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How to check your jet utilities
VACUUM Classified A b s t r a c t s
II
V a c u u m Apparatus and Auxiliaries
--
-
-
II
Abs~r~c~ xo. and References
Contd.
On the Rate of D e c o m p o s i t i o n of Diffusion P u m p Oil Japan. I t is k n o w n t h a t decomposition of the p u m p fluid m a y affect the u l t i m a t e v a c u u m obtainable b y an oil diffusion p u m p . Decomposition of the p u m p fluid could be caused either b y catalytic action of the construction material of the p u m p or b y the gases evacuated from the vessel which is p u m p e d . The a u t h o r studied this prob, lem by practical e x p e r i m e n t e m p l o y i n g the p u m p fluid silicone DC-703 and n - d i o c t y l h e x a h y d r o p h t h a l a t e for t h e test. The rate of decomposition was m e a s u r e d b y a specially developed flow m e t e r which h a d a sensitivity of 6 × 10 -a litre micron/see. Details of the construction of the flow m e t e r are given. The flow m e t e r was positioned between the diffusion p u m p and a specially designed a p p a r a t u s which was p a r t l y inserted in an oven to facilitate the collection of gaseous decomposition p r o d u c t s for t h e period necessary to obtain a q u a n t i t y large e n o u g h to p r o d u c e an indication on the flow meter. I t was found t h a t the rate of deco .mposition is of t h e order of 10 -6 Iitre micron H g . / s e c . per sq. era. of surface for b o t h t y p e s of oil. A slight catalytic effect could be traced in the case of the ester. No effects could be observed from the flowing gases while p u m p i n g hydrogen, oxygen, air and w a t e r v a p o u r . The results obtained b y the a u t h o r suggest t h a t the u l t i m a t e v a c u u m of the p u m p o p e r a t e d w i t h either fluid should be in the region of 1 x 10 -7 micron Hg. Sommaire : On a 6tudiG p o u r les p o m p e s ~ diffusion ~ huile, des huiles silicones et de p h t h a l a t e duns le b u t de savoir si ces huiles contiennent des p r o d u i t s de d6composition, et s i c e s derniers reduisent ou c h a n g e n t le vide m a x i m u m p o u v a n t 6tre obtenu.
45/1I
Article by C. Hayashi ,
J. Phys. Soe Japan
9, March-April 1954 287-290
O The Ultimate Vacua of Two-Stage Rotary Oil P u m p s See A b s t r a c t No. : 7 0 / I
46/i1
H o w to Check Your Jet Utilities United States. D a t a has been collected from various published sources on the s t e a m and w a t e r r e q u i r e m e n t s of v a c u u m ejectors. Such information can provide a basis on which to estimate the m e r i t s of choosing ejectors or other e q u i p m e n t for a specific operation, leaving final design and performance g u a r a n t e e s to the m a n u f a c t u r e r . B o t h condensing and non-condensing ejectors h a v i n g up to four stages are discussed. Selections from the t a b u l a t e d d a t a are s h o w n below. The t y p e of jet is indicated b y checking off the n u m b e r of stages and the intercondenser a r r a n g e m e n t s . Stage one is nearest the process space.
47/I1
No.
1
C
Type of Jet 2 C 3 C
Ejector Steam and Water Re uirements Capacity Abs. Air %apov Stea,m Press Lb.~ Lb.~ H~'. Hr. 4 I Mm. Hg Hr. Psiy. I Zb./
°F
Water @
Lb. Steam per Zb. Mixture As As tread Corr.
