i c l e s t o 'w et o u t '
The t u r b u -
i n t o the l i n e
l e a d i n g t o o r d i r e c t o n t o t h e b e a r i n g s u r f a c e s where they then form a p r o t e c t i v e f i l m of oil. In o r d e r t o c r e a t e ' d r y '
f o g, o i l i s f i r s t drawn i n t o a compressed a i r stream
as i t passes th r ou gh a V e n t u r i l o c a t e d on t o p o f t h e l u b r i c a t i o n c o n t r o l u n i t (Fig.23).
O i l p a r t i c l e s o f a p p r o x i m a t e l y 0.002mm
i n diameter a r e c o l l e c t e d i n
t h e a i r stream and can be t r a n s p o r t e d l on g d i s t a n c e s i n t h e d r y c o n d i t i o n .
Lubricator head A i r bypass a d j u s t i n Low pressure w i t c h
lligh pressure s w i t c h Electrical conduit ent Auxiliary requlatcr
Supply t o pressur j e t reclassifier
Waste pipe e x i t
/
Fig.23
Lubrication control unit.
Since M i c r o - f o g systems r e q u i r e no r e t u r n l i n e s they can be designed t o easy i n s t a l l a t i o n and assembly;
hence, l o w c o s t i n s t a l l a t i o n , w i t h o u t t h e problems
a s s o c i a t e d w i t h s i n g l e - l i n e s e r i e s o i l c i r c u l a t i n g systems w hich i n c o r p o r a t e q u i t e s o p h i s t i c a t e d and r e l a t i v e l y expensive v a l v e b l o c k s t h a t have a b u i l t - i n self-reversing operation.
Al t ho ug h such systems may r e q u i r e no separate reverse
and r e c y c l e v a l v e o r v e n t i n g phase d u r i n g t h e l u b e c y c l e , they do have, however, a d i s t i n c t d is a d va nt ag e because t h e y r e q u i r e a m u l t i p l i c i t y o f system t u b i n g (Fig.20). Moreover, Once a M i c r o - f o g system has been i n s t a l e d i t i s much less demandi n g t h a n o t h e r a ut oma t i c l u b e systems.
The system
s e a s i l y assembled,
using a
b u i l d i n g b l o c k approach, wh i ch i s designed f o r easy s e r v i c i n g , r e p a i r s and general maintenance.
421 17.6.3.2
O i l Quality.
C o r r e c t o i l s e l e c t i o n i s i m p o r t a n t as some o i l s i n c o r p o r a t e polymers w hich suppress a e r o s o l p r o p e r t i e s , w h i l e h e a v i e r g rade o i l s may r e q u i r e h e a t i n g up t o between 4Oo/45OC
t o a t t a i n t h e v i s c o s i t y f o r maximum o u t p u t . For a l l normal
purposes t h e c o n t r o l u n i t s w i l l p e r f o r m w e l l when w orking w i t h o i l s up t o 700 c e n t i s t o k e s a t 20°C. Summarised l u b r i c a t i n g o i l req ui re men t s f o r a s a t i s f a c t o r y M i c r o - f o g system are:(i)
Good a e r o s o l p r o p e r t i e s .
(ii)
Low r a t e o f co nd en sat i on t hro ug h p i p e s .
( i i i ) Low l e v e l o f s t r a y i n g by t h e p a r t i c l e s . (iv)
A h i g h degree o f r u s t i n h i b i t i o n .
(v)
Absence o f c l o g g i n g t e nd en ci es a t t h e v e n t u r i n o z z l e o r any polymer precipitation.
17.6.3.3
Compressed A i r
2
A c c e p t in g t h a t most i n d u s t r i a l compressed a i r i s s u p p l i e d a t 7 bar (100 l b / i n ) 2 i n a M i c r o - f o g l u b r i c a t i o n system i t has t o be reduced t o about 2 b a r (30 l b / i n 1. Dur in g i t s passage t h r o u g h t h e v e n t u r i o r i f i c e on t h e c o n t r o l u n i t , a p r e s s u r e
2
dro p o f 0 . 7 bar (10 I b / i n ) t ake s pl a ce. 17.6.3.4
System Design Con si de rat i o ns
To c a l c u l a t e t h e l u b r i c a t i o n req ui re men t s o f bearings, an e m p i r i c a l f a c t o r r e f e r r e d t o as a ' l u b r i c a t i o n u n i t '
(L.U.)
has been evolved,
e n a b l i n g a l l moving
s u r f a c e s r e q u i r i n g l u b r i c a n t t o be co nve rt e d t o t h e i r e q u i v a l e n t L.U. The amount o f l u b r i c a n t main
rating.
and b ran ch l i n e p i p e bores and r e c l a s s i f i e r nozzles
may t h e n be s i z e d t o p r o v i d e t h e c o r r e c t amount o f l u b r i c a n t a t each l u b r i c a t i n g point.
I n t h i s manner, a n t i - f r i c t i o n b ea ri ngs, j o u r n a l bearings, s l i d e s , gears,
c h a in s , and o t h e r wea ri ng s u r f a c e s r e q u i r i n g l u b r i c a t i o n can a l l be converted t o e q u i v a l e n t L.U.
r a t i n g s and serve d by a p p r o p r i a t e l y s i z e d M i c r o - f o g l u b r i c a t i o n
systems. 17.6.3.5
Some T y p i c a l A p p l i c a t i o n s
F i g u r e 24 i l l u s t r a t e s a t h r e e S t ran d Aluminium F o i l M i l l o p e r a t i n g a t 1000 t o 1500 m e t r e s / m in u t e w i t h two 1000 L.U. g e n e r a t i n g heads ( t h i r d a c t s as a standby) s e r v i n g t h e m i l l s t a c k and e x i t a n c i l l a r i e s , w i t h a s e p a r a t e 300 L.U. u n i t serving the entry a n c i l l a r i e s .
2.5 l i t r e s p e r w o r k i n g hour. motor oears.
generating
The t o t a l amount o f o i l used i s l e s s than
F i g u r e 25 i l l u s t r a t e s t h e l u b r i c a t i o n o f v i b r a t o r
422
423
i
I
Fig.25
17.6.4
"i" 'i' 0-
I
Lubrication o f vibrator motor gears.
Check List
Based o n the foregoing, prior to actual selection of the appropr ate lubricant and associated equipment, it is advisable to draw up a check 1 st of known The following list, in simplified form, is for guide purposes only and can naturally be elaborated upon to suit the spec fic needs o f facts and requirements.
the designer o r plant engineer. Specification o f Plant t o be lubricated: Type of plant and machinery to be lubricated. Industrial Application, including operating environmental conditions, e.g. is i t dirty, abrasive, wet, hot, etc.? Surfaces, sizes and speeds to be lubricated, e.g. Bearings (plain), Bearings (roller), Grease (type), Slideways, Chains, etc. Number and Location of lubrication Points (Fixed) and (Moving) and proposed site (if known) for lubricator enabling assessment of pipe and flexes: Frequency plant and machinery operators and whether lubrication needs to be continuous, semi-continuous, or intermittent.
424
-
L u b r i c a n t t ype and s p e c i f c a t i o n S e r v i ces a v a i l a b l e i n t h e P l a n t
-
Grease, O i l , o r M i c r o - f o g ,
etc
e l e c t r i c , pneumatic.
H e a l t h and S a f e t y a spe ct s e.g. normal, flameproof, a c c e s s i b i l i t y any h i s t o r y o f p r e v i o u s l y t r i e d l u b r i c a n t s / e q u i p m e n t . Method proposed f o r f i l l i n g t h e l u b r i c a t i o n t a n k / r e s e r v o i r , e.g. manual, semi-automatic, b u l k storage. Recommended L u b r i c a t i o n Equipment: Why? E s timat ed performance w i t h any known Case Studies and References. Econom ic s
.
Spares and S e rvi ce. Sometimes equipment s e l e c t i o n i s an i n e v i t a b l e compromise as a r e s u l t o f c o n f l i c t i n g l u b r i c a t i o n req ui re men ts;
i n such circumstances i t i s
im p o r t a n t t o a p p r e c i a t e a l l t h e f a c t s and t o subsequently gauge p l a n t performance a c c o r d i n g l y . 17 7
SUMMARY
T h i s c h a p t e r has a t t emp t e d t o c l a r i f y t h e more g e n e r a l l y accepted methods o f l u b r i c a t i o n , where necessary i l l u s t r a t i n g a c t u a l examples o f p l a n t and l u b r i c a t i o n equipment.
I t i s n o t i n any way i n t e nded t o i n f e r t h a t t h i s i s t h e o n l y
l u b r i c a t i o n equipment a v a i l a b l e ; from Trade J o u r n a l s , e t c .
o f cou rse, t h e r e a r e o t h e r s r e a d i l y determined
L i k e w i s e , t h e r e a r e many more s e l e c t items o f l u b r i -
c a t i o n equipment t a i l o r - m a d e t o meet t h e needs o f s p e c i a l i s t p l a n t . For example, Overhead and F l o o r Conveyors which can t r a v e l up t o 50 metres/ m in u te , u n l e s s e f f e c t i v e l y l u b r i c a t e d (and cl eaned where t h e environment demands) can wear and s e i z e , r e s u l t i n g i n c o s t l y stoppages. l n i t i a l y , c o n v e n t i o n a l s t a t i c l u b r i c a t o r s were used where a m i x t u r e o f a i r and o i l
-
not only
and now more r e c e n t l y j u s t o i l
- was
shot over a gap, w hich r e s u l t e d
n t h e f a i l u r e t o a de qu at el y l u b r i c a t e (Fig.1)
b u t a l s o caused d r i p -
page w i t h c o n s e q ue nt i al pro du ct c o n t a m i n a t i o n and h e a l t h hazards. These problems were c o m p l e t e l y overcome by i n t r o d u c i n g a range o f s p e c i a l purpose l u b r i c a t o r s ;
(F i g. 26 ) shows one such example.
The c o n c l u s i o n i s t o d et ermi n e a l l t h e f a c t s r e g a r d i n g t h e p l a n t t o be l u b r i c a t e d and t o t h en e v a l u a t e t h e l u b r i c a n t s and l u b r i c a t i o n equipment ava i 1a b le .
