Gate, Globe, Ball, Butterfly and Check Valves: Selection Basics for Plant and Building Services

Five valve families cover the great majority of lines in a process plant or a building services installation: gate, globe, ball, butterfly and check. Each is designed for one job and tolerates a second one badly, and most field problems with valves trace back to a type chosen for the wrong duty. This article explains what each type does well, where it should not be used, and which pressure class and standard to write on the requisition.

Start from the duty, not the valve

Before comparing types, decide whether the valve is for isolation, regulation or backflow prevention, what the fluid is, the design pressure and temperature, and how often it will be operated. Those answers eliminate most options before price enters the discussion.

Gate valves: isolation with minimal pressure drop

A gate valve raises a wedge or parallel disc completely out of the flow path, leaving a full-bore straight passage with very little pressure drop. It is the standard isolation valve for water, steam, oil and gas lines that stay open or closed for long periods.

Do not use a gate valve to throttle: a partly open disc vibrates in the stream and the seats erode, after which the valve no longer shuts tight. Gate valves are also slow to operate and need headroom for the stem.

For steel gate valves the usual purchase standards are API 600 for bolted-bonnet cast steel valves in petroleum and gas service, API 602 for compact forged steel valves in NPS 4 and smaller, and API 603 for corrosion-resistant bolted-bonnet valves in Classes 150, 300 and 600. Building services commonly use cast iron, ductile iron or bronze gate valves to the relevant BS, EN or MSS standards.

Globe valves: the regulating workhorse

In a globe valve the fluid changes direction twice and passes through a seat ring closed by a plug or disc that moves perpendicular to the seat. The design gives precise control of flow with repeatable positioning, and the seating is less prone to erosion in throttling service than a gate. The price is a higher pressure drop even when fully open and a practical size ceiling, since actuating force rises with seat area.

Globe valves are the right choice for bypass lines, cooling water balancing, steam and condensate regulation and any manual duty where the valve is held part-open. Angle and Y-pattern bodies reduce the pressure drop where that matters. Flow direction is marked on the body and must be respected; a globe valve installed backwards can chatter. For steel globe valves the ratings and construction requirements come from ASME B16.34.

Ball valves: fast, tight shut-off

A ball valve closes with a quarter turn of a bored sphere against soft or metal seats. Fully open, a full-bore ball gives an unobstructed passage suitable for pigging; a reduced-bore ball is cheaper and lighter at the cost of some pressure drop. Soft seats such as PTFE give bubble-tight shut-off, which makes ball valves the preferred isolation valve for gas, compressed air, chemicals and instrument lines, and the easiest valve to automate with a compact actuator.

The limits are temperature and throttling. Soft seats have a temperature ceiling set by the seat material, so hot services need metal-seated designs and, where required, fire-safe certification. A ball left part-open erodes its seats and the trailing edge of the ball, so standard ball valves are for on-off duty only; characterised V-port balls exist for control. API 608 covers Class 150 and 300 metal ball valves for on-off service, and API 6D covers ball, check, gate and plug valves for pipeline systems.

Butterfly valves: light, compact and economical in large sizes

A butterfly valve turns a disc on a shaft across the bore. Wafer and lug bodies sit between flanges, so a large butterfly valve weighs and costs a fraction of a gate valve of the same size and takes far less space. Resilient-seated concentric designs dominate HVAC, fire water and raw water services; double- and triple-offset metal-seated designs extend butterfly valves to higher pressures and temperatures.

The disc never leaves the flow, so there is always some pressure drop and the valve cannot be pigged. Resilient seats share the temperature limits of elastomers, and a butterfly valve throttles acceptably only in mid-travel; near closed, velocity across the disc edge causes cavitation and seat damage. A wafer valve cannot be used as a dead-end isolation on an open flange, whereas a lug or double-flanged valve can, within the manufacturer's rating. API 609 covers double-flanged, lug and wafer butterfly valves for tight shut-off and flow regulation.

