Project Synopsis

Engineering projects to resolve approximately 150 process hazard analysis (PHA) action items related to process relief systems and flare loading.

Project Summary


The client owns and operates a petroleum refinery and contracted with Process Engineering Associates, LLC (PROCESS) to lead a multi-disciplinary engineering team tasked to execute engineering projects to resolve approximately 150 process hazard analysis (PHA) action items related to process relief systems capacities and flare loading.  For resolution of each action item, the team executed the following steps:

  • Determine the process scenarios that could lead to the consequence of interest identified during the PHA
  • Determine through process simulation and engineering calculations whether or not the consequence of interest could actually occur
  • Develop engineering solutions to mitigate the consequence of interest
  • Prepare the engineering documentation required for implementation of the engineering solutions
  • Initiate solution implementation via interfacing with the appropriate client / contractor project personnel.

American Petroleum Institute (API) standards and discussions with refinery engineering/operations personnel formed the basis for the determination of process scenarios that could lead to consequences of interest.  API standards were also used as the basis for the engineering calculations required to determine if the consequences of interest could actually occur.  Process simulation (with HYSIS process simulation software) was used as appropriate to enhance the accuracy of actual process conditions calculations.  For example, without process simulation for a power failure scenario, normal tower overhead vapor rates are often used as the basis for the pressure relieving calculations; process simulation of the towers, however, resulted in the calculation of overhead rates at the actual pressure relieving conditions.  This resulted in the determination of more realistic relief requirements, which prevented several unnecessary process modifications.  Engineering solutions were developed based on the team’s experience with, and knowledge of general refinery operations as well as the specifics of the client's facility.  The proposed solutions, including the requisite engineering documentation, were presented to the appropriate client or contractor personnel such that implementation could be initiated.

Typical engineered solutions developed during the course of the project include the following:

  • Design and installation of new or retrofit process relief systems, including pressure relief valves and relief valve inlet and outlet piping systems
  • Retrofit of steady-state process controls for decreasing relief loadings to the refinery flare system
  • Design and installation of interlock shutdown controls on refinery utilities systems for minimizing energy input to process equipment during power failure events
  • Insulation of process vessels to minimize external fire scenario relief loadings
  • Installation of valve car seals and locks and the development of administrative control procedures and safe operating limits to mitigate accidental releases and/or provide adequate relief paths to refinery flare header systems.

Refinery units covered by the scope of work included fluidized catalytic cracking, naphtha and gas oil hydrotreating, alkylation, vacuum, coking, hydrogen recovery, catalytic cracking gas plant, Penex isomerization, MTBE, amine, sour water stripping, sulfur recovery, caustic treating, flare, and propane truck loading.

Industry Type

  • Petroleum Refining

Utilized Skills

  • PHA action item resolution
  • Computer process simulation
  • Pressure relief valve (PRV) or pressure safety valve (PSV) sizing
  • API standards implementation
  • Multi-disciplinary project team management

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