Gate valve

How to read it

A gate valve opens or shuts a line by sliding a disk, the “gate”, into or out of the flow. The US Department of Energy’s Mechanical Science handbook describes it as a valve for starting or stopping flow that does not regulate or throttle it, and Tony Kuphaldt’s textbook Lessons In Industrial Instrumentation says gate valves are more often used for on/off control than for throttling. Fully open, the disk is out of the flow stream altogether.

In the DOE’s chart of P&ID valve symbols, the gate valve is the plain pair of triangles meeting point to point, with a pair of triangles and a short bar through the middle as an alternative. The same handbook warns that globe and gate valves are often drawn with the same symbol. The valve type may then be given by the component number or the drawing’s notes and legend, and sometimes not even there.

Also searched as: gate valve p&id symbol, gate valve symbol.

Look-alikes

A filled dot where the triangles meet makes the symbol a globe valve, and a hollow circle there makes it a ball valve. A pair of triangles shaded solid black is a different thing: in Kuphaldt’s chart, solid-coloured valve symbols show a valve’s status, and a solid valve is closed. If no valve on the diagram is solid, either every valve is drawn open or status is not shown at all.

Differences between symbol charts

Not every chart uses the plain triangles for a gate valve. In Kuphaldt’s chart the plain pair of triangles is a generic valve of unspecified type, and the gate valve is drawn as two short uprights across the line with a taller stroke between them. A diagram’s legend sheet says which convention it uses.