425
Fig.26
A dog c h a i n assembly engages t h e conveyor c h a i n which moves t h e o i l - d i s p e n s i n g n o z z l e p l a t e s i n and o u t o v e r t h e p i n l i n k s . O i l i s f o r c e d t h r o u g h each n o z z l e .
REFERENCES
1 2
3 4
5
Mechanical L u h r i c a t i o n o f E.O.T. Cranes by D r . H . P e t e r J o s t and P e t e r W. Murray. A F u l l y Automatic B u l k H a n d l i n g L u b r i c a t i o n System f o r a S i n t e r P l a n t by G. W i l l i a m s . An E n g i n e e r i n g Approach t o t h e s e l e c t i o n o f C e n t r a l i s e d Grease L u b r i c a t i o n Systems by D r . H. P e t e r J o s t . Modern B r i t i s h and European Steelworks L u b r i c a t i o n Developments by D r . H. P e t e r J o s t . E!ew M i s t L u b r i c a t i o n Concepts f o r Tapered R o l l e r Bearinos used on High C.H. West and Speed R o l l i n g M i l l Back-up by R o l l s by \!.E.McCoy, P.E. W i l k s .
426
6
7
8
9
10
Aerosol L u b r i c a t i o n Systems - t h e i r c o n t r i b u t i o n t o savings i n o p e r a t i n g and maintenance c o s t s by R.E. K n i g h t and J.G. M e r r e t t . Micro-Fog L u b r i c a t i o n f o r b e a r i n g e f f i c i e n c y by J.G. M e r r e t t . Automatic L u b r i c a t o r s and Cleaners Increase Conveyor L i f e by J.G. M e r r e t t . Automatic L u b r i c a t i o n o f Chain and Conveyor Systems by R.M. Dombroski. The James C l a y t o n L e c t u r e - "Energy Saving through T r i b o l o g y " by D r . H. P e t e r J o s t and D r . J. S c h o f i e l d .
17
CENTRALISED LUBRICATION SYSTEMS DESIGN
J.G.MERRETT,
17.1
Managing D i r e c t o r , E n g i n e e r i n g and General Equipment L t d .
INTRODUCTION
W h i l s t we a r e k e p t c o m p a r a t i v e l y w e l l informed o f t h e l a t e s t developments i n o i l and grease technology and t h e v i t a l r o l e i t p l a y s i n i n d u s t r i a l and commerc i a l applications,
v e r y l i t t l e has been w r i t t e n about t h e e q u a l l y v i t a l "Centra-
I i s e d L u b r i c a t i o n Systems" and some o f t h e methods a v a i l a b l e t o Engineers by which grease and o i l may be t r a n s m i t t e d t o t h e p o i n t o f l u b r i c a t i o n . I n our s o c i e t y where energy, machinery and l a b o u r a r e now (1981) expensive commodities,
i t i s c l e a r t h a t i n t h e p a s t i n s u f f i c i e n t a t t e n t i o n has been p a i d
t o the d i r e c t and i n d i r e c t losses o f energy, occasioned by wear and f r i c t i o n and t o t h e savings o f m a t e r i a l s .
However,
i n 1977 a government f i n a n c e d Ameri-
can Report suggested t h a t $16.25 b i l l i o n p.a.
( a t 1976 v a l u e s ) c o u l d be saved
by a "Strategy f o r Energy Conservation through T r i b o l o g y "
U.K.
[l].
Converted i n t o
(1980) v a l u e s , t h i s i n d i c a t e s an e q u i v a l e n t s a v i n g o f energy through t r i -
bology i n excess o f €1;
b i l l i o n p.a.
I n s h o r t , c o r r e c t l y s e l e c t e d l u b r i c a n t s and t h e i r methods o f a p p l i c a t i o n by C e n t r a l i s e d Systems can e f f e c t s i g n i f i c a n t savings, e.g. machine t o o l s , conveyors, cranes, r o l l i n g m i l l s , b l a s t furnaces, b a l l m i l l s , sugar machinery, paper m i l l s , heavy m o b i l e p l a n t , e t c . t o v a r y i n g degrees, a l l r e q u i r e t h e a p p l i c a t i o n o f lubricants.
A c o r r e c t l y designed and i n s t a l l e d C e n t r a l i s e d L u b r i c a t i o n
System i s t h e e n g i n e e r ' s insurance a g a i n s t some o f t h e severe t r i b o l o g i c a l problems, i . e .
f r i c t i o n and wear, which would o t h e r w i s e occur i f t h e p l a n t and
machinery were i n a d e q u a t e l y l u b r i c a t e d . U n f o r t u n a t e l y , a l l t o o o f t e n i n t h e supply of p l a n t and machinery t h e s e l e c t i o n o f t h e l u b r i c a n t and C e n t r a l i s e d L u b r i c a t i o n equipment a r e considered a t a l a t e stage i n t h e manufacture o f t h e p l a n t which, coupled w i t h t h e c o n f l i c t i n g i n t e r e s t s o f machinery b u i l d e r s , can r e s u l t i n u n s u i t a b l e l u b r i c a t i o n equipment being s e l e c t e d .
L i k e w i s e , t h e l u b r i c a t i o n equipment supply companies have a
r e s p o n s i b i l i t y , n o t o n l y t o know t h e i r own p r o d u c t , b u t a l s o t o a p p r e c i a t e t h e t r i b o l o g i c a l requirements o f t h e p l a n t and machinery which r e q u i r e s t o be
396 lubricated.
F a i l u r e i n t h i s area i n v a r i a b l y r e s u l t s i n the p l a n t user being
p l a c e d i n t h e u n e n v i a b l e p o s i t i o n o f h a v i n g t o a p p l y , a t an e a r l y stage, f o r a d d i t i o n a l c a p i t a l t o r e c t i f y new p l a n t o r , more o f t e n t h a n n o t , t o l i v e w i t h t h e problems and r e c t i f y as and when t h r o u g h a maintenance budget
-
both o f
which the p l a n t u s e r would be t h e f i r s t t o agree i s e n t i r e l y u n s a t i s f a c t o r y . T h i s paper endeavours t o deal w i t h some o f these f a c t o r s a f f e c t i n g t h e c h o i c e o f l u b r i c a n t and l u b r i c a t i n g equipment, t h e b a s i c elements o f t h e machinery t o be l u b r i c a t e d , and t h e c o n d i t i o n s under which i t o p e r a t e s . 17.2
POINTS OF LUBRICATION
Bearings, t h e e s s e n t i a l components o f p l a n t and machinery, may be g e n e r a l l y grouped i n t o j o u r n a l , t h r u s t , conveyor c h a i n p i n and l i n k , a n t i - f r i c t i o n , ways and crane r a i l s .
slide-
Each wear s u r f a c e must be t r e a t e d s e p a r a t e l y w i t h r e g a r d
t o l u b r i c a n t and l u b r i c a t i o n t e c h n i q u e . The l u b r i c a t i o n requirement o f a p l a i n j o u r n a l b e a r i n g i s t h e p r o v i s i o n o f an adequate and c o n s t a n t f l o w o f l u b r i c a n t o f s p e c i f i e d v i s c o s i t y t o g i v e a f l u i d f i l m o f high-load bearing capacity.
The j o u r n a l b e a r i n g has i n h e r e n t l y a
convergence between t h e s h a f t and t h e b e a r i n g .
When r e l a t i v e m o t i o n takes p l a c e
a f i l m o f l u b r i c a n t i s induced between t h e s u r f a c e s , e f f e c t i v e l y s e p a r a t i n g them. Bearings employed t o absorb t h r u s t and p r e v e n t misalignment of s h a f t s v a r y g r e a t l y i n t y p e and l u b r i c a t i o n requirement, w h i l s t a n t i - f r i c t i o n b e a r i n g s r e q u i r e l e s s l u b r i c a n t than p l a i n b e a r i n g s .
Most a v a i l a b l e formulae d e a l i n g
w i t h t h e a p p l i c a t i o n o f grease t o these b e a r i n g s t r e a t speed as an i m p o r t a n t factor.
For small a n t i - f r i c t i o n b e a r i n g s such as those employed i n l i g h t l y
loaded f r a c t i o n a l horse-power motors, t o o much grease can be damaging. I n such cases, recommended l u b r i c a t i o n i n t e r v a l s o f up t o s e v e r a l years have been e s t a blished.
Chain p i n s and l i n k s p r e s e n t m a j o r c r i t i c a l wear p o i n s on f l o o r and
overhead ( i n c l u d i n g Power and Free) conveyors.
I n t h e automobi e i n d u s t r y ,
c h a i n l e n g t h s o f s e v e r a l hundred metres, h a v i n g thousands o f
PO
nts requiring
l u b r i c a t i o n , a r e commonplace ( F i g . 1 ) . Slideway and crane r a i l l u b r i c a t i o n r e q u i r e s t h e r i g h t l u b r i c a n t and t h e r i g h t a p p l i c a t o r (see Fig.10,
S e c t i o n 17.6.1).
Too l i t t l e l u b r i c a n t r e s u l t s i n
r a p i d wear; e x c e s s i v e l u b r i c a n t can be a hazard t o l i f e o r l i m b . Every case i s d i f f e r e n t , y e t i n e v e r y case i t i s c r i t i c a l t h a t t h e l u b r i c a n t i s a p p l i e d i n l i n e w i t h the requirements o f t h a t component,
b o t h w i t h r e g a r d t o mechanical
wear and t o energy conservancy.
17.3
SELECTING THE LUBRICANT
-
O I L OR GREASE?
I n modern machinery l u b r i c a t i o n ,
l u b r i c a n t s and t h e means o f t h e app i c a t i o n
must be considered t o g e t h e r . The b e s t l u b r i c a n t w i l l s e r v e no u s e f u l purpose i f i t i s n o t a p p l i e d a t t h e
397
Fig.1
Excessive p i n and l i n k wear i n a conveyor c h a i n . A 3mm p i n wear p e r p i n on a 732111 conveyor increases t h e c h a i n l e n g t h by 23 metres.
r i g h t t i m e , a t t h e r i g h t p l a c e , and i n t h e c o r r e c t q u a n t i t y .
