Need of Anchor block 1

[B.L.Smith]

Dear friends,

As I know the anchor block is used if there is a need to avoid transmitting the UG pipeline's displacement to AG. But a question raises how much displacement is a concern?
I am working on a project which involves an 18-inch gas pipeline with 1.2 km length from pig receiver station to a plant. This pipeline is buried in most of its route, and it has some elbows(not cold or hot bends) on it. So, does this pipeline need anchor blocks near the receiver station and plant?

 

[LittleInch]

If you design it right, no pipeline needs an anchor block, IMHO.

However it all depends how you deal with whatever expansion you might get at the far end. Allowing the end connection to move 40-50mm will allow most pipelines to be built without an anchor block. but I've seen 70-80mm in some high temperature lines.

But it all depends on details such as installed temp vs operating temp (not design temp), actual orientation and location of your elbows, pipe coating, ground conditions etc etc

Piping designers generally hate movement from something that isn't theirs and can impose low limits if you let them. They love anchors as it allows them a known zero point. Pipeliners generally hate them.

You really need to analyse this and design it as a complete unit or at least for the initial 200m or so of buried pipe. Doing it as a "free end" is just worthless as it will never be a free end.

A Fuel gas line should be virtually ambient temperature so there is no real expansion going on.



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[B.L.Smith]

Thank you LittleInch for your response.
One end of the pipeline is connected to a branch in the plant and another end is connected to a branch from the pig receiver inlet pipeline. If I don't use anchor blocks at both sides, it may need to consider the expansion loop fo the line. Is it a practical solution for such cases?
Is there any reference such as handbook or standard for making the decision about the need for anchor block?
After I modeled the AG piping and 200 meters UG pipeline in CAESAR II with the free end, still there is movement at the free end. Shall I model the full length of the pipeline?

 

[LittleInch]

Well you're more into pipiing design.

You need to lok at temperature deviations here.

200m is usually good enough to create a virtual anchor so at the end of 200m you just anchor it in your analysis to give it a reference point.

If you can model the whole thing then do so.

What's your temperature rise from as laid condition?

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

 

[MJCronin]

BradSmith...

What type of piping joints are you using in the underground portion of the system ?

Are they "bell and spigot" joints or are they 100% butt welded ?


MJCronin
Sr. Process Engineer

 

[B.L.Smith]

All joints are butt weld. and the operating temperature is 70.

 

[LittleInch]

70F or 70 C?

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

 

[B.L.Smith]

Sorry for the lack of data. The operating temperature is 70 C.