DIP polywrap 2

[blackheart716]

I have a DIP that is spec'd out to be wrapped in Polyethylene encasement, 8 mil thick. I've never used or been on a job that called for polywrap, and basically I'm afraid that the contractor will have a difficult time keeping wrap intact during installation and when he taps the main. Has anyone used this product before? If so, was it flimsy and easily damaged by construction activities?

 

[coloeng]

Yes, we use it for any ductile pipe we install. Polywrap is standard when installing ductile iron pipe. It comes as a tube (think of a really big thin walled straw) that is just longer than each joint of pipe so that it is placed on the pipe just before they install the pipe and then you seal both ends to the adjacent pipe. It is fairly resistant to construction, but will get rips if the contractor is not careful.

If you haven't seen it used before, or your contractor hasn't used it, I believe DIPRA has a brochure that shows how to properly install.

If they are going to do taps on the line after it is wrapped, you need to make sure that the polywrap is sealed good around the tap.

Also as with all metal pipes you should make sure you have some type of cathodic protection.

 

[bimr]

This material is tougher than you would think.

You can actually pull the material through the bore hole with the pipe without problems when you are directionally drilling.

Contact DIPRA for further information.

 

[cvg]

cathodic protection may or may not be necessary and should only be recommended based on a corrosion analysis of the site conditions. polywrap does provide significant corrosion resistance.

 

[rconner]

I would recommend reading the document at

http://www.dipra.org/pdf/ddm.pdf

(as well as consensus standard ANSI/AWWA C105/A21.5, and/or ISO 8180 if international/metric pipe involving loose p/w is involved) regarding corrosion and corrosion protection of ductile iron piping.
I think DIPRA and/or DIP manufacturers also have other specific publications, and videos etc., that are helpful specifically in installer training/instruction etc. involving such means of corrosion protection.

 

[cvg]

Thanks Ron, I had not read the Design Decision Model publication before - wish I had read it last week. However, it confirms my current understanding anyway.

 

[coloeng]

CVG, you are correct, they should evaluate the need for cathodic protection in conjunction with the polyethylene sleeve. I get so used to using cathodic protection in our system because of the corrosive soils that I sometimes forget that the potential for corrosion needs to be evaluated.