Conversely, t h e
best l u b r i c a t i o n equipment, a p p l y i n g l u b r i c a n t q u i t e c o r r e c t l y , w i l l be o f l i t t l e use i f t h e l u b r i c a n t i t feeds i s u n s u i t a b l e f o r t h e d u t y i t has t o perform. L u b r i c a n t s g e n e r a l l y , e i t h e r o i l s o r greases, a r e s u p p l i e d by o i l companies supported by s p e c i a l i s t o i l and grease m a n u f a c t u r i n g companies, who w i l l p r o v i d e advice on any p a r t i c u l a r l u b r i c a n t and a p p l i c a t i o n as w e l l as on t h e c h o i c e o f lubricants i n general.
The s u p p l i e r o f t h e l u b r i c a t i o n equipment w i l l a l s o
o f t e n be a b l e t o a d v i s e , e s p e c i a l l y on l u b r i c a t i o n d e s i g n problems, o r a c t as an intermediary
.
The s u b j e c t o f l u b r i c a n t s i s t r e a t e d h e r e o n l y i n i t s v e r y broadest terms under t h r e e headings:"OIL"
o r GREASE";
when t o use one and when t h e o t h e r .
LUBRICATING GREASE;
t h e types and how t o s e l e c t them.
LUBRICATING OILS; types and how t o s e l e c t them.
17.3.1
O i l o r Grease? When t o Use One and When t h e Other
Movement between two d r y s u r f a c e s causes heat and wear.
The purpose o f
i n t r o d u c i n g a l u b r i c a n t between t h e two s u r f a c e s i s t o reduce f r i c t i o n , heat, and wear.
O i l has t h e f o l l o w i n g advantages: and i t scavenges.
A t t h e same t i m e ,
i t flows,
i t penetrates,
i t removes heat,
i t has l i m i t e d s e a l i n g q u a l i t i e s and poor
' s t a y i n g ' power, t h e r e f o r e r e q u i r e s more f r e q u e n t r e p l e n i s h i n g than grease.
398 L u b r i c a t i n g grease, a s e m i - s o l i d p l a s t i c - l i k e m a t e r i a l , has e x c e l l e n t s e a l ing characteristics,
possesses good ' s t a y i n g ' power,
i.e.
i t adheres t o surfaces
more r e a d i l y and l o n g e r t h a n o i l and i t can be an e x c e l l e n t c o r r o s i o n p r e v e n t a tive.
Unlike o i l ,
i t i s a poor conductor o f heat and a poor scavenger;
n o t f l o w o r spread e a s i y where c o n t a m i n a t i o n by
-
i t does
t h e l a t t e r p r o p e r t y can, however, be an advantage
u b r i c a n t s must be avoided such as i n f o o d and b o t t l i n g
and t h e t e x t i l e i n d u s t r es and where t h e l u b r i c a n t i s used as a s e a l i n g medium. Where an a p p l i c a t i o n e n t a i l s HEAT REMOVAL, o i l i s t h e r e f o r e g e n e r a l l y t h e choice.
I t can be appl ed i n t h e f o r m o f a l i q u i d o r as an o i l m i s t ,
m i c r o - f o g comprising an o i l - a i r m i x t u r e .
i.e.
I n severe cases o f h e a t removal, o i l
can be r e c i r c u l a t e d and, d u r i n g t h e c i r c u l a t i o n ,
i t can be c o o l e d and cleaned.
Large t u r b i n e b e a r i n g s and f a s t gear t r a i n s a r e t y p i c a l examples where o i l c i r c u l a t i n g systems a r e used and l a r g e amounts o f o i l a r e c i r c u l a t e d . For a p p l i c a t i o n s where heat removal i s n o t a p r o b l e m , b u t LUBRICATION o r t h e PREVENTION OF INGRESS OF DIRT, WATER, DUST and OTHER EXTRANEOUS MATTER i s l u b r i c a t i n g grease can be used.
-
I t s a p p l i c a t i o n ranges from heavy m i l l b e a r i n g s
and s l i d e s t o t e x t i l e machinery, e t c .
I t i s a l s o t h e most s u i t a b l e where a p p l i -
c a t i o n o f t h e l u b r i c a n t i s r e q u i r e d a t LONG INTERVALS. N e a r l y a l l B a l l and R o l l e r Bearings, except those i n r e s p e c t o f which heat removal i s e s s e n t i a l , a r e g e n e r a l l y grease l u b r i c a t e d .
Where DIRTY/DUSTY and
WET CONDITIONS e x i s t , grease
s generally preferable.
The convenience o f grease
l u b r i c a t i o n makes grease t h e
p r e f e r r e d ' l u b r i c a n t f o r the vast m a j o r i t y o f
r o l l i n g bearings. G e n e r a l l y , o i l l u b r i c a t i o n i s employed i n t h e r e l a t i v e l y few cases where i t i s n o t p o s s i b l e t o t a k e advan age o f t h e m e r i t s o f grease as a r o l l i n g b e a r i n g
1u b r i c a n t . Where motion i s INTERMITTENT o r OSCILLATING, grease i s o f t e n t h e more s u i t able lubricant. Summarising, where heat conveyance away f r o m r u b b i n g s u r f a c e s o r p e n e t r a t i o n o f t h e l u b r i c a n t i s o f importance, o r t h e scavenging f u n c t i o n i s necessary, o i l i s p r e f e r a b l e , w h i l s t l u b r i c a t i n g grease can and,
i n most cases, should be
considered as t h e p r e f e r r e d l u b r i c a n t f o r slow moving machinery,
long l i f e
l u b r i c a t i o n , and where d i r t and d u s t has t o he kept o u t o f t h e b e a r i n g s , s l i d i n g surfaces, etc.
17.3.2
L u b r i c a t i n g Grease
-
The Types and How t o S e l e c t Them
Greases designed f o r l u b r i c a t i o n a r e e s s e n t i a l l y a m i x t u r e o f m i n e r a l o i l and t h i c k e n e r , a c c o r d i n g to t h e a p p l i c a t i o n requirement.
I n t h e most w i d e l y
used modern grease t h e t h i c k e n e r i s a m e t a l l i c soap, u s u a l l y o f l i t h i u m o r calcium, w i t h t h e q u a n t i t y o f o i l a d j u s t e d t o g i v e a s o l i d , s e m i - s o l i d o r semi f 1u i d consistency.
399 The soap f i b r e s form a s t r u c t u r e t h a t r e t a i n s t h e o i l , t h e dimensions and arrangement o f t h e f i b r e s v a r y i n g a c c o r d i n g t o t h e metal and t h e f a t t y a c i d from which t h e soap was made.
The q u a n t i t y , dimensions and d i s t r i b u t i o n o f t h e
f i b r e s a r e t h e main parameters c o n t r o l l i n g t h e s t a b i l i t y and f l o w p r o p e r t i e s o f this lubricating material. One o f t h e most i m p o r t a n t p h y s i c a l f e a t u r e s o f grease i s s t i f f n e s s ( f o r s i s t e n c y ) which i s i n d i c a t e d by a t e s t t h a t measures t h e d e p t h t h a t t h e cone s i n k s i n t o a sample o f grease.
The d e p t h measured i s a t e n t h o f a m i l l i m e t r e ,
and r e f e r r e d t o as t h e degree o f p e n e t r a t i o n .
F i g u r e 2 shows one c l a s s i f i c a -
t i o n system f o r greases. Grade Number. 000 OD 0 1 2 3
445
-
355
-
400 310 265 220
4 5 6
Fig.2
Worked p e n e t r a t i o n a t 25'C
175
130
85
-
-
-
475
430 385 340 295 250 205 160 115
Description Very f l u i d Fluid Semi - f 1 u i d Very s o f t Soft Semi-firm Firm Very f i r m Hard
NLGl c l a s s i f i c a t i o n o f t h e c o n s i s t e n c y o f greases.
Although lithium-based greases today s a t i s f y a v a s t number o f l u b r i c a t i o n requirements f o r cranes, conveyors, f o r g i n g presses, continuous c a s t i n g p l a n t s , r o l l i n g mills, etc.,
t h e r e a r e a number o f s i t u a t i o n s r e q u i r i n g l u b r i c a n t s w i t h
s p e c i a l p r o p e r t i e s , f o r example, t h e a b i l i t y t o w i t h s t a n d h i g h temperatures such as those encountered i n power s t a t i o n t u r b i n e s , bakery oven conveyors, e t c . These l a t t e r greases i n c l u d e t h e c l a y - t h i c k e n e d and o t h e r s o l i d - t h i c k e n e d compounds which w i t h s t a n d c o n s i d e r a b l y h i g h e r temperatures, e s p e c i a l l y when employed w i t h h i g h temperature s y n t h e t i c l u b r i c a n t s , e.g.
polyglycol, s y n t h e t i c esters,
and s i l i c o n e s . The upper temperature l i m i t a t which any grease may be used i s dependent p a r t l y on t h e t y p e o f t h i c k e n e r , p a r t l y on t h e f l u i d and i t s r e q u i r e d s e r v i c e life.
Higher o p e r a t i n g temperatures have t h e e f f e c t o f s h o r t e n i n g t h e l u b r i -
c a n t ' s s e r v i c e l i f e and r e d u c i n g p e r m i s s i b l e o p e r a t i n g speeds.
I t i s therefore
convenient t o express t h e working l i m i t s o f a grease i n terms o f b e a r i n g speeds and temperatures, as shown i n Fig.3.
T h i s diagram shows t h a t l i t h i u m , sodium
and calcium-based greases have upper temperature l i m i t s o f 130, 110 and 7OoC r e s p e c t i v e l y , and t h a t clay-based and calcium-complex greases can be used a t up t o 150°C.
400
Fig.3
17.3.3
Lubricating 011s
Working l i m i t s o f m i n e r a l o i l greases
-
Types and How t o S e l e c t Them
Vegetable and animal o i l s a r e e x c e l l e n t l u b r i c a n t s , b u t have s h o r t l i f e as they o x i d i s e and tend t o go r a n c i d ; as a r e s u l t , t h e i r main use i s f o r 'one s h o t ' a p p l i c a t i o n s such as f o r f o r g i n g o r as a d d i t i v e s f o r m i n e r a l o i l s . G e n e r a l l y , t h e o r i g i n o f t h e o i l determines i t s use ( F i g . 4 ) O i l Origin
ADD1
ication
Mineral O i l
e.g. p e t r o l e u m base f o r general l u b r i c a t i o n o f mechanical p a r t s such as engines, gears and g e n e r a l e n g i n e e r i n g p l a n t .
