HDPE or FRP jacket for pre-insulated buried steam piping

[PagoMitch]

Just designed a project with a couple thousand feet of small (2" through 6") buried steam and CD piping. I have specified pre-insulated FRP cased 10g steel piping for the buried lines. Considered using HDPE with all other pipe/insulation characteristics the same, (there is a lot of it out there) but convinced myself of the superiority of FRP primarily due to its impact strength (40-60 ft. lbs/in versus about 8ft. lbs./in.) and readily visible indications of damage.

My concern with the HDPE (other than injection voids in the insulation)is that it can be abused, break the insulation, and then rebound with no "visible" damage; until 10 or 20 or 30 years later. From the time it is loaded on a truck with a forklift, cinched down with ratchet straps on the flatbeds, trans-shipped, delivered to a contractor warehouse, re-loaded, re-ratcheted, offloaded on site, and installed, there are a lot of potential damage situations. Heck, I have seen contractors run over the pipe with a truck. The HDPE bounces back, the insulation is now crap, and "no one will ever know". The HDPE vendor actually alludes to this on his site, in a comparison of HDPE vs: FRP casings. But it is treated as a benefit: "...take a hammer and forcefully strike both samples (HDPE and FRP), the results will speak for themselves". Sure, the casing bounces back, but the insulation is now cracked or compressed, and definitely NOT equal to the rest of the "un-hammered" sections.

Conversely, if the FRP is abused beyond its impact strength, it is very visible to all via cracked casing, exposed fibers, etc. It cannot be ignored and must be repaired to factory specs.

The contractor has submitted on the cheaper (HDPE) route. His feelings are that the FRP is proprietary. My comment is that it is on the plans and detailed in the specifications. Any firm can produce the product, but only a few companies do; it is more expensive, and they do not get much demand for it.

So, does anyone with experience in both these systems have any relevant comments, other than "we have installed miles of this stuff"? I am not convinced that having a piping system/methodology in service for 5 years extrapolates to a 50 to 70 year lifespan IF there are (unknown) insulation failures as weak points.

Thanks

 

[BigInch]

You could have him submit a suplementry installation quality control plan and procedure to eliminate the possibility of installation damage in light of your specific concerns.

"I am sure it can be done. I've seen it on the internet."

"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com

 

[PagoMitch]

BigInch,
Thanks for the reply. That is indeed a good idea once the product is on-site (IF everybody is honest); but it still does not address the potential for damage in shipping. In particular, running into it with a forklift and over-zealous ratchet strap damage.

I commute a lot on the Interstate, and have seen many big rigs transporting bare steel piping with the ratchet clamps cinched down so hard that 40 ft lengths of 2" through 4" steel piping have multiple locations of more than 2" deflection (note that this is an estimate based upon driving next to the truck at 75mph...) While the pipe (and the HDPE) would probably bounce right back, the insulation will be damaged, and we now have our failure locations; except no one will ever know for years...

 

[BigInch]

And the pipe is still going down the highway after all these years. Because the continuous quality control at the mill, at shipping and receiving, storage, during stringing, welding, coating, xray, lowering and burial, gaging and hydrotesting all combine to make it safe and reliable to continue doing it.

If you throw something on site, don't watch it, let trucks hit it, folks walk off with pieces they've cut out of it, gouge it with improper handling and installation "techniques" and bury it, I'd expect it wouldn't last a year no matter what it was.



"I am sure it can be done. I've seen it on the internet."

"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com