INSTRUMENT CONTROL VALVES

1.1          Control Valves

Control valves shall be installed with the actuator in the vertical position on a horizontal line. Control valves shall be installed so that they are readily accessible from grade or platforms.  Wherever possible, they should be located at grade for ease of maintenance. Clearance shall be provided above and below a control valve so that the bottom flange and plug or the actuator and plug may be removed with the valve body in the pipeline.  Sufficient clearance shall also be provided for valve removal.

1.2          Shutdown/ Blowdown Valves

All actuated ball valves shall be of the 90º rotation type and be complete with all necessary controls mounted on the valve. Actuator types shall be Pneumatic Spring Return. The valve stem orientation shall be as stated on the data sheet. Correct operation of the valve shall not be affected by the position of the valve or actuator.

1.3          Pressure Relief Valves

All pressure relieving devices shall be sized in strict accordance with applicable local, state, and national code requirements. Safety relief valves shall be sized by calculating ASME areas required for the most severe relieving case and shall follow the ASME requirements. Nomenclature and formulas used shall be according to API RP 520. Valve selection and installation shall be based on API RP 520, Part I and Part II.  Closed relief valve discharge systems shall be designed in accordance with API RP 521.