Project Synopsis

Evaluate options and specify appropriate equipment for pressure/vacuum relief and tank blanketing requirements for a 1,000,000 gallon o-xylene storage tank as part of a tank recommissioning project.

Project Summary


Process Engineering Associates, LLC (PROCESS) was subcontracted by a detail engineering company to evaluate the pressure and vacuum relief and tank blanketing requirements for a major specialty chemical production client’s 1,000,000 gallon o-xylene storage tank as part of the engineering company’s work to recommission this storage tank for service.  PROCESS was also required to specify appropriate relief devices for purchase by the client.

The client was engaged in a fast-track project to restart the o-xylene storage tank for service.  PROCESS upgraded its in-house proprietary relief device sizing program to utilize the guidelines in API Standard 2000 for atmospheric and low pressure storage vessels.  PROCESS then used the revised program to determine the required relief capacities for the credible relief (pressure and vacuum) scenarios.  PROCESS then used vendor supplied sizing programs and product literature to specify appropriate devices for this storage tank.

PROCESS evaluated and specified the following:

  • 8” combination pressure/vacuum (P/V) conservation vent
  • 20” combination P/V manway mounted emergency vent
  • Pressure relief valve (3/4”-D-1) for thermal expansion of blocked-in material
  • Tank blanketing regulator (nitrogen).

PROCESS used it’s licensed commercial computer process simulation software (CHEMCAD) to determine the physical and chemical properties of the chemical compounds involved in the relief scenarios.

Industry Type

  • Chemicals Manufacturing

Utilized Skills

  • Application of API standards
  • Pressure relief valve (PRV) or pressure safety valve (PSV) sizing