Scaling GRP/FRP Pipes

[BRIS]

We have water with a high calcium carbonate content which can be expected to be scaling. Previous experience using concrete and cement mortar lined pipe has shown an increase in pipe friction due to scaling.

my concern is the mechanism of scaling in GRP/FRP pipe - I can envisage the scale building on the pipe wall and subsequently shearing of in sheets. particulary if the pipe is subject to changes in load/pressure that cause deflection.

Any experience of this problem ?

 

[rconner]

I noticed you have not yet gotten any response to your inquiry. Despite perhaps some inference/hype/perception cultivated by some in the plastic pipe business that same does not occur, I have heard various scales and even quite thick slime films do in fact occur in at least some working plastic/polymeric type pipelines. However, with regard to specifically GRP/FRP-type pipes, the only specific case of internal build-ups I am aware of in large pipes is a sliplining installation involving ~2-1/4 miles of new 60” fiberglass pipes in Rochester, NY circa 1991. If I remember correctly, this new plastic pipe installation was done to renovate the first/an old brick tunnel portion of a roughly hundred years old much longer water transmission pipeline, with most length of the main composed of then century old downstream metal pipes that had been cement mortar lined in place about a half century ago (and said older cement mortar lined portion still reportedly measured/exhibited a C=130 flow coefficient, prior to the new construction).
I understand that within nine months of start-up of a new filtration facility the transmission capacity of the renovated gravity-feed water pipeline decreased 10 percent from its initial start-up and roughly 20 percent after about three years before the situation was first addressed. After a lengthy investigation of what could have been causing the problem (exhausting first mechanical and air blockage etc. as causes), that pipeline was opened up for internal inspection first in the old cement mortar lined portions, and not finding the problem there they reportedly eventually arrived at the reported “scene of the slime” in the relatively new fiberglass pipes -- apparently a rather thick, “rippled” layer of slime that provided subsequently in actual flow test for the relatively new FRP tunnel portion only of C=114 for this portion of piping, that apparently the Owner had expected to be in the range of 140-150!
I provide this information not to say that this slime (apparently/reportedly a result of some of unanticipated post-precipitation for whatever reason adhering to the plastic pipe wall) would be like your “scale”; however, some upfront thinking about internal depositions/build-ups as a result of water chemistries and who knows what in all pipes, and what one would/will do if/when they occur may indeed be worthwhile. Apparently the folks in this case were under the circumstances understandably resistant to mechanical cleaning means, but were able to eventually/somehow at least temporarily restore most of the carrying capacity by some sort of new water treatment involving chemical dissolution of the film. While they reportedly did not however fully return the main to initial capacity, and I have not heard what has occurred in the time since, I did not hear then of any sloughing off of the inner build-up nor any other ramifications of such.