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FEATURES
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Wedge-shaped gate valves allow for the
fluid to be tightly shut off and come in three
separate designs. The split wedge allows for
disk flexibility. This flexibility helps the valve
to seal easily. Solid wedges are simple and
strong. They are the most common valve
because they are suitable for almost every
situation. Flexible wedge valves are mostly
used for steam systems and are available in a
variety of different sizes and shapes.
• Ball valve
A ball valve is a form of quarter-turn valve that
uses a hollow, perforated and pivoting ball to
control flow through it. It is open when the
ball’s hole is in line with the flow and closed
when it is pivoted 90 degrees by the valve
handle. The ball valve should also not be used
as a flow restricting valve since cavitation
will result in ‘wire drawing’ of the seal edges,
resulting in failing to close completely.
The many different types of valves all have
different names. The most common ones are
the butterfly, cock or plug, gate, globe, needle,
poppet, and spool:
• Ball: In a ball valve, a hollowed-out
sphere (the ball) sits tightly inside a pipe,
completely blocking the fluid flow. When
you turn the handle, it makes the ball
swivel through 90 degrees, allowing the
fluid to flow through the middle of it.
• Butterfly: A butterfly valve is a disk that
sits in the middle of a pipe and swivels
sideways (to admit fluid) or upright (to
block the flow completely).
• Cock or plug: In a cock or plug valve, the
flow is blocked by a cone-shaped plug that
moves aside when you turn a wheel or
handle. This type of valve is normally only
used in very low pressure installations, that
is, water tank locking cock.
• Gate o r sluice: Gate valves open and
close pipes by lowering metal gates
across them. Most valves of this kind are
designed to be either fully open or fully
closed and may not function properly
when they are only part-way open. Water
supply pipes use valves like this.
• Globe: this valve is different from a
ball valve: it is a type of valve used for
regulating flow in a pipeline, consisting
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of a moveable disk-type element and a
stationary ring seat in a spherical body.
They are named for their spherical body
shape with the two halves of the body
being separated by an internal baffle.
This has an opening that forms a seat
onto which a moveable plug can be
screwed into (or shut) the valve. The
plug is also called a disc or disk. In globe
valves, the plug is connected to a stem
that is operated by screw action using a
handwheel in manual valves. Typically,
automated globe valves use smooth stems
rather than threaded and are opened and
closed by an actuator assembly.
Needle: A needle valve uses a long,
sliding needle to regulate fluid flow
precisely in machines like car engine
carburettors and central-heating
systems.
Poppet: The valves in car engine
cylinders are poppets. This type of valve
is like a lid sitting on top of a pipe. Every
so often, the lid lifts to release or admit
liquid or gas.
Spool: Spool valves regulate the flow of
fluid in hydraulic systems. Valves like this
slide back and forward to make fluid flow
in either one direction or another around
a circuit of pipes.
The function of a water tank float valve is to
control water flow into the tank. Most water
tank float valves use a long lever attached to a
buoyant float called a ball float. When the water
level rises to a certain point, it lifts the ball float,
which then lifts the lever, closing the valve.
One of the most common applications for
water tank float valves is in toilet tanks. Most
toilet tank float valves use a hollow plastic
or rubber ball float attached to a long metal
lever, but some models use a plastic ball
float attached directly to the valve without
a lever. When a person flushes the toilet, a
rubber valve opens in the tank’s base, and
water flows out of the tank and into the bowl,
causing the ball float to drop. When the
person lets go of the flush lever, the rubber
valve seals the tank, and water flows back in
until the ball float rises sufficiently to cut off
the supply.
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