Gate Valve Introduction
A Gate valve is an on-off or a shut-off valve. It is not used to regulate flow as erosion of disc and seat may cause leakage. A gate valve in partially open or closed position is also susceptible to vibration.
Where quick and frequent operation is essential use of quarter turn valves such as ball valves and plug valves must be considered.
Gate valves are available with variety of disks.
Solid Wedge
Flexible Wedge
Split Wedge
Parallel Disk
The Solid Wedge gate valve is the most commonly used valve. This valve may be installed in any position.
A Flexible Wedge gate valve has a disk with a cut around the perimeter. A shallow cut gives less flexibility. A deeper cut provides more flexibility.
Flexible Wedge gate valves are often used in steam systems. The flexible gate prevents the disc from binding into the seat when the lines are heated and could cause some distortion in the valve bodies
Split Wedge gate valves are of ball and socket design.
Industry Codes and Standards
API 600 - Steel Gate Valves, Flanged and Butt-welding ends, Bolted and pressure seal bonnets
API 602 - Compact Steel Gate Valves, Flanged, Threaded, Welding and Extended-body ends
BS 5352 - Specification for Steel Wedge Gate, Globe and Check 50mm and smaller
MSS SP 80 - Bronze Gate, globe, check and angle valves
API 598 - Valve Inspection and Testing
Solid wedge gate valves 40mm and below are generally specified to BS 5352.
Solid wedge gate valves 2-inch and above are generally specified to BS-1414 or API-600 as appropriate.
Compact Solid wedge gate valves 4-inch and below are specified to API-602.
Split wedge gate valves 1-inch and above are specified to API-600.
Conduit valves 2-inch and larger are specified to API-6D.
Double disc gate valves 1-inch and larger are specified to API-6D or API-600 as appropriate.