Composite Pipe Inspection

Key details

  • Dual laser highly accurate and repeatable measurements

  • Monitoring of the pipe integrity during the test program

  • Internal and external pipe ovality monitoring are available

  • Traceable measurement results

Why?

Flexible pipes for use offshore are a valuable alternative to rigid risers. This type of pipe is constructed from a range of materials serving a variety of purposes. For instance the Internal carcass constructed of spiral stainless steel, plastic external and internal pressure sheath, high strength tapes and tensile armour wires and pressure sections. The pipe has to be able to resist high internal pressures as well as high external pressures subsea together with the forces of tides, waves and vessel motion. However, a significant additional challenge come about through the presence of H2S which can cause damage to the integrity of the stainless steel and ultimately result in the failure of the pipe.

Solution

In order to ensure that the pipe is suitable for a given project it is sometimes necessary to submit a pipe to testing. The test used in this project was to submit the pipe to tension and to pressure and to additionally subject the pipe to H2S over a period of time in order to monitor the effect on the integrity of the pipe. Even with an accelerated test program such an investigation takes time and failure could occur at any time or hopefully, and just as usefully, not at all. OMS were commissioned to create a tool that would monitor the external shape of the pipe at least once a day over a period of up to three years per test and provide the dimensional variation between the initial pipe geometry and the final geometry at the end of the project.

How?

The test arrangement for the project had to be able to sustain a pipe failure and the release of dangerous H2S gasses. As a result the entire system was enclosed within its own controlled room. The basic design is illustrated in the following figure.The two outer pipes are the rams which are designed to stretch the middle darker pipe. The OMS system was moved along rails along the length of the test pipe and had to be removable from the test rig. In order to facilitate the removal it was necessary to design the measurement system in a “C” shape to allow removal from the pipe when required.

The “C” shaped measurement tool partially rotated. Two lasers were mounted on the rotating C in order to measure the diameter of the pipe. As the lasers were rotated the angle of rotation was measured and both diameter and angle were stored.

The entire tool and it’s support electronics were then moved along the guide rails to specific location along the test apparatus.

The record of the original shape of the pipe was then compared to subsequent measurements to establish whether there was any change to the pipe over the period of the test.