20/05/2020
VACUUM LEAK DETECTOR
VLR ..
and
VLR .. MV
- 15 -
4.2 Normal Operating Conditions
The vacuum leak detector is connected to the interstitial space via
suction, measuring, and connection line(s). The vacuum generated by
the pump is measured and controlled by a pressure sensor.
When the operating vacuum is reached (Pump OFF), the pump shuts
off. The vacuum slowly drops due to slight, unavoidable leaks in the
leak detector system. When the Pump ON switching value is reached,
the pump turns on and the interstitial space is evacuated until the op-
erating vacuum is reached (Pump OFF).
In normal operating conditions, the vacuum swings between the
Pump OFF and Pump ON switching values, with short periods when
the pump is run and longer standstills, depending on the tightness
and temperature fluctuations of the entire unit.
4.3 Air
Leaks
If an air leak occurs (in the outer or inner wall, above the liquid level),
the vacuum pump switches on to restore the operating vacuum. If the
leak causes the incoming air to exceed the pump’s capacity limit, the
pump remains on continuously.
Increasing leak rates lead to a further decrease in pressure (with the
pump running) until the Alarm ON switching value is reached. This
triggers the visual and audible alarms.
4.4 Liquid
Leaks
In the event of a liquid leak, the liquid enters the interstitial space and
collects in the low point of the interstitial space.
The incoming liquid decreases the vacuum, which causes the pump
to turn on and evacuate the interstitial space(s) until the operating
vacuum is reached. The process repeats itself until the liquid stop
valve in the suction line closes.
Because of the vacuum that still exists on the measuring line side,
additional stored or conveyed product or water is sucked into the in-
terstitial space, the measuring line, and, if applicable, into a pressure
compensation vessel. This causes the vacuum to drop until the
“Alarm ON” pressure is reached. This triggers the visual and audible
alarms.
Comment:
It is also an option to use a liquid sensor in conjunction with a sole-
noid valve instead of the liquid stop valve. The liquid alarm is then
triggered when the sensor comes into contact with liquid.
4.5 Pressure Increase Above Atmospheric Pressure in the Interstitial Space When Using a
Leak Detector VLR .. with Solenoid Valve (MV)
If a pressure increase of more than 50 mbar above atmospheric pres-
sure occurs in the interstitial space, the solenoid valve in the connec-
tion line is closed and the pump switches off.
Design and Function