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Gate
Valves
Gate valves are used when a straight-line flow of water with
minimum flow restriction are needed.
They get their name from the gate-like disk that slides
across the path of the flow. Gates are formed by machining both
sides of the metal disk and both faces of the vertical valve
seat.
Gate valves are classified as either rising-stem or
non-rising-stem valves.
In the non-rising stem design, the stem is stationary and the
gate rises on a spindle. As the hand wheel on the stem is
rotated, the gate travels up or down the stem on the threads
while the stem remains vertically stationary. This type of valve
will almost always have a pointer indicator threaded onto the
upper end of the stem to indicate the position of the gate.
In a rising stem design the gate is affixed to the stem and
the stem itself rises along with the gate. Valves with rising
stems are used when it is important to know at a glance whether
the valve is open or closed and when the stem and gate could
become damaged by fluid contaminants if exposed to the fluid. In
this type of valve, the stem rises out of the valve when the
valve is opened.
The non-rising stem type is more common in residential water
systems.
In either case, the gate is usually wedge-shaped. When the valve
is wide open the gate is fully drawn up into the valve bonnet.
This leaves an opening for flow through the valve the same
size as the pipe in which the valve is installed.
The valve provides an unobstructed waterway when fully open.
It is best suited for main water supply lines and for pump
lines.
Flow-control is impractical with these valves because of
their design, and the flow of fluid pressing against a partially
open gate can cause extensive damage to the valve. Except as
specifically authorized, gate valves should not be used
partially closed.
They're typically sold with a hand wheel handle. These valves
usually require several turns of the handle to fully close or
open.
They have long been the choice for main shutoff valves in
residential plumbing systems, but are now often being supplanted
by ball valves.
Their main weakness is the gate itself, which sometimes
detaches from the stem and fails after long-term use. And in an
emergency, they require several turns of the handle to close
whereas a ball valve closes in a quarter turn
Water Valves
Ball
Valves
Check
Valve
Gate Valves
Build-In
Valve
Floating
Valves
Angle
Valves
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