Vegetable O i l
e.g. c a s t o r , palm, and rape seed o i l s f o r s p e c i a l a p p l i c a t i o n s where h i g h l u b r i c i t y i s d e s i r a b l e such as k i l n s , bakery ovens.
Animal O i l
e.g. sperm o r o t h e r f i s h o i l s from sheep wool f o r a p p l i c a t i o n s such as k i l n s , bakery ovens.
Synthetic O i l
e.g. glycol d e r i v a t i v e s and d i e s t e r f o r extreme h i g h temperature. Fig.4
Origin of Oils
401 F i g u r e 5 i l l u s t r a t e s how v i s c o s i t y o f o i l s change w i t h temperature, becoming t h i n n e r when they a r e heated, b u t they do n o t change v i s c o s i t y a t t h e same r a t e . The r a t e o f v i s c o s i t y change w i t h temperature i s r e f e r r e d t o as the ' v i s c o s i t y index'.
-40-30-20 -10 0 10 20 30 $0 50 60 70 80 90XX)11O1201X)14015MM)710
degrees fahrenheit
Fig.5
17.3.3.1
V i s c o s i t y vs Temperature f o r two o i l s h a v i n g v i s c o s i t y indexes o f 0 and 100 r e s p e c t i v e l y .
The p r o p e r t i e s o f t h e o i l must be c a r e f u l l y considered when d e s i g n i n g
a l u b r i c a t i o n system, e.g.
conveyor chains passing through a p r e - t r e a t m e n t oven
may reach a temperature o f 180/200°C.
O i l s w i t h s p e c i a l i n c l u s i o n s such as
g r a p h i t e o r molybdenum d i s u l p h i d e i n g l y c o l as used i n bakery ovens must have p r o v i s i o n f o r a g i t a t i o n o r r e c i r c u l a t i o n w i t h i n t h e l u b r i c a t o r s t o r a g e tank t o prevent s e t t l i n g o u t o f t h e g r a p h i t e o r molybdenum. Bakery ovens g e n e r a l l y use molybdenum d i s u l p h i d e i n g l y c o l w h i l s t f o r extreme p r e s s u r e l o a d i n g c o n d i t i o n s on Power and Free t r o l l e y s , as i n the c a r i n d u s t r y , chains and t r o l l e y wheels r e q u i r e s p e c i a l l u b r i c a n t s , h a v i n g a h i g h adhesion c h a r a c t e r i s t i c - a s w e l l as i m p a r t i n g r u s t - p r o o f i n g and w a t e r - p r o o f i n g .
402
17.3.3.2
A f u r t h e r s p e c i a l i s t l u b r i c a n t i s rape seed o i l ;
f a t t y vegetable o i l .
t h i s i s a low a c i d
Because o f i t s r e l a t i v e l y h i g h f l a s h - p o i n t
i t i s suitable
f o r h i g h temperature work when r e f i n e d and g i v e n a g r a p h i t e i n c l u s i o n . uses a r e f o r continuous c a s t i n g moulds, f o r g i n g , metals.
Typical
and as a c u t t i n g o i l f o r harder
Here a g a i n , i t s s p e c i a l p r o p e r t i e s must be considered when p r o v i d i n g
t h e l u b r i c a t i n g means.
17.3.4
Summarising L u b r i c a n t S e l e c t i o n
For t h e f i n a l s a t i s f a c t o r y s e l e c t i o n o f l u b r i c a n t t h e f o l l o w i n g f a c t o r s must t h e r e f o r e be determined.
The c o n s t r u c t i o n and m a t e r i a l s employed i n t h e compon-
e n t s t o be l u b r i c a t e d , o p e r a t i n g speeds and l o a d i n g , l i f e requirement o f l u b r i c a n t and machine, o p e r a t i n g environment, e.g.
t h e presence o f w a t e r , steam,
chemicals o r a b r a s i v e m a t e r i a l s i n t h e atmosphere; and l a s t , b u t n o t l e a s t , t h e method o f a p p l i c a t i o n , t h e t y p e o f system t o be employed, t h e diameter of p i p e runs, e t c .
17.4
PIPE DIAMETER vs
FLOW CHARACTERISTICS
To determine t h e l u b r i c a n t f l o w r a t e and volume,
t h e l e n g t h and diameter o f
t h e p i p e l i n e s should be c a r e f u l l y c a l c u l a t e d t o ensure t h a t t h e l u b r i c a n t can s a t i s f a c t o r i l y reach t h e wear p o i n t s a t t h e extreme ends o f t h e p i p e l i n e s .
The
f o l l o w i n g t a b l e summarises some p r a c t i c a l r e s u l t s f r o m t e s t s t o prove optimum measurements and e n d - o f - l i n e p r e s s u r e , u s i n g a l i t h i u m - b a s e d grease o f No.2 consistency a t
15OoC. Nominal bore (mm)
50 38 25 19 17.5
Applied pressure (kPa)
P r e s s u r e drop (kPa/m)
1100
36.1 61.5 144.7 210.3
1 a75
4410 6410
LUBRICATION REQUIREMENTS FOR PLAIN BEARINGS
For normal w o r k i n g c o n d i t i o n s i t has been found t h a t t h e amount o f grease required f o r p l a i n bearings i s equivalent t o a layer o f O . l m m b e a r i n g area (0.1 x d x L) p e r hour o f b e a r i n g o p e r a t i o n .
on t h e developed
Figure
6 illustrates
a c h a r t f o r c a l c u l a t i n g t h e grease requirements f o r p l a i n b e a r i n g s . p l e t o c a l c u l a t e t h e grease r e q u i r e d f o r a b e a r i n g o f long,
i n t e r s e c t diameter and l e n g t h a s a t
*
As an exam-
75mm diameter by 250mm
f o l l o w l i n e o f a r r o w and where i t
i n t e r s e c t s t h e t o p s c a l e , t h i s i n d i c a t e s t h e amount o f grease r e q u i r e d , b e i n g i n t h i s example 6 g m o r 0.21 oz p e r hour.
403
D
LENGTH OF BEARING L
Fig.6
17.6
Grease requirements f o r a p l a i n b e a r i n g .
SELECTING THE RIGHT TYPE OF LUBRICATION SYSTEM
L u b r i c a t i o n systems f o r p l a n t and equipment, whatever t h e a p p l i c a t i o n , i n d i v i d u a l design.
t h e b e a r i n g requirements and t h e d e s i g n e r s ' a p p l i c a t i o n s p e c i f i c a t i o n . regard t o t h e human element, chapter deal w i t h : 17.6.1
require
They must be f u n c t i o n a l and c o r r e c t l y engineered t o s a t i s f y they must be f o o l - p r o o f .
With
Systems i n c l u d e d i n t h i s
Grease, O i l and Micro-Fog.
Grease L u b r i c a t i o n Systems
A l l C e n t r a l i s e d Grease L u b r i c a t i o n Systems a r e o f t h e n o n - r e c i r c u l a t i n g t y p e and o p e r a t e on t h e t o t a l loss p r i n c i p l e .
They a r e b a s i c a l l y d i v i d e d i n t o D i r e c t
Feeding systems and I n d i r e c t Feeding systems, o t h e r w i s e r e f e r r e d t o as L i n e systems, as i l l u s t r a t e d i n F i g . 7 .
17.6.1.1
D i r e c t Feeding Systems a r e those where t h e volume o u t p u t o f t h e D i r -
e c t Feeding l u b r i c a t i n g pump i s p o s i t i v e ;
t h e pumping p l u n g e r s and means o f
m e t e r i n g t h e o u t p u t t o i n d i v i d u a l wear p o i n t s b e i n g i n c o r p o r a t e d i n t h e l u b r i c a t i n g pump.
T h e r e f o r e D i r e c t Feeding systems o p e r a t e on a P o s i t i v e Volume P r i n -
ciple,
t h e y i n t r o d u c e a metered volume o f l u b r i c a n t i n t o t h e pipes, and
i.e.
s i n c e t h i s volume i s n o t a f f e c t e d by p r e s s u r e i n t h e p i p e s , t h e pumps can work c o n t i n u o u s l y a g a i n s t h i g h back pressures.
- -I
I
GREASE SYSTEMS TOTAL LOSS SYSTEMS
DIRECT FEEDSYSTEMS
INDIRECT FEED M T E M S
I
PR0GRESSI:E MSTEMS
I
I
Y DUAL L I N E
FIG.7
FUNDAMENTAL LUBRICATION
DIVISION OF C E N T R A L I S E D GREASE SYSTEMS.
PARALLEL SVSTEMS
405 D i r e c t Feeding systems can be d i v i d e d i n t o those where each o u t l e t has i t s own m e t e r i n g p l u n g e r (F i g . 8 )
and t ho se where a s i n g l e moving plunger d i s t r i b u t e s
p r o g r e s s i v e l y t h e metered amounts o f grease i n t o t h e v a r i o u s o u t l e t s ( F i g . 9 ) . N o r m a lly , d i r e c t f e e d i n g l u b r i c a t o r s o b t a i n t h e i r pumping a c t i o n e i t h e r by means o f moving p l u n g e r s , combined w i t h a system o f p o r t i n g , o r by the use o f p l u n g e r s i n c o n n ect i on w i t h s p r i n g - l o a d e d b a l l v a l v e s .
The l a t t e r type should
be a v o id e d i n t h e case o f d i r t y o r d u s t y c o n d i t i o n s as any i n g r e s s o f e x t r a n eous m a t t e r may l o dg e i n t h e s e a t i n g o f t h e b a l l v a l v e and render t h e l u b r i c a t o r inoperative. I t f o l l o w t h a t where a l u b r i c a t o r i s d r i v e n by a moving p a r t o f a machine, an amount o f l u b r i c a n t r e q u i r e d r e l a t i v e t o t h e movement o f t h e s h a f t i n t h e bearing be in g l u b r i c a t e d , a d i r e c t f e e d i n g l u b r i c a t o r should be used (Fig.10) l u b r i c a t o r d r i v e n v i a t h e d i r e c t d r i v i n g elements, e.g.
w i t h the
E c c e n t r i c D r i v e s , Throw
Plates, o r O f f s e t P i n Drives. 17.6.1.2
I n d i r e c t o r L i n e Systems have t h e pumping and m e t e r i n g elements geo-
g r a p h i c a l l y separated;
t he y a r e connected by means o f one o r s e v e r a l p i p e l i n e s .
