under ground GRE pipe failure 2

[Krahim4]

thread378-413013
The main underground firefighting ring has been designed and executed in1998 to deliver water to all the firefighting outlets i.e. hydrants, monitors… etc.; the main ring has been executed from 12-inch size Glass reinforced epoxy (GRE) pipes and 4-inch branches pipes, with the following data:
1. Working pressure up to 12 bar
2. Connections: total length of the main ring is about 6 km, Standard fittings (integrated with the existing main ring) are (90° Elbows, Reducers, and Flanges). All the pipes and fitting are
(to cover all crude oil storage tanks area )
connected in either one type of the following:
 Adhesive joints: (adhesive-bonded taper-taper joint)
 Mechanical joints: (O-ring with locking key)
 Flange joint: standard and heavy-duty with a flat gasket.
was extended in 2003 to cover new 3 crude oil storage tanks (The post was edited for more info, based on some request)

 

[LittleInch]

I'll have a further go tomorrow but is this

Buried?
Type of joint?
Age?
What sort of leak?

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[mk3223]

we are in the stage of assigning a contractor to repair, but I need some knowledge in, methods of repair, the main cause of failure, and how to avoid it in future

May have a third party to investigate the failure of the leaking joints and provide a root cause and proper repair option as you requested.

 

[LittleInch]

GRE pipe can be great, but is very susceptible to poor installation and damage if not treated right.

If the joints are simple taper fit glued joints, then any movement before the resin has set or any poor application of the resin will result in leakage.

GRE moves a surprising amount under pressure as it contracts (it has a Poisson ratio of about 0.6 to 0.7) so if you have long straight lengths, then tees or bends, they could get stressed beyond the limits of the pipe joint.

YOu need to uncover the joints and pressure it up so you can see where it is leaking from.

Leaking from the pipe to fitting join, then usually they just drain it off, apply a load of resin and fibre over the joint and that does the job.

But if the pipe or fitting material has suffered damage or excess stress and leaking though the material itself, then it's time to cut it out and fit another one.

The repair options though are not great and usually this means cutting a pipe at 90 degrees, getting rid of the outer coating for about 1m either side and then wrapping the pipe joint in multiple layers of resin and fibre, creating two bulging over wraps. Sometimes you need to add a mechanical restraint joint over that to give you the axial strength you need.

Like I said earlier, you always need to think about the fact the pipe will contract under pressure and hence pull out of any joint system.

GRE also suffers from poor resistance to abrasion, so sometimes even a small pebble or rock can wear away at the pipe and drill a hole in the pipe or fitting.

For info I attach a typical installation guide from a vendor - you should be able to get a similar one from whoever has supplied the pipe.

Let us know how you get on please.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[HTURKAK]

Eng. KRAHIM4,

Typical root cause is the sustained pressure in this case 12 bars together withy high ambient temp. The leaking joints are typically the joints at fittings ( bends and tee )...
It will be speculation but i suspect, the proper thrust blocks are not provided..

Will you post the network, thrust block details, ambient temperature.. type of GRE to get better responds?..

 

[LittleInch]

For GRE, the last thing you normally want is thrust blocks. Just concentrates forces and loads.

But then we don't have any details and for GRE, the axial contraction is more than thermal expansion.

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Also: If you get a response it's polite to respond to it.

 

[Krahim4]

This methods of repair will apply to all types of joints

 

[HTURKAK]

This is the copy and paste from FLOWTITE catalog..
(Owens-Corning’s standard fittings, as described in this catalogue, are utilized with the Flowtite® coupling to join to adjacent pipe sections. They are not designed to be used in a pressure system where thrust restraints, i.e., thrust blocks, are not utilized. Please refer to the Owens-Corning Pipe Handling and Installation Instructions, Pub. No. 15-PS-19596, for further details on proper construction of thrust blocks.)..

My experience is that, GRP pipe has certain disadvantages if ambient temperature and sustained pressure is high . The use of pull out resistant joints for pressures more than 5-6 bars is not reasonable..If the pressure is higher than 5 bars, the bends and tee branches should be fully embedded in thrust block to resist the developing bending and axial forces..

Moreover, the GRP fire loop in general fails during test or when it is necessary emergency cond.'s

Just saying ....

 

[LittleInch]

Ok. Flow tite is a form of push fit and so yes, in that application they would need anchors.

