Always make sure that your relief valve on gas are always pointing away from van and tow vehicle.As if the pressure for some reason builds up and the relief valve releases the gas it wont make as much mess to van and vehicle.
They are a pressure relief valve. Personally never known one to go off unless overfilled (no vapour space to allow for liquid expansion when in sun for example) but have known them to have wasps build nests in them, so keep an eye out for that. Could have a plastic cap on to prevent the wasp issue and if the relief valve goes off it blows the cap off. Denis you are correct in your understanding of the relief valve, after all a gas bottle is a pressure vessel, albeit low pressure.
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Cheers Jeff
Ticking off the bucket list before we kick it!
200 TTD with Evernew 22'6" and 40+ years in the oil & gas industry, now retired. CMCA Member.