(64b) Modeling Pressure Relief Devices Mounted on a Common Inlet Manifold

It is common practice for large equipment items, such as distillation column systems, to be protected by multiple pressure relief devices. Often, multiple pressure relief devices are required to provide adequate relief capacity to handle the large relief requirements from certain overpressure scenarios affecting these large systems. Additionally, the set pressures of these relief devices can be staggered to better address varied relief requirements, and to improve relief device stability.

It is also fairly common practice for these multiple relief devices to be mounted on a common inlet manifold. Installing these devices on such a piping manifold can provide easier access for maintenance and inspection, as well as providing a strong structural support for multiple heavy relief devices.

However, in selecting this type of design, the potential exists to inadvertently overlook the flow characteristics associated with such a common inlet manifold. Modeling the flow hydraulics to multiple relief devices on such a manifold is more complex than most companies realize, and the potential exists to overlook the impact that the inlet manifold has on the stability of each component relief device. This could lead to valve chatter due to excessive inlet pressure losses and excessive built-up backpressure, decreasing the valve capacity and creating the potential for valve damage and vibrational issues.

ioMosaic has developed a methodology to effectively model flow through multiple pressure relief devices mounted on common inlet manifolds. This approach ensures accurate representation of flow through each pressure relief device, intends to avoid the potential pitfalls of a simplified system, and in doing so should help to design a stable pressure relief system.