Surge blocks for underground GRE Piping

[uaepiping]

Surge analysis is carried out for underground firewater networks. Then the forces from surge analysis are taken and modelled in Caesar model and system is analyzed. Based on results, the recommendations for surge blocks are provided.
Question has been raised that why surge blocks are needed for buried piping. The soil is all around the joints and is stiff enough to resist any load then why blocks are needed in addition to that?
I request your opinion / experience on this.

 

[LittleInch]

"and is stiff enough to resist any load"

Are you sure?

"Soil" is rather vague and most have an elastic and plastic limit which allows some movement of pipe especially at bends/elbows.

Push fit pipe doesn't have to move much for leaks to appear.

Getting uniform soil back fill is difficult and it only takes one joint to fail for the network to fail. Especially for a fire water system, you don't want to take chances. IMHO.

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

 

[MJCronin]

I agree with Littleinch .... "Soil" is a vague term and a tiny displacement can fail the fire protection network.

Instead of putting money into analysis and surge blocks, why not invest in a proven DI piping system with positive joint engagement ?

I have been on several projects where MEGALUG FP systems have been successfuly used

There are savings in pipe routing, rework, thrust blocks etc.....

https://ebaa.com/files/pdf/brochures/Brochure.1100.pdf

You are Welcome....

Please respect us, .... Tell us more about you specific system, soil conditions and eventual solution ...

https://ebaa.com/files/pdf/misc/Misc.Joint Restraint per NFPA 24.pdf

MJCronin
Sr. Process Engineer

 

[HTURKAK]

The correct term is thrust block rather than surge blocks. The joints of GRP pipe in general socket spigot or double bell coupling with rubber gaskets and this type of joints are not pull-out resistant. The pressurized water exerts pushing force to bends and branches.The developing force shall be resisted either by pipe with longitudinal stress or by thrust blocks.

Although there are pull-out joint type with locking key, the bends are miter type and prone to rupture wthout embedded in thrust blocks.

If the fire loop is for an industrial plant, the pressure should be in the range of 15 bars , and if the ambient temp. is high , GRP is not correct alternative. The initial investment cost for GRP is cheaper ..agreed, but the consequences will be more costly.

If it is not late, change pipe material to DI as Mr CRONIN proposed or to steel .

If you share the diametre and the test pressure of the loop, you may get better opinions.

The following doc. shows the pull-out joint type with locking key ;

https://pipes.sa/wp-content/uploads/2014/02/4.pdf

The following doc. is useful for installation and thrust block concept ;

https://www.flowtite.com/wp-content/uploads/1901_Flowtite-Installation-Guide-Buried-Pipes_web.pdf

 

[LittleInch]

What you don't say is the jointing system.

If it's just push fit then you probably need thrust blocks. If it's glued or some other connection that provides axial strength maybe not. Usually its a bad idea to restrain pipe.

Note GRE has a high poissons ratio so is normally in tension once you put pressure on.

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

 

[bimr]

The usual joints for underground pipe and fittings are expected to be held in place by the soil in which the pipe is buried. Gasketed push-on and mechanical joints without special locking devices have limited ability to resist separation due to movement of the pipe. All tees, plugs, caps, bends, and hydrant branches on pipe installed underground shall be restrained against movement.

The problem with thrust blocks is that the soil conditions are generally not known, and the installer generally does not properly install thrust blocks.

You best option is to follow the pipe manufacturer's installation instruction instead of making up your own installation criteria.