-Condensing
28 34
O
x x x x x x
Condensing 2 x X x x 9 12 x x 29 x x 31 36 x 49 x x 51 x x x x 52 x 59 X 60
x × x
89 95 100 9 13 2.5
I 15.0 [ 10.0 I 40.0 5 100 10
I 0 ~ 10.0 0 10 0 0
100 110 i00 ii0 100 i00
137 100 575 800 3850 1056
X x x x x x x x x x X
10 25.4 45 2.5 9 9 9 9 9 0.5 0.5
100 165 10 10 5 5 5 5 5 5 5
0 15 20 0 0 10 0 10 10 0 0
100 100 110 100 110 115 125 125 110 ii0 ii0
1100 1210 99
x x X x x x x
x x x X x x x X
X
x X
222
65 160 123 196 202 290 540
85 90 70 9O 90 90 90 90 90 90
65 75 8 20 5 15 161 25 25 35 50
9.1 5.0 5.8 53.4 38.5 .05.6
9.1 5.1 5.8 54.8 38.5 105.6
11.0 6.7 3.3 22.2 13.0 10.7 24.6 13.1 13.5 58.0 .08
11.0 7.0 5.7
22.2 13.4 18.6 26.2 23.4 23.5 59.5 111
I t is seen t h a t the r i g h t - h a n d figure gives the u n i t weight of s t e a m required to r e m o v e u n i t weight of load, the figure being amended, where necessary, to correspond to a s t e a m s u p p l y pressure of 100 psig. I n the case of condensing jets allowance is also m a d e for the presence of non-condensables i n t h e load. No correction is m a d e for the composition of condensable v a p o u r s b u t information on this would be needed for actual operation. I t is also s h o w n t h a t in the case of condensing jets the s t e a m r e q u i r e m e n t s are affected b y the precise location of the condenser b e t w e e n the stages. S t e a m supplies lower t h a n 100 psig are n o t suitable as t h e y involve high s t e a m r e q u i r e m e n t s and possible u n s t a b l e operation. F o r low processing pressures condensing jets are the more economical, b u t non-condensing ejectors are useful for pressures above 100 m m . Hg. Three-stage ejectors are particularly useful for quick p u m p i n g . W a t e r c o n s u m p t i o n is based on the use of barometric condensers. I t is necessary t h a t the t e m p e r a t u r e of the inlet w a t e r should be low enough to condense the v a p o u r s and where
April, 1954
Vacuum Vol. I V No. 2
232
VACUUM
Classified Abstracts
II
•
--
Apparatus
Vacuum
and
Auxiliaries
--
Ii
Contd.
the condensable v a p o u r s have a low v a p o u r pressure, chilled w a t e r m a y be required. Surface intercondensers require more w a t e r b u t are useful where height is limited or where the condensable v a p o n r s m u s t be recovered undiluted. To illustrate the application of the i n f o r m a t i o n provided in graphical form, s t e a m and w a t e r c o n s u m p t i o n s are calculated for a process to be r u n at an absolute pressure of 6 m m . H g w i t h a load consisting of 10 lb. of air, 5 lb. of steam, plus 12 lb. per h o u r of alcohol v a p o u r . Motive d r y s t e a m can be supplied at 125 psig and the cooling w a t e r m a y h a v e an initial s u m m e r t e m p e r a t u r e of up t o 80°F. F o r such a case it is calculated t h a t a b o u t 275 l b . / h r , of s t e a m would be required and w a t e r c o n s u m p t i o n would be 19-20 g a L / m i n .
Sommaire : Aflh d'aider les chimistes duns le choix judicieux de p o m p e s p o u r des t r a v a u x donnds, une liste de diff6rentes t y p e s d%jecteurs, d o n n e n t 1ear c o n s o m m a t i o n , est fournie.
