When a component does not comply with the manufacturing drawings, we can evaluate the effect of this discrepancy on residual life or determine the revised safe operating limits to achieve the design life.

The reasons for the non compliance may be a manufacturing defect or will commonly be due to corrosion. In this case we usually work from an inspection survey, eg ultrasonic test report.

Typical examples are:

· Re-rating of gas cylinders.

Task - The Client owned a number of transportable gas cylinders that had suffered internal corrosion. They had been shot blasted and ultrasonically scanned to map the variation in wall thickness. He needed to know the safe operating limit for his intended use.

Response - Based upon the measured wall thickness, mechanical test data obtained using a sample and the phase behaviour of the intended gas mixtures, we determined the maximum permissible filling pressure for each cylinder, based upon the requirements of BS5045.

· Fatigue Life of Tubes in Shell and Tube Heat Exchanger

Task - The operator of an offshore installation sought advice on the viability of extending the inspection interval of tube bundles, based upon previous inspection data and operating experience with similar units.

Response - A review of the original design calculations for flow induced vibration and calculation of the lowest natural frequency for a U-tube revealed a degree of conservatism in the design calculations. Examination of bundles from sister units together with a review of the current operating conditions led to the conclusion that deferral of the next inspection for one year was viable.