LP 72's

[Packhorse]

I have just won an auction for 3 72cf tanks.

I have not taken delivery yet so dont know the specs but from what I gather they are all pretty much the same regardless of manufacture. Is this correct?

Now I assume these are 2250 psi tanks ( we dont use the +10% in NZ) but I am wondering what most users pump these up to. 2500psi sounds reasonable given the + rating but does anyone go higher regularly?

Do these tanks fail hydro often or is it pretty much a given that if they are rust free they will be OK?


Now, when it comes to doubling these up what bands are prefered and what valve centres do you end up with?


Thanks

 

[Packhorse]

A pic....

Looks like they may be galvinsed? Is this likely?

 

[OldNSalty]

They should be galvanized and for your sake, lets hope so. I think the only ones that weren't had a plastic coating over them but even those were usually galvanized under the coating so in that regards you should be OK. As for overfilling, I put 2500 in mine when I can get someone to do it.

 

[herman]

Those are galvanized but only on the exterior. It is possible for them to look fine on the outside and be in bad shape on the inside....not likely but possible. It is common for steel tanks to need rust on the inside to be removed. A light coating of rust, known as flash rust is common and no big deal but heavy rusting can prevent a tank from passing. The first thing you need to do is to open them up and check for internal rust....and remove the boot from the Healthways, it makes rinsing impossible, holds water and hide any rust that is forming.
The + rating is only valid for the first hydro unless recertified...at least here in the US. + recerts are hard to come by here. 2500 should be OK if you can find a shop that will do it but I would not suggest going higher, if you need more gas, get bigger tanks.

As for doubling them, you do realize they are 6.9in diameter tanks which is a smaller diameter than most current tanks and will require 6.9 in bands. They can be had but are not as common these days.

 

[Jim Lapenta]

Some also had an epoxy type coating inside that can degrade if the tanks were not properly cared for. Does not necessarily mean they are bad and some can be tumbled out but I had one that was left on the tumbler for 2 days and still did not get all the coating off, OK for air but I was setting these up for doubles to do PP blending for nitrox and trimix. Luckily the shop owner had an extra one he traded me even up for. All it cost me was a vis to do the swap. But they are great tanks and make a wonderful set of warm water doubles or for those times when 95's and even my lp 85;s are just not needed.

 

[DA Aquamaster]

They do appear to be galvanized. As noted above some were epoxy lined in the inside and that coating had a tendency to develop pin holes allowing moisture in and then trapping it next top the tank wall. It was also a dark color and prevented inspection of the underlying metal so it needs to be removed. How much needs to be removed depends on the inspector. Some want it all removed, others are ok with isolated spots remaining where it is also obviously intact and not obscuring underlying rust. I am strongly in the remove it all category, and that can take a week or more of tumbling with an aggressive media.

Most of the epxoy lined tanks were marketed by US Divers and will be marked USD or US Divers. They also offerred tanks that had a heavy tool dip type coating on the outside and these could be ordered in both galvanized and non galvanized flavors. In most cases you will need to strip the exterior coating for the same reasons - the coating can develop holles but unlike paint, does not fall off so it can trap water and hide rust.

Buoyancy of steel 72's varies a bit from +1.5 pounds empty to about -1 pound. Shoulder and neck profiles also very even amopng tsanks made by the same company so matching them for a set of doubles can be interesting.

6.9" bands are around and someone is usually selling new ones on e-bay for reasonable money. The normal barrel o-ring manifolds from Dive Rite, Sea Elite, Halcyon, etc, work fine, but they are screwed almost all the way in when you are done.

Fill wise, the internal volume is about the same as an HP 100, so overfills don't goive you that much extra gas.

They hold:
64.7 cu ft at 2250 psi
71.2 cu ft at 2475 psi
74.8 cu ft at 2600 psi
77.7 cu ft at 2700 psi
80.5 cu ft at 2800 psi

So in other words they are about equal to a full AL 80 at 2700 psi and are comparable to the average underfilled to 2800 psi AL 80 at about 2500 psi. I do fill them to 2600 on occasion but I don't tend to exceed that.

It's almost unheard of for a steel 72 to fail a hydro test - rust is by far their biggest killer.

 

[rstofer]

You can also get 6.9" bands here:
Reproduction Bands by Rick Green [DHP-RBRG] - $79.95 : Vintage Double Hose!, Your online source for all things related to vintage diving

If you haunt eBay, you can come up with a manifold that will fit but it may not be what a normal doubles diver uses. I have one with a left post and a center outlet. It was designed for a double hose regulator and a backup reg on the left post.

Al 50s are also 6.9" diameter.

Richard

 

[Eric Sedletzky]

I have a set of bands and a manifold for 6.9" 72's.
I ordered the bands/manifold from Leisure Pro several years back and they just happened to be the exact same ones I got also from Leisure Pro earlier to band up a set of AL 80's.
The 72's are skinnier but the bands squeeze in further and the end result is that the distance from post to post remains the same as 7.25" tanks.
At first I thought it wouldn't work but it does.

I love 72's. I have a whole gang of them that people have given me and others I've picked up at garage sales and such. I've never run accross an epoxy coated one yet. I made my own tools to clean the insides...basically wire brushes welded onto long steel shafts that I can put on an electric drill and scrub the rust off without taking off any clean metal. If their really bad inside when I get them I have the hydro place shot blast the inside then they hyrdo them.

I've never had one fail a hydro yet and some were badly pitted.
They're small, but a hell of a good tank.
I love them for beach diving and climbing down goat trails, climbing over rocks to get into the ocean and doing short recon dives to check out a new area.

One thing you have to make sure is that the 72 isn't a really old one, because then it's possible the valve thread is 1/2" tapered pipe thread and not 3/4" straight thread w/ O ring for modern valves. This of course would be if you're buying it online, if you can see it before you buy it then it's obvious.

 

[laguna230diver]

i have one of those 70's heathways too but mines painted. Let me know if you find any awesome prices on bands/manifolds, I have a thread open on that search.

 

[Packhorse]

Thanks for the info guys.

I will be picking these up tomorrow so will let you know what they are like.