Industrial valves

01Which industrial valves we supply, and what each is for

Ball, gate, globe, check, butterfly and knife-gate cover almost every isolation, throttling and check duty. We supply all six, in the materials and pressure classes the duty calls for. We also supply the pressure-reducing, safety and steam equipment around them and the actuators and fittings that connect them.

Each type does one job well. A ball valve gives a tight, fast, quarter-turn shut-off. A gate valve gives a full bore with almost no pressure loss. A globe valve holds a repeatable throttling position. A check valve closes itself against reverse flow. A butterfly valve is the lightest and cheapest closure on a large water line. A knife-gate cuts through solids. The duty decides, not preference.

02Match the valve type to the duty

The first question is what the valve is for, not the medium or the pressure. Isolation means fully open or fully shut, nothing between. Ball, gate, butterfly and knife-gate valves are built for it. Most are damaged by being left part-open. Throttling means holding an intermediate position. A globe valve does it by design. A characterised ball or offset butterfly can, within limits. A gate valve never should.

Backflow prevention is a check valve's job alone. An isolation valve left open will not stop reverse flow when a pump trips. One valve rarely does two jobs well. Where the line needs isolation and throttling, specify two valves. Where it needs isolation and check, put an isolation valve each side of the check so it can be serviced. The gate versus ball versus butterfly comparison covers the three isolation types.

03Ball, gate, globe, check, butterfly and knife-gate compared

Each cell names the duty a type suits, the duty it fails at, and the design standard. Read the failure line first: most field problems are a valve doing the wrong job.

04Selecting by medium: water, steam, hydrocarbons, slurries, seawater

The medium decides body and trim material first. Chilled and heating water is undemanding: cast iron, ductile iron, bronze or carbon steel, stainless or bronze trim, resilient seat to Rate A. Potable water turns on wetted-material approval, not pressure: dezincification-resistant brass or an approved lining, every elastomer certified separately.

Saturated steam fixes its own temperature, so the body is rated against the relief setting. Carbon steel (ASTM A216 WCB) runs to about 425 °C. Chrome-molybdenum (A217 WC6, WC9) goes above it, with metal seats. Hydrocarbons add three qualifications the pressure rating ignores. Fire type-test (API 607 or 6FA). Fugitive-emission class (ISO 15848-1). In wet H₂S, the hardness limits of NACE MR0175. Slurries want a knife-gate or a full-bore ball with a hard-faced seat. Seawater is decided by chloride pitting. The alloy's pitting resistance equivalent number, proven under ASTM G48, puts super duplex in and 316L out. The service-condition article takes each medium in turn.

05Reading the ASME B16.34 class with the material group

A class number is not a pressure. Class 150, 300, 600, 900, 1500 and 2500 are rating groups in ASME B16.34. Each is a curve of allowable pressure against temperature for one material group. Carbon steel is group 1.1; stainless 316 is group 2.2; chrome-moly sits in group 1.9 and 1.10. The curve falls as temperature rises, at a different rate for each group. So the class on the nameplate means nothing until the material group is read beside it.

The method is mechanical. Take the design temperature, not the operating temperature. Read the allowable pressure for that class and material group at that temperature. Compare it with the design pressure, usually the relief setting. If design pressure exceeds allowable, step up a class or change the material group. A class 150 carbon-steel body holds a little under 20 bar g cold and loses most of it by 400 °C. Class 300 holds close to its cold rating to about 200 °C, then falls away. The B16.34 ratings article tabulates the curves.

Reference values: confirm against the current edition of the standard and the manufacturer's rating table.

06Size and actuation: where quarter-turn stops making sense

Below about DN 50 (NPS 2) a ball valve is hard to beat: compact, cheap, quick and tight. Between DN 50 and DN 300 the choice opens up. Ball valves grow heavy, and torque grows with the square of the bore. Gate valves suit lines that rarely operate. Butterfly valves take over on water, where weight and face-to-face matter. Above DN 300 the butterfly valve wins most water duties. Gate and trunnion-mounted ball valves hold the high-pressure and hydrocarbon lines.

Actuation follows the same logic. A quarter-turn valve takes a compact pneumatic or electric actuator on an ISO 5211 pad, and strokes in seconds. A rising-stem gate or globe valve needs a multi-turn actuator, a longer stroke and a larger budget. Above DN 200 it needs a gearbox for manual operation. Cycling frequency decides the seat: hourly cycling needs seats and stem seals chosen for wear, yearly cycling needs seats that will not stick. Where the valve must fail safe on loss of power, size the spring return against torque at full differential pressure. See actuators, dampers and fittings.

07End connections: flanged, threaded, welded and wafer

Flanged ends to ASME B16.5 (NPS ½ to 24) or EN 1092-1 (PN 10 to PN 40) are the default above DN 50. The valve comes out without cutting pipe, and the flange rating matches the valve class. Raised face is usual; ring-type joint for class 900 and above. Threaded ends serve small-bore lines to about DN 50 where pressure is modest. Use NPT to ASME B1.20.1 or BSP to ISO 7.

Socket-weld and butt-weld ends (ASME B16.11 and B16.25) remove the flange joint for high-pressure, high-temperature or lethal service. The valve becomes part of the pipe and is serviced in place. Wafer and lug patterns clamp between two pipe flanges, and suit butterfly and some check valves. A wafer valve cannot hold a dead-end line alone; a lug valve with threaded lugs and a suitable rating can. ASME B16.10 or EN 558 fixes face-to-face, so a replacement drops into the existing spool. Always state the series on the enquiry: the same DN and class exists in more than one length.

08Governing standards (confirm the current edition)

Four kinds of document govern a valve: the rating standard, the design standard for the type, the test standard for shell and seat, and the qualification documents the duty adds. A specification names one of each. The glossary defines every designation.

09Documentation to request with every valve

A valve without its documents is a casting of unknown origin. Ask for the six items below on the enquiry, not after delivery. A certificate never raised at the mill cannot be raised later. The sourcing and documentation guide explains each one. The MTC and test-certificate article shows a compliant example.

10Product lines relevant to isolation and check duty

We supply from several established manufacturers' lines, because no one maker covers every type, material and class well. The three lines below do most isolation and check duty. The full set is on the product-lines page. Appointment status with any principal is To confirm and is never implied by a listing here.

11Where to go next

If the service condition is not fixed, start with the valve selection by standard guide. It runs from medium to class to material group to document list. For a narrower question, the gate vs ball vs butterfly comparison covers the three isolation types. Chilled-water terminals have their own guide, district cooling and HVAC, because balancing and control valves follow different rules. All guides are indexed under Insights. Technical support and testing describes how we check a valve on site.