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8 Control Mode
8.2 Valve Leakage Test
The valve leakage test checks whether the main gas valves are leak-tight. The supply gas
pressure is used for this purpose. Since the valve leakage test line (space between the two
main valves) burns empty in the event of a shut-off, this part is normally without pressure when
starting (gas pressure > min. = 0). The ETAMATIC checks this. Main gas 1 is then opened
shortly and gas flows into the test line (gas pressure > min. changes from 0 to 1). This pres-
sure must then subsist for 30 seconds. The valve leakage test is then deemed to be complet-
ed.
If the valve leakage test line is not empty at the start (e.g. as a result of a previous fault shut-
down), main gas valve 2 opens first. The valve leakage test line is vented (into the combustion
chamber or over the roof, depending on the system; for suggested circuit, see Appendix). It is
checked, whether the line remains pressureless for 30 seconds. Otherwise the procedure is,
as described previously.
The valve leakage test is performed before ignition.
The pressure monitor for the valve leakage test line must be connected to "Gas pressure
>min" input (terminal 47). It also monitors the minimum pressure during operation. If another
minimum pressure should to be monitored during operation, the pressure monitor is, to be
looped into the gas safety interlock circuit, for this purpose.
However, the test line must be designed to ensure that the test time of 30 seconds per valve
is sufficient for reliable detection of a 0.1% leak of the fuel gas consumed at maximum com-
bustion heat output, but at least 50 dm
3
/h.
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