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TWI to Develop New Pipe Pre-Straining Capability

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Thu, 17 October, 2019

TWI already has the facilities to carry out a number of types of tests on full scale pipes (including resonance fatigue testing).

To enhance our capabilities, TWI will be commissioning a new pipe pre-straining machine in Q1 2020.

Overview
Offshore pipelines can be subjected to high levels of strain during installation (e.g. due to reeling), or in operation (e.g. by local buckling). High levels of strain may impact the of the pipeline by affecting the fatigue performance of the girth welds, causing local tearing of embedded flaws, or wrinkling of liners in CRA lined pipes.

Operators often require assurance that high levels of strain won’t adversely affect the performance of new pipelines, and so require representative levels of strain to be applied to pipes before they are tested to qualify them for service.

New Pre-Straining Test Machine
TWI will be commissioning a new test machine for pre-straining full-scale pipes. The machine will use hydraulic jacks to bend pipes around formers of different radii, in order to apply strains above yield. The applied strain depends on the pipe geometry and the radius of the former that the pipe is bent around.

The TWI machine design will accommodate pipes with diameters 6”, 8.625”, 10.75”, 12.75” and 14”, and bending formers with different radii will be available.

Pipes which are as short as 4m can be pre-strained in the test machine.

Existing Pipe Testing Capabilities

The new test machine compliments TWI’s existing in-house capabilities, which include welding (such as end plug welding), strain gauging and testing (ranging from resonance fatigue testing, to full scale corrosion fatigue testing, four point bend testing and pressure testing in a specially designed pressure pit).

Contact us
For more information about the pre-straining test machine, please contact carol.johnston@twi.co.uk

Figure 1. TWI’s pre-straining rig design
Figure 1. TWI’s pre-straining rig design
Figure 2. TWI’s resonance fatigue testing facility
Figure 2. TWI’s resonance fatigue testing facility
Figure 3. TWI’s full scale sour corrosion fatigue test machine
Figure 3. TWI’s full scale sour corrosion fatigue test machine

For more information please email:


contactus@twi.co.uk