Project Synopsis

Perform a plant relief valve study for an ethanol production facility.

Project Summary

Process Engineering Associates, LLC (PROCESS) was contracted by the client, an ethanol production facility, to update the facility Heat and Material balance to the current production rate and perform a review of all pressure relief devices located in their ethanol plant.  The plant is partially covered by OSHA’s Process Safety Management (PSM) regulations.

Specific tasks for this project included:

  • Generation of a Heat and Material Balance (HMB)
  • A site visit to document equipment physical data and generate isometric sketches of relief valve piping for approximately 80 devices
  • Calculation of required relief flows vs relief device capacity for both PSM and non-PSM processes
  • Execution of hydraulic calculations to adequately size inlet and outlet piping.

PROCESS used its commercial computer process simulation software (CHEMCAD) to update the facility throughput information which was required for the relief valve evaluation.  The computer process simulation software was also used to determine relief stream detailed chemical/physical properties which are required for the pressure relief calculations.

PROCESS used the CHEMCAD software hydraulics package and chemical/physical component database, along with its proprietary in-house relief device capacity design program with calculations based on the guidelines given in API standards 520, 521 and 2000, to determine the pressure relief requirements for each piece of equipment.  The in-house program was used to evaluate the vapor and liquid relief capacities of each relief valve as well as relief requirements for identified potential pressure relief scenarios, including:

  • External pool fire
  • Blocked flow (vapor and/or liquid)
  • Loss of cooling
  • Loss of column reflux
  • Gas blow-by
  • Control valve failure
  • Heat exchanger tube rupture
  • Abnormal heat input
  • Hydraulic expansion
  • Normal in/out-breathing.

PROCESS supplied the client with pressure relief device sizing documentation packages that included safety device calculations and relief valve datasheets for those valves recommended for replacement so that quotes could be obtained from vendors.  In addition to sizing packages, documentation was provided for the venting requirements for various sizes of floating roof tanks.

Industry Type

Alternatives Fuels Production


Utilized Skills

  • Process simulation
  • Relief systems evaluation
  • Relief device sizing.

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