Valve Identifications and Markings for Boiler Operation

This section covers identifications and markings that permit identification of individual relief valves and safety valves and the symbolism used in piping and instrumentation diagrams (P&ID) to designate these valves. Safety valve capacity and blowout information is listed on the name/data plate on the safety valve.

Accurate valve identification is critical to valve installation, removal for inspection/maintenance or testing/adjustment, and reinstallation. To permit accurate identification, most manufacturers mark data on the body of a valve and/or on a manufacturer’s plate that is attached to the valve body. This data includes the following:

  • ‘’‘Manufacturer’s Name, Trademark, or Symbol’’’: Specifies the valve manufacturer.
  • ‘’‘Rating Designation’’’: Specifies the appropriate pressure rating class designations or specific maximum pressure/temperature designations for the valve.
  • ‘’‘Cold Working Pressure’’’: The letters and designations listed below stand for the following parameters at normal-range ambient temperatures (-20 to 100degrees Fahrenheit; -29 to 36degrees Celsius):
  1. WO - Water and oil pressure

  2. OWG - Oil, water, and gas pressure

  3. WOG - Water, oil, and gas pressure 4. GLP - Gas and liquid pressure

  4. WWP - Working water pressure

  5. W - Water pressure

  6. WSP - Working steam pressure

  • ‘’‘Material Designation’’’: Specifies the materials of construction for the body and the bonnet of the valve. Forged and fabricated valves are usually identified with () American Society for Testing Materials (ASTM) numbers and grade identification symbols.
  • ‘’‘Melt Identification’’’: Cast valves are marked with the melt numbers or melt identification symbols.
  • ‘’‘Valve Trim Identification’’’: Identifies materials of construction for internals such as the stem and the disc when these materials differ from the materials of construction for the valve body.
  • ‘’‘Size Designation’’’: Specified in nominal pipe size.
  • ‘’‘Identification of Threaded End’’’: Standard ring joints that comply with applicable ANSI and API standards are marked with ‘‘R’’.
  • ‘’‘Special Function Requirements’’’: Manufacturers may place catalog numbers, dates, reference numbers, and other data to distinguish valves used for special functions.
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