ST Services had a requirement to prove the integrity of the pipework at their tank farm at Eastham in the UK. They contemplated achieving this by hydrostatic testing. However, this approach suffered from serious disadvantages. The lines would be out of action for significant periods. The supply and particularly the disposal of water are costly and the period out of service and cost are increased by the need to dry the lines. ST Services therefore called on TWI's wholly owned subsidiary, Plant Integrity Ltd (P i), to survey the pipework using Teletest®. The purpose of the survey was to locate any areas of corrosion. Pipe diameters were 4", 6", 8", 10", 12" and 14". Some pipes were spirally welded. Also some were insulated, some elevated, some buried and some steam jacketed. Despite the challenge presented by these various conditions, the survey was very successful. Test ranges depended on pipe condition, geometric features, contents, etc. However, in some cases it was possible to test 200m of pipe from a single point (100m in each direction). Testing productivity was up to 500m tested in a day. Following the survey, pipes were sorted into categories: -
- No corrosion
- Minor corrosion
- Moderate corrosion requiring further assessment
- Severe corrosion
The position of corrosion detected, was accurately located along the line, so that further assessment could be carried out. ST Services' Terminal Manager, Andy Smith, said that he was very pleased with the outcome. Cross-checking Teletest®'s findings has given confidence in the predictions. Consequently, they have abandoned hydrostatic testing. Furthermore, their confidence is such that they have prioritised the pipes and extended the period between Teletest® surveys for all pipes found clear of indications.
