An issue at with an emergency vent line has come up. When the bursting disc goes the vent line will suddenly go from ambient temp & pressure to 104degC & 5.4barg pressure.
My questions are:
1. Do I need to model any forces other than the ones from the thermal expansion?
2. If the answer to 1 is yes - how do I do this?
Thanks,
James.

ANSWERS
1.YES.
2.THE CORRECT WAY.

Answer 2 is not being flipant,just that it is such a big question to answer, also the codes
are (in my opinion) a little 'grey' when it comes to the compliance.

the real answer is to read the codes, read the excellent training manuals that COADE supply,
Look at previous examples, ask experiance people.
formulate an solution, and have it checked.

Although, the fact that you have asked the question at all suggest you should book a place immediatly on the COADE training course before you attempt any analysis.

Regards

Hello 'Superpiper',

I don't think you're much help. I've done the course and it deals with a water hammer but not much else of relevance to this situation.
I'm just looking for some guidance on the route to go, not your flippant smart ass remarks.

I have been in exactly the same situation
as you are in and i am just stating that the answer is not simple.

I stated that i was not being flippant.
As for smart-ass remarks, i will ignore.

On my COADE training, the issue of relief
was touched upon by the lecturer

Some pointers to a solution:-

1.Calculate Recoil forces for BD (search this forumn) F=2PA

2.Assess distance between elbows if nessesary
And apply forces to suit.(note i tend to balance forces out if distance is small.)

3. Apply 'Jet force' at outlet of BD line

4. Asses your engineering situation and apply good judgement to suit.

6.Meet client expectations for analysis.

Note

There are important differences between BD events and PRV events.

I would also be wary of allowing for a fire case
which requires the pipework to stay intact during
fire/BD events.

Hope this Helps

In good faith

Superpiper,

Thanks for your very helpful remarks.

Can this be solved using Static analysis only or is dynamic analysis involved?

Thanks.

(This advise is based on our systems which are fairly simple BD lines you need to asses Your situation to suit!)

My advise is to run at worst case.
If you cannot get a satisfactory solution,
then keep refining the model.

There will come a point using static analysis where you have
A- a good solution.
B- No solution.

If you cannot get a satifactory solution using
static analysis, then assess how large your overstress's are.
If you feel you can have (Code compliance)
by further refining the model using dynamic analysis, then do so.
But this is a time-costly exersise.
otherwise a piping redesign is in order.

I would be very suprised unless you have excesive conditions that a static analysis will not suffice.

Regards

James,

It may help you to read this paper:

http://www.iomosaic.com/iomosaic/pdf/scdiers.pdf

Also, try to find a copy of ASME B31.1 and review the non-mandatory Appendix II, "Rules for the Design of Safety Valve Installations". This appendix addresses some of your vent pipe issues.

And if you can find a copy of API RP-520 you can find some help there also.

Regards, John.