Air receiver questions

[monkeymark]

Yep, more questions from me i'm afraid

For those that have built air receivers. Did you weld in a pre-made 1/4" female nipple of some sort (if so, what are they called please?) or weld in some pipe which you tapped to the 1/4 thread?

Also, what sort of fittings do people use? I was thinking of a t piece, both valved with quick release for input/output. A separate pressure gauge and separate release valve.
Sound ok?

 

[normspanners]

I would use 1/2" bsp 'threaded sockets'
But building an air receiver is a little specialized and should be tested.

 

[brightspark]

I would use 1/2" bsp 'threaded sockets'
But building an air receiver is a little specialized and should be tested.

err test a callor gas bottle after its been converted ok . no need for an extra safty valve or a pressure gauge as u allready have them on your compressor .the tanks will equalise

 

[monkeymark]

I would use 1/2" bsp 'threaded sockets'

I can only find stainless steel ones but ill keep looking.

But building an air receiver is a little specialized and should be tested.

Ill keep that in mind. I can pressure test to a degree at work but I know the calor bottles are built to withstand higher pressures than normal air receivers anyway.

 

[Bill Edwards]

I would suggest you buy these http://www.airsupplies.co.uk/weldable-socket-10894.html

They weld in place. Whatever you do make no attempt to buy cheaper ones that don't state they can be welded. They're cheap and not classed as weldable because they simply are not weldable - they're awful!


I would go for a minimum of 3/8" for most applications, ideally 1/2". If you're dealing with large stuff bigger still.
Remember that elbows, T pieces etc restrict flow so the bigger the better. I also like to use larger fittings on the basis that they'll be less prone to damage from knocks. Better to have a 1/2" T piece with adapters to then take it to 1/4" if needed and be left knowing that a knock won't damage anything that isn't easy to replace.

Assuming that when you say release valve you're talking about the safety valve to protect the cylinder from going bang if the pressure gets too much - you must have one of these!
(sorry if I'm stating the obvious and I don't wish to treat you like an idiot, but if overlooked the potential for injury or death is there).
Also, you need to be sure that you're a good welder, use the right materials in the right configuration and depending on what you're doing be sure you are complying with all the rules regarding testing.
Not trying to put you off, just pointing out that you need to be careful with pressure vessels.

 

[wyn]

What i did for one of my air tanks was to machine a fitting with a thread that was "top hat" shaped.
This fitting was then welded into a hole in a rectangular plate with the top hat bit on the inside.
A smaller rectangular hole was cut in the tank and the plate put in and turned 90*......this meant that all the bits couldn't physically come back out.

 

[normspanners]

err test a callor gas bottle after its been converted ok .

as it didnt mention gas cyl's I presumed he was starting from scratch

 

[monkeymark]

I would suggest you buy these http://www.airsupplies.co.uk/weldable-socket-10894.html

They weld in place. Whatever you do make no attempt to buy cheaper ones that don't state they can be welded. They're cheap and not classed as weldable because they simply are not weldable - they're awful!

Good link, cheaper than i expected and some great advice there, thank you.

I would go for a minimum of 3/8" for most applications, ideally 1/2". If you're dealing with large stuff bigger still.
Remember that elbows, T pieces etc restrict flow so the bigger the better. I also like to use larger fittings on the basis that they'll be less prone to damage from knocks. Better to have a 1/2" T piece with adapters to then take it to 1/4" if needed and be left knowing that a knock won't damage anything that isn't easy to replace.

Good point regarding the restriction of air flow. Ill go for 1/2" with reducers where needed.

Assuming that when you say release valve you're talking about the safety valve to protect the cylinder from going bang if the pressure gets too much - you must have one of these!
(sorry if I'm stating the obvious and I don't wish to treat you like an idiot, but if overlooked the potential for injury or death is there).

yes that is what i was referring to. As you say, essential!

Also, you need to be sure that you're a good welder, use the right materials in the right configuration and depending on what you're doing be sure you are complying with all the rules regarding testing.
Not trying to put you off, just pointing out that you need to be careful with pressure vessels.

Im fairly new to welding myself (though id like to think im not bad for the time ive spent) however im fortunate enough to know someone who teaches engineering and fabrication at a college and is time served so with something like this I may borrow his skills for the day.

 

[monkeymark]

What i did for one of my air tanks was to machine a fitting with a thread that was "top hat" shaped.
This fitting was then welded into a hole in a rectangular plate with the top hat bit on the inside.
A smaller rectangular hole was cut in the tank and the plate put in and turned 90*......this meant that all the bits couldn't physically come back out.

Good idea! I was trying to think of something like actually.

 

[anjum]

If it's a Calor gas bottle why do you need to weld anything into it. I don't know but surely they have a threaded BSP hole at the tap end. If you want a safety valve you could use a tee piece.
Sorry if I'm missing something.

