HDPE pipe used in Combined Cycle Power Plants 1

[Eduardo1982]

Dear sirs.
Some of you guys have had experience using HDPE pipe in Combined Cycle Power Plants? Especially in Cooling Water Systems?
I am facing a problem with HDPE pipe of big diameter (2 meters diameter) and some people are thinking that this material is not suitable for this purpose.
Some advice will be highly appreciated.
Thanks.

 

[bimr]

While the material might be suited for cooling systems, PE pipe may not provide an ideal installation. PE pipe may be less expensive because it has a low cost for the base pipe, but the extra cost to install PE pipe eliminates the price advantage.

PE pipe does not have the mechanical properties of other alternatives. It will look like crap when you are finished because it will not be straight. PE pipe is subject to high thermal expansion, so all anchorage points will have to be carefully considered, especially where it is going into and out of the ground and where the pipe is exposed to the sun.

 

[LittleInch]

I've not used it is sizes that big, but in theory there is no big issue, but as ever it depends on the circumstances.

Size is a bit big, but temperature and pressure is key. At that size I would assume this is buried? If not PE doesn't like being unsupported and will creep over time if put on supports.

However with virtually no context or information provided this is like saying steel pipe might be unsuitable.

Vague question so I'm afraid it's a vague answer....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[if7005]

Not recommended using PE pipe with extra large size. Why dont use double or triple lines instead of single line, with smaller size. It will be costly, but provide more safety,reliability,and easy for installation.

 

[MarGwy]

My company receives RFPs, reviews engineering specifications, and supplies large-diameter cooling water piping for combined cycle plants. I have not seen HDPE specified for any of the combined cycle plants that we are aware of. The thermal expansion/contraction issue is likely a concern and the elevated temperature of the cooling water during operation (which would de-rate the pressure capacity of HDPE or any thermoplastic pipe) would be another. The multiple relatively large-diameter outlets at both the condenser and the cooling tower, combined with the external loadings on these nozzles, could also be a problem for HDPE. The installation concerns mentioned previously are valid as well as concerns with the integrity of field-fusion welds on large-diameter HDPE (how can you NDE an HDPE "weld" prior to a full field hydrotest?). There are plenty of qualified AWWA C200 steel pipe manufacturers that can supply cooling water piping at a reasonable cost and with material that experienced installing contractors are familiar/efficient with.

 

[zdas04]

Another option is cement slip-together pipe with an HDPE liner. I've done one of these liner jobs (8-inch old pipe instead of 2 m new construction). The makers of these liners make them to your specifications and the resulting strength of constrained HDPE is quite good (the job I did had pipe that I rated at 265 psig before the liner and 600 psig after the liner using ASME B31.8 composite material calcs). I would expect an HDPE liner in concrete pipe to end up better than ASME B16.5 Class 150, and maybe Class 300 pressure rating.

The transitions to heat exchangers can be a challenge, but there are ways to do that too.

With the weight of 2 m of water already there, adding the weight of the concrete shouldn't be a major concern. For all the reasons above, I wouldn't run bare HDPE (even buried) for cooling water or cooling water return.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[SlideRuleEra]

If the cooling water system is closed-loop, the water contains concentrated contaminants that the cooling tower "washes" out of the air on an ongoing basis. This makes the water corrosive and it tends to attack steel pipe. For these "circulating cooling water systems" on electric generating stations, we have used prestressed concrete pipe exclusively. This solves the temperature, pressure, and thermal expansion issues at the same time.

For a open-loop cooling system, concentrated contaminants are not an issue.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[racookpe1978]

2 meter diameter? So, in sunshine (if above ground as noted above) and if running the hot water side, the structural strength will lower (a little bit) and will (over time) sag between supports. Less movement than the sag between supports, but at highest temperature, the pipe will also try to sag out-of-round at each support because of the "kinking" of high local stresses under each pipe support.

A fully-buried pipe, supported all around by the trench fill, will reduce both distortions.

 

[MarGwy]

Modern AWWA C200 steel pipe can have a cement mortar lining per AWWA C205, an epoxy lining per AWWA C210, or a polyurethane lining per AWWA C222. I have seen all specified for combined cycle buried cooling water systems; aboveground risers are not typically cement mortar lined. Reference AWWA M11 and AWWA C200 for modern steel pipe. PCCP fittings are essentially AWWA C208 steel fittings. The track record of PCCP pipe and corrosion is well documented in the AWWA Journal and the proceedings from ASCE Pipelines Conferences - under normal municipal water transmission service.

Including AWWA C200 steel pipe in your cooling water specifications is the only way to ensure sufficient competitive pricing and availability for your power plant projects. The companies that manufacture PCCP also manufacture C200 steel pipe, and there are a few more companies that only manufacture C200 steel pipe - you never can know which pipe company has better freight costs to your project location or which pipe companies are already at capacity.