The a c t i o n i s h y d r a u l i c ,
t h e pump s e r v i n g as a p r e s s u r e c r e a t i n g u n i t f o r pumping
grease i n t o a p i p e l i n e whi ch i s t h e r e b y s e t under pressure.
As t h e pressure
i nc r e a s e s , so t h e v a r i o u s m e t e r i n g elements e j e c t t h e i r charges e i t h e r progressi v e l y , o r a c c o r d i n g t o t h e back pre ssure s a g a i n s t which t h e y operate. D u r in g normal o p e r a t i o n s each element, ha ving g i v e n up i t s metered amount,
blocks i t s e l f and w i l l n o t pass any f u r t h e r l u b r i c a n t t o t h e p o i n t s o f a p p l i c a tion.
When a l l elements have g i v e n up t h e i r metered charge, a r a p i d r i s e i n
pre s s u r e o c c u r s i n t h e main l i n e .
U t i l i z i n g e i t h e r t h i s i n c r e a s e i n pressure a t
t h e pump o r a t t h e end o f t h e l i n e , a s i g n a l i s g i v e n i n d i c a t i n g t h a t t h e l u b r i c a t i n g phase i s completed. Thereupon t h e main l i n e has t o be d ep ressurized, w hich i s u s u a l l y e f f e c t e d by opening i t t o t h e grease sup pl y u n i t , e.g.
the reservoir.
Depending on the
t y p e o r make o f system, t h e p l u n g e r s o f t h e m e t e r i n g v a l v e s a r e then r e s e t t o p e r m i t t h e i r f u r t h e r o p e r a t i o n , o r t h e y a r e a l r e a d y s e t f o r another a p p l i c a t i o n phase wh ic h moves them back i n t o t h e i r o r i g i n a l p o s i t i o n , thereby completing a system c y c l e .
The method and mechanics o f r e s e t t i n g depend on t h e p a r t i c u l a r
ty p e o f system; a l s o whether one complete c y c l e o f t h e system i n v o l v e s one o r two a p p l i c a t i o n ( l u b r i c a t i o n ) phases. The fundamental d i v i s i o n o f ' l i n e systems' p a r a l l e l t y p e s o f systems.
i s t h a t between p r o g r e s s i v e and
I n t h e p r o g r e s s i v e system t h e l u b r i c a n t must pass
thro u g h t h e m e t e r i n g elements o r v a l v e s p r o g r e s s i v e l y ,
i.e.
o n l y a f t e r having
a c t u a t e d t h e f i r s t element t o f ee d l u b r i c a n t t o t h e p o i n t o f a p p l i c a t i o n w i l l t h e l u b r i c a n t be passed t o t h e second element, and so f o r t h .
T h i s i s i n con-
t r a s t t o t h e o p e r a t i o n o f t h e p a r a l l e l system, on w hich t h e m e t e r i n g u n i t s a r e
YOl>INNO> OlNW
m
YOU3NN03 a 3 a ~ 33 1 1 ~ 1 s
SNOIWINNOJ L l l A n O
YJMOllOJON 3AVH Sl3aOW (110)V l
*I
:S)ltlOM 1 1 MOH
NOllV3l11!fll 01Slll11lN33 311VWOlflV 11Oj 1102V3111!111 0334 1331110 90P
407
408
Application: Lubiicat/onoluplo I W p ~ ) i n l ~ . ~ l l h g ~ e a l e o r o s . pafl(IcUlar1yon presses. machine lools, packagmg machinery
Introducingcentral lubrication in stages:
Design:
A m a n pipe l m m a simple fillinp 01 lubricalion pump loads lo the dislrtbulor; the quantities of lubricant delivered are diitiibuled by the. d w i b u l o r 10the outlels in a parlicular pie. arranged sequence If required. the Iubricanl lrom the distributor can be led lo other distrtbulors lor lurlhet redislribulion
11 . .tg.: L u b r m i c o nof not more lhan 20 points by means 01 a grease nipple screwed into the dislributor andsgreasegun whichisoperaled untiltheflow indjcatoc shows tihat the lubr#calionoperation has been compleletl.
2nd .lago: A hand pump and dlslrlbUIorSin Series. WhlCh distribute the lubr~csnllo the lubrication point6 in a specified manner.
Fig. 11.
Examples o f Progressive Systems.
Fig. 12.
Progressive Lubrication on a plate shear.
409 a c t u a t e d as p r e s s u r e i n c r e a s e s i n t h e main l i n e . Each group i s f u r t h e r d i v i d e d i n t o systems u t i l i z i n g one l i n e o n l y and systems u t i l i z i n g two l i n e s , t h e f o r m e r b e i n g c a l l e d s i n g l e - l i n e systems, t h e l a t t e r d u a l - l i n e systems.
The most p o p u l a r t y p e s o f systems used a r e :
P r o g r e s s i v e Systems, o p e r a t e o n p r e s s u r e / v o lu m e c y c l e s ;
i n t h e i r case t h e
i n c r e a s i n g p r e s s u r e c r e a t e d by t h e pump a c t u a t e s a m e t e r i n g v a l v e w h ic h , h a v i n g g i v e n up i t s s e t amount o f l u b r i c a n t . a l l o w s t h e g r e a s e t o pass i n t o t h e main l i n e leading t o the next metering valve.
When s u f f i c i e n t p r e s s u r e has been
b u i l t up, t h e v a l v e i s a c t u a t e d and l u b r i c a n t a l l o w e d t o f l o w t o t h e n e x t m e te r i n g v a l v e , and so o n p r o g r e s s i v e l y , u n t i l i t r e t u r n s t o t h e l u b r i c a t o r o r where, when s u f f i c i e n t p r e s s u r e has been b u i l t up, a r e v e r s i n g v a l v e i s a c t u a t e d w h ic h reverses t h e f l o w o f t h e grease.
The s e l e c t i o n o f p r o g r e s s i v e systems i s depen-
dent upon t h e number o f p o i n t s t o be l u b r i c a t e d .
F i g u r e 1 1 i l l u s t r a t e s some
o p t i o n s a v a i l a b l e , and F i g . 1 2 shows a t y p i c a l i n s t a l l a t i o n o f a p r o g r e s s i v e l u b r i c a t i o n system on a P l a t e Shear. Dual L i n e Systems ( P a r a l l e l ) , o p e r a t e o n t h e same b a s i c p r i n c i p l e , v i z : t h e m o t o r i z e d l u b r i c a t i n g pump ( F i g . 1 3 )
f o r c e s g r e a s e i n t o one o f two main f e e d
l i n e s i n w hi ch a r e p l a c e d a number o f d u a l - l i n e m e t e r i n g e le m e n ts , each o u t l e t
M U orised BS-A h
p
SC-A Diffaeraial R c Un
MODE L BSA
Fig.13
Dual l i n e system.
410
I
Line 1 weuurising
2oo
I_
I_
Line 2 pressurising
I
Fig.14
Interval
end of line 1 b 2
Dual l i n e system p r e s s u r e .
66
Main Line 2
Fig.15
2
Dual l i n e m e t e r i n g element.
D u a l - l i n e m e t e r i n g elements o p e r a t e h y d r a u l i c a l l y w i t h o u t t h e use o f b a l l s and s p r i n g s o r check v a l v e s .
A c o n t r o l p i s t o n d i r e c t s t h e supply o f grease t o
e i t h e r s i d e of a m e t e r i n g p i s t o n which i s f i t t e d w i t h an i n d i c a t o r p i n , e n a b l i n g easy i n s p e c t i o n o f o p e r a t i o n a t each p o i n t on t h e system.
R e g u l a t i n g screws
f i t t e d t o each i n d i c a t o r housing p e r m i t adjustment down t o 20% o f maximum o u t p u t . The p o s i t i o n o f t h e c o n t r o l p i s t o n ( 2 ) and t h e feed p i s t o n (6) a r e shown i n ' A ' a f t e r the f i r s t p a r t o f the d u a l - l i n e cycle.
P r e s s u r i s e d l u b r i c a n t f r o m main
411 l i n e 1 has moved o v e r c o n t r o l p i s t o n ( 2 ) and then a t t h e upper s i d e o f t h e feed
( 6 ) , d i s p l a c i n g i t and d i s c h a r g i n g a measured q u a n t i t y o f l u b r i c a n t v i a c ros s p o r t i n g (7) and a cross spool (1) t o o u t l e t ( 8 ) . P o s i t i o n ' B ' i s t h e second
piston
p a r t o f t h e d u a l - l i n e c y c l e and p r e s s u r i s e d l u b r i c a n t from main l i n e 2 has moved c o n t r o l p i s t o n ( 2 ) and d i s p l a c e d t h e m e t e r i n g p i s t o n (6) thus d i s c h a r g i n g a measured s h o t o f l u b r i c a n t v i a cro ss p o r t (5) and across spool ( 3 ) t o o u t l e t ( 4 ) . For e x t r e m e ly d i r t y and a b r a s i v e environments such as those found i n a B l a s t Furnace, P i g Caster o r Coal P r e p a r a t i o n and Washery P l a n t , i t i s a d v i s a b l e t o have t h e d u a l l i n e m e t e r i n g elements housed i n toughened g l a s s - f r o n t e d p r o t e c t i o n boxes, s i m i l a r t o t h a t shown i n F i g. 16 .
F i g. 16
P r o t e c t i o n box.
412 17.6.1.3
Comparison o f P a r a l l e l Systems - S i n g l e l i n e and D u a l - l i n e .
B o th systems d e p r e s s u r i z e t h e l i n e , b u t i n t h e case o f t h e S i n g l e L i n e System the r e s e t t i n g o f t h e p l u n g e r s i n t h e m e t e r i n g elements i s u s u a l l y e f f e c t e d by s p r i n g p r e s s u r e , whereas i n t h e Dual L i n e system. when main feed l i n e No.2 i s p r e s s u r i s e d , a second s e r i e s o f dual l i n e m e t e r i n g elements d i s c h a r g e l u b r i c a n t t o the points o f application.
