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  for Metal Finishing since 1989
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Pipeline Refinishing

 

Can anyone give me a rough idea of the per foot costs involved in stripping and painting a raw water pipeline which is suspended under a bridge? The pipe is 10" ductile iron. The stripping must be done in a contained environment due to the protected waterway below. The finish must be able to withstand constant exposure to salt water.

Kirk Noonan
- Vero Beach, Florida

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 Kirk,

Pardon me for asking, but just WHY was a plain steel pipe used for a pipe exposed to salt?

Why in the heck didn't they use a plastic pipe? No maintenance, no painting, no corrosion, no ferric contamination of the drinking water.

There are 3 different types of plastic pipe in the l0" size range l. ABS ... but this is mine-line piping. 2. PVC and lastly 3. hdPe. (sure, there are other plastic materials but we are thinking about cost/installation and UV resistance all at the same time)

The only advantages that ABS and hdPe have is that they are more impact resistant and better at lower temperatures, a consideration of zero importance in Florida.

The problem with plastic piping is support and thermal expansion. PVC's thermal expansion rate is about 2-1/2 times LESS than hdPe and it is stronger and is available with expansion joints. It really depends how long the bridge is as far as expansion joints are concerned.

Then there's FRP, fibreglass, which is more rigid, stronger still and has an expansion rate about 3 times less than PVC. But joining would be costly. And is it suitable for potable water? I don't know. Maybe not. Depends.

Sorry that I can't help you with your exact question. If you did opt for a plastic pipe, being biased, I'd opt for a white PVC (available, I believe, @ l60 and 200 psi) rather than Sch. 40 or sch. 80 grey PVC.... because the white coloring would not affect the expansion rate so much as the grey.

Food for thought.

Cheers!

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).