Stored Energy Calculation & Safe Distance for Underground Pipeline

[nanil]

We are planning to do pipeline inline inspection pigging using pneumatic pressure of 20 Bar. Pipeline length is 20",16km, with a total volume of 3060m3. I performed Stored energy and safe distance calculation as per ASME PCC-2 part 5 article 5.1. The value is very high with a safe distance of around 330m. Maintaining this distance is practically not possible. Equivalent TNT value was 2186.2Kg. This is an underground pipeline. Is equations for Stored Energy in ASME PCC-2 applicable for underground pipeline also. Please advise. Is there any other ways to compute this.

 

[LittleInch]

Yes and the key fact is that a pipeline that long pipelines do NOT behave like a pressure vessel.

I'll post links to other posts in Monday but look in the pipeline forum FAQ.

You also need to define"safe". Most buried pipelines have acceptably low risk if you stand over the top of it.

Have you any experience of pipelines at all??

That equivalent tnt value in particular is absolutely useless and I would advise you never to bring it up in front of a pipeline engineer.

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

 

[nanil]

Thank you LittleInch for the feedback. I had this same doubt whether the pipeline such long behaves like a pressure vessel. But the query came from client. And yes, I am learning and do not have wide experience with pipelines.

 

[LittleInch]

This is about pneunstic testing but the same issues apply.

https://www.engineering.com/story/p...ines-as-an-alternative-to-hydrostatic-testing

Why is the client so worried?

What is the design pressure of the pipeline?

But you really need to throw away everything you've calculated so far and think again.

What is your role? The inspection company should be able to address your questions surely.

Is it in a very corroded state?

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

 

[nanil]

What is the design pressure of the pipeline?- 65 barg

What is your role? The inspection company should be able to address your questions surely.-
We have already requested the inspection company for feedback. I thought of finding an answer meanwhile.

Is it in a very corroded state?- its a new line, yet to hand over

Just saw below clause in ASME PCC-2 501-6.2, point e,
"When calculating the stored energy of a piping system, a maximum volume based on a length of 8 pipe diameters may be considered for any single failure analysed."

And honestly i do not know the reason for clients worry . May be they are also learning along with others.
I have discarded my calculation. It was a big mistake.

 

[LittleInch]

Thanks for the feedback.

The inspection company might be trying to ignore the question...

That's a good shout on the pcc code. Sounds about right to me.

If you want to calculate the size of a crater due to a pipeline rupture there are calculations to do this. I'll post one on Monday. Usually about 3 to 5m diameter.

EDIT - see the attached.

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

 

[LittleInch]

With a design pressure of 65 bar and presumably a test pressure of ~80 bar and you're operating at 20 bar, it would seem that the potential for rupture is very very low.

Your clients appear to be worrying about something that doesn't happen.

It is hard to prove a negative sometimes.

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

 

[r6155]

More information in ASME B31.4 and API RP1110.

Regards

 

[LittleInch]

You can't apparently add an attachment when you edit so here it is.

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