Info On These Tanks

[LAP57]

I saw these on the bay:
http://tinyurl.com/yd7oonn

I am looking for a set of vintage tanks and these are within driving distance so I could save on the shipping. I know that passing a hydro and viz is a crap shoot on tanks this age and is a risk. I am looking at manifold on the tanks and have no idea what it is. To me it looks like something that was cobbled together. Any idea about what it is? If the manifolds are throw away is $200 reasonable for a pair of 38's. Would these most likely be some type of 1/2 in thread and something that is readily available?

Opinions appreciated.

[1969ivan1]

The manifold is somewhat collectable but a PITA since it is pipe thread. Hold out for a no worries solid bar manilfold. JMO. Also u want some peanut king bands and Allan K harness. JMO There is one forum member that hates harnesses, at least some times? He may weigh in and tell u they are dangerous, but he may say they are great the next minute ha ha

[antique diver]

They look too long for 38's, so I'm guessing they are closer to the 53's that were once available from USD in the 70's (but those had modern oring sealed necks instead of the pipe threads on these).

[LAP57]

Do all 3/4 inch threaded manifolds use O rings?

Are all 1/2 inch manifolds tapered or are there straight and tapered. Are they all 1/2 thread manifolds pipe threaded or do some use O rings?

Once you have experience can you tell by looking when a manifold it pipe thread vs O ring or do you just need to know by the make and model?

For manifolds that are pipe thread how are they sealed to prevent leaks? Is a sealant used just like threaded plumbing pipes?

Thanks.

[captain]

Those will be problem to get filled unless you have a compressor. It looks like 1" to 1/2" bushing was used to adapt the tanks to the manifold. Although technically legal and safe most or all shops will not touch them.

Except for some Sportways tanks and manifolds all other 1/2" manifolds are taper pipe. you can use Teflon tape or Permatex pipe sealer with Teflon.
Try to stay away from the 1/2" thread tanks, too much hassle.

[captain]

Those will be problem to get filled unless you have a compressor. It looks like 1" to 1/2" bushing was used to adapt the tanks to the manifold. Although technically legal and safe most or all shops will not touch them.

Except for some Sportways tanks and manifolds all other 1/2" manifolds are taper pipe. you can use Teflon tape or Permatex pipe sealer with Teflon.
Try to stay away from the 1/2" thread tanks, too much hassle.

Here is a nice set on ebay. Made with the newer 6061 alloy and a solid manifold and harness.

http://cgi.ebay.com/Navy-configured-twi ... 2c538f4cf0

[simonbeans]

Here is my take on your questions. I will also give way to more knowledgeable people.

1. I believe all 3/4" valves use an O ring. So much simpler than 1/2" taper. I have only one 1/2" tapered valve left of all of the tanks I have.

2. Sportsways started using a 1/2" straight thread with an O ring. Not sure if anyone else did.

3. Again, if you have a 1/2" it is very likely a tapered valve. Sportways will be marked on the valve. If another company used a 1/2" straight, O-ringed valve, there will be a space at the top of the threads for the O ring. Tapers will thread to the top.

4. 1/2" tapered were sealed with pipe dope originally. Today we use teflon tape. They will seal fine, but remember that they are supposed to be vizzed annually (not my belief, but what do I know?) and the tapered valve removed and reset annually will decrease its life.

IMHO, the solid bar manifold is the way to go. And 3/4" valves are a no brainer.
As much as I hate Al tanks, they do make nice smaller doubles (45 or 50 cu ft). If going larger, 72s are my choice.

[simonbeans]

3. Again, if you have a 1/2" it is very likely a tapered valve. Sportways will be marked on the valve. If another company used a 1/2" straight, O-ringed valve, there will be a space at the top of the threads for the O ring. Tapers will thread to the top.

Here is a photo to illustrate this comparison:

http://i6.photobucket.com/albums/y206/s ... arison.jpg

[antique diver]

The valves in the photo of the doubles in question are a standard 1/2" NPT (tapered pipe thread). I am almost certain that no manufacturer other than Sportsways ever used the 1/2" straight thread with O-ring seal. Keep in mind that pipe thread stated size isn't a measurement of the outside of the threads, but is a "nominal" measurement of the inside of a standard 1/2" pipe, so is quite a bit larger than 1/2" on the OD.

The bushings on the cylinders appear to be either 1" or 1.25" pipe threads. If they are the appropriate material for high pressure, i.e. not hardware store pipe fittings, then they are fine to use... but most dive shops will not fill bushed cylinders.

I don't share most peoples' opinion of the 1/2" NPT threads. I just don't find them that difficult to deal with, since I have a pipe vise that firmly holds the cylinder while removing and installing the valves. It is not really a problem with the right tools and the right inspection light. I have heard lately of additional concerns about "wearing out" tapered pipe threads from too many cycles of removal and replacement, but I have not found this to be a problem if you just don't over-tighten the valves. Use plenty of teflon tape. I use 5 to 6 wraps on 1/2" NPT - not the often stated "2 wraps", and It is not necessary to tighten to extreme torque. I don't have a torque figure for you, but after years of experience just have a feel for it. Too much torque may indeed stretch the cylinder neck, and/or cause galling or distortion of the brass valve threads.

The larger NPT thread sizes do require more torque for sealing. If you are using bushings, do not remove or tighten them into place without an appropriate valve or plug snugly installed into the female thread of a bushing, or you risk crushing or distorting the female thread of the bushing!

No offense to my friends who dislike the NPT threads, as they are certainly more trouble to remove and replace annually for inspections... but I do have a number of cylinders that have survived this nicely for many years, and they are Vintage appropriate for the 1950's and 60's!

[JES]

Here is a nice set on ebay. Made with the newer 6061 alloy and a solid manifold and harness.

http://cgi.ebay.com/Navy-configured-twi ... 2c538f4cf0

Very nice!

[capn_tucker]

Yeah, the 1/2" tanks can be aggravating, but are still very serviceable. There are some shops out there that will fool with them. I'm lucky that my LDS is one of them. They have a vise to hold them down while installing/removing the valves, and even made an inspection light to fit the narrow 1/2" tank opening.
They do grump and complain about having to work on "Neolithic scuba gear", but still do it..