This chapter describes automatic pressure-relieving devices commonly used in the oil and petrochemical industries. It is intended as a guide for the inspection and control of these devices in the user's plant to ensure proper performance. This information is not intended to supersede requirements established by regulatory bodies. Included in this chapter are automatic devices such as spring-loaded pressure-relief valves. pilot-operated valves. and rupture disks. Inspections and tests made at manufacturers' plants@ however@ which are usually covered by codes or purchase specifications. are not discussed in this chapter. Other items not included are weak seams or sections in tanks. explosion doors. fusible plugs@ control valves. and other devices that either depend upon an external source of power for operation or are manually operated.