On this page
Key takeaways
- Isolation valves (gate, ball, plug, butterfly) are either fully open or fully closed.
- Globe valves and control valves regulate flow; check valves prevent backflow.
- Offshore and weight-sensitive services favour compact designs such as ball and butterfly valves.
Isolation valves
Gate valve. A wedge moves across the flow path. Low pressure drop when fully open, but slow to operate, poor for throttling, and tall. Traditional choice for onshore isolation in larger sizes.
Ball valve. A ball with a bore rotates a quarter turn. Fast, tight shut-off and compact. Floating ball designs are used in smaller sizes and trunnion-mounted designs in larger sizes and higher pressures. Very common offshore and for hydrocarbon isolation. Full-bore ball valves are used where pigging is needed.
Plug valve. A tapered or cylindrical plug rotates a quarter turn. Good for slurries and services where sealing is difficult; lubricated plug valves are used in some gas and dirty services.
Butterfly valve. A disc rotates a quarter turn in the flow. Very light and compact, especially in large sizes. Triple-offset metal-seated designs give tight shut-off at higher pressures and temperatures. Common for water, seawater and cooling systems, and increasingly for hydrocarbons.
Regulating valves
Globe valve. A disc moves towards a seat. Good for throttling and manual flow control, higher pressure drop. Used for bypasses around control valves, drains and vents in some specifications.
Needle valve. A small globe-type valve with a fine tapered stem, used for instrument connections.
Control valve. Usually a globe or rotary valve with an actuator, driven by the control system. Sized by the instrument team.
Non-return valves
Check valve. Stops reverse flow. Types include swing check (simple, needs enough flow), dual plate (compact, common offshore and in larger sizes), piston/lift check (small bore, high pressure) and axial nozzle check (fast closing, used at compressors to limit slam).
Summary
| Valve | Main job | Strengths | Weak points |
|---|---|---|---|
| Gate | Isolation | Low pressure drop | Tall, slow, poor throttling |
| Ball | Isolation | Fast, tight, compact | Cost in large sizes |
| Plug | Isolation | Dirty services | Torque, lubrication |
| Butterfly | Isolation, some throttling | Light, compact | Disc in flow path |
| Globe | Throttling | Good flow control | High pressure drop |
| Check | Prevent backflow | Automatic | Slam, needs flow to open |
Code reference
API 600 / API 602 Steel gate valves (flanged and butt-weld / compact).
API 6D / ISO 14313 Pipeline and piping valves.
API 608 Metal ball valves.
API 609 Butterfly valves.
API 594 Check valves: flanged, lug, wafer and butt-welding.
What to take back to your desk
When a P&ID shows a valve, check the type against the job. A gate valve shown for throttling, or a globe valve on a pigged line, is worth a question to process.
Educational content. Always design to your project specification.