0
A Simple Electrical Control for A u t o m a t i c Toepler P u m p s United SlaXes. Toepler p u m p control units are available on the m a r k e t b u t usually are of a design which requires high glass-blowing skill to effect repairs, etc. A control unit fabricated in the l a b o r a t o r y f r o m s t a n d a r d p a r t s and requiring little skill for its construction is described. Essentially the unit consists of a flask (ciosed w i t h a r u b b e r stopper) which has a pipe connection to the piston of the Toepler p u m p . This c o m m u n i c a t i n g pipe is filled w i t h m e r c u r y and the rise and fall of the m e r c u r y in the reservoir causes a corresponding fall and rise of t h e m e r c u r y in the p i s t o n of the Toepler p u m p . A pipe passing t h r o u g h the s t o p p e r connects to a mechanical v a c u u m p u m p and carries an air leak which can be opened and closed b y electrical relay action. The r e l a y action is controlled b y an electrical circuit, details of which are given, which in t u r n is controlled b y t h e changing level of t h e m e r c u r y in t h e flask. T w o wire electrodes connected to the electrical circuit are passed t h r o u g h the s t o p p e r and project into the flask at different lengths. The joint lead of the two relay circuits also projects into the flask b u t is insulated against the m e r c u r y b y a sleeve and its tip is p e r m a n e n t l y in contact w i t h the m e r c u r y irrespective of its level in the flask. U n d e r the action of the mechanical v a c u u m p u m p , the m e r c u r y in the flask, in c o n t a c t w i t h one electrode (air-leak closed), rises until it reaches the s h o r t electrode, w h e r e u p o n the o t h e r relay opening the air-leak is actuated. This stage signifies the end of the suction stroke of the Toepler p u m p . Consequent to the admission of a t m o s p h e r i c air t h r o u g h the leak t h e m e r c u r y level in the flask is lowered producing a reciprocating stroke in the Toepler p u m p . This m o t i o n continues until the m e r c u r y level in the flask has been lowered to a point where it is no longer in contact w i t h the longer electrode. At this stage the air-leak is closed and the cycle of operation is repeated. The special a d v a n t a g e s claimed for this a r r a n g e m e n t are: 1. The control electrodes are n o t on the v a c u u m side 0f the Toepler p u m p , 2. No metal-to-glass seals are required. Sommaire : On d~crit un simple contrSle dlectrique, p o u v a n t ~tre fabriqud en laboratoire, qui facilite Ie travail a u t o m a t i q u e des p o m p e s Toepler.
2I --
GAUGES
--
Abstract No.
and References
Article by P. Nessina J. J. Brown & J. Bohnlofink Chem. Engng. 61, Jan. 1954
161-164
48/IL
Note by F. I-Iohnsted~ & M. J. Steindler 2?ev. Set. lnstrum. 25, March 1954 296-297
21
A Survey of Gauges for M e a s u r e m e n t of Low Absolute Gas Pressures
49/II
See A b s t r a c t No. : 63/I
0
Measurements of Vapour Pressures. See A b s t r a c t No. : 8 9 / I I
S o m e Problems on V a c u u m Techniques
M e a s u r e m e n t of H i g h V a c u u m at Low Temperatures
50/II
51/II
United States. Calorimetric m e a s u r e m e n t s at liquid helium t e m p e r a t u r e s require adiabatic conditions such t h a t t h e , t h e r m a l influx to one mole of sample is less t h a n one erg per second. Adiabatic demagnetisation e x p e r i m e n t s often require a heat influx t e n times less t h a n this. This order of t h e r m a l insulation calls for a v a c u u m between b a t h and specimen of the order of 5 × 10 -9 ram. H g and 5 × l0 -10 ram. H g respectively. The m e a s u r e m e n t of these pressures m u s t , of necessity, be carried o u t b y a gauge at r o o m t e m p e r a t u r e connected to this region b y a pipe, along which there will be n o t only a pressure gradient due to the thermol.ecular effect b u t also a concentration gradient of helium. This precludes the use of a convertional ionisation gauge which u n d e r such conditions would record pressures of the order, of 10 -6 m m . H g (mainly air pressures) and a gauge capable of m e a s u r i n g p a r t i a l pressure of helium is therefore essential. F o r these reasons a helium m a s s spectrom e t e r leak detector is used as a backing p u m p for the diffusion p u m p evacuating the insulation space. The s p e c t r o m e t e r is initially employed to check the region for leakage in excess of 5 × 10 .6 micron litres per second (at r o o m t e m p e r a t u r e ) and can be calibrated b y m e a n s of a calibrated leak. I t t h e n serves as a kinetic v a c u u m gauge, i.e. the pressure at the source P1 is given b y the t h r o u g h p u t Qr m e a s u r e d at r o o m t e m p e r a t u r e b y the s p e c t r o m e t e r and the equivalent r o o m t e m p e r a t u r e speed Sr defined as S t = Qr/P~. A s s u m i n g (a) molecular flow (b) a t u b u l a t i o n long c o m p a r e d w i t h its diameter (c) a small gradient of P / T k , the basic equations of the t h e r m o m o l e c u l a r effect are used to s h o w t h a t Sr m a y be directly c o m p u t e d from :
s~ -
4 (2=Rr~)~ ( r , , ¢ 3~/M
April, 1954
,-1 E i~l
li \ T I ] -ai ~ Vacuum Vot. I V No. 2
233
II
V a c u u m Apparatus and Auxiliaries
--
-
-
II
Abs~r~c~ xo. and References
Contd.
