Teletest® survey of tank farm pipework
| Pipework at ST Services' Eastham Tank Farm |
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Following years of service, the integrity of tank farm pipework needs to be verified.
An option might be to contemplate hydrostatic testing. However, this approach suffers from serious disadvantages. The lines need to be out of action for significant periods. In addition, the supply and particularly the disposal of water is costly and the period out of service is increased by the need to dry the lines.
Plant Integrity was therefore asked to carry out a survey of the pipework using Teletest.
Pipe diameters were 4, 6, 8, 10, 12 and 14 inch. There were seamless, conventionally or spirally welded pipes, several of which were insulated, elevated, buried or 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., but in some cases, it proved possible to test 200m of pipe from a single point (100m in each direction). Testing productivity was up to 500m of pipe tested in a day.
Following the survey, pipes were sorted into categories:
- No corrosion
- Minor corrosion
- Moderate corrosion requiring further assessment
- Severe corrosion
When corrosion was detected, its position along the pipe was located accurately, so that further assessment could be carried out. Cross-checking Teletest's findings has given the Terminal Manager a high level of confidence in the predictions and consequently he has completely abandoned future hydrostatic testing. Furthermore, his confidence is such that he has selected some pipes for regular Teletest inspection whilst extending the period between surveys for those pipes found to be clear of flaw indications.