piping stress analysis required?

[SIMONMAGSUCANG]

Hi all,

I am going to change out a section of corroded piping, since hotwork is not allowed thus I will go for "like for like" replacement with same new piping material but fittings component will be using "compression swaging" type fittings. Do I need to do piping stress analysis for this case?

 

[pennpiper]

I do not feel anybody can give you an answer based on just the little information you have provided.
What is the Operating pressure and temperature?
What is the commodity?
Why is Hot Work (welding) not allowed?
Please provide a sketch showing the configuration of the total piping system with a clear indication of what is the existing and what is the new piping.

Sometimes its possible to do all the right things and still get bad results

 

[SIMONMAGSUCANG]

The operating pressure is between 5~10 bar and operating temperature is just around room temp. The reason of hotwork is not allowed because this is an offshore gas platform, we are trying to reduce any possibility of hotwork especially weldings.

There are basically no changes on the configuration of piping, its just cutting out the corroded portion and change with new spool which is swaging type connecting to the existing, piping material remain the same, all pipe hangers and supports will be using the same.

 

[XL83NL]

Based on pressure and temperature Id say no, but other (dynamical) effects for offshore structures may be in effect. Not knowing the size and routing makes it difficult, although your mention of "compression swaging" type fittings makes me think you're in the small bore range (typically less than 1"). I think you still need to provide more info.

 

[SIMONMAGSUCANG]

There are no re-routing, just follow exactly the same piping layout, just cut off the corroded section and replace with new one, the joint are connected using swaging fitting instead of welding. The total linework is around 120m and I'm planning to cut and replace around 70~80m of them.

Yes you are right, the size is for 3" and below, target instrument gas line.

 

[XL83NL]

Although you know the routing, we don't. Too little info

 

[1gibson]

Don't know about stress analysis, but be conscious of potential vibration / fatigue. To be clear, you are replacing hard pipe (welded and/or threaded fittings/elbows) with tube (swage connectors and bends) right?

 

[LittleInch]

I would be much more concerned with the possible reduction in axial strength. Swaged fitings rely on deformation of the pipe to achieve this. 3 inch sounds rather big to me. What is the pipe wall thickness, material and connector?

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

 

[SIMONMAGSUCANG]

It is seamless carbon steel A106 Gr B, sch40.

 

[LittleInch]

Can you post what this coupling is as it is crucial to seeing if it is a good thing or not.

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

 

[SIMONMAGSUCANG]

Its lokring. You can see

http://www.lokring.com.

 

[LittleInch]

Ok. I didn't know it went up to 3". I would definitely try one before you cut it out....

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

 

[SIMONMAGSUCANG]

Just checked with a friend who is an expert in Caesar piping stress analysis, he said it is not necessary to do stress analysis, the stress analysis is not for couplings..

 

[bellowsmfg]

If you are operating at ambient temperatures a stress engineer won't blink at it unless you have other design criteria that will raise concern (seismic or offshore in your case). If the new connections are adding flexibility into the system then you'll need to review the support system. Too much flexibility will cause it's own issues.

Conor

Bellows Manufacturing and Research, Inc.

https://bellowsmfg.com