advantages of using gate valves
Gate Valves are primarily designed to start or stop flow, and when a
straight-line flow of fluid and minimum flow restriction are needed. In service,
these valves generally are either fully open or fully closed.
The disk of a
gate valve is completely removed when the valve is fully open; the disk is fully
drawn up into the valve bonnet. This leaves an opening for flow through the
valve at the same inside diameter as the pipesystem in which the valve is
installed.
A gate valve can be used for a wide range of liquids and provides
a tight seal when closed.
Advantages of using Gate Valves:
- Good shutoff features
- Gate Valves are bidirectional and therefore they can be used in two directions
- Pressure loss through the valve is minimal
The major drawbacks to the use of a gate valve are:
- They can not be quickly opened or closed
- Gate Valves are not suitable for regulate or throttle flow
- They are sensitive to vibration in the open state
CONSTRUCTION OF A GATE VALVE
Gate Valves consists of three main parts: body, bonnet, and trim. The body is generally connected to other equipment by means of flanged, screwed or welded connections. The bonnet, which containing the moving parts, is attached to the body, usually with bolts, to permit maintenance. The valve trim consists of the stem, the gate, the disc or wedge and the seat rings.
DISKS OF A GATE VALVE
Gate Valves are available with different disks or wedges. Ranging of the gate valves is usually made by the type of wedge used.
The most common were:
- Solid wedge is the most commonly used disk by its simplicity and
strength.
A valve with this type of wedge can be installed in each position and it is suitable for almost all liquids. The solid wedge is a single-piece solid construction, and is practically for turbulent flow. - Flexible wedge is a one-piece disc with a cut around the
perimeter to improve the ability to correct mistakes or changes in the angle
between the seats.
The reduction will vary in size, shape and depth. A shallow, narrow cut gives little flexibility but retains strength.
A deeper and wider cut, or cast-in recess, leaves little material in the middle, which allows more flexibility, but compromises strength. - Split wedge is self-adjusting and selfaligning to both seats sides. This wedge type consists of two-piece construction which seats between the tapered seats in the valve body. This type of wedge is suitable for the treatment of non-condensing gases and liquids at normal temperatures, particularly corrosive liquids.
