FRP (GRE) Piping - Installation by burying

[BonnKK]

If FRP pipes are to be buried. The thickness of the FRP pipe is to be determined and recommended by the supplier of the FRP pipes? How is it being determined?

Appreciate if someone can recommend industrial standards which will assist on the above question.

 

[Oceania]

The most often standard for buried FRP pipe is the AWWA M45 code usally in conjunction with the AWWA C-950. Also look at AS2566 this has some good info in it too.

These standards allow a theortical stiffness/strength of pipe to be matched with the indicated burial conditions.

However, this is theory...a rabbit hole survives without a pipe...ie everything is about soil. Installation, ie back-fill stiffness, compaction and the care taken by the sub-contractor will make or break a buried pipeline.

Hope this helps.

 

[BonnKK]

But for GRE behaviour towards hydrocarbon (middle distillates) and water, is there a huge difference between the 2 medium? i.e will presence of hydrocarbon in such GRE piping causes more movement as compared with water.

Also is it a good idea to use nitrogen to test for leaks in the piping or using water to hydrotest the pipe (section by section) is a better choice?

 

[BigInch]

HC weigh less, so loading to the soil might be less. In any case, don't worry about the difference between HCs and water when considering difference in burial conditions.

Always better testing with low compressibility nonflamable liquids. Less dangerous in case of explosion and it makes the test results easier to determine if any pressure variations were due to temperature change or an actual leak.

http://virtualpipeline.spaces.msn.com

 

[STYMIEDPIPER]

Review the technical section of a "Smith Fibercast" catalog.
It will give you all the technical information you need to know about burying FRP pipe

 

[BonnKK]

Currently, I am experiencing pipe leakage due to the pipe movement in between valve pits. I wonder how to arrest this kind of movement so that the pipe will not be 'pushing' against the concrete walls of the pits and cracking itself.

How different is it as compared to steel pipes burying? Are there methods or standards that specify how pipelines should be laid? e.g we put thermal expansion loops on above ground pipelines. But what about underground pipelines esp GRE pipes which have the tendency to expand axially when there is a change in temperature and also when there is flow.

 

[Oceania]

Depending on the distance between the pits the effect of thermal expansion should of been assessed. The usual method of relieving changes in expansion and contraction is through an O ring articulated joint either at the pit or at one or more locations along the length of the pipe. Alternatively concrete thrust blocks are used to lock in the thermal stresses and resist the resulting thrust through the gound rtaher than through the pit wall.

Part of the pipe expansion is taken up through friction between the pipe and the soil, therefore if the installation is poor the pipe will be free to transmit the axial loads. It is also worth remembering that with an FRP pipe as the pressure increases there is a reduction in length due to poissons ratio effect.

 

[SJones]

Look at ISO 14692, all parts, and ISO TR 10465, all parts.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[stanier]

Check out Recommended Guidleines for NDT of GRP from Norsok.

GRP has a low level of strin tolerance. Thus the design of a pipe/soil structure require more care than for steel pipes.

Check out AS 2566.1 & .2 Buried Flexible Pipeline Design & Installation from Standards Australia.

Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au

 

[rconner]

BonnKK,
I happened to notice just today at

http://ww.pennnet.com/display_artic...-specified-for-hydroelectric-plant-in-Brazil/

it appears one GRP pipe manufacturer for a penstock application has claimed (apparently rather persuasively to a new buyer!) that "expansion joints are not needed".