California Code of Regulations
Title 8 - Industrial Relations
Division 1 - Department of Industrial Relations
Chapter 4 - Division of Industrial Safety
Subchapter 2 - Boiler and Fired Pressure Vessel Safety Orders
Article 4 - Installation
Section 762 - Safety Valves and Pressure Relieving Devices, Fired Pressure Vessels

(a) Boilers (or vaporizers) of the Dow-therm, mercury vapor or similar types shall be fitted with adequate safety relieving devices to assure their safe operation. Safety valves of Dow-therm vaporizers and similar equipment shall be removed at least once each year for inspection and cleaning of any deposits that might affect their operation. (To eliminate the necessity of shutting the unit down for this inspection, a three-way stop valve may be installed under 2 safety valves, each with the required relieving capacity, and so installed that both safety valves cannot be closed off from the vaporizer at the same time; or 2 or more separate safety valves may be installed with individual shutoff valves, in which case the shutoff valve stems shall be mechanically interconnected in a manner which will allow full required flow at all times.)

(b) Fired pressure vessels other than those mentioned in (a) above shall be fitted with safety relieving devices of sufficient capacity to relieve all vapor that can be generated in the vessel during normal operation and shall be fitted with proper controls to assure their safe operation.