Assessing Structural Integrity of a Buried HDPE Pipeline

[nqeng]

Hi Everyone,

I work in local government and we are currently trying to develop a method for assessing the structural integrity of a buried HDPE pipline that is about 1000m long and was constructed about 20 years ago. The end of the pipe is about 300mm off shore and is the only location the pipe comes back above ground. There are essentially no valves along the length of the pipeline. At it's landside end it connects to an old 375mm dia AC pipe which continues on for a few more km's. The pipe is used for discharging effluent.

Anyone have any suggestions on how to go about assessing the strutural integrity of a pipe line in this situation. Ultimately the work will be done by consultants but we need to develop an understanding of the process and methods that should be used to make sure this is done right.

 

[BigInch]

Corps of Engineer TM 1110-2-2902 explains the basics of underground pipe design pretty well.
There are also numerous pamphlets available from HDPE pipe associations that address the HDPE particulars.

http://publications.usace.army.mil/publications/eng-manuals/

Otherwise we need more details as to the exact configuration and perhaps why you believe it is in need of an integrity review at this time.


Independent events are seldomly independent.

 

[cvg]

reviewing the design will only take you so far. you need to review the as-built condition of the pipe as well as the operations history. For instance document and then review with original design if you have it

depth of bury / cover - is cover sufficient to prevent movement and is it within the allowable loading?
horizontal alignment - was the pipeline installed with any bends or has it moved since it was installed?
you may need divers or ROV to verify some of this.

operating pressures, temperatures and fluid properties - is the operating pressure within recommended design limits, any surges?

Is temperature within design range? Any solids that could cause abrasion to the inside of the pipe?

What is the operating velocity of the pipe and will it transport solids through the pipe?

What about the connection to AC pipe, is that acceptable?

What about erosion or scour of the seabed affecting the pipe alignment?

Can you get a CCTV through the pipe to do an interior inspection?