Pressure Relieving Systems

Manage Risk and Reduce Costs

Equity Engineering is a leader in developing technologies that manage risk, and pressure relieving systems are a keystone in achieving process safety. Effective pressure relieving systems help clients meet their risk management targets, compliance requirements and business objectives.

Our engineers have been involved with the API’s Pressure Relief Subcommittee for over 15 years. Many are internationally recognized experts in the area of pressure relief system design and installation, and have contributed to establishing improved worldwide industry standards. Phil Henry, PE, an industry leader in pressure relief systems, has served as the task force chairman for the development of API RP 520, "Sizing, Selection, and Installation of Pressure-Relieving Devices in Refineries" for the past 10 years. Mr. Henry and other Equity engineers teach the official API Pressure Relieving Systems course, covering API RP 520, 521 and STD 2000.

Our pressure relieving engineers can assist clients with:

Assessment of existing relief systems for adequate overpressure protection utilizing the current ASME, API and international standards. If deficiencies are found, we will recommend options to bring the system into compliance
Analysis of relief valve performance concerns (e.g., chattering, nuisance lifting, and failure to lift) and recommendation of remediation methods to rectify the RV’s functionality
Audits of pressure relieving systems to provide assurance that the methodology and engineering analysis used in the design is in compliance with ‘Recognized and Generally Accepted Good Engineering Practice’ or RAGAGEP
Design of new relieving systems to provide adequate and economical overpressure protection (note that over-sized relief protection may also be a safety hazard)
Risk-Based Inspection analysis for relief devices

These tasks require extensive knowledge of the mechanical design of the various pressure relieving devices, process piping fluid dynamics (liquid, vapor and 2-phase) and a working familiarity with the latest industrial pressure relief guidelines and standards. Our engineers have the required experience in these areas to provide proficient and reliable consulting regarding relief device applications. Additionally, we can perform analyses of the consequences of an overpressure event or release from a relief device.

In addition to these services, we can perform the following types of reviews:

Assessments of a heat exchanger internal failure relating to the credibility of considering a full tube rupture as an overpressure scenario. We have the capability of performing tube vibration analyses and transient pressure surge analyses as part of a tube rupture scenario evaluation
Application of paragraph UG-140 (formerly Code Case 2211) of ASME Section VIII, Division 1. This permits, under certain circumstances, the use of system design and/or instrumentation safeguards for overpressure protection in lieu of a pressure relief device
Assessment of criteria and required conditions for the use of isolation valves in the pressure relief path
Dispersion analysis of atmospheric discharges
Flare system design reviews involving overpressure scenario assessments and possible simultaneous discharges of multiple relief devices; we can also assess the credibility of any flare load reduction credits (e.g. dynamic modeling, HIPS, favorable instrument response)
Flare radiation and acoustic studies
2-phase relief system evaluation and sizing

Featured Experts

Philip Henry
P.E.

Mr. Henry is responsible for engineering consulting services in the areas of Pressure Relief, Heat Transfer and Fluid Flow. He is a specialist in the design, installation...

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Philip Henry, P.E.

Mr. Henry is responsible for engineering consulting services in the areas of Pressure Relief, Heat Transfer and Fluid Flow. He is a specialist in the design, installation, sizing and selection of pressure relief devices and relieving systems, and is currently chairman of the API Pressure Relieving System Subcommittee’s Task Force on API 520 related to the design and installation of pressure relieving systems. He conducts audits of pressure relieving systems to ensure compliance with OSHA PSM legislation and ASME, API and DIERs Standards, Codes and Publications. He also teaches the official API Pressure Relieving Systems course.

He is actively involved in the development of technology for the API Risk-Based Inspection (RBI) methodology, is co-author of the re-write of API 581, Risked-Based Inspection Base Resource Document. He has been responsible for the development and implementation of RBI programs for pressure relief valves and heat exchanger bundles at many refining and petrochemical plants.

Mr. Henry is also an expert in the area of mechanical and thermal design of unfired heat exchangers, including troubleshooting of performance problems, fouling evaluation, network optimization and pinch analysis, mechanical vibration and field performance testing. He performs steady state and transient hydraulic evaluation of piping systems, including multi-phase flow systems, and develops bolting procedures for flanged joints including use of hydraulic torquing, tensioning, and ultrasonic elongation equipment. Mr. Henry has significant experience with the design and analysis of in-service fixed equipment. He has been responsible for rerating vessels to the ASME Code and NBIC and has applied FFS assessments in accordance with API 579. He has provided problem-solving support during numerous refinery shutdowns.

Becky Thomas

Ms. Thomas is responsible for engineering consulting services in the areas of Pressure Relief, Process Safety Management and Process Technology. She is a specialist...

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Becky Thomas

Ms. Thomas is responsible for engineering consulting services in the areas of Pressure Relief, Process Safety Management and Process Technology. She is a specialist in the design, installation, sizing and selection of pressure relief devices and relieving systems and is currently an active member of the API Pressure Relieving System Subcommittee’s Task Force on RP 520 and RP 521, related to the design and installation of pressure relieving systems. She conducts audits of pressure relieving systems to ensure compliance with OSHA PSM legislation and ASME, API and DIERs Standards, Codes and Publications. She also evaluates pressure relieving systems including scenario development, relief device sizing, collection header design and evaluation, relief device equipment recommendations and documentation.

Ms. Thomas is also proficient in developing Process Safety Management Systems. She is a Certified PHA Facilitator, LOPA Facilitator, and has been involved in the design of Safety Instrumented Systems. Ms. Thomas has provided Process Safety Reviews for grass-roots facilities, project implementation, and cyclic reviews for existing facilities. These reviews involved petro and non-petro chemical plants, refineries, pipelines, and municipalities.

Ms. Thomas has experience as a plant engineer responsible for day-to-day operations and design and management of plant projects, including troubleshooting, problem solving, and technical support for continuous plant improvements. Her responsibilities include leading the design and development of process systems, associated control instrumentation, process calculations, heat and material balances, process flow sheets, Piping & Instrumentation Diagrams (P&ID’s), equipment specifications and operating procedures.