A California oil refinery capable of refining 240 thousand barrels of crude oil per day needed to evaluate a vapor break-through scenario from a high-pressure vessel to a low-pressure vessel using dynamics. In their desire to ensure compliance with OSHA PSM regulations, the client retained ioMosaic Corporation to complete an evaluation. According to the OSHA Petroleum Refinery PSM National Emphasis Program (NEP), failure to document relief system design and design basis is one of the most common types of PSM non-compliance.
The project was conducted using SuperChems™, a component of Process Safety Office®. Modeling vapor gas blow-by scenario through the control valve was based on the following steps:
The existing relief device was found inadequate. As a result, the ioMosaic team conducted several two-phase dynamic simulations (mitigation) until the system was found to be adequate. The final results consisted of replacing the current relief device with two 6R8 PRVs, one set at the protected equipment MAWP, and the second PRV at the MAWP plus 5% allowable accumulation per code.