Atmospheric PSV Consequence Analysis Case Study


The Challenge

An American energy company needed an assessment of the adequacy of their Emergency Relief System (ERS) discharging to the atmosphere for two refineries with a combined processing capacity of 120 MBD. Their main concern was the possibility of ammonia release into the atmosphere and the potential for a toxic dispersion.

Our Approach

The ioMosaic team conducted an Emergency Relief System (ERS) evaluation following Recognized And Generally Accepted Good Engineering Practices (RAGAGEP) and standards such as American Petroleum Institute (API) 520 and 521. The evaluation determined the required relief rate, system capacity, and stability in the event of the following overpressure contingencies:

  • External Fire Exposure
  • Closed Outlets
  • Failure of Automatic Controls

Their first step was to determine dynamically the source term phenomena using the two-phase dynamic model in Process Safety Office® SuperChems™. The second step was to characterize the associated toxic dispersions based on the following data and criteria:

  • Meteorological Data
  • Toxic Damage Criteria

The Benefits

PSV discharge is often routed to a flare through a flare header, which gathers various relief sources through a flare network of headers and sub-headers. Alternatively, depending on the complexity of a system, PSV discharge can occasionally be transmitted directly to the atmosphere. This, however, requires special safety attention and considerations.

The ERS evaluation study showed the clients’ system was found to have adequate capacity and was operating in a stable manner. The allowed intake pressure drop and backpressure readings led to recommendations that the relief device be left where it was. The client was pleased to have SuperChems™ executable files for each of the relief devices, a thorough report outlining the evaluation results and techniques, along with the study's results.

Learn More

Our mission is to help you protect your people, your plant, your stakeholder value and our planet. To learn more about how we can help you manage risk, call us at 1.844.ioMosaic.