Butterfly valve
A butterfly valve, which turns a disk inside the pipe to start, stop or regulate flow. It is drawn as a slanted stroke between two short uprights across the line.
Easily confused with
How to read it
A butterfly valve has a disk about as wide as the inside of the pipe, which turns on an axis. In the DOE’s Mechanical Science handbook, it is a rotary valve used to stop, regulate and start flow: open when the disk lies along the pipe, shut as it turns across it. The handbook names large flows of liquids or gases at relatively low pressure, and slurries, as what it is especially suited to. Kuphaldt’s Lessons In Industrial Instrumentation adds that a tight shut-off is hard to get from the classic design unless the seat is lined with a soft material.
The DOE’s chart draws it as a short slanted stroke between two uprights across the line. One of the DOE’s alternatives, and Kuphaldt’s chart, add a dot at the middle of the stroke.
Also searched as: butterfly valve p&id symbol, butterfly valve symbol.
This explains what a symbol represents on a diagram. Companies vary the symbols, and a diagram's own legend sheet takes precedence.
Look-alikes
The ball valve is also drawn between two short uprights, with a circle between them instead of the stroke. In Kuphaldt’s chart the gate valve is drawn between uprights too, with an upright stroke in the middle rather than a slanted one.
Read next
- Next in P&ID symbolsCheck valveA check valve, which lets flow pass one way and closes if the flow reverses. It is drawn as a Z-shaped break in the line, with a small arrow giving the direction of flow.
- The same shape in African flagsFlag of EthiopiaEthiopia’s flag is green, yellow and red in equal horizontal stripes with a blue disc in the centre holding a yellow star of equal lines with yellow rays. Ethiopia’s Flag Proclamation makes the green labour, fertility and development, the yellow hope, justice and equality, and the red sacrifice and heroism for freedom and equality; the blue disc is peace and the star the unity of Ethiopia’s nations, nationalities and peoples.
More P&ID symbols
The same shape elsewhere
Browse symbols drawn with circles or lines.
Sources
- DOE Fundamentals Handbook: Mechanical Science, Volume 2 of 2, DOE-HDBK-1018/2-93, January 1993, U.S. Department of Energy (University of Cambridge Engineering Department mirror), Module 4, Valves: Butterfly Valves
- Lessons In Industrial Instrumentation, Tony R. Kuphaldt, version 2.33, 2024 (CC BY 4.0), Tony R. Kuphaldt (ibiblio.org), 27.2.2 Butterfly valves
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research
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