Valve Servicing

Valve Servicing Notes

Spot the problem? Its a nasty one that will blow the roof off the compressor room… Simple – DOT-3AL3000 Cylinders use American 3/4 x14tpi NPSM threaded valves NOT European M25 x2 valves Its true that with a big enough monkey wrench it can be turned all the way in – but – the threads will now, officially be toast’ and the valve will explode out of the cylinder during filling with disastrous results. The same dangerous thread mis-match can also occurs with British 3/4 BSP(F) valve.

It can also be screwed into an American DOT-3AL3000 cylinder about 5 turns before it binds. The last few turns will require a really big wrench, and will destroy the valve/cylinder threads during the tightening exercise.

Torque value for USA 3/4x14tpi NPSM brass valve inserted into DOT-3AL3000 aluminum cylinder is 50ft/pound Torque value for M25x2 metric valve, parallel threads into steel is 100-130N/M (EN13341 applies) Torque value for M25x2 metric valve, parallel threads into Aluminum is 85-100N/M (EN13341 applies)

Thermo DIN/INT valve picture - courtesy of Dive Supply, Phuket Thermo valve exploded_dwg.pdf

Thermo Pillar Valve schematic (INT only)

SMT ‘ Genesis ‘ Cylinder valve schematic (INT Only)

Differences between Thermo & Sherwood INT valve schematic

Valve Suppliers:

Valve Servicing Information