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Pressure vessel liner implosion

Pressure vessel liner implosion

Pressure vessel liner implosion

(OP)
Question:

A pressure vessel is designed for steam service.

It has both an internal and external design operating condition.

The vessel has a small section of internal shell wall that contains a thin liner to protect the shell locally from process impingement wear.

The liner is seal welded all around and is not vented to the atmosphere or to the internal side of the vessel.

The vessel is cooled externally sufficiently to condense the steam.

The vessel external wall will then see external pressure form the atmosphere.

However, the liner may not see external pressure as it is not open to the atmosphere.

Will the liner locally be subject to external pressure in the space between the liner and the internal vessel and thus have the possibility of imploding towards the inside of the vessel?

I would appreciate an answer and if possible the physics behind why or why not there would or would not be an external pressure on the liner under the conditions where the vessel outer shell is seeing external pressure due to condensing the steam.

Thank you,

RE: Pressure vessel liner implosion

Well, lets think about this. Let's assume the liner was installed at ambient pressure (I am betting it was) and is truly sealed to the inside of the vessel wall.

Now the vessel is pressured up. The pressure on the exposed liner surface is the vessel internal pressure. The pressure on the liner surface in contact with the vessel wall is, roughly, ambient, ignoring any temperature effects. The liner is held to the wall by the pressure difference.

Now the vessel is subjected to the internal vacuum condition, stated as external pressure. The pressure on the exposed liner surface is below ambient. The pressure on the liner surface in contact with the vessel wall is, roughly, ambient.

Now, what is the liner going to want to do? Whether it can do it or not kind of depends on how rigid (thick) it is.

Unvented spaces are generally not a good idea.

Regards,

Mike  

RE: Pressure vessel liner implosion

(OP)
Thanks - pretty much what I thought

RE: Pressure vessel liner implosion

We had two plate clad vessel where the lining buckled inward.  The vessels were about 6' x 10' with the lining stopping at the tangent line of the top and bottom SS heads.   
Both of these events were caused by process getting behind the clad and corroding the CS shell.  The leak was at a nozzle that was install 6 months before.  The last one wasn't investigated due to production demands.  
It was from these excursions that we didn't allow plate cladding requiring Detaclad, full welding or strip cladding.
     

RE: Pressure vessel liner implosion

while the main vessel is stiff, the steam will vac the liner and destroy it.
just pinch your arm skin and pull it, a perfect test...

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