Problem welding air compressore tank

[Seadog]

My compressor has a test rating 50% above operating pressure.

 

[zeppelin builder]

i would get someone that can weld to do it
6013 will be just fine , propane cyls despite there chunky appearance are only around 2mm thick , best practice is to weld a compensating plate on first "think big washer about 6mm thick prepared so that the pipe is being set into the countersunk hole ,that way you get fusion into both surfaces and can leave a bit more of a fillet weld
safety of course should be seriousely taken
on any used fuel vessel , should be wet steam cleaned and purged during welding

glass fibre propane vessels are fairly common we had them run off a rig in denmark as we were using them for pre heat
on welding ops not realy a good idea !

 

[daleyd]

My compressor has a test rating 50% above operating pressure.

Same as mine - I've never heard of anything as high as 3 x pressure for testing anything, certainly pipework was always 1.5 X working pressure (Though it's been an age since I was involved in anything to do with that). I would have thought that testing stuff to 3 X would place completely unnecessary stresses on fittings, welds etc.

 

[Memmeddu]

Same as mine - I've never heard of anything as high as 3 x pressure for testing anything, certainly pipework was always 1.5 X working pressure (Though it's been an age since I was involved in anything to do with that). I would have thought that testing stuff to 3 X would place completely unnecessary stresses on fittings, welds etc.

TBH it's what I'll do on a project .
I will use a CO2 bottle which is tested for 300MPa (300bar ) , I'll drill a hole and weld an ½" NPT female fitting to it .
Then I'll test it at 30 bar but it will work at maximum 10 bar
I think that I have enough tolerance for mistakes (just little bit tolerance but always better than no tolerance at all)

 

[Cobbler]

TBH it's what I'll do on a project .
I will use a CO2 bottle which is tested for 300MPa (300bar ) , I'll drill a hole and weld an ½" NPT female fitting to it .
Then I'll test it at 30 bar but it will work at maximum 10 bar
I think that I have enough tolerance for mistakes (just little bit tolerance but always better than no tolerance at all)

Can’t you use the existing thread in the co2 bottle, then you avoid any stresses that arise from the welding. There would be no need to retest the bottle then. I’m wary of drilling & welding any pressure vessel if it can be avoided.

 

[Memmeddu]

Can’t you use the existing thread in the co2 bottle, then you avoid any stresses that arise from the welding. There would be no need to retest the bottle then. I’m wary of drilling & welding any pressure vessel if it can be avoided.

Stupid thread pitch
It's metric on the bottle and I need NPT ½" but it's not a bad idea if my local machinist has ½" NPT tap .
He should use a piece of M30 all thread and drill and tap an hole in the centre
I should always drill a moisture release hole in the tank itself

 

[the snooper]

Either drill and tap it or get someone that can weld properly to do it for you, if your weld fails that will come out like a bullet

 

[Shox Dr]

Threads like this always remind me of the joke;

A bloke jumps out an airplane, with no idea how a parachute worked. As he hurtling towards the ground, he sees another bloke sat on a gas oven...
So he shouts over "Do you know anything about parachutes?"
"NO!" came back to reply. "Do you know anything about Gas ovens?"

 

[Capt]

Are you Italian?

yes
no im not italian is that a problem ??

 

[mike os]

yes
no im not italian is that a problem ??

Nope not a problem, just curiousity

 

[daleyd]

yes
no im not italian is that a problem ??

Memmeddu is also from Italy, hence the question. You may be neighbours !! (He has some good tools if you need to borrow any...)

 

[Memmeddu]

yes
no im not italian is that a problem ??

No problem

Nope not a problem, just curiousity

Exactly

Memmeddu is also from Italy, hence the question. You may be neighbours !! (He has some good tools if you need to borrow any...)

Well on this I would say something.
Tools are like wives , no-one else than you can touch them .

 

[premmington]

Can’t you use the existing thread in the co2 bottle, then you avoid any stresses that arise from the welding. There would be no need to retest the bottle then. I’m wary of drilling & welding any pressure vessel if it can be avoided.

Not a stupid suggestion at all - I did this with a full size empty O2 bottle years ago.

The issue you got using an empty gas bottle is draining the condense off. I had to mount the O2 bottle "upside down" and had a collection of Galv pipes to make a manifold with a drain port at the bottom of it. None of this was ideal...

Air receivers have ports at the top/middle for air inlets/outlets and at the bottom for condense draining for a reason.

 

[Capt]

I'd like to avoid to weld this kind of stuff TBH.
Expecially without tools suitable for the task.
Working with compressed gases is really dangerous ,few people do that even professional welders many times refuse to do things like that .
In this case welding would even be not necessary .
Using 6013 for most of application is an Hazzard ,and critical stuff like a pressure vessel could even translate in suicide to my eyes .
Personally I should have to do something similar but I'm able to get rid of most of the issues of the case + test the weld safely .
I'm pretty confident that you would not be able to work safely or obtain a good weld with your actual equipment and materials .
I would like to make you aware of the hazards involved in what you're trying to do .
1st despite the fact many people use propane tanks as air tanks , it's not the better idea , but you didn't blow up so you managed to clean it up from the LPG residue .
Contamination of the base metal would make difficult to weld on it
At least in Italy those tanks are rated for 30Bar ,more than enough for the purpose .
2nd it should have a 3/4" NPT female thread , left or right hand depends on the manufacturer.
So wouldn't be necessary to weld a piece of pipe on it because there are correct size nipples available .
3rd weld on one of this tanks expecially nearby where the valve is fitted could cause to melt safety pressure release caps , and could be dangerous once pressurised
4th a piece of galvanized pipe (zinc coated) gives problems ,causes porosity , contaminations ,slag inclusions and others frustrating situations .
5th the electrode you can't weld critical stuff with 6013 , you need correct stored and baked 7018 , good metal preparation , correct manipulation etc
6th last but not least , you have to test the tank after welded , once it's cooled down to ambient temperature , you must fill the tank with water and use a pump to take the pressure up to 1.5 times the working pressure and leave it in pressure for 24-48 hours and then check if the pressure went down .
NEVER NEVER PRESSURISE A VESSEL WITH AIR FOR TESTING ,IT COULD BLOW UP INJURING PEOPLE OR KILLING THEM

I'm pretty sure that your welder wouldn't run 7018 ,the tank is already compromised .
Cut it and make a barbecue .

