The differential pressure method Product description
EN 3925-0060 V207-00 MANUAL R03.doc
HeMaTech
Prüftechnik
The testing process consists of three phases:
1. Filling
With the filling and isolating valve open, the testing pressure set on the pressure regu-
lator is applied to reference volume, measuring transducer and specimen The filling
time is determined by the performance of the pressure regulator, the total volume of
the facility including testing and reference volume, the piping resistance and the cross-
section of the valves.
2. Stabilizing
This is the phase of pressure and temperature stabilization in the entire system. The
reference volume shown in the illustration – one normally uses a pressure tight original
work piece – serves the purpose of creating the highest possible symmetry level be-
tween testing and reference circuits. This enables a reduction of stabilization time, be-
cause possibly existing interfering influences affect both circuits of the system and thus
reduce the effect on the measuring result. Empirical values reveal that with volumes
< 5000 ccm a reference volume is normally not needed.
3. Measuring
The actual measuring phase starts after the stabilization time has expired. By closing
the filling and isolation valves the measuring and references branches are separated
from each other. If the specimen has a leak, the pressure in the measuring branch will
drop in comparison to the reference branch. The measuring transducer shows the re-
sulting pressure difference in the measuring value display. If the pressure difference ex-
ceeds the preset limit value during the measuring phase, a signal
Reject
will be
submitted and the test stopped.
Pressure course in the test system during the test process
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