Case study

Sector: Oil and Gas

Objective: Implement pilot Risk Based Inspection (RBI) study on downstream oil and gas facilities

Client benefits: A formalised and auditable risk based methodology (RISKWISE) was used to safely justify increases in time between inspections for refinery pressure equipment, utility boilers, storage tanks and pipelines.

Project background: TWI was selected to conduct a RBI pilot study on a representative selection of the plant. Following a comprehensive internal study, an extended run-length of five years between turnaround and inspections (T&Is) had been approved. The basis for setting inspection intervals was standard practice, ie. by detailed evaluation of historical inspection findings, and corrosion rates from ultrasonic thickness measurement.

The results of the assessment in terms of RLI (Remaining Life Indicator - TWI's safe future operating period based on risk) were presented.

All the equipment were found to be non-critical in terms of RLI, i.e. the RLI is greater than or equal to the T&I interval of 48 months Approximately 40% of the equipment had a RLI of 96 months, and approximately 50% of the equipment have a RLI greater or equal to 180 months. The calculated RLIs indicate that the proposed T&I interval of five years (60 months) is entirely acceptable. This proved the scope for large possible increases in run lengths between inspections without the need for additional inspection.

For more information please contact: aim@twi.co.uk