Valve Proving Controls
The tightness control TC checks the fail-safe function of both valves before each start-up or after each shut-down of a system with two safety valves. The aim is to identify an inadmissible leak on one of the gas valves and to prevent burner start. The other gas valve continues working properly and takes over the safe shut-off of the gas supply. It is used in industrial thermo processing equipment, in boilers and forced draught burners. European standards EN 746-2 and EN 676 stipulate tightness controls for capacities over 1200 kW (NFPA 86: from 117 kW or 400,000 Btu/h in conjunction with a visual indicator). Pre-purge of the combustion chamber can be dispensed with under certain conditions in accordance with EN 746-2, if a tightness control is used. In this case, the system must be vented into the open air.