Valve Specification Sheets: How to Write a Complete Valve Datasheet

A valve datasheet (also called a valve specification sheet or valve data sheet) is the primary technical document that defines exactly what valve is required for a specific process application. A complete, accurate valve datasheet eliminates ambiguity in procurement, ensures that bids from multiple vendors are on an equivalent technical basis, and provides the document of record for the valve's design basis throughout its service life. Writing a thorough valve datasheet requires systematic consideration of all the parameters that influence valve selection, sizing, materials, and accessories.

Process Data Section

The process data section of the valve datasheet captures all the process conditions the valve must handle. Fluid identification, including chemical name or service description, is listed along with the fluid phase (liquid, gas, or two-phase). Normal, maximum, and minimum operating pressure and temperature define the operating envelope. Inlet and outlet pressure and temperature at maximum, normal, and minimum flow conditions are required for control valve sizing calculations. Fluid properties including density, viscosity, vapor pressure, critical pressure, and specific heat ratio are needed for accurate Cv calculations and for evaluating cavitation, flashing, and compressible flow effects.

• Fluid identification: chemical name, service description, phase (liquid/gas/two-phase)

• Pressure: normal operating, maximum allowable, minimum operating, design pressure

• Temperature: normal operating, maximum, minimum, design temperature

• Flow: maximum, normal, and minimum flow rates with corresponding P&T conditions

• Fluid properties: density, viscosity, vapor pressure, Cp/Cv ratio for gases

Valve Design Requirements

The valve design section specifies the mechanical construction of the valve. Valve type (gate, globe, ball, butterfly, check) is selected based on the application requirements. End connection type and facing (ASME flanged, butt weld, socket weld, threaded) and pressure class are specified. Valve size and Cv rating are determined from the process data. Body material, bonnet material, trim material (plug, seat, stem), and packing material are specified based on compatibility with the process fluid and operating conditions. Special requirements such as fire-safe design, fugitive emissions packing, cryogenic extension, or noise attenuation trim are noted in this section.

Actuator and Instrumentation Requirements

For automated valves, the datasheet must specify the actuator type (pneumatic spring-return, double-acting, electric, hydraulic), the fail position (fail-open, fail-close, or fail-in-place), the available actuating medium and supply pressure, and the required operating speed. Positioner type (pneumatic, electropneumatic, digital HART, Foundation Fieldbus), signal type (4-20 mA, digital), and any required diagnostic features are specified. Accessories including solenoid valves, limit switches, position transmitters, handwheels, and lockout provisions are listed with their functional requirements. Air supply quality requirements (instrument air quality per ISA-7.0.01) are noted to ensure proper positioner and actuator performance.