GB 03302 - Edition 03 - July 12
1/11
A 200
About leak detection
Overview
Leak detection is used to detect micro-openings, porosities, permeation
through materials etc. The means of detection is a tracer gas: Helium.
This gas is so light that it can penetrate microscopic cracks very fast.
The analyzer cell measures helium partial pressure created by helium
molecules that come from the leaking parts. These molecules are
pumped in by the vacuum pumps of the helium leak detector and end
up inside the analyzer cell. This partial helium pressure is converted
into a flow rate. The analyzer cell is tuned to detect three gas species,
hydrogen (M2), helium isotope (M3) and helium (M4). For more
information on the operating principle, please go to the end of this
chapter.
The ASM 310 helium leak detector has a wide measuring range
capability. It can detect a leak as large as 10
-2
mbar l/s down to a
leak as small as 3x10
-11
mbar l/s.
A leak of 10
-2
mbar l/s is equivalent to a bubble of 1 cc escaping a
part every 100 seconds.
A leak of 3x10
-11
mbar l/s corresponds to a bubble of 1 cc escaping
a part every 1,050 years.
As for reference, please see below for more leak rate correlations.
For the same size crack, a part will leak out helium at different rates
based on the internal helium pressure. The greater the internal helium
pressure, the higher the leak rate.
Leak testing large leaks versus leak testing tiny leaks will require
different settings, for more information, please go to chapter C.
Leak
Rate
3x10
-11
mbar l/s
1x10
-10
mbar l/s
1x10
-09
mbar l/s
1x10
-08
mbar l/s
1x10
-07
mbar l/s
1x10
-06
mbar l/s
1x10
-5
mbar l/s
1x10
-04
mbar l/s
1x10
-03
mbar l/s
1 cc
Bubble
over time
frame
1,050
years
317
years
31.7
years
3.17
years
116
days
11.6
days
1.2
day
2.7
hours
17
minutes
adixen Vacuum Products - ASM 310 Operating instructions
Summary of Contents for ASM 310
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