Casing Spacers
Casing Spacers
(OP)
We have an 8 inch PVC water line in a 12-inch ductile iron pipe. The contractor installed the casing and the water pipe without using spacers so the carrier pipe is laying on the bottom of the 12-inch pipe. The owner wants spacers in the carrier pipe. The pipe spans about 14 feet PVC DR-18. Why use spacers ? The contractor does not think they are needed. The pipe is installed already- is there any purpose/ reason to try and put spacers in now ?





RE: Casing Spacers
RE: Casing Spacers
Typically run an aluminum gauge plate first and inspect at least the leading 10m of carrier pipe to confirm no damage during pull.
I can see how casing spacers with runners that extend to fix the carrier pipe in place inside the conduit may be required when there is risk of the carrier pipe "walking around" in the conduit due to operating conditions (e.g. liquid lines with aggressive slug flow?).
RE: Casing Spacers
RE: Casing Spacers
Spacers provide an easy insertion of the carrier into the casing pipe preventing damage of carrier pipe coating. Spacers are designed and tested to maintain continuous and long term support for the carrier pipe and its contents. Casing spacers are used on steel carriers when installed within steel casings to prevent electrical contact and shorting out the cathodic protection.
With the installation already completed, there is not much point to installing spacers. However, if the Owner is a railroad, don't believe the railroad will be persuaded.
RE: Casing Spacers
RE: Casing Spacers
"(b) Plastic pipe that is installed in a vault or any other below grade enclosure must be completely encased in gas-tight metal pipe and fittings that are adequately protected from corrosion.
(c) Plastic pipe must be installed so as to minimize shear or tensile stresses." and
"(f) Plastic pipe that is being encased must be inserted into the casing pipe in a manner that will protect the plastic. The leading end of the plastic must be closed before insertion." [Translation, if a significant enough shear load is applied it is not going to be the very strong steel or ductile iron pipe that shears, and the specific means and methods on how to accomplish the minimization of stresses to the weaker plastic are not supplied.]
Finally, I'm going to hazard a guess you now have (assuming an empty pipe is not now floating in a casing full of groundwater) more than 3" of space between the OD (9.05"?) of the 8" pvc barrel and the (normally larger than nominal) ID of the 12" ductile iron, and this should be understood.