I n d o i n g s o , t hey r e s e t t h e dual l i n e m e t e r i n g
elements i n main l i n e No.1, w i t h which t h ey f orm an i n t e g r a l u n i t . 17.6.1.4
S e l e c t i n g Grease L u b r i c a t i o n Systems.
Wherever p o s s i b l e , l u b r i c a t i o n systems sh ould be avoided w hich use equipment i n c o r p o r a t i n g s p r i n g s and v a l v e s , p a r t i c u l a r l y where t h e l u b r i c a t i o n systems a r e r e q u i r e d t o o p e r a t e i n arduous and a b r a s i v e environments. I n g e n e r a l p r a c t i c e , t h e m a j o r i t y o f C e n t r a l i s e d L u b r i c a t i o n Systems used a r e e i t h e r o f t h e ' D i r e c t Feed' o r ' P a r a l l e l - D u a l be in g o p e r a t e d ' m a n u a l l y ' o r ' a u t o m a t i c a l l y ' .
L i n e ' type;
b o t h a r e capable o f
The c h o i c e o f Grease L u b r i c a t i o n
Systems i s u s u a l l y d i c t a t e d by t h e number o f p o i n t s o f a p p l i c a t i o n and t h e i r l o c a t i o n , always b e a r i n g i n mind t h a t f o r utmost r e l i a b i l i t y and minimal maintenance D i r e c t Feed Systems sh ou l d be s e l e c t e d wherever i t i s p r a c t i c a l . o f explanation,
By way
a P a r a l l e l - D u a l L i n e system can c y c l e and y e t f a i l t o d e l i v e r
l u b r i c a n t t o some of t h e p o i n t s o f a p p l i c a t i o n w hich i s o n l y e v i d e n t i f t h e o p e r a t o r v i s u a l l y examines t h e p o s i t i o n o f e very dual l i n e element i n d i c a t o r pin. Q u i t e o f t e n t h i s i s i m p r a c t i c a l because o f elements b e i n g l o c a t e d i n hazardous areas
o n l y b e in g a c c e s s i b l e when t h e p l a n t and machinery a r e shut down.
T h i s cannot o c c ur w i t h D i r e c t Feed pumps, f o r t h e y w i l l o n l y o p e r a t e e f f e c t i v e l y providing
the points o f application are receiving lubricant;
course, broken f ee d-p i pe s
barring, o f
(which can a p p l y t o b o t h types o f system).
I n prac-
t i c e , a D i r e c t Feed pump can u s u a l l y c a t e r f o r up t o 40 p o i n t s o f a p p l i c a t i o n . 17.6.1.5
L u b r i c a t i o n o f P l a i n o r Sleeve Bearings.
These b e a r i n g s , p a r t i c u l a r l y t h ose o v e r 4" diameter, r e q u i r e as near c o n t i n uous l u b r i c a t i o n as i s p o s s i b l e .
I t i s n o r m a l l y recommended t h a t b e a r i n g s of
t h i s t y p e be f e d by D i r e c t Feeding l u b r i c a t o r s d r i v e n from t h e moving s h a f t . T h i s ensures l u b r i c a n t i s f e d t o t h e b e a r i n g s when t h e s h a f t i s i n o p e r a t i o n and no l u b r i c a n t i s f e d t o t h e b e a r i n g when t h e s h a f t i s i n o p e r a t i v e . 17.6.1.6
Lubrication o f Anti-Friction
( B a l l and R o l l e r ) Bearings.
A n t i - f r i c t i o n be ari n gs r e q u i r e c o n s i d e r a b l y s m a l l e r q u a n t i t i e s o f l u b r i c a n t tha n p l a i n b e a r ings.
Except i n t h e case o f l a r g e a n t i - f r i c t i o n b e a r i n g s , they
w i l l n o t n o r m a l l y be l u b r i c a t e d c o n t i n u o u s l y . Where a n t i - f r i c t i o n b ea ri ng s a r e c l o s e t o g e t h e r , a hand-operated o r t i m e c l o c k c o n t r o l l e d d i r e c t f e e d i n g pump may be used.
Where they a r e spaced over
413 some d i s t a n c e , a l i n e system, e i t h e r hand-operated o r t i m e c l o c k c o n t r o l l e d ,
is
preferred. For l a r g e a n t i - f r i c t i o n b e a r i n g s and t h ose i n s t a l l a t i o n s where t h e g r e a t e s t r e l i a b i l i t y o f D i r e c t Feeding systems i s d e s i r a b l e
b u t t h e number o f p i p e s
should be k e p t low, d i r e c t f e e d i n g pumps w i t h P o s i t i v e D i v i d e r s may be used, s p l i t t i n g v o l u m e t r i c a l l y metered amounts o f l u b r i c a n t independent o f v a r y i n g back p r e s s u r e s . Very f a s t o p e r a t i n g a n t i - f r i c t i o n b e a r i n g s such as those running a t 1400 rpm should n o t be f e d c o n t i n u o u s l y .
However, o v e r - g r e a s i n g w i l l do no harm t o l a r g e
s l o w - r u n n in g a n t i - f r i c t i o n b e a r i n g s where q u i t e o f t e n t h e grease i s used as a s e a l a n t , p r e v e n t i n g d i r t and o t h e r f o r e i g n m a t t e r a n t i - f r i c t i o n bearings
-
t o e n t e r t h e b ea ri ng .
-
the greatest destroyer o f
Therefore i t i s essential t h a t
t h e grease i s k e pt c l e a n a t a l l t i mes, w i t h t h e l u b r i c a t i n g pump c o n t a i n e r o r r e s e r v o i r b o t to m f i l l e d v i a a grease keg o r b u l k grease s t o r a g e system.
17.6.2
O i l L u b r i c a t i o n Systems
O i l L u b r i c a t i o n Systems s e r v e two purposes:
t o l u b r i c a t e and/or c o o l .
On
many a p p l i c a t i o n s . p a r t i c u l a r l y i n t h e absence o f h i g h ambient temperature o r where t h e h e a t g ene rat ed i n t h e b e a r i n g s o r t h e gears i s n o t g r e a t . t h e removal o f h e a t by t h e o i l need n o t f e a t u r e as a se parate c o n s i d e r a t i o n i n t h e s e l e c t i o n o f t h e o i l c i r c u l a t i o n system.
T h i s can be arranged on t h e b a s i s o f l u b r i c a t i o n
c o n s i d e r a t i o n s a l o ne .
i n t h e case o f many o t h e r a p p l i c a t i o n s , the
However,
c o o l i n g p r o p e r t i e s o f t h e o i l a r e o f g r e a t importance. O i l systems may t h e r e f o r e be grouped under t h r e e main headings:Group 1
Systems designed f o r l u b r i c a t i o n on a t o t a l loss basis.
Group 2
Systems designed f o r l u b r i c a t i o n and w i t h a small amount o f heat removal.
Group
3
Systems designed f o r l u b r i c a t i o n where an a p p r e c i a b l e degree o f c o o l i n g i s a l s o r e q u i r e d because o f operating conditions.
Group 1 and 2 systems v a r y a c c o r d i n g t o t h e t y p e o f machine and i t s l u b r i c a t i o n requirements.
Systems o f t h e t o t a l l o s s t y p e may be operated e i t h e r manually,
m e c h a n ic a lly , o r mo t o ri sed , whereas systems o f t h e t y p e which c o l l e c t t h e used o i l and r e c i r c u l a t e i t must be a u t o m a t i c .
V arious combinations o f these systems
can be employed, and t h e f o l l o w i n g a r e some t y p i c a l examples: 17.6.2.1
Group 1
- Total
loss systems designed f o r l u b r i c a t i o n purposes o n l y .
I n t h i s t y p e o f system t h e l u b r i c a n t , a f t e r l u b r i c a t i n g t h e b e a r i n g s o r gears, i s n o t used a g a in. pumps.
The group c o n s i s t s o f manual, mechanical o r motor operated
The fo r m er g e n e r a l l y a p p l i e s on sma l l items o f p l a n t , e.g.
machine t o o l s ,
414 mechanical h a n d l i n g equipment, j i g s and f i x t u r e s , presses, e t c .
These systems
may be f u r t h e r s u b - d i v i d e d i n t o D i r e c t P o s i t i v e Systems or P o s i t i v e S p l i t Systems. D i r e c t P o s i t i v e Systems u s u a l l y comprise one o r more d i f f e r e n t i a l p l u n g e r ty p e o i l l u b r i c a t o r s , e.g.
Se ct i o ns 6.1.1
(F ig.9)
shows t h e o p e r a t i o n o f a man-
u a l l y o p e r a te d 8 - o u t l e t g rea se pump whi ch i s a l s o a d a p t a b l e f o r o i l , w i t h Fig.17 i l l u s t r a t i n g a t y p i c a l a p p l i c a t i o n on a pre ss l u b r i c a t i n g t h e slidew ays and crosshead.
For a p p l i c a t i o n s where a ut oma t i c l u b r i c a t i o n i s r e q u i r e d , mechanical
l u b r i c a t o r s h a v ing u s u a l l y 28 t o 32 pumping u n i t s may be f i t t e d ( F i g . 1 8 ) .
These
l u b r i c a t o r s may be d r i v e n e i t h e r m e c h a n i c a l l y t h r o u g h a r a t c h e t from t h e machine be in g l u b r i c a t e d o r by geared e l e c t r i c motor.
Each pump u n i t can be r e g u l a t e d
fro m z e r o t o maximum, t o f e e d m i n u t e p r e c i s e q u a n t i t i e s o f o i l t o t h e p o i n t s o f lubrication application.
F i g. 17
D i r e c t p o s i t i v e system.
415
Fig.18 P o s i t i v e S p l i t System.
D i r e c t p o s i t i v e system.
T h i s t y p e o f system i s used where q u a n t i t i e s o f o i l
per a p p l i c a t i o n p o i n t a r e g r e a t e r t h a n can be s u p p l i e d by t h e p r e v i o u s l y described d i r e c t f e e d i n g p l u n g e r system.
