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IGEM/UP2/Edition 2

IGEM/UP2/Edition 2

Within IGEM/UP/2 Edition 2 it highlights the potential risks surronding the control of gas solenoid valves (AIV's) and automatic restarting.

POTENTIAL HAZARDS

“A potential hazard could arise from the use of an AIV (valve) if it were to close and reopen without ensuring that any appliance installed downstream is isolated.”

“Under such circumstances, when the valve is re-opened, gas would escape from any appliance which had not been turned off (automatically or manually) thus creating a potential hazard.”

“A potential hazard is most likely to occur on a valve that restores itself automatically to an open position on removal of the fault which caused it to close.”

Examples of such an event are:

  • a transient loss of electrical supplies (which can lead to significant operational problems)
  • activation upon testing a fire alarm.
  • a transient or intermittent fault of an interlock that actuates the valve.

It is argued that a boiler installation is a sealed installation and all appliances have flame safety devices fitted (FSD) so therefore proving is not required.

However if you consider that flame safety devices can take up to 10 seconds to close after a valve has isolated the gas supply then the gas pressure between the closed valve and the burner can be reduced to 0 mbar. This would then require a tightness test before the supply could be restored.

Let us take the example of a fire system activation, emergency stop activation or power failure which deactivates a safety shut off valve controlling the gas supply to the boiler room.
After the test or activation the control panel is reset and the gas supply is normally automatically re-established.
The boilers are then relit and operated as normal. In most cases the supply has been re-established successfully with no apparent hazard or risk.
However we must note, as indicated by the Health and Safety Executive and the gas industry in general, where we identify any risks which may create a hazard we should introduce control measures such to either alleviate or reduce these risks.
Gas pressure proving is used as a measure to confirm the integrity of the system either to negate any leakage or, if confirmed, warrant investigation and repair.

The installation of a gas proving system has many additional benefits the main one being that if the system is isolated as a result of a power failure, once power is resumed the system will automatically restart and perform a pressure prove, reducing the potential for site down time or damage subsequent to pipes freezing.

Every year as part of an on site DSEAR risk assessment for the plant room a leak test should be carried out of all the installed low pressure pipe work, an installed and correctly designed gas proving system can be used to complete this test. The system is simply switched off and back on again and the test completed, the alternative would be to call out a Gas safe engineer to complete the test and the subsequent costs associated.

If you require any additional information on our systems to help meet these design standards or wish to discuss the standards further please don't hesitate to contact us.
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SEC-B

SEC-B

The SEC-B, a multi-function solution designed for boiler rooms

Gas proving
Gas detection
Electrical isolation
Auto-restart after power failure
Auto-restart after a fire alarm reset

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