Valve Proving With Separate Pressure Switch (P Lt) X9-04 - Siemens LMV36.520A1 Basic Documentation

P P
min LT
P LT
Figure 1: Valve proving with separate
pressure switch (P LT)
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Caution!
The OEM must set the evacuation, filling and test times for atmospheric or
mains pressure on every plant in compliance with the requirements of EN 1643.
It must be ensured that the 2 test times are correctly set. It is to be checked whether the
gas required for the test may be fed into the combustion chamber (on the relevant
application). The test times are safety-related. After a reset and in the case of aborted or
prevented valve proving, the unit performs valve proving on the next startup (only when
valve proving is activated). Prepurging with valve proving is active during the startup
phase, even if it was deactivated.
Examples of aborted valve proving:
If the safety loop or the start prevention input for gas (containing Pmin) opens during
valve proving.
Valve proving – calculation of leakage rate
(P G - P w ) • V • 3600
t Test = 
P atm Q Leck
•
Q in l/h Leakage rate in liters per hour
Leck
P in mbar Overpressure between the valves at the beginning of the test phase
G
P in mbar Overpressure set on the pressure switch (normally 50%
W
of the gas inlet pressure)
P in mbar Absolute air pressure (1013 mbar normal pressure)
atm
V in l Volume between the valves (test volume) including valve volume
and pilot pipe, if present (Gp1 mod)
t in s Test time
Test

7.5.3 Valve proving with separate pressure switch (P LT) X9-04

Step 1: t80 – evacuation of test space.
Gas valve on the burner side is opened to bring the test space to
atmospheric pressure.
Step 2: t81 – atmospheric pressure test.
When the gas valve has closed, the gas pressure in the test space must
not exceed a certain level.
Step 3: t82 – filling of test space.
Gas valve on the mains side opens to fill the test space.
Bild 410e/1010
Step 4: t83 – gas pressure test.
When the gas valve has closed, the gas pressure in the test space must
not drop below a certain level.
Legend
t80 Evacuation of test space (parameter 242)
t81 Atmospheric pressure test (parameter 243)
t82 Filling of test space (parameter 244)
t83 Gas pressure test (parameter 245)
V... Fuel valve
P LT Pressure switch – valve proving
Pmin Pressure switch-min
Input/output signal 1 (ON)
Input/output signal 0 (OFF)
Input permissible signal 1 (ON) or 0 (OFF)
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CC1P7544en
25.09.2013