On the Rate of D e c o m p o s i t i o n of Diffusion P u m p Oil Japan. I t is k n o w n t h a t decomposition of the p u m p fluid m a y affect the u l t i m a t e v a c u u m obtainable b y an oil diffusion p u m p . Decomposition of the p u m p fluid could be caused either b y catalytic action of the construction material of the p u m p or b y the gases evacuated from the vessel which is p u m p e d . The a u t h o r studied this prob, lem by practical e x p e r i m e n t e m p l o y i n g the p u m p fluid silicone DC-703 and n - d i o c t y l h e x a h y d r o p h t h a l a t e for t h e test. The rate of decomposition was m e a s u r e d b y a specially developed flow m e t e r which h a d a sensitivity of 6 × 10 -a litre micron/see. Details of the construction of the flow m e t e r are given. The flow m e t e r was positioned between the diffusion p u m p and a specially designed a p p a r a t u s which was p a r t l y inserted in an oven to facilitate the collection of gaseous decomposition p r o d u c t s for t h e period necessary to obtain a q u a n t i t y large e n o u g h to p r o d u c e an indication on the flow meter. I t was found t h a t the rate of deco .mposition is of t h e order of 10 -6 Iitre micron H g . / s e c . per sq. era. of surface for b o t h t y p e s of oil. A slight catalytic effect could be traced in the case of the ester. No effects could be observed from the flowing gases while p u m p i n g hydrogen, oxygen, air and w a t e r v a p o u r . The results obtained b y the a u t h o r suggest t h a t the u l t i m a t e v a c u u m of the p u m p o p e r a t e d w i t h either fluid should be in the region of 1 x 10 -7 micron Hg. Sommaire : On a 6tudiG p o u r les p o m p e s ~ diffusion ~ huile, des huiles silicones et de p h t h a l a t e duns le b u t de savoir si ces huiles contiennent des p r o d u i t s de d6composition, et s i c e s derniers reduisent ou c h a n g e n t le vide m a x i m u m p o u v a n t 6tre obtenu.
45/1I
Article by C. Hayashi ,
J. Phys. Soe Japan
9, March-April 1954 287-290
O The Ultimate Vacua of Two-Stage Rotary Oil P u m p s See A b s t r a c t No. : 7 0 / I
46/i1
H o w to Check Your Jet Utilities United States. D a t a has been collected from various published sources on the s t e a m and w a t e r r e q u i r e m e n t s of v a c u u m ejectors. Such information can provide a basis on which to estimate the m e r i t s of choosing ejectors or other e q u i p m e n t for a specific operation, leaving final design and performance g u a r a n t e e s to the m a n u f a c t u r e r . B o t h condensing and non-condensing ejectors h a v i n g up to four stages are discussed. Selections from the t a b u l a t e d d a t a are s h o w n below. The t y p e of jet is indicated b y checking off the n u m b e r of stages and the intercondenser a r r a n g e m e n t s . Stage one is nearest the process space.
47/I1
No.
1
C
Type of Jet 2 C 3 C
Ejector Steam and Water Re uirements Capacity Abs. Air %apov Stea,m Press Lb.~ Lb.~ H~'. Hr. 4 I Mm. Hg Hr. Psiy. I Zb./
°F
Water @
Lb. Steam per Zb. Mixture As As tread Corr.
