A different kind of breakdown

A different kind of breakdown

S e available for educational tocopies for non-profit ectlyfrom Elrevier Science Rights & ox SOD,Oxford OX5 IOX, UK;

ome folk say that the English and the Americans are two peoples separated by a common

ways of pronouncing

language. It’s not simply two different

the word ‘tomato’ or spelling ‘manoeuvre’

‘maneuver’ (or vice-versa!)

that differentiates

as

the two cultures. There

are also different definitions of what we mean by the same phrase. For example, there are US compani&

selling pumps that contain

up to four mechanical

seals and are labelled hermetically-sealed.

However, mechanical

seals will typically contain a stationary seat,

gasket, rotating sealing ring and a spring or springs and while they perform their primary function of drastically reducing leakage they duce tables of contents or prepare lists of acts fw internal clrcolation within their

are not gas tight. A flow of fluid across the seal faces is essential for lubrication

and cooling.

4 m differential re

elertronically

A small seal in perfect condition

with a

head will leak 0.4 mm3/h but not show any visible

signs of leakage. According

to a generally accepted European definition,

hermetical

seal is gas-tight and you have to break a physical barrier

(the seal) to enter that environment.

Everything

a

else about the seal

is static, there are no moving parts, gaskets or joints etc. The seal is not designed to be opened. ideas contaiiwd in the material in the medical sciences, in f diagnoses and drug II advertising mate&l is cal) standards, inclusion in e a guarantee or endorsement product or of the claims made of it

Hermeticity

is the process that keeps the internal environment

components

secure from contamination

of the

from the outside. In this

case, hermetic refers to static packaging technology designed to preserve an internal gas fill and to prevent moisture from entering

:erdW~

and payments and packing) ($264 USA and 7.00 ,subjectto exchange rate es from Caroline Champney,

and candensing environment.

inside the enclosure during exposure to the service For the European pump engineer, this is quite different

from a mechanical

seal that is a dynamic system in its own right.

Where language becomes important is in a breakdown. In the US, moving fluid seals with back-up systems are complicated

and

breakdowns can be attributable to a chain of events. The European T@werHouse, Sovereign Park, gh, Leicestershire,LE16 9EE WORLD ~~~~~i~~ Pumps Pompes ‘~J@~R%I b^$d~li&d monthly by ElsevierAdvanced ~~~,~y, & &ox lSU,Kidkington,Oxford OX5 %$,%&. The ediB%?wi~ibe glad to considercontri&&&w but no res&sibility for the safe keeping or ‘retuti of qhlsblicitedmaterial will be accepted.

’

WORLD PV&fPS is printed by Headley Brothers Ltd. EAT 02113 Kent, UrC.,f%N 0262 1762

definition of a breakdown needs a physical failure of a component e.g. a weld, or pressure-vessel failure, in other words a major fracture. So when the works manager or whoever shouts “breakdown” do they mean a system failure that could be one of a number of factors or something more straightforward.

I guess it would depend upon the

accent you use to explain it. ALAN BURROWS EDITOR

VhiorM Pumps is a member .tifEPA~ernatienal, the leading buiinw

world auditor publications.

cvf

WORLD PUMPS

March 2002

13