Now I will tell you how I would proceed .
CO2 fire extinguisher bottle
Once emptied remove the valve body it should have an M30 thread .
Go to the local machinist and ask him to make you an adapter .
If too expensive you may consider to buy a steel fitting ,chamfer the bottle neck put the fitting inside and weld It with vacuum sealed 7018 H4 R .
Pressurise the bottle using water and a manual test pump if it doesn't blow open (it will not blast because you're using water and not air) after reaching 30 bar it should be able to contain 10 bar of compressed air

thank you for your answers
i appreciate your explanation
and i agreed with you
by the way the bottle i want to use for air compressore project 8BAR MAX for hobbies paint
blow tires
blow dust on my garage ....

i couldnt find a fitting thread so thas why i i used it
also i have a fire extinguisher (9kg)
i couldnt finde the right thread

maybe i can measur it and help me to find the right thread online s i can buy it.....
thank you

 

[Capt]

thank you for your answers
i appreciate your explanation
and i agreed with you
by the way the bottle i want to use for air compressore project 8BAR MAX for hobbies paint
blow tires
blow dust on my garage ....

i couldnt find a fitting thread so thas why i i used it
also i have a fire extinguisher (9kg)
i couldnt finde the right thread

maybe i can measur it and help me to find the right thread online s i can buy it.....
thank you

 

[Memmeddu]

First advice throw away that caliper
It's hard to read because its cheap construction ,I used to have one of this but during technical school I've had to understand that's pointless , measurement instruments has to enough good because it's the base for every work and project .
It seems to be ¾" or even a metric thread , you'll probably have a tap and die set from Lidl like I do .
There's a thread pitch tool , which will say you the right thread
The thread seems to be not tapered so I'd exclude NPT
Strange but at least it's right hand so wouldn't be difficult to find
Give me few minutes I'll search if we can figure out the exact thread pitch and if we can find a correct nipple on eBay

Edit the gpl tank or maybe better say LPG since we are in this foreign forum is surely ¾" right hand so you should easily find it
Buy both NPT and BSPT on eBay
The other one is from the co2 fire extinguisher and it's surely an M30

 

[Capt]

First advice throw away that caliper
It's hard to read because its cheap construction ,I used to have one of this but during technical school I've had to understand that's pointless , measurement instruments has to enough good because it's the base for every work and project .
It seems to be ¾" or even a metric thread , you'll probably have a tap and die set from Lidl like I do .
There's a thread pitch tool , which will say you the right thread
The thread seems to be not tapered so I'd exclude NPT
Strange but at least it's right hand so wouldn't be difficult to find
Give me few minutes I'll search if we can figure out the exact thread pitch and if we can find a correct nipple on eBay

Edit the gpl tank or maybe better say LPG since we are in this foreign forum is surely ¾" right hand so you should easily find it
Buy both NPT and BSPT on eBay
The other one is from the co2 fire extinguisher and it's surely an M30

grazie mille provero ad andare a bricoman
e comprero questo https://www.bricoman.it/it/nipple-ridotto-ottone-cromo-1-2-x-3-4-12091788/

ma dovo vedere dopo se va perfetto con un raccordo f-f 1/2 di ghisa

 

[Capt]

First advice throw away that caliper
It's hard to read because its cheap construction ,I used to have one of this but during technical school I've had to understand that's pointless , measurement instruments has to enough good because it's the base for every work and project .
It seems to be ¾" or even a metric thread , you'll probably have a tap and die set from Lidl like I do .
There's a thread pitch tool , which will say you the right thread
The thread seems to be not tapered so I'd exclude NPT
Strange but at least it's right hand so wouldn't be difficult to find
Give me few minutes I'll search if we can figure out the exact thread pitch and if we can find a correct nipple on eBay

Edit the gpl tank or maybe better say LPG since we are in this foreign forum is surely ¾" right hand so you should easily find it
Buy both NPT and BSPT on eBay
The other one is from the co2 fire extinguisher and it's surely an M30

i have tap and die set of parkside
but i dont know if the are npt or bsp
and i dont know which one to use for 1/4 or 3/8 .... i didn't study this stuff
on the manuale they show hmjusy measurment are different .......

 

[Memmeddu]

grazie mille provero ad andare a bricoman
e comprero questo https://www.bricoman.it/it/nipple-ridotto-ottone-cromo-1-2-x-3-4-12091788/

ma dovo vedere dopo se va perfetto con un raccordo f-f 1/2 di ghisa

Non è permesso dalle regole del forum scrivere in italiano

Translation
Thank you so much , I'll try to get a ¾" to ½" reduction from Bricoman.
I have to figure out if it fits the threads ,if it'll do I'll solve the problem with a cast iron female/female extension .

My answer it's not allowed writing in Italian on the forum.


I'm pretty confident it will work

 

[Memmeddu]

i have tap and die set of parkside
but i dont know if the are npt or bsp
and i dont know which one to use for 1/4 or 3/8 .... i didn't study this stuff
on the manuale they show hmjusy measurment are different .......

It would be helpful for the co2 bottle