All fire tube boilers fitted with a Gas Burner are will have a Valve proving system to check the soundness of the gas solenoid valves on the burners for any leakage online and provide a safety trip mechanism.
Simply put, a valve-proving system is a safety control used on gas fuel-fired equipment that verifies the effective closure of two safety shutoff solenoid valves in series by detecting gas leakage.
What is a Valve Proving System?
Valve proving system VPS-504 on a Double solenoid valve
Normally a Burner is supplied with a gas multiblock consisting of 2 gas solenoid valves, a pilot ignition valve, and a gas pressure switch.
The valve proving system VPS 504 is a safety assembly that can be fitted to this gas multiblock.
It consists internally of a motor-driven pump, differential pressure switch, solenoid valve with operating relays for changeover and interlocks and displays for fault and okay signals, and a reset switch with an inbuilt program.
At one end it is connected to the inlet of the first gas valve and the other end is connected between the 1st and 2nd gas valves.
Operation:
The valve proving system operates on the pressure buildup principle.
The program is activated at heat request. Valve proving is carried out before every time burner starts. The VPS 504 carries out a self-test during the switching sequence. If a fault occurs, burner start is prevented and the message “lockout” is displayed.
Program Sequence:
Shutdown condition: Valves 1 and 2 are closed
Pressure build-up: The internal motor pump increases the gas pressure in the test section by approx 20 mbar when compared to the gas inlet pressure at the inlet of 1st gas solenoid valve.
During the test phase, the inbuilt differential pressure switch checks the test section for soundness. Once the test phase has been reached, the motor pump is switched off (end or test phase). The release period (10 to 26 sec) depends on the test volume.
Results of valve proving:
If the test section is gas-tight, the contacts to the burner control circuit are released after 26 seconds. If the test section leaks or if the pressure increase of 20 mbar is not reached within the test period (26 seconds) the VPS 504 goes to lockout. The red signal lamp is illuminated.
An automatic restart is carried out following short-term voltage loss during the test phase or during burner operation.
Take advantage of the Valve proving systems safety features:
A valve-proving system provides safety benefits. It actively checks the integrity of both safety valves on every startup or shutdown. It detects safety shutoff valve problems that other safety controls ignore. It is equally safe with heavier-than-air fuels as with lighter-than-air fuels. Also, it gives the user at least some idea of the condition of the safety valve seat leakage rate.
When a valve-proving system is used as an alternative to a vent valve, no gas is released to the atmosphere. As a result, it is environmentally friendly. Furthermore, a valve-proving system is a "self-checking" safety control, which means that the system faults and does not allow ignition. So this is an essential safety feature the customer should look out for while purchasing a Boiler/burner.
Comments
Post a Comment