DIY pressure pot from scratch?

[julianf]

Ive just been looking at pressure pots, and theyre not as cheap as i remember them being.


If the bottom valve needs to be replaced anyhow, as per brightspark's recommendations, then, so far as i can tell, the things for sale are a tank, a couple of ball valves, and a hose - which seem very easy to diy?


Is that the case?

I have a large bore ball valve somwhere. Im thinking that, if i purchased a weldable nipple for it, i could use that as the fill hole. Another 1/2" nipple for the pressure feed to the top of the tank, and one of the media valves mentioned in other threads, and it job done, right?

 

[Shox Dr]

Tere's a few builds on here, mine been one, used black iron fittings, and ball valves.

Mines in this thread. http://www.mig-welding.co.uk/forum/threads/diy-pressure-pot.15311/

 

[armalites]

Someone on here built one out of a old gas cylinder but used a proper poppet valve. Cut the top of the cylinder and inverted it.

 

[diogofcr]

I made one out of a old gas cylinder, drilled a hole, welded and inverted it. I can explain my diagram and I can post pictures of the incomplete project. If you want I can also post more pictures tomorrow of the almost completed project (needs painting). Check:

http://imgur.com/a/n67Xx

In the pictures I posted the top part is not complete, but it is now, and I can add the most recent ones, I just need to take them.

Things I would change in my design:

The top valve is 3/4" but the part (T fitting) that connects to the gas cylinder is 1/2" so it takes really long to fill, if I would do it again I would use a much bigger fitting so it would fill up faster.
I don't know how I could fix this but the bottom part of the pressure pot is almost plain, it isn't very steep so I believe lots of abrasive gets "trapped" inside, if the gas cylinder was like a funnel at the bottom it would be more efficient I think.

Part List:

Top Part of the pot:
3/4" M/M Ball valve
3/4" to 1/2" F/F reducer
1/2" Male BSP Tee (one end welded to the gas cylinder)
1/2" F/M tube
First 1/2" Female Tee, one end connected to the tube, another end to another Tee of the same kind (through a 1/2" M/M fitting), and the other end with a euro connector fitting (that will connect to the compressor)
Second 1/2" Female Tee, one end is connected to the other tee as said above, the other to a safety valve, and the other to a 1/2" valve that is connected to a 3/8" normal air hose that is connected to one end of the bottom part Tee (it will push the abrasive with air)
Instead of using 2 equal Tee fittings I could have used a 1/2" Female Cross fitting but I couldn't find one in my town but it would use less parts.


Bottom Part of the pot:

3/4" M/M fitting
3/4" F/F ball valve
3/4" to 1/2" M/F reducer
1/2" Male BSP Tee

Sandblast hose:
3/8" sandblast hose
Hose tail (3/8"), 1/2" Male BSP fitting (the one to connect to the bottom part on the pressure pot)
Hose tail (3/8"), 1/2" Female BSP fitting (the one for the sandblast gun)

Sandblast gun:
Hose tail (3/8"), 1/2" Male BSP fitting
1/2" Ball valve
1/2" M/M fitting
A kind of a 1/2" nut thing
Car spark plug (will change this)

 

[brightspark]

here's a couple of mine. fast fill quick release filler

 

[diogofcr]

Total price would be like 102 euros or maybe a bit more. I got lots of free parts so I didn't pay that much and I also got a new and empty gas cylinder for free because my neighbor works in the gas company "expiration date" is 2030. I traded an empty old one for an empty new one

 

[brightspark]

Total price would be like 102 euros or maybe a bit more. I got lots of free parts so I didn't pay that much and I also got a new and empty gas cylinder for free because my neighbor works in the gas company "expiration date" is 2030. I traded an empty old one for an empty new one

the expiry date wont make any odds if u have carved it and welded it up

 

[julianf]

brightspark - how do you make those fillers? i get that the bar clamps down, but how is the actual seal done?


you know, in all the threads ive looked through, you're the prime source of information? : )

 

[brightspark]

I make a round recessed boss on lathe about 3inch diameter. cut out the top of bottle and weld on the boss then turn a plug to fit in to it 2 x 1 inch pillars are welded on to the top of bottle drilled ant tapped 12mm then a bar is drilled to fit the pillars and slotted on one side to pull away to remove the plug for filling. it has a threaded hole in the middle to tighten a bolt that holds down the plug il get some piccys of it as its difficult to explain

 

[Maker]

Those claw connectors look serious, how big is your compressor Brightspark?

 

[brightspark]

the plug is stepped and an o ring fitted in

 

[brightspark]

I use the c couplings on both pots, 0ne comp is 28cfm on a 3mm jet and the mobile is 90cfm on a 6mm jet . easy and quick to fill using a large funnel with the outlet shortened

 

[julianf]

My compressors are

1x 14cfm unit that's right on the edge of what i can pull through a 13 amp fuse
1x unknown belt drive with a 2kw motor (that one i was fixing up recently)

Im assuming those two combined will result in slowish work, but usable? (the venturi style gun is just useless...)

Im wanting to do my defender 110 sills and b posts before going to galvanising. It wont be a rush job but i dont want to be spending all day on them, else i may as well have paid someone else to do them.


Thank you (brightspark) for the photos of the loading. Im sure i have a large bore ball valve somwhere - im hoping that would last some time, or, if i cant find it, ill make up somthing like yours (or possibly get a weldable barrel nipple, and an end cap)

 

[brightspark]

a 3inch cap is a decent size to use probnably of an old heating oil tank if u cant turn one down on a lathe

 

[julianf]

Ive had a look, and i have a couple of 1.1/4" ball valves.

They look wide enough that i can put a decent sized funnel in/through them and the abrasive will never touch the sides.

Sadly all my weldable nipples are 1.1/2" so ill have to fork out about £7 (with postage) for one of them!

The media valve on the base - youve linked to them before (not that i can find the link right now), but worth buying one of them, or go with another one of these 1.1/4 ball valves, and a suitable tee? (which might cost me more than the media valve - just i have the ball valves)


One thing that i dont 100% understand - the regulator. I thought the plan was to just try and whack as much air through as possible?

 

[rtbcomp]

This is my filler



It's the top half of a 7Kg? gas bottle with a 1-1/4 BSP boss welded on for a gate valve.

It wasn't all that brilliant to be honest, if you can fit a proper pop-up valve it would be better.

 

[rtbcomp]

Flow depends on pressure.

 

[julianf]

It wasn't all that brilliant to be honest, if you can fit a proper pop-up valve it would be better.

Ill look up the cost of pop up valves.

What was the issue with your setup / my proposed setup?

 

[brightspark]

Ill look up the cost of pop up valves.

What was the issue with your setup / my proposed setup?

wouldn't bother with the hassle and cost of a popup valve just a big quick release filler hole and a large funnel .your not blasting the 4th bridge

 

[julianf]

Ok. lll go and measure up my proposed tank in a bit, and post up here, to make sure im not wasting my time.