bladder tank be made into an air tank?

[chopped]

I have just had to replace a slowly leaking bladder tank that is in fairly good shape other than the slight air loss. I was wondering if anyone had converted the tank into portable air storage tank?
My plan would be to remove the bottom nipple so as to get something in to rip the air bag open as much as possible.And then just add some fittings to the bottom.I see it says operating pressure of 100 lbs.But assume that it could stretch up to about 120 possibly without failure.
Any ideas? Oh Also a big thanks for the replies on my posts about the water pump they really helped me.

[mrcaptainbob]

I would be wary. Since the bladder was compromised, water got to the steel. Not knowing how long the water was in contact with the metal there's no way of knowing if rust got to it enough to weaken it. You can remove the bottom flange and with much difficulty pull the old bladder out. I use a razor knife to slit the remains away enough so at to pull it out in pieces. I'd be reluctant to trust it even if I tested it at 140. I wonder what the wall gauge is compared to a real compressor tank. Another issue, and probably the biggest one, is that the bottom flange that holds the bladder in is plastic. That alone is untrustworthy.

[pat32rf]

I've had great luck using old propane tanks. I fill them with cold water then stick a 400psi gauge on them and put them in the hot sun. Once the pressure reaches over 300psi I drain and use them at 150psi max air pressure. (normally 110psi) I make sure to install a condensate drain as well. My water tank is designed for about 80psi

[sixdogs]

Just my two cents but I would not do it. If it works, you save $35. If it doesn't work you could lose your life. The real McCoy only costs a few bucks.

[stevensg56]

You are getting very bad advice about using any kind of tank that is NOT specifically designed to be a pressure vessel. I have a friend who tried this idea and when the pressure relief valve failed the old tank went right thru his house and whipped out his fireplace. Many thousands of dollars of dammage. Its not worth the risk to try to save a couple of bucks, You may end up dead. Do a quick search and Im sure you will find other simmilar stories.

[SensibleNick]

Anyone here a Pneumatics specialist? *Nick raises hand

I don't want to piss on anyone's chips, but Buffer-tanks such as the one you're describing ARE specifically designed as pressure vessels. Not only that, but they can usually take a far greater beating than air compressor tanks.

A compressor's tank failing is extremely rare. Tanks usually go pourous without ever getting weak enough to "explode". Most air-tank breaches are a result of people messing with safety valves, using innapropriate tanks (water storage tanks etc) or in some really rare cases, using the wrong oil in the compressor itself, (it can lead to an explosive gasseous mix in the tank with obvious results) or just being plain incompetent idiots. What ever the cause, it always results in people running about screaming about how the only thing that can withstand compressed air is a compressor tank. These are usually the same people who insist upon deflating bike tyres for international flights. *rolleyes*

First things first: From what I understand you simply plan to fill this tank at the pressure your exising compressor can supply, to enable to you to lug a little air around? Unless the tank is pretty large, it'll be little use for anything other than topping up a tyre...

A compromised bladder shouldn't cause a pressure vessel any issues when compared to their Compressor counterparts. Compressor tanks spend most of their time with water swilling around in the bottom: A stunning amount of people never remember to drain them.

There are however some other things you should consider. If you slash the bladder where it sits, you'll end up with rubber contaminating your airlines, or even flapping over the outlet and blocking it. There will be a place where the bladder was put into the vessel itself. Probably a radially bolted plate. Remove the bladder that way, and inspect the vessel. Use the neck of the bladder as the gasket to re-seal it.

As you'll be filling with a known pressure, you've got one base covered. I'm guessing you plan to max out at 150psi? Assume you're going to fill with the max pressure your compressor will supply - so when you forget to adjust the pressure or want to push it that "little bit further" you've already tested your limits.

Follow pat32rf's text-book-perfect testing technique. As you know your max operating pressure, I'd only bother testing it to 150% of the pressure you intend to use.

**************

Someone has said "the end cap is plastic", but I'm not sure where that info was stated. If it IS plastic, then after consider the amusing effect of dropping the tank cap-end-down on a pointy stone, Shelve the project.

[Egon]

Just to add to Nick's comment's do the first pressure test with the tank filled with water.

[SensibleNick]

Just to add to Nick's comment's do the first pressure test with the tank filled with water.

'Tis the standard way. I love the way as prescribed by pat32rf though: to use the sun to heat the tank and build up the pressure that way I've always done it using a narrow piston and a weight system... Sun is FAR more simple

[J_J]

Just to add to Nick's comment's do the first pressure test with the tank filled with water.

Sure, some have used the water tanks as air pressure tanks, and some have got away with it, and some have been hurt, and I bet probably some body has been killed with a ruptured tank.

Who knows what the test pressure was, considering that the max water pressure a home owner would see is maybe 60 lbs, which is the highest cutoff on the regulator

And if it does burst, just what everybody needs, a high powered douche

[Egon]

Who knows what the test pressure was, considering that the max water pressure a home owner would see is maybe 60 lbs, which is the highest cutoff on the regulator

Thats why you do a hydro on it to 50% above the rated pressure of the tank. It's pretty standard procedure in industry.