Pipe comparison - I need to make a

[BRIS]

Pipe comparison - I need to make a comparison of ductile iron steel and GRP pipes. Diameters are 600 to 1700mm and pressure ratings 6 to 30 Bar. carrying raw water.


I have no experience of GRP.

Is there anyone out there with experince of large diameter GRP pipes who can give me some pointers on their advanatges and disadvantages.

 

[RWF7437]

What does "GRP" mean ?

 

[BRIS]

Glass Reinforced Polymer (fiberglass)

Brian

 

[RWF7437]

Thank you.

Fiberglas (one "s" not two) is a trademark, not a generic name for all reinforced plastics.

What sort of comparison are you trying to make ? Do you want to compare costs, hydraulic properties, strengths, useful life, all of these? You can find many such comparisons in the literature and on the web with a little searching. How do you plan to use this comparison ? To make a purchasing decision? To select a pipe for a particular application? Pressure or gravity flow? Water or other fluid?

Your question is so broad I'm afraid it cannot be answered in one short email message.

 

[stanier]

Both materials have limitations in respect of a soil/pipe structure. The DICL Ductile iron cement lined pipoe ahs limits of deflection as in the larger dioameter damage to the lining can occur if the pipe is deflected beyond the limit. GRP has limitations of strain compared to other materials.

AWWA standards should be consulted for the design and specification of these materials.

Certainly in Europe, Canada, SE Asia, teh Middle East and the Asia Pacific authoriies/companies are moving away from these materials in favour of thermoplastics such as ABS, PE , PP and the PVCs.

Sharing knowledge is a way to immortality

 

[c4eng]

Typically, for potable water, the pipe selections are limited to: ductile iron, Polyethylene, PVC, and concrete. There are limitations on size for some of these. Consult the manufacturers' literature.

 

[Zambo]

BRIS asks about raw water not potable (c44eng) - GRP is a perfectly acceptable high pressure water pipe.

I think the main consideration is cost because both ductile iron amd GRP will provode a suitable water main.

Try GRP!!

Zambo

 

[BRIS]

Thanks for the replies.

I have now been to visit the local GRP pipe manufacturing factory - Future Pipes - I am in Lebanon, and I am impressed with the standards of manufacture and the quality control. Pipes are manufactured up to 2.4 m diameter. I am told that they can be supplied at pressure ratings up to 30 bar but it appears that for pressures above 16 bar there is some difficulty with fittings and the allowable joint deflection is limited to less than 0.5 degrees which could make laying 12m lengths difficult.

There appears to be a lot of prejudice in the industry against GRP but I am having trouble finding any technical disadvantages - assuming that its cost is less than alternatives.

Because it is flexible it needs better quality backfill and good site supervision but providing this is allowed for in the cost estimate it appears to me that GRP has many advantages. (No corrosion, low roughness, light weight)

Brian

 

[stanier]

BRIS,

There was a number of catastorphic failures of GRP in the Middle East, Australia and other parts of the world back in the 1970's. Engineers have been cautious as to its use ever since. Like all materials if it isnt designed, manufactured and installed well it will fail.

With projects driven by costs rather than sound engineering one has to ahve a very tight specification in order to prevfent the purchasing department from procuring materials that do not have the capacity to perform the job.

From memory one of the standards to consider is BS 4995. There has been a lot of research into the materials particularly at the University of Strathclyde.

One particular product has a lower strain tolerance. The reinforcement is not a continuous roving of a fibreglas bandage rather a centrifugally spun concoction of sand, chopped glass and a resin. It is of lower cost initially but one has to be knowledgable about its design and installation to achive a satisfactory result. As one does with any other material.

One has to ensure that the design of the soil/pipe structure takes this into account . (refer AWWA modified Iowa equations or ATV design approach) The design should consider the static and dynamic loading on the pipe to ensure that the long term properties are not exceeded. This includes such things as rising groundwater, traffic, construction vehicles etc.

Sharing knowledge is a way to immortality

 

[KRSServices]

For a true comparison, you have to evaluate the manufacurers design criteria of the ppie, installation recommendations, and design limitations (ie: burst pressures, maximum working pressures, embankment loading ratings, etc.) and some historical limitations (such as those mentioned in the previous threads) to be able to determine the best for your circumstances. You should try to evaluate the comparisons relative to the prospective design life of the pipe with an unbiased "what if" scenario as the pipe nears the endo of it's design life.

As an example, I have had the unfortunate experience of dealing with pipe that at the time of installation, was known to have limitations, but installed anyway due to cost. By the time I was involved, those limitations had exacerbated into serious risks to the public due to shortsighted planning of the original designers. I urge you to not to make rushed and sometimes biased decisions based on a suppliers sweet story or the lure of cost.

KRS Services

http://www.krs-services.com

 

[Earley]

Quality of manufactured product is only one piece of the jig saw. Have you looked around at the local quality of construction. GRP pipe is very unforgiving of poor construction. Check also your Client preferences and consider his future maintenance problems. How easily can fittings be provided if a piece of the pipe has to be replaced for any reason.