Is it a pressure vessel if it contains a solid instead of a liquid or gas?

[HDS]

I have a small chamber where powder is compressed under a few thousand pounds of force. There is no liquid and the air can escape. All of the PC stuff I have looked at like the CE PED seems to apply only to compressed liquids and gases but not solids. Do I understand them correctly?

 

[DavidCR]

Good question.
ASME defines in scope....
...vessels or containers for the containment of internal or external pressure.
My opinion, if it is not a container or sealed it is not a PV. If it can break apart but not explode it is not a PV.
It is there a local regulation that considers it a PV to obtain a permission to operate, or in case of an accident, would it be considered a PV by an insurer for example. Or it is legally just another mechanical equipment.

 

[REGRUMBLE]

Lots of presses stamp out parts by compressing powders or pellets with thousands of pounds pressure in a die form without being a pressure vessel. I would think your chamber would be considered a form not a pressure vessel.But i am not an engineer

 

[HDS]

PC should read PV.

 

[stanweld]

How are the particles compressed? Mechanically or by pressurized fluids?

 

[JakeR82]

It does not sound like a pressure vessel. A pressure vessel as a general meaning is any pressurized container (ie, piping or container) that has an internal/external pressure over 15psi. 15 psi (or generally one atmosphere) is what most technical standards use as a pressure minimum.

 

[HDS]

It is mechanical pressure on the powder from an electric press.

Thank you everyone for commenting. I didn't want to over look anything. I think the key is that there isn't any significant stored energy. When the force is removed there is not a significant expansion of the compacted powder. Of course even though it is not a pressure vessel we are going to be safe in our design. We just do not have to do the paperwork for a pressure vessel and our customers don't have to talk to their insurance company.

 

[stanier]

You say it is a 'small" chamber. You may find the dimensions are outside the limits of any pressure vessel code in any event. That said the mechanical design needs to be done so dig out the first principles books and do some mechanical engineering.

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[jtseng123]

I deal with all kinds of pressure vessels all the time, liquid, gas, solid.
In your case, take the " few thousand pounds of force" plus some margin as your design pressure at the top, find out the maximum packed density of the powder or solid and height and you can calculated the static head at the very bottom. Then you can apply code formula, very easy.
If you have software, just finish it in a minute.

You can always apply code regardless size and pressure if you undersatnd the basic concept from the code is "stress", unless you have very high pressure and very small diameter which leads to very thick plate such that R/T<10, (where R is mean diameter, T is the thickness), then you don't apply the code. It has different formula for thick vessel. You can use stress formula PR/T <= allowable stress to run a quick check on thickness.

 

[HDS]

jtseng123

Thank you. I understand the math and have done the calculations of pressure and stress. We have proven it is safe (the most important thing). My question is does it fall into the area of the code that requires an ASME stamp or a "notified body" for CE.

I recently looked at the guidelines published by CE for the PED and I believe they say that solids are not regulated by the PED only fluids.

 

[jtseng123]

We have storage type vessels containing powder only, such as catalyst, but under pressure from the inlet, and it fit to the limit of Div 1, so we stamp it. I do not think content is a factor to exempt from stamping.

However, it seems your cylinder is only a mechanical part to take the occasional pressing load as pointed out by other people, not really a pressure containing equipment, then you don't need to stamp it. If you have doubt, you can talk to qualified U stamp vessel shop.

Just curious what kind of shop will fabricate the cylinder, will they provide code calculation? what NDE will be done? any certified ASME material and test report ? any third party authorized inspector(AI) involved ? You all need these to get a stamp if you want.

When you stamp a vessel, and later on you want to modify the pressure part, you will need proper code calculation and details for AI to review to get a R stamp, very tedious.

There are many pressure containing cylinder without stamping, which you will see around the street on a truck bed, such as propane, oxigen cylinder, etc that people use for welding and many other purpose.