Anchor Block Mitigation in Pipeline 1

[jonjose123]

Hello All,

Currently we are designing a pipeline 12" CS (API 5l X 52) with a design pressure of 140 barg and design temperature of 93 deg c. The length of the pipeline is 1.6 km.

We wanted t o remove the requirement of Anchor block. currently we are trying to change the routing to station approach by providing a loop and also increasing the cover depth.

Is there any other method with which we can mitigate the same.

Regards,
B

 

[MJCronin]

I believe that you should investigate the various pipe joining restraint systems available.

MEGALUG is one such system :

http://www.ebaa.com/products/dip/mechanical-joint-restraint

Also see:

http://www.eng-tips.com/viewthread.cfm?qid=422047

MJCronin
Sr. Process Engineer

 

[pennpiper]

jonjose123,
You wrote: "we are designing a pipeline 12" CS (API 5l X 52)"
It seems to me that if you are using Butt Welded Carbon Steel piping (and fittings) you would not need "Anchor Blocks" of any kind.

So,
(a) what makes you think you may need Anchor blocks?
(b) how many anchor blocks will you have? and where would you place them?
(c) what kind of soil will you encounter in this 1.6 km?
(d) how big are these anchor blocks going to be?



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

 

[LittleInch]

jonjose123

I've had a look at a couple of your previous posts, the most recent being a similar question about above ground pipelines at the same temp and pressure.

you don't seem to be very good ant answering questions or responding to posts so before I spend much longer you need to answer the questions above and give us a bit more response / feedback / explanation.

It would seem the pipeline is buried and welded, but please confirm?
what is operating temp?
what is the issue - excessive expansion, stress, what?
What is the installed temp?

LI



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

 

[jonjose123]

Dear All,

Apologies for the delayed response as I was on medical leave for week.

Little Inch: from here on I will be participating in all forums related to pipelines.

Regarding the question, the pipe is buried and and the operating temp is 78 deg celciuis.

We have done an analysis in Caesar ii and the displacement we are getting at the pig trap is around 24 mm.

However, there is an existing 30" pipeline from which we are taking a tap off with build barred tee. The Tap of size is 30 x 12" bared tee.

Client has raised the concern regarding the expansion at this barred tee.

From the buried barred tee the line connects it to the by pass line of the above said 12 inch pipeline which runs of r1.6 km.

Its a desert area.

Client is insisting on Anchor block as they concerned about of 25 mm expansion at pig trap and also asked to check the expansion at the underground barred tee 30 x 12".

Once again apologies for my less participation.

Regards,
J

 

[LittleInch]

jonjose.

Thanks for the update, but next time please add this sort of relevant information to your first post.

Expansion and stress issues at buried tie-ins are complex and very much depend on the potential movement of each item, space available, etc.

If the 30 x 12" tee is in the middle of a long straight run of pipe it basically shouldn't move. However the end of your pipeline will.

You therefore need to look at various layouts which can either accommodate that movement such that the stress on your buried tee is within design limits. A section of above ground pipework with an expansion loop arrangement might work, but the devil is in the detail. Similarly if you can include some buried bends just before you come into the pig trap then this will reduce your movement.

This may be one place where some sort of restraint or anchor block is required.

If you can post or sketch an arrangement of this connection it might be possible to offer some guidance, but otherwise it's all a bit vague.

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

 

[jonjose123]

Thanks Little Inch for the valuable explanation..

Will put a snap shot of our arrangement.

We had run an analysis for the system and we could find that the expansion we are getting at the pig trap is 28 mm and as per client requirement it shall be not more than 25 mm.

We have tried increasing the cover depth near the station approach but however doesn't seems to work.

We won't be in a position to try an offset as there are existing lines near by and space is a concern.

Regards,
J

 

[LittleInch]

Where does 25 mm come from? That sounds like a very artificial requirement. 28mm is low for such a high temperature. The only way to analyse this is to do the entire system.

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