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  • LPG Changeover Valve Safety

    LPG Changeover Valve Safety has become an issue recently.

    One of the most common issues is you have a changeover valve with only one gas bottle connected.

    The pigtails (Rubber hoses that connect to the valve ) have a built-in non-return valve that sometimes leaks gas.

    Non-return valves operation at low pressure. Relates to BSS TN 01.10 FAQ02 Check(s) 7.7.2

    Reasons for inclusion


    We witnessed an owner changing a gas cylinder on an LPG system with an automatic changeover device.

    The remaining connected cylinder had its valve left open slightly.

    Despite having a non-return valve (NRV) fitted.

    There was a slight but noticeable escape of LPG from the open end of the disconnected flexible hose (pigtail).

    We then tested the NRV at full pressure, and it worked fine.

    We then contacted the BSS Office to see if the NRV was faulty, was the valve designed to work at low and high pressure.

    Answer:

    Non-return valves are on LPG systems where two or more gas cylinders connect onto the high-pressure side of the gas system.

    Designed to prevent gas let by when changing gas bottles.

    It should prevent any gas from escaping when a gas cylinder is changed over.

    The BSS asked one of the major suppliers of high-pressure hose assemblies to comment.

    These responses incorporated the view of their manufacturers/distributors.

    We learned that high-pressure hoses with fitted non-return valves could allow small amounts of LPG to backflow when the gas pressure becomes very low.

    However, at normal working pressure, the valve will activate to stop gas from returning.

    The majority of high-pressure pigtails incorporate a non-return valve and should stop gas from flowing back.

    Some models also have an excess flow valve fitted to restrict gas escape should the hose (Pigtail) becomes cut or severed.

    Most automatic changeover devices also include an NRV built into the regulator body.

    The built-in NRV should prevent LPG from passing from one cylinder flexible hose to another.

    However, small amounts of gas may still pass through this valve.

    NRVs are permitted to allow a backflow of LPG at low pressure, for example, this can enable the resetting of any excess flow valve (OPSO)

    Any escape of gas occurring from the open end of a high-pressure hose should be minimal.

    It may be noticeable it should not be regarded as abnormal.

    Concerning manual changeover devices.

    The connected high-pressure hoses may incorporate the same NRV/excess flow valve, same features as described above.

    However, the device itself relies upon the manual operation of the valve, diverting the supply between connected cylinders.

    The type of changeover valve on manual devices is generally different and provides a more positive degree of control that does not allow gas to pass by it when in the closed position.

    Implications.

    There are no direct implications however, it is useful information to pass on to boat owners.

    How to remain safe when changing LPG cylinders.

    Connected to changeover devices as they may believe that the NRV’s operate at all pressure ranges.

    Where changeover devices are in use, the best advice is always to have two cylinders connected and thus when exchanging a cylinder to have the replacement ready to hand.

    LPG gas users should be advised that when changing empty cylinders, before removing it fully, the connection should be cracked open to check that cylinder pressure from the full cylinder has not bypassed the NRVs.

    If a spare cylinder is not to hand, then it is better to practice shutting down the systems rather than leaving the open-ended hose exposed with the potential to leak.

    The biggest issue we find with the LPG changeover valve safety is on mobile home sites.

    We see many changeover valves only connected to one gas bottle.

    When left like this for months on end, the non-return valves becomes stuck either closed or partly open due to rust build up around the valve.

    It happens more often in the winter months of the year.

    The weather gets to the NRV spring within the pigtail and rusts up causing, it to stick.

    When we do an LPG gas safety inspection, if we see only one gas bottle connected, we have to fail the inspection and class the gas system as at risk.

    Why do we need to class it as at risk?

    Gas regulations state that no gas supply pipe or hose be left open-ended they must be capped off for safety.

    Just having an isolation valve switched off is not enough.

    The reason being the isolation valve may let gas by or be accidentally open by mistake.

    This regulation applies to all types of gas Propane, butane and natural gas.

    Once a second gas bottle is connected, the non-return valve may not work.

    If it gets stuck in the closed position, gas will not flow when the other gas bottle becomes empty.

    If the NRV has become stuck, it’s advisable to replace the pigtail as soon as possible.

    All gas pigtails should be changed every five years, sooner if they start to deteriorate.

    If you are only ever going to have one gas bottle connected at any one time.

    It’s better to remove the changeover valve for a single bottle regulator.

    If you decide to go down this route, it is advisable to speak to a registered LPG gas engineer and explain what you would like to do.

    He may even tell you it’s not possible, as your gas demand may need to have two gas bottles or more connected to comply with regulations.

    Single gas bottle regulators come in many different gas outputs, you will need to ensure the correct one is purchased.

    The LPG engineer can size up your gas appliances and get the correct regulator for your needs.

    LPG Changeover Valve Safety, as well as appliance safety, tends to get overlooked until something happens. Is this you?

    When was the last time you had your changeover valve and pigtails examined for age as well as safety?

    When living close to the sea, the sea air tends to deteriorate the changeover valve and pigtails quicker, than if you lived inland.

    Boats are more susceptible to the changeover valve and pigtails failing due to the sea air.

    We hope you found this article helpful in your search for LPG Changeover Valve Safety.