How to Read a Valve Datasheet — Complete Field-by-Field Guide

A valve datasheet (also called a valve data sheet, VDS, or valve specification sheet) is a structured document — typically a one or two-page form — that captures all the technical and commercial parameters required to fully define, procure, and inspect an industrial valve. It bridges the gap between the P&ID (which shows what valve is needed) and the purchase order (which commits to buying it). Misreading or misinterpreting any field on a datasheet can result in specifying the wrong valve, receiving non-compliant material, or failing an inspection.

Section 1: Identification Fields

Tag Number (Item No.)

The tag number is the valve's unique identifier on the P&ID. A typical format is 'HV-1234' where 'H' denotes the service (hydrocarbon), 'V' denotes valve, and '1234' is the instrument loop or line number. Emergency Shutdown Valves (ESDVs) use the prefix 'XV'. Control valves use 'HCV' or 'FCV'. The tag number ties the datasheet to a specific location on the drawing — always verify it matches the P&ID before accepting supplier confirmation.

Service / Fluid Description

This field identifies the process fluid handled by the valve. It should include the full fluid name and any relevant service conditions: 'Crude Oil — sour service (H₂S > 50 ppm)', 'Demineralised Water — 90°C', 'LPG (propane/butane mixture) — cryogenic storage service'. The fluid description drives every downstream selection: body material, trim material, seal type, and applicable standards. Vague descriptions like 'water' or 'oil' are insufficient — always capture the complete service including contamination, phase, and corrosive content.

Section 2: Design Conditions

Design Pressure and Temperature

Design pressure is the maximum operating gauge pressure (in bar g, kPa g, or psig) at which the valve must operate, with the appropriate safety margin applied. This must not be confused with maximum allowable operating pressure (MAOP) or test pressure. Similarly, design temperature is the maximum (and minimum) fluid temperature — not just the normal operating temperature. Both extremes matter: a valve specified for 150°C at 40 bar is a different product from one specified for 300°C at 40 bar, even if the normal operating point is 120°C at 25 bar.

Pressure Class Selection from Design Conditions

The pressure class (ASME 150, 300, 600, 900, 1500, 2500 — or PN6, PN10, PN16, PN25, PN40, PN64, PN100 in EN/metric systems) must be selected based on the design pressure AND design temperature combined. An ASME B16.34 pressure–temperature table gives the maximum allowable pressure for each material group at each temperature. A carbon steel (A216 WCB) Class 300 valve can handle 51.1 bar g at 38°C, but only 43.8 bar g at 200°C, and 38.1 bar g at 300°C. Many datasheet errors occur because engineers specify a pressure class at ambient temperature without checking it holds at the design temperature.

Section 3: Valve Type and Configuration

Valve Type

This field specifies the operating principle: Ball, Gate, Globe, Butterfly, Check, Plug, Needle, Diaphragm, Safety/Relief, or Pressure Reducing. For ball valves, also specify: floating or trunnion-mounted, full bore or reduced bore, and single-piece/two-piece/three-piece body. For butterfly valves: concentric, double-offset, or triple-offset. For gate valves: solid wedge, flexible wedge, or knife gate. Each sub-type has different flow characteristics, pressure ratings, and maintenance requirements.

Size (DN / NPS)

Valve size is specified in DN (Diameter Nominal, metric) or NPS (Nominal Pipe Size, imperial). DN50 = NPS 2", DN100 = NPS 4", DN300 = NPS 12" (approximately). The valve's bore size should match the line size unless a reduced bore is specifically required. For ball valves: always state if full bore (FB) or reduced bore (RB) is needed — a DN100 Class 300 full-bore ball valve and a reduced-bore ball valve in the same size are different products with different Cv values.

Section 4: Materials

Body Material

Specify the complete ASTM designation: not just 'carbon steel' or 'stainless steel', but 'ASTM A216 Grade WCB' or 'ASTM A351 Grade CF8M'. The grade governs the mechanical properties (yield strength, impact test temperature), which in turn determine the pressure-temperature rating. Common body materials: A216 WCB (carbon steel, standard), A352 LCB (carbon steel, low-temperature −46°C), A351 CF8M (SS 316, general corrosion), A351 CF3M (SS 316L, weld-on applications), A217 C5 (5Cr-0.5Mo, high temperature), A217 C12A / P91 (advanced creep-resistant, 593°C service).

Trim Material

Trim refers to the internal wetted parts: seat, disc/ball, stem, and sometimes the seat rings. Specify each separately where different materials are used. Common combinations: 'TRIM 8 per API 600' means hardened 13% Cr seats and disc for gate valves. For ball valves in clean service: SS 316 ball and seats is standard. For sour service (NACE): trim must comply with NACE MR0175/ISO 15156 — typically low-hardness SS or Alloy 825/625 for stem.

Seat/Seal Material

Soft seats (PTFE, RPTFE, PEEK, DEVLON, Nylon) provide Class VI (bubble-tight) shutoff for clean, non-abrasive services. Metal seats are required for high temperatures (>260°C), steam, abrasive slurries, and fire-safe applications. Always verify the seat material temperature limit — standard PTFE seats are rated to 200°C maximum; PEEK to 260°C; metal seats to 540°C+. For cryogenic service (below −46°C), specify cryogenic-grade PTFE or metal-seated per BS 6364.

Section 5: End Connections

End Connection Type and Facing

Specify: Flanged (RF = Raised Face, FF = Flat Face, RTJ = Ring Type Joint), Butt Weld (BW), Socket Weld (SW), Threaded (BSPT / NPT), or Wafer/Lug (for butterfly valves). Flange facing must match the pipe flange facing: RF for standard Class 150–600, RTJ for Class 600 and above in critical services, FF only for cast iron and non-metallic systems where full-face gaskets are required. Specify the flange standard: ASME B16.5 (NPS ½" to 24"), ASME B16.47 (NPS 26" and above), or EN 1092-1 (metric flanges).

Section 6: Testing Requirements