I t comprises o f one o r more small h i g h
p r e s s u r e pumps f i t t e d w i t h i n t e g r a l r e l i e f v a l v e s , and s u p p l i e s l u b r i c a n t t o t h e b e a r i n g s through volume d i v i d e r s .
The d i v i d e r s may be used e i t h e r t o i n -
crease t h e number o f p o i n t s o r t o m o d i f y t h e q u a n t i t i e s f e d t o t h e l u b r i c a t i o n points.
416
Fig.19
17.6.2.2
P o s i t i v e s p l i t system.
Group 2 - Systems designed f o r l u b r i c a t i o n w i t h s m a l l amount o f
heat removal.
T h i s t y p e o f system s u p p l i e s t h e l u b r i c a n t t o t h e b e a r i n g s and
r e t u r n s i t under g r a v i t y through t h e r e t u r n p i p e s and/or drainways t o t h e s u p p l y tank f o r r e c i r c u l a t i o n .
T h i s group can a l s o be s u b - d i v i d e d i n t o D i r e c t P o s i t i v e
Systems o r P o s i t i v e S p l i t Systems.
The former c o n s i s t s o f t h e m e c h a n i c a l l y
operated d i f f e r e n t i a l p l u n g e r t y p e o i l l u b r i c a t o r as d e s c r i b e d i n Group 1.
417 T y p i c a l a p p l i c a t i o n s i n c l u d e paper machines, l a r g e k i l n s , o r g e n e r a l l y where a l a r g e number o f b ea ri ng s a r e t o be f e d p o s i t i v e l y w i t h an a d j u s t a b l e feed. Systems o f t h i s t y p e r e q u i r e a minimum amount o f maintenance and a t t e n t i o n .
The
l u b r i c a t i o n r e s e r v o i r s o f c o n t a i n e r s can be kept f i l l e d e i t h e r by a header t a n k s u p p l y i n g s e v e r a l l u b r i c a t o r s , o r each l u b r i c a t o r can be f i t t e d w i t h s p e c i a l b u i l t - i n s u c t i o n pumps wh i ch sup pl y t h e c o n t a i n e r w i t h l u b r i c a n t from t h e main s u p p ly tank.
Each l u b r i c a t o r pump u n i t ( o u t l e t ) can be connected d i r e c t t o t h e
l u b r i c a t i o n p o i n t s o r t o a p o s i t i v e volume d i v i d e r , depending on t h e number o f feeds and t h e l u b r i c a t i o n req ui re men t s o f t h e p o i n t s . The l u b r i c a n t i s r e t u r n e d under g r a v i t y t o t h e main supply tank through d r a i n ways o r r e t u r n p i p e s (which can be a rran ge d w i t h b e a r i n g sump l e v e l c o n t r o l dev ic e s ) f o r r e c i r c u l a t i n g t o t h e l u b r i c a t o r c o n t a i n e r s o r header t a n k by means of s u c t i o n pumps, as d escri b ed , o r t o t h e t a n k by a f l o a t - c o n t r o l l e d gear pump (Fig.20).
-
Discharge f i l t e r
I
I
b
d
L
&
6
6
b
d
b
b
b
b
1
b b b
b b d
\ l b
/
b
O
b
l
d
b
b b
Reservoir
F ig . 20
System w i t h smal l amount o f heat removal
As i n t h e case o f t h e p r e v i o u s group,
t h e l u b r i c a t o r can be d r i v e n e i t h e r
d i r e c t f r o m t h e machine b e i n g l u b r i c a t e d o r f i t t e d w i t h i t s own motor,
Each
pump can be f e d e i t h e r f ro m t h e machine sump o r from a separate d r a i n and supply tank.
The system i s u s u a l l y i n s t a l l e d on machine t o o l s , sugar machinery, gear
boxes, p r i n t i n g machines, and sp eci a l -pu rpo se machinery.
17.6.2.3
Group
3
-
Systems designed f o r l u b r i c a t i o n c o o l i n g .
Where t h e r e i s c o n s i d e r a b l e ambient h ea t o r where t h e power t r a n s m i t t e d by t h e p a r t b e in g l u b r i c a t e d c r e a t e s a h i g h degree o f h e a t , t h e c o o l i n g f u n c t i o n o f t h e l u b r i c a n t assumes g r e a t importance.
I t i s necessary i n such cases t o
ap p ly s u f f i c i e n t l u b r i c a n t t o e x t r a c t t h e he at and t o m a i n t a i n t h e bearings o r gears a t an optimum t e mpe rat ure .
Arrangements must a l s o be made f o r r e t u r n i n g
t h e l u b r i c a n t t o a su pp l y t a n k f o r c o o l i n g , f i l t r a t i o n , and r e c i r c u l a t i o n , between t h e l u b r i c a t i o n equipment man uf act urer, t h e p l a n t designers, and t h e operators. Such a system u s u a l l y comprises a l a r g e o i l r e s e r v o i r o r s t o r a g e tank; motor d r i v e n pump ( n o r m a l l y a gear t y p e pump a d j a c e n t t o o r on t h e s t o r a g e t a n k ) ; coolers;
f i l t e r s ; p r e s s u r e gauges; a l a r m and f l o w c o n t r o l equipment; t o g e t h e r
w i t h t h e necessary v a l v e s and i n t e r c o n n e c t i n g pipework. and s e l f - c o n t a i n e d w i t h a c a p a c i t y o f 3 8 c c / s e c
The system may be simple
t o 750cc/sec
complex system c a pa bl e o f d e l i v e r i n g s e v e r a l l i t r e s / s e c .
p e r minute, o r a
These systems can be
p r o v i d e d w i t h s i m p l e o r e l a b o r a t e f l o w c o n t r o l , w arning d e v i c e s , and o t h e r i n s t r u m e n t a t i o n a c c o r d i n g t o t h e needs o f t h e i n s t a l l a t i o n (Fig.21).
Fig.21
T y p i c a l example o f l u b r i c a t i n g and c o o l i n g system packaged u n i t f o r t h e l u b r i c a t i o n o f rubber machinery.
419 17.6.3
Micro-Fog L u b r i c a t i o n Systems
Aerosol l u b r i c a t i o n i s t h e g e n e r i c term f o r o i l m i s t o r M i c r o - f o g systems which have been used s u c c e s s f u l l y f o r o v e r t w e n t y y e a r s .
Compared w i t h Centra-
l i s t e d Grease o r O i l l u b r i c a t i o n , a M i c r o - f o g system, t o p e r f o r m t h e same t a s k , r e q u i r e s l e s s l u b r i c a n t and energy and t h e i n i t i a l c o s t i s r e l a t i v e l y low. i s a l s o a h i g h l y f l e x i b l e system,
It
r e a d i l y i n s t a l l e d o n t o e x i s t i n g p l a n t as w e l l
as a t t h e new machine stage.
17.6.3.1
Working P r i n c i p l e s (Fig.22) o u t 1 i n e s t h e e s s e n t i a l and a u x i 1 i a r y
elements o f t h e M i c r o - f o g system and p r o v i d e s a g u i d e t o some o f t h e more common areas o f a p p l i c a t i o n .
During operation,
t h e system produces c o n t i n u o u s l y a dense
c o n c e n t r a t i o n of m i c r o p a r t i c l e s o f o i l which a r e conveyed i n a ' d r y ' f o g i n a low p r e s s u r e d i s t r i b u t i o n system.
On r e a c h i n g t h e p o i n t of a p p l i c a t i o n t h e
' d r y ' f o g i s passed t h r o u g h r e c l a s s i f i e r s , which a r e r e a l l y m e t e r i n g and condens i n g o r i f i c e s , so as t o a c c u r a t e l y f e e d an e x a c t q u a n t i t y o f l u b r i c a n t t o s u i t the operating conditions.
M i cro-foq
1u b r i c a t i o n
lubrication 1u b r i c a t i o n
Fig.22
M i c r o - f o g system.
420 To ensure t h a t t h e f o g reaches t h e r e c l a s s i f i e r d r y ,
the d i s t r i b u t i o n piping
i s sized t o allow o i l p a r t i c l e s t o travel along the piping a t a v e l o c i t y less tha n 7.3 metres/sec,
which i s sl o w enough t o p r e v e n t condensation.
l enc e i n t h e r e c l a s s i f i e r s causes t h e o i l p a r t i c l e s t o 'w et o u t '
The t u r b u -
i n t o the l i n e
l e a d i n g t o o r d i r e c t o n t o t h e b e a r i n g s u r f a c e s where they then form a p r o t e c t i v e f i l m of oil. In o r d e r t o c r e a t e ' d r y '
f o g, o i l i s f i r s t drawn i n t o a compressed a i r stream
as i t passes th r ou gh a V e n t u r i l o c a t e d on t o p o f t h e l u b r i c a t i o n c o n t r o l u n i t (Fig.23).
O i l p a r t i c l e s o f a p p r o x i m a t e l y 0.002mm
i n diameter a r e c o l l e c t e d i n
t h e a i r stream and can be t r a n s p o r t e d l on g d i s t a n c e s i n t h e d r y c o n d i t i o n .
Lubricator head A i r bypass a d j u s t i n Low pressure w i t c h
lligh pressure s w i t c h Electrical conduit ent Auxiliary requlatcr
Supply t o pressur j e t reclassifier
Waste pipe e x i t
/
Fig.23
Lubrication control unit.
Since M i c r o - f o g systems r e q u i r e no r e t u r n l i n e s they can be designed t o easy i n s t a l l a t i o n and assembly;
hence, l o w c o s t i n s t a l l a t i o n , w i t h o u t t h e problems
a s s o c i a t e d w i t h s i n g l e - l i n e s e r i e s o i l c i r c u l a t i n g systems w hich i n c o r p o r a t e q u i t e s o p h i s t i c a t e d and r e l a t i v e l y expensive v a l v e b l o c k s t h a t have a b u i l t - i n self-reversing operation.
Al t ho ug h such systems may r e q u i r e no separate reverse
and r e c y c l e v a l v e o r v e n t i n g phase d u r i n g t h e l u b e c y c l e , they do have, however, a d i s t i n c t d is a d va nt ag e because t h e y r e q u i r e a m u l t i p l i c i t y o f system t u b i n g (Fig.20). Moreover, Once a M i c r o - f o g system has been i n s t a l e d i t i s much less demandi n g t h a n o t h e r a ut oma t i c l u b e systems.
