Gauges put subsea pipes to the test

Mitsui Babcock uses HBM's strain gauges and Catman data analysis equipment to gain maximum value from its testing operations.

Mitsui Babcock, a global leader in the design validation and testing of subsea oil pipelines, has selected HBM's strain gauges and Catman data analysis equipment to gain maximum value from its testing operations.

During deployment, subsea oil pipes are subjected to bending moments and sheer forces while, during use, other factors, such as temperature and pressure, can affect the pipes' performance.

It is critical that the integrity of the pipes is tested to prevent failures which could have major production and environmental implications.

Comments Albert Holt, Mitsui Babcock's Principal Test Engineer: "One reason for choosing HBM's equipment is that it gives the structural engineers access to many more channels than we previously had available for determining stress levels".

A four-point bending rig, designed by Mitsui Babcock, is used to test pipe sections up to 12m long, and test durations can vary depending on the complexity of the program.

Advanced techniques are deployed to optimise the information gained from the test.

For example, high-resolution cameras are inserted in the body of the pipe to provide visual evidence of the structural damage at the onset of buckling.

The largest pipe that Mitsui Babcock has tested is 660mm in diameter.

Notes Holt: "HBM was a great help as they developed a customised interface for us that works very well by allowing our engineers to see the effect of pipeline bending under an applied load".

He adds that Catman is an excellent tool.

Most tests at the facility are static although some dynamic testing is also performed and testing to destruction using compression, tensile and burst testing can also be a customer requirement.

HBM's strain gages are used to determine the levels of strain that, for static tests, is 3% above nominal strain.

The pipes are tested to temperatures of 165C and pressures of 34.5MPa.

Remarks Holt: "HBM's equipment is quick to set up, allows us to use a wide range of transducers and represents excellent value for money".

There are several different processes used in the construction of pipelines to gain the balance between cost and fitness for purpose.

These include a uniform stainless steel liner fitted inside a carbon steel pipe, with some manufacturers, making the inner pipeline slightly smaller than the outer pipe and then hydraulically expanding the inner pipe to meet the outer carbon steel pipe.

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