Odd ball pressure vessel needed

[FTBagain]

Hi all,

First of all I am no welder, but I am working on something that may need a specialist pressure vessel. As I did my apprenticeship with CompAir years ago I am well aware of the danagers of compessed gasses and what can happen if a pressure vessel should fail, so I am not about to do a back street DIY job.

I need to be able to put a device that I am developing under external pressure. This means that I will need access at one end of the pressure vessel. Further more there will need to be at least two isolated electrical connectors to allow electrical connectivity to the device under pressure.

As you can see it is a bit unusual so it would be expensive to get one built from scratch and my name is not Donald Trump . This really gives me only two options. Find a second hand one, possibly an ex-process pressure vessel or get a standard pressure vessel modified.

Any leads or advice you may have would be much appreciated.

Thanks

 

[jugs]

Hi all,

First of all I am no welder, but I am working on something that may need a specialist pressure vessel. As I did my apprenticeship with CompAir years ago I am well aware of the danagers of compessed gasses and what can happen if a pressure vessel should fail, so I am not about to do a back street DIY job.

I need to be able to put a device that I am developing under external pressure. This means that I will need access at one end of the pressure vessel. Further more there will need to be at least two isolated electrical connectors to allow electrical connectivity to the device under pressure.

As you can see it is a bit unusual so it would be expensive to get one built from scratch and my name is not Donald Trump . This really gives me only two options. Find a second hand one, possibly an ex-process pressure vessel or get a standard pressure vessel modified.

Any leads or advice you may have would be much appreciated.

Thanks

Q 1 What size is the device
Q 2 What's MAX - Min pressure
Q 3 What Max - Min tempritures
Q 4 Air or Gas (if so which)
Q 5 Water or another fluid (if so which)
Q 6 Whats max volts & amps
Q 7 Do you need to view device under test

 

[FTBagain]

Q 1 What size is the device
Q 2 What's MAX - Min pressure
Q 3 What Max - Min tempritures
Q 4 Air or Gas (if so which)
Q 5 Water or another fluid (if so which)
Q 6 Whats max volts & amps
Q 7 Do you need to view device under test

Q1. Up for grabs at the moment, but I would think about 300mm x 400mm.
Q2. Max pressure again optional as I am just looking to establish basic behaviours with varying pressures. 60psi would probably be OK 120 would be nice to have. Min pressure is dependent on Q4.
Q3. Temperatures - nothing especial just room temperature.
Q4Initially compressed air but pure oxygen or nitrogen in the future which means I may need to use a vacuum pump to maintain purity. Not sure.
Q5. No liquids just gas.
Q6. Volts and Amps - at this stage very low, standard 12volt / 1 amp would be more than enough.
Q7. No. Just need to get a couple of voltages out.

Thanks for you interest. Appreciated.

 

[Weldingartisan]

You could try looking for an old autoclave, which will be pressure rated. Or an air receiver made from pipe (say 24" or 30") then a standard slip-on welding flange and blank flange could be used for access. Using standard fittings to the pressure rating you require, then a hydraulic test to twice maximum working pressure and a safety (relief) valve set to 20% above max working pressure. Electrodes could be set in resin for electrical connections. W/A

 

[FTBagain]

W/A, thanks for the suggestions. The pipe construction sounds particularly interesting. I checked ebay for autoclaves and they are mostly steam autoclaves, not really suitable.

I will need to find a suitably qualified welder in my area I think.

Thanks for the input. Very useful.

FTB

 

[Wedg1e]

I know where there's an autoclave (probably going cheap as well)... only slight drawback is you'd need to move it yourself, and as it's big enough to walk into...

 

[wyn]

Big enough for an F1 car ?

 

[hareng]

Usually dabble in hydraulics as well, up to 300bar way in excess of your initial requirements 4 bar.
Need more info without giving the game away.
Do you need access inside the vessel, in other words take it apart?
Part inside vessel?
Or does the vessel supply the pressure to the part?
Wires to the part or measurement inside vessel?
Size of part a big plus and if it moves or not.

Any of us may have something that could easilly be modded.

 

[jugs]

Q1. Up for grabs at the moment, but I would think about 300mm x 400mm.
Q2. Max pressure again optional as I am just looking to establish basic behaviours with varying pressures. 60psi would probably be OK 120 would be nice to have. Min pressure is dependent on Q4.
Q3. Temperatures - nothing especial just room temperature.
Q4Initially compressed air but pure oxygen or nitrogen in the future which means I may need to use a vacuum pump to maintain purity. Not sure.
Q5. No liquids just gas.
Q6. Volts and Amps - at this stage very low, standard 12volt / 1 amp would be more than enough.
Q7. No. Just need to get a couple of voltages out.

