Selecting the correct standard for a new Pressure Vessel 2

[DW1006]

I am currently in the process of ordering a new pressure vessel from a manufacturing company. They have requested that I specify the standard to which the vessel should be built, considering the appropriate safety factor for its construction. The vessel is expected to operate within a temperature range of ambient up to 50 degrees and will have a pressure rating of 10psi (most likely 5psi). Vessel will contain clean dry air.

After conducting some research, I believe the most suitable standard to request for the construction of this pressure vessel is PD5500, but I am also very new to this area, it is not my expertise (yet). However, I have also reviewed the information on the two links below, and any additional input or advice on this matter would be highly appreciated.

https://info.thinkcei.com/think-tank/asme-standards

https://info.thinkcei.com/think-tank/pd-5500

 

[LittleInch]

Most legislation and design codes themselves would not classify a 10psi tank as a Pressure vessel and designing it as one will simply add cost for no benefit.

There might be some issues in terms of CE marking depending on the size of the air tank x pressure, but as you haven't said what it is I can't comment.

Location of where this tank is going is also important to determine what legislation covers it (Europe, USA or somewhere else?)



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DW1006]

Hi, cheers for your input. Ill try obtain some extra details around the size, ive its a 3rd party company thats designing it as part of larger project. What I do know is its will be in the UK, aerospace industry, and will form part of a new "test rig" and vessel will be representative of "something" - apologies for being so cryptic.

 

[DW1006]

Based on the additional information ive found out, it appears that the vessel's internal volume is 1.95m³, and the operating pressure is 10 psi (approximately 0.689 bar). As the vessel's bar litres is well below the 250 bar litres threshold, it won't be subject to the Pressure Systems Safety Regulations (PSSR).

Regarding the safety factor to be considered when creating the vessel, is it not reasonable to expect the manufacturer to provide this information using sound engineering practices. The manufacturer should demonstrate that appropriate margins of safety have been incorporated into the design. We would request the manufacturer demonstrates a leak check and the vessel's ability to hold pressure for a specific duration, such as 1 hour at the maximum working pressure.

Since this will be a UKCA marked product, the manufacturer should comply with the relevant safety standards and regulations. The responsibility lies with the manufacturer to specify the standards used and the appropriate factor of safety to ensure compliance and safety, and not for myself to specify? Would you agree? Ive heard other colleagues state there is actual documentation (but cant show me any) stating theres a standard which states vessels should be built with a safety factor of 4? Ive not seen this though

 

[LittleInch]

These sort of small vessels at low pressure (MAWP <1 bar / 15 psi) fall into a bit of a grey area in terms of design standards, but you can ask the vendor if he builds to a certain standard.

I would expect a test pressure of absolute minimum 1.5 x MAWP and for that pressure I might ask for 2 x MAWP and then min 1 hr at 1.1 x MAWP.

It's not unreasonable to give the vendor a data sheet and simple specification and state what you want to see in terms of testing and certification to show it was tested, plus a certificate of conformity or UKCA / CE approval.

They can provide some calcs, but often just give you a drawing and then say they've made x hundred of them.

Just make sure it has a drain connection and drain it regularly or test it to make sure.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DW1006]

cheers!

 

[LittleInch]

So long as it "looks" like a PV, i.e. circular section body and dished ends then the min thicknesses required will be good for multiples of 10 psi.

Some sort of weird square or sharp edged "box" - run a mile from it.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

API 620 for high pressure tanks allows design pressures up to 15psig. What's to be in this tank, some toxic fluid ? Materials selection is equally important of there are trace amounts of some corrosion inducing chemicals. Internal / external corrosion is what causes failure and loss of containment of most vessels in the long term

 

[LittleInch]

George, the OP says it's clean dry air and it's pretty small - 1.95 m3, so don't think API 620 is the right code here....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

What we would do here across the pond is to specify the tank as 15 psi non code pressure vessel designed to ASME Code Section VIII and be done with it.

 

[LittleInch]

"Non code PV" ??

How does that work?

It's designed to a code or it isn't.

You can say it's not a PV, but is "designed in accordance with ASME VIII".

But this is a small air tank. Let's not go too far here....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

It's somewhat common over here to have non code pressure vessels. I personally don't like the idea, but some cheapskates do it to save de minimus amounts of money.

I think you pointed out that 15 psi is the minimum limit for Section VIII. There is no problem having a pressure vessel used for less than 15 psi being designed according to the Section VIII standards and not being code stamped.

 

[georgeverghese]

At 1.95m3, if D = 0.9m (36inch seamless pipe, sched 40), L turns out to be just over 3m. Weld the dished end caps on and ask a tank engineer to see if it complies with API620. Add on nozzles. No fabrication dramas. Once calcs are done, tank is ready in next to no time.

BTW, you say bar litres < 250??
Bar. litres = 0.7 * 1950 = 1365

 

[shvet]

"Non code PV" ??
How does that work?

A vessel designed according to a customer specification. A customer has options:
- specify a code, or
- specify a set of requirements to design, fabrication, and quality control, or
- rely on manufacturer reputation
Second option is not the best in the world but it is not prohibited if a vessel is planned to be installed in a non-jurisdiction location and a customer is satisficed with results.

Note that ~200 years ago codes did not exist and first PVs were built such way. If something did existed in the past why the same is not able at this time?

 

[DW1006]

thanks again everyone, some great info shared again, really appreciate everyone's input.

 

[shvet]

@DW1006
It is a commonly used practice in oil&gas industry to construct small vessels from piping details and certify per a piping code, e.g. ASME B31.3. This is much cheaper while the result is the same. What is the reason you should certify this PV as PV, not piping?

 

[Louisiana Inspector]

If it needs to be certified as a vessel and your company has no specifications on design requirements for vessels outside the limits of ASME VIII, I would suggest still following ASME Sec. VIII and just do away with getting it stamped by the national board. Better to be safe than sorry! Most companies have to follow RAGAGEP depending on their jurisdiction and this will cover you. Also, if it doesn't have to be certified as a vessel you can follow ASME B31.3 as mentioned above.

 

[hacksaw]

Don't forget, if you chose the standard for the vessel design, your customer will blame you if it fails.
If it does not comply with the local and national fire safety standards, everyone is in trouble.