Alcatel ASM 180 TD User Manual page 22

Spray method
Response time
2/4
Testing methods
This involves removing air from the test part, connecting it to
the analyzer and then spraying helium over the outer surface.
Global test
He
Part
Detector
The part is placed under a
cover, into which helium is
injected.
The leak cannot be
located.
The detector measures the flow of helium penetrating the part.
When spraying starts, the leak signal is not displayed instan-
taneously on the analyzer:
there is a response time which depends on the volume V
being tested and the helium pumping speed S of the system
at the opening of the part, according to the following
relation:
V
T = (T in seconds, V in litres, S in l/s)
S
T is the time required for the signal to reach 63 % of the
final value.
Alcatel Vacuum Technology France - ASM 180 TD/TD+ - ASM 181 TD+ User's Manual
Spray test
Spray
Part
or
or
He
Areas liable to leak are
sprayed with helium.
The leak can be located.
A 40
Detector