TWI assist Mobil during turnaround inspection

Mobil's Beaumont Refinery hydrocracker

As part of the scheduled maintenance programme at their oil refinery in Beaumont, Texas, Mobil Oil Corporation carried out a 100% automated ultrasonic inspection of all the welds in the three operating reactor vessels of the hydrocracker unit.

Automated ultrasonic testing was chosen because Mobil needed to ensure the best possible repeatability so that the condition of these vessels can be monitored with enhanced confidence.

The inspection involved a three-phase procedure:

Pulse-echo ultrasonics from which the condition of the welds was assessed.
Time of flight defraction (TOFD) to provide a 'fingerprint' so that TOFD on its own can be applied for future inspections.
Detailed evaluations using both pulse-echo and TOFD ultrasonics to determine the type and size of any significant indications.

TWI's role was to support Mobil in specifying the inspection, validating the procedures, supervising the data acquisition and performing the detailed evaluation of the inspection results.

The entire inspection, including preliminary reporting, took 10 days and involved two other US-based inspection contractors, who carried out the initial 'detection' scans.

This approach is believed to be very progressive and provides Mobil with much higher confidence in the continued safe operation of these vessels than would be the case had traditional manual ultrasonic techniques been applied.