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Forcemain thrust blocks from a sanitary pump station

Forcemain thrust blocks from a sanitary pump station

(OP)
I have to design thrust blocks on a sanitary force main. I figured out the horizontal 1/16 bends. However, I have an 1/8 bend that are rolled down to drop the line to the pump station entrance and the next one rolls up to level out the line as it goes through the pump station wall. Should I use the largest of the thrust blocks as calculated for the one rolled down? The upper vertical bend thrust block or some combination of vertical and horizontal calculation?

Richard A. Cornelius, P.E.
WWW.amlinereast.com

RE: Forcemain thrust blocks from a sanitary pump station

You should forget the thrust blocks and use restrained pipe joints. Restrained pipe joint design will be simpler and the end results are more reliable as you do not know the soil conditions or the method that Contractor will use to install the thrust blocks.

RE: Forcemain thrust blocks from a sanitary pump station

Your "rolled-down" angle includes a force component pointed up, which means sizing the block for weight, using gravity to resist the upwards force component). Allowable soil bearing pressure doesn't help here. I posted an analysis of pipeline thrust restraint on the PTC Mathcad forums that includes two Mathcad documents (in both Mathcad Prime 3.0 format and Adobe Acrobat .pdf format) and a copy of the Ductile Iron Pipe Research Association booklet "Thrust Restraint for Ductile Iron Pipe" (the principle apply to more than just DIP). You can find it here: http://communities.ptc.com/docs/DOC-4895

==========
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

RE: Forcemain thrust blocks from a sanitary pump station

I hit send before I was finished. I agree with bimr about the use of restrained joints here in lieu of thrust blocks.

==========
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

RE: Forcemain thrust blocks from a sanitary pump station

(OP)
Thanks. I will look at that site you gave. I know restrained joints are better but we are doing pipe lining and cutting the bends out as access locations for liner insertion. the owner is afraid that mega Lugs may damage the 50 year old DIP.

Richard A. Cornelius, P.E.
WWW.amlinereast.com

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