-Condensing
28 34
O
x x x x x x
Condensing 2 x X x x 9 12 x x 29 x x 31 36 x 49 x x 51 x x x x 52 x 59 X 60
x × x
89 95 100 9 13 2.5
I 15.0 [ 10.0 I 40.0 5 100 10
I 0 ~ 10.0 0 10 0 0
100 110 i00 ii0 100 i00
137 100 575 800 3850 1056
X x x x x x x x x x X
10 25.4 45 2.5 9 9 9 9 9 0.5 0.5
100 165 10 10 5 5 5 5 5 5 5
0 15 20 0 0 10 0 10 10 0 0
100 100 110 100 110 115 125 125 110 ii0 ii0
1100 1210 99
x x X x x x x
x x x X x x x X
X
x X
222
65 160 123 196 202 290 540
85 90 70 9O 90 90 90 90 90 90
65 75 8 20 5 15 161 25 25 35 50
9.1 5.0 5.8 53.4 38.5 .05.6
9.1 5.1 5.8 54.8 38.5 105.6
11.0 6.7 3.3 22.2 13.0 10.7 24.6 13.1 13.5 58.0 .08
11.0 7.0 5.7
22.2 13.4 18.6 26.2 23.4 23.5 59.5 111
I t is seen t h a t the r i g h t - h a n d figure gives the u n i t weight of s t e a m required to r e m o v e u n i t weight of load, the figure being amended, where necessary, to correspond to a s t e a m s u p p l y pressure of 100 psig. I n the case of condensing jets allowance is also m a d e for the presence of non-condensables i n t h e load. No correction is m a d e for the composition of condensable v a p o u r s b u t information on this would be needed for actual operation. I t is also s h o w n t h a t in the case of condensing jets the s t e a m r e q u i r e m e n t s are affected b y the precise location of the condenser b e t w e e n the stages. S t e a m supplies lower t h a n 100 psig are n o t suitable as t h e y involve high s t e a m r e q u i r e m e n t s and possible u n s t a b l e operation. F o r low processing pressures condensing jets are the more economical, b u t non-condensing ejectors are useful for pressures above 100 m m . Hg. Three-stage ejectors are particularly useful for quick p u m p i n g . W a t e r c o n s u m p t i o n is based on the use of barometric condensers. I t is necessary t h a t the t e m p e r a t u r e of the inlet w a t e r should be low enough to condense the v a p o u r s and where
April, 1954
Vacuum Vol. I V No. 2
232
VACUUM
Classified Abstracts
II
•
--
Apparatus
Vacuum
and
Auxiliaries
--
Ii
Contd.
the condensable v a p o u r s have a low v a p o u r pressure, chilled w a t e r m a y be required. Surface intercondensers require more w a t e r b u t are useful where height is limited or where the condensable v a p o n r s m u s t be recovered undiluted. To illustrate the application of the i n f o r m a t i o n provided in graphical form, s t e a m and w a t e r c o n s u m p t i o n s are calculated for a process to be r u n at an absolute pressure of 6 m m . H g w i t h a load consisting of 10 lb. of air, 5 lb. of steam, plus 12 lb. per h o u r of alcohol v a p o u r . Motive d r y s t e a m can be supplied at 125 psig and the cooling w a t e r m a y h a v e an initial s u m m e r t e m p e r a t u r e of up t o 80°F. F o r such a case it is calculated t h a t a b o u t 275 l b . / h r , of s t e a m would be required and w a t e r c o n s u m p t i o n would be 19-20 g a L / m i n .
Sommaire : Aflh d'aider les chimistes duns le choix judicieux de p o m p e s p o u r des t r a v a u x donnds, une liste de diff6rentes t y p e s d%jecteurs, d o n n e n t 1ear c o n s o m m a t i o n , est fournie.
