Edwards ELD500 Series, Инструкция по эксплуатации

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D13510840D - Calibrated leak - He 4-6
Page 65
Figure 47 Unscrewing valve for sniffer probe tip access
The leak outlet orifice itself is on the face of the sealed-in tubulation which is now visible. The
sniffer probe can be inserted into this small orifice. With the screw cap removed the port
leaks at the desired reference level.
Figure 48 Leak out orifice location
Clogging of the leak capillary
The measured leak rate will depend on the distance between sniffer tip and leak, and also on
the speed at which the sniffer tip is moved past the leak.
The size of the leak will depend on the pressure as indicated on the pressure gauge and it may
be determined from the calibration curve.
Using search gases other than helium
When using test gases other than helium, leak rates can only approximately be determined,
the reason being that the 10
-8
to 10
-4
mbar Is
-1
range includes just the transition-flow region
between molecular and laminar gas flow. Moreover, the individual flow profile of the
respective capillary will affect the conversion factor. In the molecular flow region it applies
for the leak rate q of different gases at otherwise equal conditions:
M= relative molecular mass
CAUTION:
The size of the leak outlet orifice can change or get choked due to contamination. Do not
touch the leak outlet orifice with the fingers or with greasy objects. When no longer using
the calibrated leak, close the valve.
q
x
q
He
--------
M
He
M
x
---------- =