Materials for the pressure tank

[cstranc]

I am trying to figure out what material to use to make the pressure tank for my ballast system. My thought was to make the pressure tank fairly large. This way it would double as ballast (instead of adding foam). I could also pump in 100psi air instead of using propell all the time.

I went off to buy some 3" PVC piping and the store got all upset when I said that I would use a pressurized gas. They said it would not fail gracefully (explode like a grenade) and could hurt people.

I have some old 3" copper pipe from renovating the house, but it's so darn heavy!

What do people make their pressure tanks from?

Many thanks,

Chris

[Rogue Sub]

you have lots of room

you have lots of room right? Have you thought about a paint ball gun air can?

[cstranc]

Well that's a cool idea.

Well that's a cool idea. I shall go look.

Thank you.

Chris

[Guest]

Aluminium is almost a third

Aluminium is almost a third the weight of copper. More difficult to join though- know any tame TIG welders?

A lot of pressurised anti-perspirent cans are now aluminium, and I reckon they would take a lot of pressure. Best to hydraulically test one to at least 50% above the pressure you want to run at.

Andy

[subshop]

pressure tank

clippard makes s/s air cylinders rated to 250 psi. neil

[Rogue Sub]

Generaly when we test a

Generaly when we test a system that we have broken into we have two pressures we will test it to. When a system is first installed or a piece we installed has not been bench tested we will press up to 130% NOP. Otherwise we will usualy press up to 100% NOP. After we reash test pressure we will perform a 30 min wait while maintaing Pressure. After 30 min we will check for leaks. With water systems this can be simply seeing water drip from fittings but, for air systems we use a leak down tester( basicly soapy water) and check for bubbles.

Well thats how we do it on the real thing. I suspect it would work on yours as well. Just stand clear of your project while pressing up especially in an untested prressure barrier.

Kevin

[anonymous]

Don't be put off PVC

Don't be put off PVC pipe too soon.

There was a useful discussion on here a few months back and someone pointed out that PVC pipe has qute a high test pressure (Check the manufacturers data.)

I would be cautious about filling it with air only - a lot more stored energy than air and water.

Talking about useful info on here I've been following your level control experiments with great interest. When is the next installment!

Davy

[robse]

Cheap, light.. & easy

I used an old fire extingvisher.. The volume is big, it's rated to 36 atm. and at the recycle-station the guy charged me only... 1 beer.

Images here:
http://www.robse.dk/pages/SSBN/ElecPres.asp (Works now...)

[himszy]

You need to buy Schedule

You need to buy Schedule 40 (or 80) PVC(u) pipe. It's pressure rated and depending on the type and environment it can deal with pressures of 800psi+. Over here 'normal' PVCu pipes are designed to store +/-60psi however you can buy some 6/10/16 bar pressure rated easily.

Also, the theory that when you 'blow up' a PVC pressure tank it'll be like a grenade isn't very accurate. It generally tends to stay in large pieces and they don't go very far. You can be stand 3 feet from one and it (is very unlikely it) won't cut you. Any shrapnel can be contained by using a cardboard carpet tube (large ID diameter).

If anyone goes now the route of using a PVC(u) pressure tank research should be done rearding the effect temperature can have on the material.

Michael

[cstranc]

Andy,
Unfortunately I don't have

Andy,
Unfortunately I don't have any significance experience with aluminum. Certainly nothing I would trust to a pressure cell.

The difference in weight between aluminum and brass astounded me. I was playing with tubing for torpedoes. Brass tubes sank, same size aluminum just floated... Hmm. Maybe I shall be doing aluminum pressure cells, and if they explode I'll say it was part of the plan

Neil, Kevin, Davy, Robse, Michael,
Thank you all for the info. I suspected this might take some thought and investigation. I certainly have lots to think about and dig into.

Davy,
Yes, I kinda stalled on the pitch control thread and my build thread. It's not that I have been idle. I have been going through all 23 pages of the R/C Modeller forum. Some great info there.

I also spent an evening getting a web server running on my machine so I could post videos there. I'm afraid my video is pretty boring. Oh look the sub takes a minute to dive in a test tank. Yawn.

Still it's time to start writing again.

[Rogue Sub]

i got a new idea

i got a new idea for you buddy. Use one of those brazing MAP gas cans and rig a small ignighter. That way when you surface it shoots flames OHHH YEAH. Itll make that fideo more intresting for sure!

[cstranc]

Please don't give me ideas.

Please don't give me ideas. I had been thinking of Shkval rocket torpedos using the little rocket model engines. I had a prototype, but I could not find it after the first launch! 5 sets of eyes following it and it still escaped....

Now I read in one of the earlier posts about a rocket engine based missile that ended up cruising around in the neighbors house for a while...

Oops.

Maybe propell is safer.

[Rogue Sub]

hey im a fan of

hey im a fan of the crazy stuff ive always wanted to do a typhoon/red october sub powered by about 8 bow thruster or equivelant
but thats a different thread

[Rogue Sub]

Hey Chris

Just checked with my

Hey Chris

Just checked with my uncle who is a plummer and he says that he has taken sch 80 PVC to 100 lbs before and also said it would probably hold 300 but dont go over 500. If your only going to 150 or so i say buid the rig and try it out itll prob work fine and be cheap.

[cstranc]

I was out at my

I was out at my favourite outdoor store and found:



1 litre aluminum bottle, with a o-ring seal. They said it was for carrying fuel or something.

I think I should be able to drill through the cap to install a piece of copper pipe. Then I would attach the fill valve and clippard to the copper. This way I would not have to weaken the aluminum at all.

That's plan #1.

Idea #2: A while back I saw a CO2 blower for cleaning your computer. It was quite cheap and came with two cylinders of gas. A servo could easily generate the force and travel for the valve trigger.

I thought at this cost and weight I could install two and have a redundant system.

I was curious how many times a fresh CO2 canister could fill my rather large ballast tank, so I tested it. It seemed to work fine when the cannister was not under water. But when started to blow the tank with the CO2 device underwater I had instant ice buildup that caused stuff in the line to the tank to block.

That was not too effective.

I think it's the venturii principal, when the gas expands quickly it cools. In this case it is expanding from 800psi to straight atmospheric pressure and that generates a lot of cooling.

Maybe a regulator would resolve the issue.

Does anyone use CO2 on their boats?