pvc pipe thrust restraint 3

[dzyn]

Currently doing a utility replacement project for gas and water systems. Plan is to convert all the the old 50' era steel lines to pvc (water) and pe (gas). The base wants thrust restraint connections. my question is, do you still provide thrust blocks with these types of joints?

any additional tips, hints, references for design/construction drawings/documents would be appreciated.

maybe some lessons learned.

 

[RWF7437]

Yes

 

[jartgo]

some of the restraint manufacturers will sell it as not being necessary, but we always include both. There are a lot of unknowns in restraint design. The cost of adding the blocking is typcially minimal in relation to the project overall.

 

[BarryEng]

I agree with the above two comments.

PVC, if solvent welded, theoretically does not require a thrust block. The problem is that there may be a valve nearby that can be closed & if the main is charged, you can get some unbalanced thrust.

PVC RRJ - use thrust blocks (just because there is no restraint developed by the soil).

PE (I assume) is either butt welded, fusion welded or screw fittings used that will allow the thrust to be taken in axial tension to a place where the thrust restraint can be developed.

Have a look at the DIPRA (ductile iron pipe research auth)web site for a very good (modern) version of how thrust is developed & restrained in practice. It is aspplicable to other pipe materials & the computer programs can be downloaded from their site.

I also have some other pubs on the subject (such as CIRIA in UK etc) BUT, as jthompson said above, there are a lot of unknowns in restraint design.

For retic situations - as above. Larger pipelines have a better quality control in both design & construction & hence we can be more critical. Any pipeline that is continuous (joints such as welding in steel pipes) the skin friction can be used to restrain the pipe axially. This is similar to a pile in sand - most of the load is taken by the skin friction against the sand (soil). See DIPRA for a version of this as far as restraint of bends are concerned.

 

[bimr]

"Thrust blocks and restrained joints are alternative or supplementary methods of providing thrust restraint. One is not necessarily better than the other. The methods for sizing thrust blocks and for calculating lengths of restraint can be found in the DIPRA brochure "Thrust Restraint Design for Ductile Iron Pipe." There is also a program that can be downloaded from DIPRAs website,

http://www.dipra.org,

which will calculate the restrained joint length needed based on the specific parameters of the job. A very conservative design sometimes employed by designers and particularly helpful for extra security/flexibility in seismic areas employs both an adequate length of restrained joints for carrying the full thrust load and, in addition, full-sized thrust blocks. ACIPCO does not object to such conservative design when applied fairly."

http://www.acipco.com/international/engineeringlibrary/techquestions.cfm#faq10

FAQ: What means of joint restraint are available?


U.S. Pipe's primary method of thrust restraint are restrained joints.

http://uspipe.com/Main/Default.asp?CategoryID=15&SubCategoryID=32

http://www.uspipe.com/Files/20061281436210.RESTRAINEDJOINT.pdf