Check valves: protecting pumps and preventing reverse flow

A check valve opens with forward flow and closes automatically when flow stops or reverses, protecting pumps and compressors from reverse rotation, keeping risers charged and preventing contamination between systems. Swing checks have low pressure drop and suit horizontal clean liquid lines; lift checks suit high-pressure steam and gas but need flow from below the disc; dual-plate wafer checks are short, light and fast-closing, which reduces water hammer; nozzle (axial) checks close fastest and are used on compressor discharge and other pulsating services.

Two points decide success. A check valve sized for the pipe rather than the actual flow will not open fully, and a disc that flutters at half-open wears its hinge and seat until it fails. Orientation also matters: not every type works in vertical lines with downward flow, and swing checks need a straight run upstream. API 594 covers flanged, lug, wafer and butt-welding check valves, and API 6D covers pipeline check valves.

Pressure class, materials and testing

Once the type is chosen, the class follows from the design pressure and temperature of the line, not from the pump head alone. ASME B16.34 sets the pressure-temperature ratings for steel and alloy flanged, threaded and welding-end valves, and flanged valves mate with ASME B16.5 flanges in Classes 150 to 2500. The rating falls as temperature rises: for material group 1.1 (ASTM A105 forgings and A216 WCB castings), Class 150 is rated 19.6 bar from -29 to 38 C, 13.8 bar at 200 C and 6.5 bar at 400 C, while Class 300 is rated 51.1 bar at ambient. Ratings for this group are tabulated to 538 C, with a caution that prolonged service above 425 C risks graphitisation of carbon steel. Refer to the current edition of the standard for the full tables and for other material groups.

Select the body material for the fluid and temperature: carbon steel for general hydrocarbon, steam and utility duty, stainless steel for corrosive or clean services, bronze or ductile iron for building water systems within their rating. Trim (seat, disc, stem) wears first and should be specified separately where erosion or corrosion is expected. Finally, require inspection and pressure testing to API 598, which covers gate, globe, plug, ball, check and butterfly valves, and ask for the certificates with the delivery.

Key takeaways

• Choose by duty first: gate and ball for isolation, globe for regulation, butterfly where weight, space and cost dominate in large sizes, check for backflow prevention.
• Never throttle with a gate or a standard ball valve; seat damage follows.
• Size check valves for the actual flow, not the pipe, and match the type to orientation and closing speed required.
• Specify the class from design temperature as well as pressure: Class 150 carbon steel drops from 19.6 bar at ambient to 6.5 bar at 400 C.
• Write the standards on the requisition: API 600, 602 or 603 for steel gate valves, API 608 for ball, API 609 for butterfly, API 594 for check, ASME B16.34 for ratings and API 598 for testing.

Frequently asked questions

Can a butterfly valve replace a gate valve for isolation?

In most water, HVAC and low-pressure utility services, yes, and it will be cheaper, lighter and faster to operate. For hot, high-pressure or hydrocarbon services, a metal-seated offset butterfly valve or a gate valve is normally required. Where a line is pigged or must be fully unobstructed, a gate or full-bore ball valve is needed.

What is the difference between a floating and a trunnion-mounted ball valve?

In a floating design the seats hold the ball and line pressure pushes it onto the downstream seat; it is simple and economical in smaller sizes and lower classes. In a trunnion design the ball is supported on a shaft and bearings with spring-loaded seats; it needs less torque and is used in larger sizes and higher classes.

Which check valve causes the least water hammer?

Fast-closing designs such as dual-plate wafer and nozzle check valves close before reverse flow builds up and produce the least slam. Swing checks are the most prone to slam on pump trip, particularly in vertical risers.

How Al Safsaaf can help

Al Safsaaf Trading & Contracting Company supplies industrial gate valves, globe valves, ball valves, butterfly valves and check valves as part of its industrial valves range. Share the valve list with sizes, classes, end connections and fluid data and our team will check it against the standards above before quoting; contact us to start.