Edwards ELD500 Series, Instruction Manual

Page: 60 / 121

D13510840D - Partial flow adaptor
Page 50
This page has been intentionally left blank.
By operating the Start pushbutton on the hand unit of the ELD500, valves V8 and V10 are
opened in order to evacuate the test sample via the external partial flow pump (generally an
E2M28 or XDS35i-enhanced) and also via the internal backing pump. If within the quick point
time (see also the ELD500 instruction manual, D13510880) a pressure of 3 mbar is reached,
the ELD500 will switch to the GROSS mode with running partial flow pump; the detection limit
is 1 x 10
-8
mbar ls
-1
. Further evacuation lets the leak detector enter the FINE mode at 0.1
mbar with active partial flow pump. The lowest detectable leak rate is now 5 x 10
-10
mbar ls
-1
.
If it is not possible to evacuate the test sample within the quick point time to below 3 mbar,
for example because the volume of the test sample is over 1 to 2 l or if a gross leak is present,
valve V10 is closed again, i.e. the test sample is then exclusively evacuated by the partial flow
pump. The only vacuum link which now exists to the ELD500 is via the bypass orifice
(see Figure 41 ). Thus, the amount of gas flowing into the leak detector is so small, that even
at atmospheric pressure (1000 mbar) within the test sample, the pressure in the inlet area of
the ELD500 will be 3 mbar so that the ELD500 can run in the GROSS mode. The detection limit
is 2 x 10
-5
mbar ls
-1
.
If a test sample pressure of approximately 500 mbar is decreased the detection limit is
5 x 10
-6
mbar ls
-1
.
Figure 41 Vacuum diagram
If 3 mbar are decreased, V10 is opened and as described before the GROSS mode is attained
with the partial flow pump (V8 and V10 open).
The partial flow valve V8 closes at an inlet pressure of < 10
-2
mbar when the "NORMAL"
partial flow mode has been selected. If the "oil-free" partial mode was selected, valve V8
closes already at a pressure of < 0.1 mbar. In both cases the ELD500 is running in the FINE
mode at its full detection sensitivity of 5 x 10
-11
mbar ls
-1
.
By actuation and pressing down the Stop key (Vent function) the test sample is subjected to
fast ventilation (V8 and V10 closed) via V9 (diameter 6 mm).
The valves are fully automatically controlled by the ELD500 via the delivered cable
(see Figure 42 item 5).