Rainbowseahorse
Marine/Ocean
- Sep 28, 2009
- 8
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.
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.
