How to Select an Industrial Valve: A Buyer’s Checklist

Why most valve selection errors are made at the enquiry stage

A valve is not a single product with a single specification. The same nominal size and pressure class can be built with different bodies, different seats, different connections and different operators, and each combination suits a different duty. When an enquiry says only “100 mm butterfly valve, Class 150”, the supplier has to guess the remaining parameters — and a guess is where mismatches begin.

The five parameters below are the ones that actually determine the answer. Everything else is detail that can be confirmed later.

Step 1 — Define the medium precisely

The medium decides the body material, the wetted trim and often the seat material. “Water” is not enough: raw water, potable water, cooling water and seawater behave very differently towards the same materials. Seawater in particular is aggressive because of chlorides, and cast iron is generally not the right choice for continuous seawater service.

State the medium, its concentration where relevant, and whether solids are present. Slurries and media carrying solids need attention to the seat design and to whether the valve will be operated with solids sitting in the bore.

Step 2 — Set the pressure class from pressure and temperature

Pressure classes such as Class 150 or PN16 are not single numbers. They define a pressure–temperature rating: the allowable pressure falls as the operating temperature rises. A valve selected on cold line pressure alone can be under-rated at working temperature.

Choose the class that covers your maximum working pressure at your maximum operating temperature, then check that the flange drilling matches the pipework.

Class / PN	Typical use
Class 150 / PN10–PN16	General water, air, light industrial and utility service — the largest share of installations
Class 300 / PN25–PN40	Higher-pressure process lines, steam distribution, oil and gas services
Class 600 – 2500	Critical high-pressure service where a heavier body and higher-rated closure are required

Step 3 — Let temperature choose the seat material

The seat and seal material usually sets the practical temperature limit, not the body. Soft seats give excellent tightness at low differential pressure; metal seats extend the range and handle abrasion, at the cost of higher operating torque.

Seat material	Working range (typical)	Suited to
EPDM	roughly −30 °C to 120 °C	Water, hot water, steam (low pressure), general service
Buna-N (NBR)	roughly −30 °C to 90 °C	Oil, air, general industrial media
PTFE	roughly up to 200 °C	Chemical and corrosive service, low friction
Viton (FKM)	roughly −20 °C to 200 °C	Acids, oils, higher-temperature process media
Metal-to-metal	up to about 538 °C (high-temperature ranges)	Abrasive slurry, steam, fire-safe requirements

Ranges above are typical for the materials, not a guarantee for every model. Always confirm against the datasheet for the series you are buying, because body, trim and seat act together.

Step 4 — Confirm size, connection and face-to-face

Size is normally the easiest parameter, but the connection is where projects slip. Face-to-face length and flange drilling come from different standards, and a valve that is correct in size and pressure class can still not fit existing pipework if the face-to-face dimension differs from the one being replaced.

Tell your supplier the flange standard you are matching — for example ASME B16.5, ASME B16.47 or EN 1092-1 / EN 1092-2 — and, if you are replacing an existing valve, the face-to-face dimension of the original.

Step 5 — Decide how often the valve will be operated

The operator follows from the duty cycle. A valve cycled once a week is normally fine with a lever or a handwheel. Frequent cycling, remote operation, or a requirement that the valve fails to a defined position, points to actuation.

• On/off, local: lever or gear operator.
• On/off, remote: pneumatic actuator with solenoid valve, or electric actuator.
• Modulating (throttling): actuator plus a positioner so the valve follows a control signal.
• Fail-safe: spring-return actuator, so the valve moves to a defined position if air is lost.

Matching valve type to duty

Valve type	Strength	Suited to	Watch out for
Butterfly	Compact, light, quarter-turn, economical at large sizes	Water, cooling, utilities, general isolation and control	Disc sits in the flow path; check for throttling limits and solids
Gate	Straight-through bore, minimal pressure drop, piggable	Isolation on pipelines and services where line cleaning matters	Tall due to rising stem; not intended for throttling
Globe	Good throttling and regulation characteristics	Control and regulating duty, steam, small-bore process lines	Higher pressure drop than a gate valve
Ball	Quarter-turn, unobstructed bore, tight shut-off	Oil, gas, chemical and general isolation	Seat materials must match the medium and temperature
Check	Automatic, prevents reverse flow	Pump discharge protection, non-return duty	Sizing for flow conditions matters more than nominal size
Knife gate	Cuts through solids and slurries	Mining, pulp and paper, wastewater, abrasive service	Face-to-face and sealing design vary widely — confirm
Slurry	Wear-resistant design for abrasive media	Mining and mineral processing, tailings, dense slurries	Wear parts are consumable; plan for spares

What to put in your enquiry

If your enquiry contains the items below, the first quotation is usually the final one:

• Medium and concentration, and whether solids are present
• Line size and required connection / flange standard
• Maximum working pressure and maximum operating temperature
• Body and seat material if you have a preference, or ask us to recommend
• Valve type, or the duty if the type is open
• Operator type (manual, pneumatic, electric) and fail position
• Quantity, destination port and any documentation or inspection requirements

If you are replacing an existing valve, a photograph of the nameplate is often the fastest way to get an accurate answer.

Sources and standards referenced

• API 609 — Butterfly valves: double-flanged, lug and wafer type (American Petroleum Institute)
• API 6D — Pipeline and piping valves
• API 600 — Steel gate valves, flanged and butt-welding ends
• API 594 — Check valves: flanged, lug, wafer and butt-welding
• MSS SP-67 — Butterfly valves; MSS SP-70 — Gray iron gate valves (Manufacturers Standardization Society)
• EN 593 — Industrial valves: metallic butterfly valves
• ISO 5211 — Industrial valves: part-turn actuator attachments
• API 598 and EN 12266-1 — Valve inspection and pressure testing
• ASME B16.5 / B16.47 and EN 1092-1 / EN 1092-2 — Pipe flanges and flange drilling

Standards are the reference; the specification for the model you buy is confirmed in the quotation. If your project names a standard, tell us at the enquiry stage so it can be confirmed before production.