Relief, vent and flare disposal systems

A relief, vent, or disposal system is an emergency system for discharging gas during abnormal conditions, by manual or controlled means or by an automatic pressure relief valve from a pressurized vessel or piping system, to the atmosphere to relieve pressure in excess of the maximum allowable working pressure or design pressure. The relief system may include the relief device, the collection piping, flashback protection, and a gas outlet. The relief system outlet may be either vented or flared. If designed properly, vent or flare emergency relief systems from pressure vessels may be combined. This chapter also discusses relief device selection; procedures for sizing vapors, liquids, two-phase liquids/gases and steam; installation considerations; and disposal system design.