Oklahoma Administrative Code
Title 380 - Department of Labor
Chapter 25 - Boiler and Pressure Vessel Rules
Subchapter 7 - General Requirements
Section 380:25-7-8 - Pressure reducing valves

(a) Where pressure reducing valves are used, one or more safety or safety relief valves shall be provided on the low pressure side of the reducing valve when the piping or equipment on the low pressure side does not meet the requirements for the full initial pressure. The safety or safety relief valve shall be located adjoining or as close as possible to the reducing valve. Proper protection shall be provided to prevent injury or damage caused by the escaping fluid from the discharge of safety or safety relief valves if vented to the atmosphere. The combined discharge capacity of the safety or safety relief valves shall be such that the pressure rating of the lower pressure piping or equipment shall not be exceeded in case the reducing valve fails in the open position.

(b) The use of hand controlled bypasses around the reducing valves is permissible. If a bypass is used around the reducing valve, the safety valve required on the low pressure side shall be of sufficient capacity to relieve all the fluid that can pass through the bypass without over pressuring the low pressure side.

(c) A pressure gage shall be installed on the low pressure of a reducing valve.