The system
s e a s i l y assembled,
using a
b u i l d i n g b l o c k approach, wh i ch i s designed f o r easy s e r v i c i n g , r e p a i r s and general maintenance.
421 17.6.3.2
O i l Quality.
C o r r e c t o i l s e l e c t i o n i s i m p o r t a n t as some o i l s i n c o r p o r a t e polymers w hich suppress a e r o s o l p r o p e r t i e s , w h i l e h e a v i e r g rade o i l s may r e q u i r e h e a t i n g up t o between 4Oo/45OC
t o a t t a i n t h e v i s c o s i t y f o r maximum o u t p u t . For a l l normal
purposes t h e c o n t r o l u n i t s w i l l p e r f o r m w e l l when w orking w i t h o i l s up t o 700 c e n t i s t o k e s a t 20°C. Summarised l u b r i c a t i n g o i l req ui re men t s f o r a s a t i s f a c t o r y M i c r o - f o g system are:(i)
Good a e r o s o l p r o p e r t i e s .
(ii)
Low r a t e o f co nd en sat i on t hro ug h p i p e s .
( i i i ) Low l e v e l o f s t r a y i n g by t h e p a r t i c l e s . (iv)
A h i g h degree o f r u s t i n h i b i t i o n .
(v)
Absence o f c l o g g i n g t e nd en ci es a t t h e v e n t u r i n o z z l e o r any polymer precipitation.
17.6.3.3
Compressed A i r
2
A c c e p t in g t h a t most i n d u s t r i a l compressed a i r i s s u p p l i e d a t 7 bar (100 l b / i n ) 2 i n a M i c r o - f o g l u b r i c a t i o n system i t has t o be reduced t o about 2 b a r (30 l b / i n 1. Dur in g i t s passage t h r o u g h t h e v e n t u r i o r i f i c e on t h e c o n t r o l u n i t , a p r e s s u r e
2
dro p o f 0 . 7 bar (10 I b / i n ) t ake s pl a ce. 17.6.3.4
System Design Con si de rat i o ns
To c a l c u l a t e t h e l u b r i c a t i o n req ui re men t s o f bearings, an e m p i r i c a l f a c t o r r e f e r r e d t o as a ' l u b r i c a t i o n u n i t '
(L.U.)
has been evolved,
e n a b l i n g a l l moving
s u r f a c e s r e q u i r i n g l u b r i c a n t t o be co nve rt e d t o t h e i r e q u i v a l e n t L.U. The amount o f l u b r i c a n t main
rating.
and b ran ch l i n e p i p e bores and r e c l a s s i f i e r nozzles
may t h e n be s i z e d t o p r o v i d e t h e c o r r e c t amount o f l u b r i c a n t a t each l u b r i c a t i n g point.
I n t h i s manner, a n t i - f r i c t i o n b ea ri ngs, j o u r n a l bearings, s l i d e s , gears,
c h a in s , and o t h e r wea ri ng s u r f a c e s r e q u i r i n g l u b r i c a t i o n can a l l be converted t o e q u i v a l e n t L.U.
r a t i n g s and serve d by a p p r o p r i a t e l y s i z e d M i c r o - f o g l u b r i c a t i o n
systems. 17.6.3.5
Some T y p i c a l A p p l i c a t i o n s
F i g u r e 24 i l l u s t r a t e s a t h r e e S t ran d Aluminium F o i l M i l l o p e r a t i n g a t 1000 t o 1500 m e t r e s / m in u t e w i t h two 1000 L.U. g e n e r a t i n g heads ( t h i r d a c t s as a standby) s e r v i n g t h e m i l l s t a c k and e x i t a n c i l l a r i e s , w i t h a s e p a r a t e 300 L.U. u n i t serving the entry a n c i l l a r i e s .
2.5 l i t r e s p e r w o r k i n g hour. motor oears.
generating
The t o t a l amount o f o i l used i s l e s s than
F i g u r e 25 i l l u s t r a t e s t h e l u b r i c a t i o n o f v i b r a t o r
422
423
i
I
Fig.25
17.6.4
"i" 'i' 0-
I
Lubrication o f vibrator motor gears.
Check List
Based o n the foregoing, prior to actual selection of the appropr ate lubricant and associated equipment, it is advisable to draw up a check 1 st of known The following list, in simplified form, is for guide purposes only and can naturally be elaborated upon to suit the spec fic needs o f facts and requirements.
the designer o r plant engineer. Specification o f Plant t o be lubricated: Type of plant and machinery to be lubricated. Industrial Application, including operating environmental conditions, e.g. is i t dirty, abrasive, wet, hot, etc.? Surfaces, sizes and speeds to be lubricated, e.g. Bearings (plain), Bearings (roller), Grease (type), Slideways, Chains, etc. Number and Location of lubrication Points (Fixed) and (Moving) and proposed site (if known) for lubricator enabling assessment of pipe and flexes: Frequency plant and machinery operators and whether lubrication needs to be continuous, semi-continuous, or intermittent.
424
-
L u b r i c a n t t ype and s p e c i f c a t i o n S e r v i ces a v a i l a b l e i n t h e P l a n t
-
Grease, O i l , o r M i c r o - f o g ,
etc
e l e c t r i c , pneumatic.
H e a l t h and S a f e t y a spe ct s e.g. normal, flameproof, a c c e s s i b i l i t y any h i s t o r y o f p r e v i o u s l y t r i e d l u b r i c a n t s / e q u i p m e n t . Method proposed f o r f i l l i n g t h e l u b r i c a t i o n t a n k / r e s e r v o i r , e.g. manual, semi-automatic, b u l k storage. Recommended L u b r i c a t i o n Equipment: Why? E s timat ed performance w i t h any known Case Studies and References. Econom ic s
.
Spares and S e rvi ce. Sometimes equipment s e l e c t i o n i s an i n e v i t a b l e compromise as a r e s u l t o f c o n f l i c t i n g l u b r i c a t i o n req ui re men ts;
i n such circumstances i t i s
im p o r t a n t t o a p p r e c i a t e a l l t h e f a c t s and t o subsequently gauge p l a n t performance a c c o r d i n g l y . 17 7
SUMMARY
T h i s c h a p t e r has a t t emp t e d t o c l a r i f y t h e more g e n e r a l l y accepted methods o f l u b r i c a t i o n , where necessary i l l u s t r a t i n g a c t u a l examples o f p l a n t and l u b r i c a t i o n equipment.
I t i s n o t i n any way i n t e nded t o i n f e r t h a t t h i s i s t h e o n l y
l u b r i c a t i o n equipment a v a i l a b l e ; from Trade J o u r n a l s , e t c .
o f cou rse, t h e r e a r e o t h e r s r e a d i l y determined
L i k e w i s e , t h e r e a r e many more s e l e c t items o f l u b r i -
c a t i o n equipment t a i l o r - m a d e t o meet t h e needs o f s p e c i a l i s t p l a n t . For example, Overhead and F l o o r Conveyors which can t r a v e l up t o 50 metres/ m in u te , u n l e s s e f f e c t i v e l y l u b r i c a t e d (and cl eaned where t h e environment demands) can wear and s e i z e , r e s u l t i n g i n c o s t l y stoppages. l n i t i a l y , c o n v e n t i o n a l s t a t i c l u b r i c a t o r s were used where a m i x t u r e o f a i r and o i l
-
not only
and now more r e c e n t l y j u s t o i l
- was
shot over a gap, w hich r e s u l t e d
n t h e f a i l u r e t o a de qu at el y l u b r i c a t e (Fig.1)
b u t a l s o caused d r i p -
page w i t h c o n s e q ue nt i al pro du ct c o n t a m i n a t i o n and h e a l t h hazards. These problems were c o m p l e t e l y overcome by i n t r o d u c i n g a range o f s p e c i a l purpose l u b r i c a t o r s ;
(F i g. 26 ) shows one such example.
The c o n c l u s i o n i s t o d et ermi n e a l l t h e f a c t s r e g a r d i n g t h e p l a n t t o be l u b r i c a t e d and t o t h en e v a l u a t e t h e l u b r i c a n t s and l u b r i c a t i o n equipment ava i 1a b le .
425
Fig.26
A dog c h a i n assembly engages t h e conveyor c h a i n which moves t h e o i l - d i s p e n s i n g n o z z l e p l a t e s i n and o u t o v e r t h e p i n l i n k s . O i l i s f o r c e d t h r o u g h each n o z z l e .
REFERENCES
1 2
3 4
5
Mechanical L u h r i c a t i o n o f E.O.T. Cranes by D r . H . P e t e r J o s t and P e t e r W. Murray. A F u l l y Automatic B u l k H a n d l i n g L u b r i c a t i o n System f o r a S i n t e r P l a n t by G. W i l l i a m s . An E n g i n e e r i n g Approach t o t h e s e l e c t i o n o f C e n t r a l i s e d Grease L u b r i c a t i o n Systems by D r . H. P e t e r J o s t . Modern B r i t i s h and European Steelworks L u b r i c a t i o n Developments by D r . H. P e t e r J o s t . E!ew M i s t L u b r i c a t i o n Concepts f o r Tapered R o l l e r Bearinos used on High C.H. West and Speed R o l l i n g M i l l Back-up by R o l l s by \!.E.McCoy, P.E. W i l k s .
426
6
7
8
9
10
Aerosol L u b r i c a t i o n Systems - t h e i r c o n t r i b u t i o n t o savings i n o p e r a t i n g and maintenance c o s t s by R.E. K n i g h t and J.G. M e r r e t t . Micro-Fog L u b r i c a t i o n f o r b e a r i n g e f f i c i e n c y by J.G. M e r r e t t . Automatic L u b r i c a t o r s and Cleaners Increase Conveyor L i f e by J.G. M e r r e t t . Automatic L u b r i c a t i o n o f Chain and Conveyor Systems by R.M. Dombroski. The James C l a y t o n L e c t u r e - "Energy Saving through T r i b o l o g y " by D r . H. P e t e r J o s t and D r . J. S c h o f i e l d .