Quote:
Originally Posted by monkeyman
It's premature to blame this on the pipe or the Engineers 50 years ago. The pipe and specifically the wires need to be properly maintained and cared for to avoid corrosion. If the wires corrode, they're going to fail, if the wires fail, the pipe will fail. Under normal circumstances the wires are shielded by a layer of cement. One of the things that compromises the cement protective layer is salt.
It really is going to take a third party evaluation to determine what went wrong here so we can avoid such failures in the future.
|
This particular generation of pipe though had higher tensile strength and reduced thickness and was designed to reduce cost. This version of the pipe had been discontinued due to premature failure.
There is no real way to maintain concrete pipe from external corrosion once buried. I think it’s reasonable given the age of this pipe to blame it. Essentially it’s monitoring for cable breakage and reline or replace.
Quote:
The initial structural design requirements for the manufacturing of PCCP tended to be conservative with high safety factors. However, as experience with using this composite pipe and understanding of the behavior of PCCP increased, along with advances in material sciences, changes in the structural design of PCCP were made to reduce the cost of manufacturing.
The increase in the tensile strength of the wire during manufacturing in the late 1960s and early 1970s reduced the amount of prestressing steel wire and allowed wire of smaller diameter, which resulted in what appeared to be a more efficient design and economical manufacturing. These practices culminated in the 1970s when pipe utilizing Class IV wire and other cost saving measures were implemented in the manufacturing process.
Problematic Classes of PCCP
Pipe from the 1970s era started experiencing a high rate of premature failures. Subsequently, the engineering standards for PCCP began to improve, resulting in improved standards for PCCP. The major revisions in the standards, design, and manufacturing of PCCP consist of changes in the maximum diameter, the quality (strength) of the concrete, the thickness of the steel cylinder, prestressing wire standards (wire diameter, wrapping stress, spacing, etc.), and the thickness of the mortar coating.
|
https://www.xylem.com/en-ca/brands/p...der-pipe-pccp/
So I agree we need to wait for the report for finality on cause I think that the material of construction here is the problem.