INFICON Sensistor ILS500 Leak Detection System - Manual (Page 56)

56 Recipes
ninb63e1-f (1410)
We will now have:
of air left in the pipe. This is equivalent to 0.57 m (1.9 ft.). This air volume is normally
small enough to be mixed into the tracer gas by turbulence and diffusion.
9.5.3 Testing Need for Pre Evacuation
The best way to establish the need for pre evacuation is to make a realistic test.
1 Use a test object with a small leak far away from the test connection.
2 Set the ISH2000 in Locating Mode.
3 Set up the ILS500 according to the specific test specification.
4 Set Pre Evacuation Level to:
-0.07 MPa
-0.7 bar
-10 psi
5 Purge the test object throughly with compressed air.
6 Check with the Hand Probe that there is no Hydrogen in the part.
7 Connect the test object.
8 Place the Hand Probe on the leak.
No signal should be heard.
9 Press Start on the ILS500.
10 Register the Signal from the leak.
The gas signal should stabilize quickly and the maximum achieved signal should be
attained in a maximum of 2 seconds after Fill Setpoint has been reached.
• Set Pre Evacuation Setpoint to half of the previous and repeat the test from step 5.
• The new pre evacuation is adequate if the gas signal is essentially the same and
develops at the same speed.
• Reduce Pre Evacuation Setpoint further and repeat test again to find the lowest
suitable Pre Evacuation Setpoint.
Pipes etc. will exhibit considerable pressure drop along its length during the
evacuation. This means the pressure in the pipe can be much closer to atmosphere
than what is registered by the ILS500. Set the ILS500 to evacuate through Test Port 1
only (this is done in the Advanced/Options Menu). In this way the vacuum will be
registered in the end of the pipe and the evacuation will be at least as deep as set by
the Pre Evacuation Setpoint.
If this is not possible, add some extra time by setting an Extended Evacuation Time.
B
A B +
------- - E =
0,03
0,5 0,03 +
------------ - 0,056 =