Doubles Tanks Must Have Same Height???

[kidsdream]

ditto to what Jeff said.



Do you have to request same tanks heights from the factory? No. Tanks are molded from molten metals. Just buy two tanks the same vendor and model. Such as Luxfer S80.

Tanks are not "molded" from molten metals to make the tank shape and create the neck. After the metal is roughly processed, it is then formed into shape under high pressure. Then the the end is machined and the threads for the valve are cut.

 

[jonnythan]

Al tanks are stamped into shape from a solid, cylindrical aluminum billet. I'm not sure how steel tanks are made.

 

[rongoodman]

I've heard of problems with E130s being significantly different in height. I have 3 Worthington LP85s and just picked the 2 with the closest serial numbers to double. No difference in height noted.

 

[Tavi]

Al tanks are stamped into shape from a solid, cylindrical aluminum billet. I'm not sure how steel tanks are made.

From PST's website
http://www.pressedsteel.com/page10.html

 

[oxyhacker]

If the shop is telling you you got to pay extra for matching tanks or that it is dangerous to dive ones that aren't perfectly matched then they are FOS and you should go elsewhere. But the comment that using unmatched tanks will strain the manifold is just the kind of idiocy we all come out with occasionally when we don't think through what we are saying.
Steel tanks can vary quite a bit in length - Leadking mentioned +or- .250 for Worthingtons in an earlier thread, which means in the absolute worst case one tank could be 1/2" longer than the other. But when this is a possibility, good tank distributors are happy to supply matched tanks when ordered as doubles, and your shop should be equally happy to provide such without extra charge. Otherwise, the only disadvantage to mismatched tanks is they won't sit exactly level. This will be hardly noticable except in extreme cases. So if you are going shopping for doubles and buying the tanks off the floor, take along your yardstick. If you don't have several to chose from, or are using used tanks, just double them up and go diving.

 

[Walter]

Technically the tanks dont have to be the same height. As long as you have roughly the same diameter for the bands, one tank can be 10" shorter than the other.

Not even that if you make your own bands.

 

[Pook-60]

Howdy Folks

First...thank you. I stepped away from the computer a bit and was quite surprised to see all the help you've offerred. I've learned more in this small thread about steel tank doubles than I knew was out there.

I can offer one point of clarification: the LDS didn't talk about any extra charge...just the requirement for matching tank height at the factory. Doesn't mean that an extra charge won't come up but you've addressed that for what it is.

Thanks again for taking the time to write...since I've joined the "Board" you all have done more for my practical dive education than any dive class I've taken thus far. I hope to return the same.

Dane

 

[JeffG]

As it is an opinion, I suppose it doesn't have a degree of accuracy.

In so much as you are calling someone an idiot just for following the recommendations of his cylinder supplier, I disagree with you.

Well, walking into a dive shop and having someone recommend a "device or gear" that they haven't used or understand the concepts tells me volumes. The answer given by the monkey is total BS and since he was able to tell someone that nonsense with a straight face tells me that I wouldn't trust his opinion on anything.


So you can say that what I said was opinion and doesn't require any degree of accuracy, but quite frankly it doesn't change the fact that the shop monkey is an idiot and is doing a disservice to his customers. and so...I disagree with you.

 

[dhampton82]

You could, but you would have a hell of a time with balance issues as the Catalina is a little heavier than the Luxfer.

Oh, and congratulations on the quitting smoking!

According to TDL tank specs -

Catalina is .26" taller, .22lbs heavier, and .4lbs less bouyant

 

[Meng_Tze]

Perhaps I'm not being clear. I'm not saying that close enough probably isn't good enough. I am saying that the following quotes are inaccurate:

Hmmm... quote inaccurate? It seems we are mismatching some other things. The factory does NOT run special orders to match things up.... a distributor/reseller may give you that option, yes. Seapearls is not a manufacturer. So my quote at least IS accurate.

But this, as usual, is turning into something else than intended.

So to the OP: tanks do technically not have to be matched up. But if you want to have an easy life with doubles, it makes sense to have two of the same tanks that can be doubled up easily.