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RiskWISE – Evaluating the condition of offshore equipment

TWI performed a risk-based inspection (RBI) of pressure vessels for a major offshore oil company in the Middle East, identifying where the company’s staff should prioritise inspection and maintenance.

The inspections were carried out by TWI engineers using RiskWISE, a specialised RBI and RBM (risk-based maintenance) solution that enables plant personnel to confidently manage the risk and associated issues for the continued and safe operation of their plant and equipment.

Critical assessment of ageing assets

TWI carried out the assessment to help the company focus its inspection and maintenance resources on the most critical areas of its ageing equipment. In parallel with the assessment, TWI also provided on-the-job training for the company’s integrity division.

As part of the assessment, normally unmanned wellhead towers (WHTs) were assessed to determine their current condition, rate of deterioration and expected condition at the next planned outage.

Because many of the assets were quite old, with many design details and much of the operational history not available, TWI employed linear regression models and inferred data from similar installations.

Providing solutions

The majority of the pressure vessels were found fit for service, but there were three issues requiring solutions that arose over the course of the assessment.

Problem: incomplete design data. Solution: as pressure vessels have a finite number of configurations and use standard fittings, the design of the vessel could typically be determined from the inspection report and therefore endorsed on that basis.

Problem: incomplete inspection data. Solution: A hydrogen damage survey was performed on several pieces of equipment and it was found that only vessels of a certain age and construction appeared to be susceptible to hydrogen-induced damage. From this survey, the susceptibility of any vessel could be inferred.

Problem: genuine internal corrosion. Solution: There were many reported instances of localised internal corrosion. These were detected by deviations in wall thickness. Checks were performed on deviations to determine the validity of the result. The system only failed endorsement when these deviations were deemed accurate and large enough to undermine its integrity.

Although the assessment found that some of the vessels could not be endorsed, those that fell under this category were already out of service and scheduled for decommission.

Contact us

To find out more about TWI’s inspection services, email To find out more about RiskWISE and other software solutions, visit