PSV for <15 psig PV? 1

[Adan G]

Hello all,

Hoping to obtain some guidance on the need for a PSV for a plastic (Tritan / Acetal) vessel of about 400ml, to be pressurized with air, to 14.7 psig. Here are the details:

The vessel will be pressurized with a air compressor rated to a maximum pressure of 18 psig. The control electronics will automatically shut off the pump at 14.7 psig. However, given variations in manufacturing tolerances, the actual cutoff pressure may be slightly above 15 psig. Afterwards, the pressure may increase further per environmental temperature fluctuations, though never above the vessel's design pressure.

Given these specifics, is a PSV required?

Thanks

 

[The Obturator]

What is the design code of the vessel? Where is it to be installed?



*** Per ISO-4126, the generic term
'Safety Valve' is used regardless of application or design ***

*** 'Pressure-relief Valve' is the equivalent ASME/API term ***

 

[MortenA]

This is from "Anderson Greenwood, Crosby and Varec products | Technical publication No. TP-V300"

"Division I of ASME Section VIII will provide rules for the new construction
of vessels which contain pressure that is supplied via an external source
or pressure generated by heat input or a combination of both. Since the
designs of these vessels can be numerous, it may be easier to provide
examples of what type of pressure containers might not be considered
an ASME Section VIII vessel. Some common examples can include the
following:
• Vessels having an inside diameter or cross section diagonal not
exceeding 6” (152 mm) of any length at any design pressure.
• Vessels having a design pressure below 15 psig (1.03 barg).
• Fired tubular heaters.
• Components, such as pump casings or compressor cylinders, of a
moving mechanical piece of equipment that are a part of the device
and designed to meet the working conditions of the device.
• Piping systems that are required to transport gases or liquids between
areas.

--- Best regards, Morten Andersen

 

[Adan G]

Thanks for the quick responses.

@The Obturator: The vessel will be portable. It is essentially a consumer product. I'm researching the need to design to a specific code and to include a relief valve.

@MortenA: The vessel is cylindrical in shape, with an internal diameter of 3.8" and length of 9". It is designed to be pressurized to 14.7 psig at room temperature, but will be exposed to temperatures reaching 100 F, so will reach pressures of about 20 psig.

With these details, do you think this vessel would be subject to ASME Section VIII or any other code?

Thanks

 

[The Obturator]

"With these details, do you think this vessel would be subject to ASME Section VIII or any other code?"
Probably not, and it's not even a metallic container. Does the vessel/system require some sort of sign off for insurance etc.?
What if...things go wrong and an injury or accident occurs?
If you need to use a Pressure-relief Valve, at least use a coded PRV. For your vessel protection these can be small screw straight through type like the Kunkle Model 541 etc.

https://www.emerson.com/documents/a...-safety-valves-kunkle-valve-en-en-5197454.pdf

*** Per ISO-4126, the generic term
'Safety Valve' is used regardless of application or design ***

*** 'Pressure-relief Valve' is the equivalent ASME/API term ***

 

[MortenA]

I would agree with Oburator, get a PRV if it you think it serves a purpose - but you wont break a code if you dont. If this is in EU you wont break PED as far as i can see.

--- Best regards, Morten Andersen

 

[LittleInch]

With those details it might be a code vessel if it exceeds the size limits, but at 3" diam you ight creep under the limits as noted above, but not in terms of design pressure.

Tritan looks like it doesn't shatter which is good. But check the material properties at your 100F

The key is knowing for definite how someone operates this thing and whether if they decide to connect a higher pressure air machine can they exceed the design pressure?

The volume is small, but could still be a hazard if it burst.

But if you're happy that there are no reasonably foreseeable circumstances where this volume could become over pressurised (i.e. above 20psi) then it seems you're good to go.

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

 

[Adan G]

Good morning. Thank you all for your feedback. Much appreciate you taking your time to help.
Responses below:

I don't anticipate needing an insurance sign off, but that my change in the future. I don't anticipate any scenario where this device could be pressurized above the design pressure or one in which it could cause injury. Essentially, the plastic vessel and components will be designed to withstand significantly higher pressures.

Adding a PSV would be problematic for various reasons, so would like to avoid doing so unless absolutely necessary.

As for the size of the vessel, I understand the limit specified by the ASME Section VIII applies towards any internal dimension, diameter, length, diagonal, etc. If this is correct, I would be over the 6in limit as the internal length of my vessel is 9".

Thanks