Older DIN valve with odd bottom diameter.

[minimalistdiver]

I went and looked at a tank I saw on Craigslist today. It was a steel tank made in 1961. I put a light in the tank and there was a little bit of rust and pitting. So it will need to be tumbled and hydro tested.
It is a low pressure smaller tank. I can't remember the size.


I will need to change that old yoke connector to a DIN. The problem is it is an odd smaller diameter hole. It is bigger than .5 inch and smaller than .75 inch. Somewhere in between. My buddy at the LDS said that I need a 300 bar and I will probably need to get an older used one. We didn't measure it but I am hoping one of you will have an idea of what size valve should I be looking for?

Visual, tumbling, and hydro will probably set me back 80 bucks. Plus whatever the valve costs. That is if it passes hydro.
Boy, picking up tanks on Craigslist is not cheep after adding in all the other costs.
I have $125 in a 1995 Aluminum tank that I just did. Saved me a few bucks. But still a chunk of change.

 

[Luis H]

The tank looks like a steel 72. It is actually about 71 cu ft at 2475 psi (the 2250 psi + 10%).

From the picture (and the description of the thread size) the valve looks like an old Sportways, but in the picture the valve doesn't show clearly. They had a very unique 1/2” straight pipe thread tank neck and valve. The actual thread size is a bit larger, but the nominal size in pipe threads refers to the size of the pipe not the threads.

The valve seals with an O-ring just like the standard 3/4 inch straight pipe threads used in about 90% of the tanks sold in the US. The only issue is that the 1/2 inch pipe threads are very rare. Only Sportways (and a few White Stag) valves were ever made for that size neck. Both companies have been out of business for decades.

Used replacement K valves are occasionally found on eBay, but (AFAIK) a DIN was never made for that size neck.

The valve should be OK, but if you have to have a DIN valve your only option is going to be having a modern K valve with machined down to that size.

Good luck.

 

[Leslie Sapp]

XS Scuba makes that valve. Third one down on the page.

 

[Luis H]

The XS Scuba valve is for tapered threads.

From the picture, I can’t tell for sure, but it looks to me like a straight thread valve that seals with an O-ring (made by Sportways).

The OP should be able to tell for sure when he removes the valve, but if it was a tapered thread you would normally see some threads showing right above the neck.

 

[scubafanatic]

I'm just wonderin' why you go to the effort of buying/refurbing old/odd tanks when your total final invested costs equal the prices of a brand spanking new/zero effort tanks ?

 

[minimalistdiver]

You are totally right about this being a sportways valve. Wow, you have a good eye. I measured the tips (points) of the threads and the bottom is 3/4" wide and the top looks like it is 13/16".
The guy at the dive shop said I need a "300 bar DIN valve". I will call XS Scuba tomorrow to see if one of their valves will fit this. And if the tank passes a hydro, that is what we will order.

The reason I try to save these old tanks is good used aluminum ones go for somewhere in the 180's. So if I pick up this tank like I did for 5 bucks, do a visual, tumble, hydro $80 and a used valve for $50, I am in it for $135 so it saves me a few bucks. And a nice used steel tank would cost me more than $180.

I'll probably put some paint stripper on this yellow one if it checks out and primer and paint it the color of my choice.

 

[vancouverdiver]

Hmmm. That seems like a bit of a financial risk, in that you pay for hydro and it may or may not pass. I don't know about the dive shop filling practices in the U.S. but you might want to confirm they will fill a 50 year old tank. If I was working in the dive shop, I wouldn't want to risk my life filling it. It could go off like a bomb. In addition, you will of course be relying on a 50 year old tank for life support under water.....

 

[halocline]

Hmmm. That seems like a bit of a financial risk, in that you pay for hydro and it may or may not pass. I don't know about the dive shop filling practices in the U.S. but you might want to confirm they will fill a 50 year old tank. If I was working in the dive shop, I wouldn't want to risk my life filling it. It could go off like a bomb. In addition, you will of course be relying on a 50 year old tank for life support under water.....

Yeah, that $5 is sure a big financial risk. LP72s almost never fail hydro, steel tanks don't really wear out, and even a new tank will have hydro and visual inspection costs. I'm glad at least a few dive shop employees have a more informed view of filling older tanks than your nutty "it's old, it must be unsafe" attitude. And, if you don't mind, please describe a scenario in which using an old tank could possibly impact your safety underwater. Or are you just mimicking the good ole "life support" line? That one's right up there with "the check's in the mail".....

O.P., assuming Luis is correct (as he usually is) you are almost certainly not going to find a DIN valve for that tank, just rebuild the one you have and accept it as a yoke valve. $80 is a pretty steep price for hydro/vis/tumble, but then again I'm rarely surprised by dive shop prices or policies regarding tank service. Around here a hydro is about $22 at a testing facility, the tumble would be maybe $15, although rather than tumble, there are brushes that work really well for the common surface rust that you sometimes see around the base of the tank, and you can do that yourself. A visual sticker with a fill at the dive shop is $20. You'll find that the LP72 is a delightful tank to dive with; nice and compact in the water, neutrally buoyant empty, and only 26lbs dry weight. And if you can coax the fill station into a slight overfill, around 2700PSI, you'll have as much air as an AL80.

What are the markings on the tank?

 

[Wookie]

There are machine shops out there that will put any threads you need on the valve. It is not a difficult proposition to convert a 3/4? straight thread to a 1/2" taper, or any other thread. Don't tell them I said it was OK, though I know plenty of rebreather owners that cut new threads on their DIN valves for their inconel spheres.

 

[minimalistdiver]

How do I determine the the size of the threads? When I measure the diameter accross with my ruler, I get 13/16 at the top and .75 at the bottom, when I measure from the tips of the threads. Am I supposed to measure the dips in the threads? If I do that I get .75 at the top, 11/16 at the bottom.
Is this really still called a .5" tapered?

Markings on tank:
ICC-3AA2250
HJ 54167
<N>
10<N>61+

4(A)68
7G84+
1 04 91 94+
PROPERTY OF P(cannot read). TAILLIEZ
VOIT
8E77