Thanks for you interest. Appreciated.

pure oxygen NO It's a bomb unless you can be 100% sure of no oil.....Only use an inert gas,

 

[aero]

I've seen large diameter gas or water pipe fittings used as a test pressure vessel before.The sort of stuff they bury in the street. The fittings have bolted flages and 6 inch diameter is common. A simple flat plate each end and hey pressto you have a sealed vessel. As to where you'd get some though?

Ceratin military spec electrical connectors are available that are sealed. We use them accross pressure bulkheads, although the px diff is very small in our case, 8 psi max.

http://www.topcomponents.co.uk/military_and_commercial.html?gclid=CNbyhdGJsZcCFQKVMAod8GYLjA

 

[snowcat]

I've seen large diameter gas or water pipe fittings used as a test pressure vessel before.The sort of stuff they bury in the street. The fittings have bolted flages and 6 inch diameter is common. A simple flat plate each end and hey pressto you have a sealed vessel. As to where you'd get some though?

]

PN16 flanges, avaliable in weld neck and screw, actually theres loads of types, with diffrent hole configarations, I just use 16s by the bucket load... your get blanking plates off the shelf for them also....

 

[Drains]

These are baby pressures here. If you want to be sure of a decent job, do any welding with MMA, and do a dye penetrant test on all welds. Grind out any flaws and re-weld. Use flanges and blanking plates as suggested above for internal access, if necessary, or for your electrical fittings/connections, or weld in threaded inserts to fit LX connections to.

Either modify an air receiver, or, easy enough, a butane/propane bottle (see numerous threads on wood burners, on this site re purging).

That's how i'd do it anyway.

 

[aero]

have you actually tried to do dye pen on a weld?

If you had you'd realise that every featue of the weld's surface holds the dye. When you put the developer on the whole weld shows as a red/ultraviolet mess.

When talking NDT on welds your are looking at x-ray.

Oh. I do use dye pen, on flat rolled ally sheet. Even then its no where near acurate.

 

[hotrodder]

I use DPI all the time on welds without problems- most of the work i do has to be air or liquid tight. The etched zone on aluminium tends to hold dye so it needs removing with some scotchbrite or similar first but other than that it's a good way of finding surface flaws

 

[snowcat]

Ditto iv done boilers in exactly the same way as above, correct materials choice, proper prep, dye pen, hydraulic test when finished, and job done, the pressures to the size of the vessel is tiny, if your confident then it wouldn't be a problem to make, to be a proper coded weld you have to do all sorts on design and prep, materials approval, wouldn't be as simple as taking it to someone and getting them to weld it... and you want to keep in budget.....

 

[runnach]

I use DPI often for a unit I teach, never had any probs with the process, perhaps you are going a tad OTT with the dye?

I also find MPI very good for seeking out surface flaws, of course MPI is limited with regards to materials it can be used on.

 

[Drains]

have you actually tried to do dye pen on a weld?

If you had you'd realise that every featue of the weld's surface holds the dye. When you put the developer on the whole weld shows as a red/ultraviolet mess.

When talking NDT on welds your are looking at x-ray.

Is that directed at me aero? If so, sorry, but you need to learn how to do dye pen properly! You're meant to clean off the excess penetrant - didn't you know?

Dye pen is a perfectly good NDT, where radiography isn't required - and for these pressures you're looking for crack and surface flaw detection. Dye pen fits the bill.

Oh, and yes, I have dye penned miles of weld in my time.

 

[aero]

aimed at me?...Do I need to break out the Lewis machine gun? I welded up a good mount for it!


For me Dye pen is the most un realible, but then I have guys on call with the latest super all singing and dancing eddy current based equipment to call out.

I hate dye pen not only is it a messy process that will highlight what can be seen by eye...BUT i had a lecturer who made me work out the depth the dye will penetrate to and the resultant size of the tell tale when developer is applied. ******. Thing is thats all well and good, but unacceptable in the real world.

And the dye still hangs in the weld. 1940's test that should be binned.

 

[English Steve]

Horses for courses - Dye pen is perfectly acceptable for it's intended application if applied properly.
ASME IIIX and BS5500 (unfired pressure vessels) do not require X-ray inspection at the lower pressures we're discussing here.

 

[hotrodder]

I hate dye pen not only is it a messy process that will highlight what can be seen by eye

And the dye still hangs in the weld. 1940's test that should be binned.

Messy... yes agree with that but there's water soluble stuff available now. Gotta disagree about it only showing up flaws visible by eye though- granted, once found flaws may be easily visible... once found

It's quick, cheap and will find very fine surface flaws with the correct prep and contact time. It is a minor pain to remove for repair but as the defect will need excaviting anyway the problem of trapped dye isn't really that big of a deal- i find it helps guide my digging sometimes