Ball, gate, globe or butterfly: which valve for which job
Most lines need two kinds of valve: one to isolate (fully open or fully shut) and one to regulate (somewhere in between). Ball, gate, globe and butterfly valves each do one of these jobs better than the others. Picking by the job, rather than by habit, saves seats, stems and money.
Ball valves
A ball with a hole through it turns a quarter turn to open or shut. Ball valves shut tight, open fast and, in full bore, let the flow through almost unchanged.
- Best for: on and off service on water, oil, gas and many chemicals, in small and medium sizes.
- Avoid: long periods part open. The edge of the ball wears the seats, and the valve then stops shutting tight.
Gate valves
A gate valve lifts a flat or wedge gate clear of the flow with several turns of the handwheel. Fully open, it barely restricts the line.
- Best for: isolating lines that stay open or shut for long periods, such as mains and pump suction lines.
- Avoid: throttling. A gate held part open vibrates and wears, and it is slow to operate in an emergency.
Globe valves
A globe valve lowers a disc onto a seat across the flow. The flow turns inside the body, which costs some pressure but gives fine control.
- Best for: regulating flow, bypass lines and services that are adjusted often, such as steam and cooling water.
- Watch: the arrow on the body. A globe valve is fitted one way round.
Butterfly valves
A disc in the bore turns a quarter turn. Butterfly valves are short and light, and they stay economical in large sizes where a ball or gate valve becomes heavy and costly.
- Best for: large water, cooling and utility lines, on and off or with moderate throttling.
- Wafer or lug: a wafer body is clamped between two flanges; a lug body has threaded lugs, so the pipe on one side can be taken away while the valve still holds the other.
Two more that protect the line
- Check valves let the flow go one way only and shut by themselves if it reverses, protecting pumps and compressors.
- Strainers catch scale and debris before they reach valves, pumps and meters.
A quick guide
- Shut tight, quarter turn, small to medium size: ball valve.
- Isolate a line that rarely moves: gate valve.
- Regulate the flow: globe valve.
- Large line, light and compact: butterfly valve.
- Open and shut it from a control panel: an actuated ball or butterfly valve, or a solenoid valve.
What to tell us
The valve type, size, pressure class, body and trim material, end connection (threaded, socket weld, flanged or wafer), what the line carries and its temperature, and the quantity. A photo of the old valve's nameplate does most of this for you.