Ten key steps to enhance pressure relief system efficiency

24 January, 2024

Step 6: Determine if additional analysis is required

As a final step in the design review and preparation phase, the engineering team will determine if additional analysis is required for the system. Examples of additional analysis include process stream flow rate and seeing if the pressure drop is sufficient to cause acoustic-induced vibration (AIV), flow-induced vibration (FIV), excessive loading on inlet and outlet piping during discharge, dispersion modelling, or runaway chemical reactions. Any steps necessary to remedy these additional issues should be performed during this step.

Step 7: Use calculations to determine adequate relief device specifications

Pressure relieving devices include mechanisms such as Pressure Safety Valves (PSV) and Pressure Relief Valves (PRV). However, there are other types of pressure-relieving devices as well, such as Rupture Disk Devices and Pin-Actuated Devices. If designed, installed and maintained correctly, these different devices will have the correct capacity for allowing anticipated pressurised fluids or gases to enter and escape so that pressure cannot build up beyond safe operating limits. Upon completion of calculations, an engineer will be able to specify and procure the correct PRV (i.e., type, code, basis, service, body, trim, manufacturer, serial no, etc.) for the requirements. Inspection and testing This final phase of ensuring optimal pressure relief system efficiency involves the design and execution of an appropriate inspection and testing programme while the device remains in the field (in service or out of service).

Step 8: Develop an ITP for each device

An inspection testing plan (ITP) helps to maintain the safety, efficiency, and effectiveness of each device. Once set, this information can be entered into the inspection database management system (IDMS) or whatever database the organisation uses.

Step 9: Perform inspection and testing

Once an ITP has been developed for each device and entered into the data management system, inspection and testing can take place following the guidelines set forth in API RP 576.

Step 10: Evergreening

A good evergreening programme will have a complimentary workflow that helps staff to identify, align, develop and execute change in a structured approach which helps a facility to protect its original investment, reduce verification burdens and not repeat expensive revalidations every 5 to 10 years.

After PRVs have been analysed, implemented and maintained in the field in “as built” status, facilities should consider implementing an evergreening workflow and strategy.

Changes that are not managed through a rigorous Management of Change (MoC) programme may result in the need to review overpressure scenarios for potential impacts. Additionally, the global flare/vent/scrubber capacity may have changed resulting in inadequate pressure relief capacity.

In these cases, revalidation of PRSs or specific PRDs may be required when process safety information (PSI) is missing/inadequate or when process or organisational changes occur that impact PRS or PRD requirements.

Conclusion

Managing PRVs is complex, challenging and often misunderstood. Implementing these 10 steps will help you to optimise your PSV programme and help it operate on solid ground.

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