Restrained Joints on Steel Pipe

[jdmont]

We have a pipeline project where both DIP and CMLCSP were listed as acceptable, we calculated RJ distances using a software but now the DIP is not acceptable anymore. I dont think it would be proper to keep the distances of RJ that were calc. for DIP, on CMLCSP. In your experiences how would it properly be shown to restrain CMLCSP since the supplied will have to calculate the distances when pipe is being fabricated. It seems to me that we could just call out the bend to be with RJ and the supplier will have to calculate the length, because I cannot find any recommendations or software to find the distances.

 

[PST09]

sorry to ask what my seem obvious, but what do your abreviations mean?

PST

 

[GoldDredger]

I follow DIP, ductile iron pipe. Not sure what RG or CMLCSP is.

 

[bpattengale]

RJ is Restrained Joint and CMLCSP is Cement Mortar Lined and Coated Steel Pipe (Had to google that one).

DIP is usually used with MJ joints and if you use glands or megalugs they're considered restrained joints for the purposes of watermains. I'm unfamiliar with the usual joint type for CMLCSP, what type of joints are used or are you welding the steel pipe?

 

[jdmont]

It will be welded steel pipe where is is called out for Restrained Joints (RJ). I am just unsure how to calculate the length and call out on plans.

Our specs. read, "Restrained Joints:
a. Double fillet-welded lap joints are required for areas of restrained length determined as outlined in AWWA M11 and as required for pipeline bending.
b. An additional length equal to 25 percent of the length as required by AWWA M11 shall be restrained with single fillet welds on lap type joints."

And "Where piping is designated to be restrained for thrust, the design of the cylinder and welded joint shall take into account the effect of stresses caused by thrust loads."

So the length will be determined by supplier, so I am unsure on how to show it on plans because you would typically call out a certain length for PVC or DIP.

 

[cvg]

CMLC steel is generally supplied in bell and spigot except where restrained is required it is welded. Length of restraint should be shown regardless and would be essentially the same as for DIP.

 

[jdmont]

Sounds good, thank you. I just did not want to show a length we calculated for DIP and then be way off of the length for the Steel Pipe.

 

[bimr]

Both materials utilize a gasket push-joint as the primary connection. Restrained joints for steel pipe are generally single weld lap-welds. DIP utilizes a number of proprietary mechanical systems to provide restraint

The length of the restrained pipe is determined by the dead weight of the pipe filled with water, the overburden and the friction forces of the pipe pulling through the soil. There are differences in the weight and coefficient of friction of the pipe materials providing different variables in the restrained length calculation.

The paper in the link provides a formula for the calculation:

http://www.tawwa.org/TW06TECH/TWfiles/Mielke, Richard.pdf

 

[coloeng]

You can also contact a steel pipe manufacturer and give them the pertinent info; pipe diameter, operating and test pressures, depth of bury, type of trench, etc. They will usually calculate the required length of restrained pipe.