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Building Technologies Basic documentation LMV37.4... CC1P7546en
7 Basic unit LMV37.4 17.12.2018
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 pressure switch-min)
opens during valve proving.
Valve proving – calculation of leakage rate
(P
G
- P
w
)
• V • 3600
t
Test
=
P
atm
• Q
Leck
QLeck in l/h Leakage rate in liters per hour
P
G in mbar Overpressure between the valves at the beginning of the test phase
P
W in mbar Overpressure set on the pressure switch (normally 50% of the gas inlet
pressure)
P
atm in mbar Absolute air pressure (1013 mbar normal pressure)
V in l Volume between the valves (test volume) including valve volume
and pilot pipe, if present (Gp1 mod)
t
Test in s Test time
7.5.3 Valve proving with separate pressure switch X9-04
P LT
P
LT
Bild 410e/1010
P
min
Figure 32: Valve proving with separate
pressure switch
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 – test time atmospheric pressure.
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.
Step 4: t83 – test time gas pressure.
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 Test time atmospheric pressure (parameter 243)
t82 Filling of test space (parameter 244)
t83 Test time gas pressure (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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