Krahim has updated his OP and trhe joints are either glued taper fit or O ring with mechanical key ( An Ameron special if I recall) which I don't think they make any more, or not when I looked last time.

If you've got 20 years out of this system you're doing well.

You might be in the donwhill spiral of constantly patching thing up. GRE can be like that sometimes.

If these are O ring joints, maybe the O rings have perished? The big issue here is how you create enough space to extract the pipe end to replace the O ring. Often needs a lot of digging.

Maybe the joints are fatigued out?

Only way it to dig each one up and look whilst it's under pressure.


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Also: If you get a response it's polite to respond to it.

 

[bimr]

In order to answer the question by the Original Poster, additional information is needed. For example, who is the manufacturer, pressure rating, velocity, climate, etc. Stop jumping to conclusions with the little information provided.

Also, locked pipe doesn't require thrust blocks.

 

[Krahim4]

manufactured by Ameron

 

[LittleInch]

That cut away shows the key issue.

Your sealing is wholly dependent on about 3mm surface length of an elastomeric band (O ring).
12 bar design probably only had one o ring fitted,

After 20 years they tend to age, crack and don't seal as well.

I think you're looking at either accepting the leakage rate or total replacement of all O rings so a major excavation of the entire network.

Ask Ameron what they suggest...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[HTURKAK]

Eng Krahim4 (Electrical),

Your ( Internet country code ) is SUDAN . If so, the ambient temperature is high enough .

Again i will speculate with the latest data.. The original network constructed at 1998 ( i assume with double bell REKA couplings and without locking inserts ) The extended portion ( extended in 2003 to cover new 3 crude oil storage tanks ) was with socket -spigot locked joints and without thrust blocks.. The leaking joints most probably the new joints .

Could you provide thrust block info. for the old and new extension?

 

[LittleInch]

I would be surprised if there are any thrust blocks.

Taper fit glued is good for high axial forces and the key lock stuff definitely is.

If it is just the joints leaking then you just need to drain it down, apply a load of resin and fibre wrap then you're probably good for another 5 to 10 years.

But yes, you're drip feeding information - please look at the other posts and address all the questions, then we might be able to help further.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Krahim4]

Dear All
Thanks for your good info
Please any suggestion for a company from the middle east or north Africa to Identify the root cause and submit a report for a repair plan
I tried to contact AMERON, but AMERON not responded

 

[Krahim4]

that what we did in last 10 or 15 years, repair here failed there, for this, we are intended to identify why this failure? is it operation failure, or a lifetime, or poor installation, or what the problem?

 

[LittleInch]

I think you're going to spend a lot of time and money finding out you have a problem, but not one reason. All of those issues you raise could contribute, plus the aging process of the sealing material of some of the pipe, i.e. that one? O ring.

Basically GRE is a great material when properly installed and not subject to any settlement, movement, flexing or not being laid dead flat or level with a good sand layer and no stones or sharp bits resting on the surface of the pipe.
I would personally consider GRE not to be a suitable material to bury - too many things to go wrong and it is basically not fit for purpose, IMHO, as a buried system to last more than 20 to 25 years. One thing is for certain - if it's causing you problems now, it won't get any better as time goes on.

I think you need to instead concentrate on how you're going to fix the issue.

You can dig it all up, possibly internally line it or just keep fixing the leaks.

The best people who know the most about GRE are in Oman and Qatar. Oman in particular has many companies able to design and build GRE pipe. I would look there for suitable consultants, but I don't have any particular names.

As said, I can see why you would like to know, but take a step back and think am I just spending money to tell me something I already know. You will know your system far better than anyone else and seem to have a good understanding of the issues and materials etc. Why don't you write the report?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Krahim4]

Do you mean breakdown report and history of failure?
Also, I need confirmation, do I need a thrust block for the pin lock pipe or not?
Indeed, I owe you the amount of information and guidance I learned from you and your wonderful interventions, and I thank you again

 

[LittleInch]

Both - You clearly know a lot about the system so you can write it all down. Also only you can see what the failures look like after digging them up!

You don't need a thrust block for either of the jointing systems you have. The O ring and pin lock pipe is locked together by the locking cable and the glued taper fit is strong enough not to need any anchors.

My guess is that who ever decides these things will try to keep it going for as long as they can before replacing it or looking at lining it from the inside. Liners are commonly used for old steel and cast iron pipes, but not common for GRE (yet), but there's no reason why it shouldn't work.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.