One of the world’s leading testing groups has developed the capability to perform industry-leading ‘tri-axial’ compression and creep testing – believed to be a global first for an independent laboratory.

With the drive to search increasing seawater depths for new production fields, in some cases down to 3,000m, extra demands are being placed on subsea infrastructures.

Specialist testing is required to ensure that the materials used to insulate the steel pipes can resist the high pressure and temperatures required.

Exova has now invested £30,000 in tri-axial compression and creep testing capabilities at its Salford, UK lab, with a custom rig constructed consisting of three test cells, with an operating range of up to 120 degrees C and a pressure representing 2,300m water depth. The laboratory is thought to be the first independent testing laboratory to offer this service.

John Carter, strategic account director and coatings expert at Exova, said: “Subsea pipelines and infrastructure are subjected to high pressures and high temperature gradients, and insulation is needed to allow oil flow to be maintained to a specific temperature to avoid reduced flow rates, blockages or physical damage.

“Passive insulation coating has become industry standard, using materials from simple unmodified polymers and foams, to more complex materials depending on temperature and depth of use.

“Insulation around a pipe or structure is subject to compression – a deformation under load with time. The industry has developed tri-axial compression and creep testing, now a requirement within many specifications for oil and gas infrastructure.

 “However, there are no accepted standards for this testing which define the apparatus and methodologies to be used.

“Often Exova sees subsea infrastructure specifications where this testing is included but with no further details of the test protocols or final properties to be reported.”

John reports that the International Organisation for Standardisation (ISO) has set up a committee to define a standard for wet thermal insulation coatings for pipelines, flow lines, equipment and subsea structures and a draft standard BS EN ISO 12736 is in circulation.

However, he warns that even this standard leaves much to be clarified by Exova and its clients.

John said: “In co-operation with a commercial partner we have developed the capability for tri-axial compression and creep testing to determine the behaviour of materials and the way they are affected by temperature and pressure, for use as thermal insulation on steel pipes.

Lynda Barron, Exova global technical leader for Coatings is giving a presentation, entitled ‘Tri-axial creep – how to develop a draft specification into an accredited test’ at the forthcoming second international conference on Protection and Insulation of High Temperature Submarine Pipelines and all aspects of Field Joint Coatings, Onshore and Offshore Pipelines, in October 2013, discussing how to develop a in house test into a fully accredited test.

John added: “This investment will allow Exova to advise customers operating at the cutting edge of subsea exploration and be of real and lasting benefit.”

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