Vintage Double Hose

When assembling double-75 cf tanks, what is the proper torque for the manifold nuts?

Thank you,
Mikhail

O-o-p-s! I meant 72 cf of course (not "75").

Oops, double post

Tight, never saw a torque spec, none in the Navy service procedures either. I use two 12" crescent wrenches at the same time.

PSI for standard tank valves recommends 50 ft. lbs. I think that is a ridiculous spec.

"ridiculous"? To low or to high?
Thank you, and sorry for the confusion.
Mikhail

too high

captain wrote: I use two 12" crescent wrenches at the same time.

Captain, is that as in one on the nut and one to hold the center yoke in position, or two on the nut 180 degrees from eachother?

One on each nut. Lay the tanks on a flat surface with either no bands or the bands loose. Position the center section and tighten both nuts at the same time by pulling on one wrench and pushing on the other. That way the center section will not tend to twist out of position.

kgehring wrote:too high

I agree, hand tight and then just enough more so that it can not be removed by hand.

Remember the seats are made of brass, over working the seats by extreme tightening will cause the brass to harden and become harder, and the valve harder to get a seal over time, this will also cause the brass inserts to become brittle. So the least amount needed to get the job done is the best. Same principle as in reloading ammo and reusing brass. I have in the passed annealed seats that were removable from the valves to make the brass soft again, then reinstalled them. As I know some will try this, be careful , removal can be tricky and not ruin the seats. They screw in. The secret is using the correct fitting screw diver blade. It has to fit the slot in width and depth, be sure the end is flat and square, and the larger the handle the better. The slots are on the leading edge,take care, lightly tap the screw driver handle when it is in place, to help break loose the seat. As I remember I had to grind a large screw driver down to size, keep the tip cool as you grind, dip it in water often, don't mess up the heat treating . -------Ron

Thank you very much for the useful and detailed tips.
One question regrading tightening the manifold nuts without the bands installed: is the brass manifold strong enough not to break when handling the tanks assembly without the bands? Of course I will trust your experience, but intuitively it looks like it may break.
Thank you,
Mikhail

Just pick them up evenly using one hand at each end of the manifold or just slip the bands on with them still laying flat

O.K., one of the guys called and asked that I explain how to anneal the seats after they are removed. So here is how I did it in detail. Items needed are two metal trays, small is fine, and easier to handle in the process, the seats are not large. Just be sure one tray is deep enough for water to completely cover the seats when dropped in to them. Of course the water in they tray has to be above the top of the seats, no matter which way they may fall into the tray.
Place the second tray, (I used a small cookie pan with no sides) on a brick or something that heat will not hurt and place the seal with the thin side down in the tray. They are cone shaped. Place the seal as near the edge of the tray as you can.
Use a torch, propane is fine, and heat the seat to a cherry red, be very careful and do not over heat or you will melt the thin edge. When you have heated it cherry red, tilt the seal into the tray of water and let it cool. You can do both seals in the same tray of water with no problem.
Do not use needle nose to pick up the seals or any thing to push or drop the seal into the water, as the metal of the needle nose, or what ever, will cool the part of the seal it touches to a cooler temp then the rest and you will get a difference in softness. Place the seal one at a time on the sheet and drop one at a time in the water. this should do the trick. and hope this helps.
I can not remember that make of manifolds Newman and I were using at the time, that was many years ago, when were having sealing problems with the doubles, on the jobs we were doing. ---Ron

I forgot to add one thing. Keep the torch moving when heating the seal, slow down on movement to heat up the seal, but do not stop moving the torch. Just move it slower to heat up the seal. If you stop or move the torch to slow, you could ruin the seal. The instant it turns red on the thick part of the seal dump it.
By the way who ever called, your name was garbled, and I did not understand it. My helpful 5 year old Gt. grand son erased the number, I managed to save the tape. Best and Thanks to all, Keep Diving---Ron