Plastic pipe and U.V. resistance

[MarkkraM]

Hi,
I am planning to run some plastic piping to recycle storm water into our cooling tower (max pump pressure 120kPag). There is little cover in this area so the pipe will get sunlight for most of the day. I was wondering if anyone could advice about how well different products perform in sunlight. I've read a HPDE product claiming it would last 5 years, and a PCV product claimed a 25% reduction in pressure rating after 2 years. I don't know if this is good or not.

Thanks,
MarkkraM

 

[moltenmetal]

A simple solution: insulate the pipe. This will shield the pipe from direct sunlight exposure. You can use a cheap, easy-to-apply closed-cell foam insulation, which can be either clad or merely painted white to provide UV protection. Then you can use PVC piping, which has very low installed cost because it can be solvent-welded rather than thermally welded. That is, provided winterization isn't something you need to worry about.

 

[25362]

Google brings some sites as the one by plasticpipe.org that may interest MarkkraM.

 

[Boomerang]

If the HDPE is black 'pressure irrigation grade' it will easily last 5 years and more in direct sunlight. What unit is max pump pressure 120kPag.? Give me psi or MPa.!
7 years ago I arranged for a ring main around a private property to collect rainwater off the roof. The ring main is mostly buried underground (2000 litres) but some of it is exposed to direct sunlight. The property is located in Western Australia, the UV capital of the world! The HDPE piping is as good as new.

 

[smckennz]

HDPE can get fairly hot in zero flow high sun applications, so some derating will be required once you have estimated the surface temperature. The lightest grade commonly available is 3.2 bar or 320kPa or 50psi. As you only need 120kPa or 18psi, the derating should not cost. As boomerand says, black HDPE lasts fine; we have some surface laid which is going strong after 14 years.
I hate PVC because it is easily damaged, but its more of a personal thing; in a properly engineered situation it works fine.

Cheers

Steve

 

[Ag93]

HDPE that is produced with 2% carbon black will provide an almost unlimited outdoor storage life. HDPE pipe that is not black will have a limited service life in the sun. HDPE is inherintly better than pvc against uv degredation.

The real design issue, as stated by smckennz, is how hot the pipe will get out in the sun. You will need to derate the pipe's pressure capability to account for the elevated temps. If your pumping head is not that high it shouldn't be a problem.

HDPE is commonly used for above ground piping in the Industrial markets. Dredging, mining, by-pass piping are common above ground applications. Good luck.

Leave room for the pipe to expand and contract with changes in temperature. Make sure you have restrained connections, otherwise you might be surprised when the pipe pulls out of the connection.

visit

http://www.performancepipe.com

- formerly driscopipe and plexco.