0
A Simple Electrical Control for A u t o m a t i c Toepler P u m p s United SlaXes. Toepler p u m p control units are available on the m a r k e t b u t usually are of a design which requires high glass-blowing skill to effect repairs, etc. A control unit fabricated in the l a b o r a t o r y f r o m s t a n d a r d p a r t s and requiring little skill for its construction is described. Essentially the unit consists of a flask (ciosed w i t h a r u b b e r stopper) which has a pipe connection to the piston of the Toepler p u m p . This c o m m u n i c a t i n g pipe is filled w i t h m e r c u r y and the rise and fall of the m e r c u r y in the reservoir causes a corresponding fall and rise of t h e m e r c u r y in the p i s t o n of the Toepler p u m p . A pipe passing t h r o u g h the s t o p p e r connects to a mechanical v a c u u m p u m p and carries an air leak which can be opened and closed b y electrical relay action. The r e l a y action is controlled b y an electrical circuit, details of which are given, which in t u r n is controlled b y t h e changing level of t h e m e r c u r y in t h e flask. T w o wire electrodes connected to the electrical circuit are passed t h r o u g h the s t o p p e r and project into the flask at different lengths. The joint lead of the two relay circuits also projects into the flask b u t is insulated against the m e r c u r y b y a sleeve and its tip is p e r m a n e n t l y in contact w i t h the m e r c u r y irrespective of its level in the flask. U n d e r the action of the mechanical v a c u u m p u m p , the m e r c u r y in the flask, in c o n t a c t w i t h one electrode (air-leak closed), rises until it reaches the s h o r t electrode, w h e r e u p o n the o t h e r relay opening the air-leak is actuated. This stage signifies the end of the suction stroke of the Toepler p u m p . Consequent to the admission of a t m o s p h e r i c air t h r o u g h the leak t h e m e r c u r y level in the flask is lowered producing a reciprocating stroke in the Toepler p u m p . This m o t i o n continues until the m e r c u r y level in the flask has been lowered to a point where it is no longer in contact w i t h the longer electrode. At this stage the air-leak is closed and the cycle of operation is repeated. The special a d v a n t a g e s claimed for this a r r a n g e m e n t are: 1. The control electrodes are n o t on the v a c u u m side 0f the Toepler p u m p , 2. No metal-to-glass seals are required. Sommaire : On d~crit un simple contrSle dlectrique, p o u v a n t ~tre fabriqud en laboratoire, qui facilite Ie travail a u t o m a t i q u e des p o m p e s Toepler.
2I --
GAUGES
--
Abstract No.
and References
Article by P. Nessina J. J. Brown & J. Bohnlofink Chem. Engng. 61, Jan. 1954
161-164
48/IL
Note by F. I-Iohnsted~ & M. J. Steindler 2?ev. Set. lnstrum. 25, March 1954 296-297
21
A Survey of Gauges for M e a s u r e m e n t of Low Absolute Gas Pressures
49/II
See A b s t r a c t No. : 63/I
0
Measurements of Vapour Pressures. See A b s t r a c t No. : 8 9 / I I
S o m e Problems on V a c u u m Techniques
M e a s u r e m e n t of H i g h V a c u u m at Low Temperatures
50/II
51/II
United States. Calorimetric m e a s u r e m e n t s at liquid helium t e m p e r a t u r e s require adiabatic conditions such t h a t t h e , t h e r m a l influx to one mole of sample is less t h a n one erg per second. Adiabatic demagnetisation e x p e r i m e n t s often require a heat influx t e n times less t h a n this. This order of t h e r m a l insulation calls for a v a c u u m between b a t h and specimen of the order of 5 × 10 -9 ram. H g and 5 × l0 -10 ram. H g respectively. The m e a s u r e m e n t of these pressures m u s t , of necessity, be carried o u t b y a gauge at r o o m t e m p e r a t u r e connected to this region b y a pipe, along which there will be n o t only a pressure gradient due to the thermol.ecular effect b u t also a concentration gradient of helium. This precludes the use of a convertional ionisation gauge which u n d e r such conditions would record pressures of the order, of 10 -6 m m . H g (mainly air pressures) and a gauge capable of m e a s u r i n g p a r t i a l pressure of helium is therefore essential. F o r these reasons a helium m a s s spectrom e t e r leak detector is used as a backing p u m p for the diffusion p u m p evacuating the insulation space. The s p e c t r o m e t e r is initially employed to check the region for leakage in excess of 5 × 10 .6 micron litres per second (at r o o m t e m p e r a t u r e ) and can be calibrated b y m e a n s of a calibrated leak. I t t h e n serves as a kinetic v a c u u m gauge, i.e. the pressure at the source P1 is given b y the t h r o u g h p u t Qr m e a s u r e d at r o o m t e m p e r a t u r e b y the s p e c t r o m e t e r and the equivalent r o o m t e m p e r a t u r e speed Sr defined as S t = Qr/P~. A s s u m i n g (a) molecular flow (b) a t u b u l a t i o n long c o m p a r e d w i t h its diameter (c) a small gradient of P / T k , the basic equations of the t h e r m o m o l e c u l a r effect are used to s h o w t h a t Sr m a y be directly c o m p u t e d from :
s~ -
4 (2=Rr~)~ ( r , , ¢ 3~/M
April, 1954
,-1 E i~l
li \ T I ] -ai ~ Vacuum Vot. I V No. 2
233