Cost and Benefit Considerations of Designing for Higher Pressure

In the process industry, there are multiple disciplines that compare the potential pressure against the equipment design to determine the likelihood of a loss of containment.  This paper reviews the cost savings associated with specifying equipment that is designed for a higher pressures.  The initial cost savings typically results from smaller relief devices, less flare capacity, fewer required layers of protection.  In addition, the higher design pressure often results in a safer system with less potential for a loss of containment.  After years of operation, there are typically multiple changes within a processing plant that can trigger a replacement of equipment, the flare system, or the installation of costly layers of protection (e.g. Safety Instrumented Systems, SIS). This paper will explore an example where a rate increase in the facility (1) requires the replacement of a relief valve with a larger one that has the subsequent impact on the flare system, (2) because of the higher pressures risk assessments require additional layers of protection (e.g. a new SIS). In addition to the immediate cost savings, these future upgrades could be eliminated by designing the equipment for the maximum possible achievable pressure. The current cost savings of designing the equipment for a higher pressure is achieved by reducing the size and cost of the relief and flare systems. This paper will provide advice that is consistent with the provisions in ASME for Overpressure Protection by System Design.