HDD Pipe and Casing Q's?
HDD Pipe and Casing Q's?
(OP)
A municipality I'm working with to design a developer funded system is requiring a casing to be drilled under a creek then a carrier pipe to be slid through, both HDPE.
I've had many HDPE pipelines installed by HDD method, but never did a casing / carrier - it just seems overkill to me.
However, before I try to argue the point that it's overkill I'd like to hear opnions from some others in the industry. Has anyone seen a fusible joint pipe fail after passing the inital pressure test?
Thanks,
Mike
I've had many HDPE pipelines installed by HDD method, but never did a casing / carrier - it just seems overkill to me.
However, before I try to argue the point that it's overkill I'd like to hear opnions from some others in the industry. Has anyone seen a fusible joint pipe fail after passing the inital pressure test?
Thanks,
Mike





RE: HDD Pipe and Casing Q's?
In a river crossing one can assume with reasonable confidence that the directionally drilled pipe is subjected to the earth
pressure from the sediments above it combined with the water pressure.
However, it is not common to use a casing pipe for HDPE.
RE: HDD Pipe and Casing Q's?
RE: HDD Pipe and Casing Q's?
Visual inspection or "Visual testing" (VT) was incidentally long promoted by the hdpe industry and its installation experts as the adequate quality control of fused joints. Revelations from the field as well as quite detailed research have indicated this is not reliable. Note the field findings of the reports including ht
"Visual testing does not seem to reveal a subtle condition like lack of fusion in a butt fusion joint. It is a surface evaluation technique and does not represent the volumetric condition of a fusion joint. Research conducted to date shows that VT only detects certain unacceptable butt fusion joint conditions. The research indicates that VT will not detect many of the conditions that should not go into service."
As cvg sort of intimates, and also e.g. ASCE MOP #89, "Pipeline Crossings"(1989) details, there are actually several intents/functions of casings that are sometimes preferred/specified by whatever authorities for different sorts of crossings, and at times for all piping materials.
All that being said, "over-kill" is relative and in the eyes of the beholder (I guess interpretation dependent on critical nature and risks of specific crossings), as I agree with bimr there are probably a whole lot of crossings out there that have not (at least yet) exhibited problems.