Udi Freeze
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Fitting valve onto an old Heiser cylinder
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are you sure that was meant for scuba and not to take some other CGA valve? Check to see if an existing valve will fit into it easily, it may just have a weird o-ring recess, but I'm not sure....
Any chance you have the valve that came on it?
Any chance you have the valve that came on it?
OP
Udi Freeze
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Yes it's a "Beuchat" tank, meant for diving.
The thread is a 3/4" and a normal imperial valve fit's perfectly.
The valve was not there when I got it.
The thread is a 3/4" and a normal imperial valve fit's perfectly.
The valve was not there when I got it.
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You may want to double check the threads.
I don't think a 3/4" NPS valve will fit 25mm metric threaded cylinder (see note), but I find the lack of an O-ring bevel a bit concerning. I have seen the European metric valves with an O-ring groove in the valve (for a face seal O-ring) instead of our typical NPS type of corner seal into the tank neck.
Here is an interesting article.
HSE - Mismatching valve threads
Note: the opposite is possible and it is bad news. It is possible for a 25-mm threaded valve to be inserted into a G3/4-inch threaded cylinder neck.
I don't think a 3/4" NPS valve will fit 25mm metric threaded cylinder (see note), but I find the lack of an O-ring bevel a bit concerning. I have seen the European metric valves with an O-ring groove in the valve (for a face seal O-ring) instead of our typical NPS type of corner seal into the tank neck.
Here is an interesting article.
HSE - Mismatching valve threads
Note: the opposite is possible and it is bad news. It is possible for a 25-mm threaded valve to be inserted into a G3/4-inch threaded cylinder neck.
OP
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This is a 3/4 valve for sure, a 25mm valve would not fit on this tank.
Sadly yes you will need the special pillar valve that went with these cylinders circa 1990
From memory the story was Heiser made these cylinders fine but as the scuba purchaser had little knowedge on the correct engineering specification required and Heiser as a manufacturer made to a number of thread forms and applications. The purchacer got it wrong and ordered the wrong thread form hence your cylinder was made for a face seal or Bonded washer seal (Dowty Seal)
The first problem found was if they were to use a bonded seal that the height of the metal dowty seal "lost" a couple of threads from the piller valve as the valve sealed higher and in turn this reduced the number of "engaged" threads to less than 9
The second was finding a bonded seal that didnt rust in salt water.
Plan B was to undercut the base of a heavy base scuba piller valve with an 0-ring groove solving the height and engaged threads problem while still effecting a face seal.
For the rest of scuba la la land suppliers pretending to be engineers a counter bore or countersunk cylinder 0-ring seal shape became the norm. While the marked and dangerous difference between 3/4 NPSM, 3/4 BSPP and M25x2 choice of threads in cylinders became more of a problem as the Germans and the French scuba importers cocked the whole thing up.
Frankly you wont find a pillar valve for this, its scrap. Scuba shops have spent the last 20 years weeding these things out and into the scrap bin, IMHO you should do the same.
Dowty seal info below:
http://www.potterassoc.com/pdf/bonded_seal_information_and_sizing_chart.pdf
From memory the story was Heiser made these cylinders fine but as the scuba purchaser had little knowedge on the correct engineering specification required and Heiser as a manufacturer made to a number of thread forms and applications. The purchacer got it wrong and ordered the wrong thread form hence your cylinder was made for a face seal or Bonded washer seal (Dowty Seal)
The first problem found was if they were to use a bonded seal that the height of the metal dowty seal "lost" a couple of threads from the piller valve as the valve sealed higher and in turn this reduced the number of "engaged" threads to less than 9
The second was finding a bonded seal that didnt rust in salt water.
Plan B was to undercut the base of a heavy base scuba piller valve with an 0-ring groove solving the height and engaged threads problem while still effecting a face seal.
For the rest of scuba la la land suppliers pretending to be engineers a counter bore or countersunk cylinder 0-ring seal shape became the norm. While the marked and dangerous difference between 3/4 NPSM, 3/4 BSPP and M25x2 choice of threads in cylinders became more of a problem as the Germans and the French scuba importers cocked the whole thing up.
Frankly you wont find a pillar valve for this, its scrap. Scuba shops have spent the last 20 years weeding these things out and into the scrap bin, IMHO you should do the same.
Dowty seal info below:
http://www.potterassoc.com/pdf/bonded_seal_information_and_sizing_chart.pdf
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