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SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

(OP)
I've an urgent problem which suggest a very strong possibility of pipeline coating design fault.

I've read a post dated 1/Nov/2007 titled "Concrete Composition of Saltwater pipe weights" with interest as it has some similarity to our pipeline.

We've started to lay a single 660.4mm dia API 52X spiral pipeline with 9.5mm plate thickness for a distance of 27 km in open sea water of up to 22 meters depth. The Laybarge is 250ft.long and fitted with 40 ton Tensioner.
 
All the pipes are internally coated with 25mm thick reinforced ordinary Portland cement, while the external is coated, first with bituminous wrapping protection, followed with 125mm thick reinforced (with Y7 bars horizontally and with rings) ordinary grade 50 cast-on ordinary Portland cement. Even with calculation by designers, we believe the relatively thick external reinforced concrete coating makes the pipes very stiff and inflexible. Normally, offshore pipes are spun-on concrete coated with BRC to hold the concrete together, as this allows flexibility and the all important S-curve to the pipeline when being laid into the seabed from a Laybarge. After welding & Radiography works on pipeline weld joints, the joint (approx. 500mm wide) is wrapped with protective wraps and the void covered with in-fill foam.

Our first pipeline buckle occurred just after 1 km in water depth of a mere 8 meters. At first we attributed this to the extra stresses exerted on the pipeline as the Laybarge started "sidewalk" to turn the pipeline at the bend. We cut-off and laid down the pipeline intending to recover and do a mid-point tie-in later.

We proceeded to the other side of the sea where the pipeline is to be joined to swamp pipeline. At just 800 meters and in 8 meters water depth, the pipeline buckled once again and this time we attributed the incident to bad weather and weaken pipe wall due to heat input on repair weld joint.

We laid down that pipeline and proceeded to start another pipeline next to it. This time, we install four buoyancy tanks to relieve stress on the pipe joints, but after 1.2km, the pipeline bucked once more at water depth of 18 meters.

We've stopped pipelaying works altogether and is now trying to figure out how best to lay the 27 km subsea pipeline without anymore pipe buckle and our options are:
1)    Secure a Laybarge that can carry out subsea pipelay with these stiff pipes.
2)    Make the pipes more flexible by: a) Cutting & removing 500mm wide of the reinforced concrete coating at the center of each pipe. b) Cut the reinforced concrete coating at 1 meter interval, and within 25mm of pipe, along the entire length of each pipe to allow more flex.

Have anybody come across a problem such as this? If so, I would really2 appreciate your input.
Thank you.
 

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

Not nearly enough tension.  I could take that little barge arm wrestling all by myself.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

Substitute lack of tension with more vertical lift points.  Got some more barges?

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

Absolutely BigInch - more tension or buoyancy or davits, etc.  Adding buoyancy got you another few hundred metres, so you're heading in the right direction ;)

Seems pretty thin wall for a 26inch line - D/t of 70 combined with X52 (and spiral pipe) would likely have problems being installed without all the extra concrete and the bizarre internal coating.

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

(OP)
Yes, we know the Laybarge is rather undersized, but that's the only one we could get at that time.

We thought of adding more tension, but due to the thin pipe wall, we don't think that would solve the pipe joint from buckling. From Diver's video cam, we can see that the pipeline is not flexing as expected and due to the heavy concrete coating, only the pipe joint (which have no concrete coating but with in-fill foam) have any flex at all. This would mean that once the pipe joint has reached the maximum resistivity, buckling will and have to occur at the pipe joint.

As mentioned, adding buoyancy tanks to relieve stress on pipe joints would be the obvious solution, but it's very difficult to control under strong underwater current. And bad weather is always foremost on everybody's mind as that would mean we have to lay down the pipeline in a hurry with all those buoyancy tanks dangling on the pipeline joint, anything can happen.

With the onset of the annual monsoon season, it's too late to restart the subsea pipe laying works for this year.  We'll have to rethink and to modify those heavy reinforced concrete pipes with thin walls so that we can have a crack at laying them next year.
 

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

Don't lay them, tow or pull them into place.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

(OP)
BigInch

Yup, Rintis method was proposed, but for 27 km long pipeline, there will be quite a number of pipe string tie-in.
However, this option might have to be taken up if, at the end of the day, nobody can lay these inflexible pipes without buckling.
 

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

dont lay the pipeline down until complete lenght
keep pipe buyond below surface water with buyancy devices
keep pipe on position using suction anchors
start with routing anchors  

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

S.O.P.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

As BigInch mentioned, you would better to tow them instead of laying.
and as you mentioned, several tie ins make it impractical.
but there is a technology named Snake lay technology provided by SLT International company can arrange it for you with 3 or 4 tie-ins. visit www.slt-international.com they may help you.

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

SLT option looks expensive, time-consuming (10km per day...yeah right!) and it is currently untested so probably not a great option for a Project in trouble.  It's also for deep water applications.  Sorry to rain on your parade...

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

Don't have to worry about that option.  That stiff pipe won't snake much.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

I'm estimating that the pipes buckled somewhere near what would be the crush depth for the bare pipe.

If you're laying the pipe with a dry interior, would it be possible to flood it while laying it and then dry it out later?



 

Mike Halloran
Pembroke Pines, FL, USA

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

It buckled in 8m water depth (0.8bar), so it can't be collapse driven - it's critical collapse depth is probably around 100m or so.

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

I calculated 20-ish meters, depending on how round it is, with no other stress applied, which is not the case.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

I'm inclined to think it is more like 100 m, but that's from memory.   

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

Looking again at your system, the stress concentration due to the outer concrete alone is about 1.6 (DNV-RP-F105 will give you guidance on this) so combined with your thin wall it is more than likely to be the discontinuities at the field joints that is your problem.  Suggest towing out long pipe strings with 'strong-backs' around the weaker field joints (i.e. the tie-ins between the pipestrings) or a strongback at each FJ (not pretty and time-consuming...) or a stiffer FJ infill which will of course reduce lay rate as well.

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

You might also want to check the diffusion-chemical-mechanical simulation forum at http://www.composite-agency.com/materials-forum.htm

They can look at steel-polymer-concrete structures in real life circumstances -  in a fully integrated manner, and provide help via their open source facility.

Kind Regards,
Rodney

RE: SUBSEA WATER PIPELINE BUCKLING DURING PIPE LAY WORKS.

Could it be the problem from spiral pipeline?

This is the 1st time i seen spiral pipeline used. Usually we use ERW,UOE line pipe.

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