 

[brightspark]

If it's a Calor gas bottle why do you need to weld anything into it. I don't know but surely they have a threaded BSP hole at the tap end. If you want a safety valve you could use a tee piece.
Sorry if I'm missing something.

its preferable to have an inlet and an outlet also a drain tap fitted a safety valve is not neccecary as the extra tank is filled of the compressor tank which has one allready fitted .so why do u need 2

 

[Bill Edwards]

Im fairly new to welding myself (though id like to think im not bad for the time ive spent) however im fortunate enough to know someone who teaches engineering and fabrication at a college and is time served so with something like this I may borrow his skills for the day.

Not knocking your skills or anything, but I would certainly go elsewhere for something like this.
I've been welding for many years and have a lot of confidence in my welds - I've been doing it long enough to see them stand up to the test of time, and to see where they have failed - but even so, I still take a LOT of care when welding anything that holds a quantity of compressed air. I make sure the preparation is perfect, and if I make the slightest mistake on the weld (which I obviously do far more of than should be needed anyway, plenty of runs) it gets ground out and done again. No chances.

 

[dannyp]

with pressure stuff, i've allways been told never have a corner, so if putting a plate on it's allways round or very rounded.

if it's holding any volume of air under any pressure really you should hydralicly test it. i use a coupl of ball valves and a regulator valve on an old pressure washer. test it at double and some the working pressure. and if it fails been waterfilled it may make a bit of a bang/ping but dose very litel else other than leack

 

[Jan]

It's not so much the peak pressures that are the problem with welded joints on pressure vessels as it is the cycling stresses. Any vessel which is internally pressurized compared to the external static pressure will expand/contract, albeit microscopically, as the differential rises and falls. Over time this will result in invisible stress fractures that can only grow larger and deeper. Eventually this will result in catastrophic failure which you might not wish to experience from close proximity!

As said: Circular additions are far superior to any other shape and sharp corners have to be avoided at all costs. The De Haviland Comet is a case in point. The square windows of the original design led to several airframes breaking up in a very short time taking dozens of lives unnecessarily. In fairness the concept of 'metal fatigue' was virtually unknown at the time.

 

[MattF]

its preferable to have an inlet and an outlet also a drain tap fitted a safety valve is not neccecary as the extra tank is filled of the compressor tank which has one allready fitted .so why do u need 2

Can't see whether it should matter whether inlet/outlet are the same point or not. The pressure is there regardless, and it's easy enough to stand the cylinder upside down and drop a drain point lower than the T piece where moisture can collect. I'd guess the extra valve is a sensible precaution. It only needs one blocked pipe or kinked hose to isolate the two tanks, hence the extra tank would then be unprotected.

 

[brightspark]

i sometimes use a secondary tank on the end of the hose line . it serves a few purposes the 1st is it can be filled off the conector at the top which also has a pipe to the bottom so open when pressurised it emptys any water collected. its portable so can pump tires up in field . it has 3 types of fittings c type for 3/4 bore pipe pcl and euro fittings on it. i normaly use it for blasting as it cools the air before going to the pot water seperator. the only safety blow of valve is on the main compressor tank to protect it in case the pressure switch does not cut out the pump and will blow off at 8 psi above

 

[monkeymark]

i sometimes use a secondary tank on the end of the hose line . it serves a few purposes the 1st is it can be filled off the conector at the top which also has a pipe to the bottom so open when pressurised it emptys any water collected. its portable so can pump tires up in field . it has 3 types of fittings c type for 3/4 bore pipe pcl and euro fittings on it. i normaly use it for blasting as it cools the air before going to the pot water seperator. the only safety blow of valve is on the main compressor tank to protect it in case the pressure switch does not cut out the pump and will blow off at 8 psi above

Are they tapped straight into the side of the bottle?

 

[brightspark]

Are they tapped straight into the side of the bottle?

they are at the mo just didnt get round to welding a boss in on them yet

 

[Parm]

i sometimes use a secondary tank on the end of the hose line . it serves a few purposes the 1st is it can be filled off the conector at the top which also has a pipe to the bottom so open when pressurised it emptys any water collected. its portable so can pump tires up in field . it has 3 types of fittings c type for 3/4 bore pipe pcl and euro fittings on it. i normaly use it for blasting as it cools the air before going to the pot water seperator. the only safety blow of valve is on the main compressor tank to protect it in case the pressure switch does not cut out the pump and will blow off at 8 psi above

I like this, very neat idea, think I'm gonna build me one !

 

[the snooper]

I can only find stainless steel ones but ill keep looking.


Ill keep that in mind. I can pressure test to a degree at work but I know the calor bottles are built to withstand higher pressures than normal air receivers anyway.

hope that's hydraulic testing, compressed air is dangerous