Why you need to verify valve thread

[Peter69_56]

I bought a supposed 3/4" NSPT manifold from a well known dive supplier in Australia. Then bought 2 Faber 12.2 litre cylinders. Before they arrived I noticed an article on a cylinder valve failure from a manifold that had been fitted. M25 manifold into a 3/4 cylinder.

Made me think to go and check mine and to my amazement my supposed 3/4" manifold was a M25 "There but for the grace of god went I".

Returned the manifold for a refund and advised them of the risk. Purchased a 3/4" NSPT manifold from another supplier, and all was well. Just goes to show however the ease with which this can happen. Many aluminium cylinders have no thread markings. Faber however do have them marked.

 

[rjack321]

To my knowledge, the M25 will go in a 3/4 straight thread hole, but it's not right, it's loose, and the threads aren't the same pitch. The 3/4" straight thread will not go in a M25 hole.

I was given a M25 valve once and it did indeed fit into a 3/4 NSPT (USA 3/4") valve opening. The sealing surfaces we gapping too large and it otherwise seemed "off". I threw it in the trash to ensure it wasn't inadvertently used in this country.

 

[Couv]

Resurrecting this important thread.

Can anyone confirm that a standard US 3/4-14 scuba tank valve is the same as and Australian 3/4" NPSM (NGS) parallel thread scuba tank valve? (not metric)

Tanks,

Couv

 

[runsongas]

do you mean 3/4-14? there is no 3/4-24 NPSM

australian npt or nps is the same as the US. the caveat is you have to watch out for BSP in commonwealth countries

 

[Couv]

do you mean 3/4-14? there is no 3/4-24 NPSM

Yes, sorry for the typo. I'll try to edit the post.

Thanks.