Valves in Industry
Valve types & classification
Zafifah binti Zamrud
Introduction to valves
• The ability for engineers to control the flow within the pipelines (starting,
stopping, throttling, regulating, checking and relieving) is one of the major
importance in industries.
• Manufactured from various materials, mostly made from steel, iron, plastic,
brass, bronze and special alloys.
• Valve is, in essence, a partial or complete obstruction which is placed in the path
of a flowing fluid to control the flow at the user’s desires.
• In the case of pipelines, the obstruction inside the pipe (valve) could be to control
the fluid flow within minimal leakage of fluid out of the pipeline.
Types of industrial valve
• There are many types of valves available to accommodate a wide
range of applications - each with a unique method of control,
function, or media application.
• There are two major methods used to classify valves – method of
control and valve function.
• Most valves fall into one or more of the classifications listed above.
• It is important to know how the valve operates, as well as how it is
best used, to reduce the need for valve maintenance and extra wear
on the valve parts.
Valve
Classification
Methods of
Valve function
control
Linear motion Rotary motion Throttle/control
Start/stop valves
valves valves valves
Gate valves, Globe valves,
Ball valves, Gate valves, ball
globe valves, butterfly valves,
butterfly valves valves
needle valves ball valves
Methods of control – Linear motion valves
• Use a closure member that moves in a straight line to start, stop, or
throttle the flow.
• The closure device could be a disc, slat or flexible material, like a
diaphragm.
• Linear motion valves tend to be slower in operation, but they have a
higher level of accuracy and stability in the position of the closure
member.
• The most common example of linear motion valves includes gate
valves, globe valves, and needle valves.
Needle valve
Gate valve
Methods of control – Rotary motion valves
• Rotate a disc or ellipse about an angular or circular shaft
extending across the diameter of an orifice.
• These valves will be in their fully open or fully closed state (0°)
after a 90° turn of the stem.
• Their operation is much quicker than linear motion valves.
• The most common examples of rotary motion valves include
ball valves, and butterfly valves.
Ball valve
Butterfly valve
Valve function – Start/stop valves
• Used for systems that do not need the flow throttled.
• The valve opens to allow flow and closes to stop flow.
• These valves are often used with a manual hand wheel, but can be automated
with an actuator.
• Start/stop valves are used when flow needs to be diverted or for mixing
applications when exact measurements are not required.
• Automated start/stop valves are used in safety management systems to
immediately shut off the system in an emergency situation e.g. relief valves.
• The most common examples of start/stop valves include gate valves and ball
valves.
Valve function – Throttle/control valves
• Control the speed and capacity of flow, temperature, or pressure, through a
system.
• Control valves can be moved into any position, including fully opened and fully
closed.
• They can be operated with a manual hand wheel or can be equipped with an
automated actuator.
• The most common examples of rotary motion valves include globe valves, and
butterfly valves.
Gate valves
• Flow is controlled by raising or lowering the valve
element.
• The gate valve MUST be either FULLY CLOSED or
FULLY OPEN and NEVER USED TO CONTROL FLOW.
• Gates are not usually used to regulate flow
because the valve internals (gate and body seats)
can be damaged by the fluid velocity when in the
partially open position.
Needle valves
• The needle valve is essentially a variation of the globe valve used
for very fine control of flow.
• Needle valves has a slender, tapered point at the end of the valve
stem that is lowered through the seat to restrict or block the flow.
• Used on shut-off
and throttling
service for liquids,
slurries and
vacuum/gas.
• The seal is
achieved by a
flexible
membrane,
usually elastomer,
and possibly
reinforced with a
metal part.
Ball valves
• Uses a ball-shaped disk to stop or start fluid flow.
• The ball has a port, also known as a bore, through the centre.
• When the valve is positioned such that the bore is aligned in the same direction as the pipeline, it is
in open position and fluid can flow through it.
• When rotated 90 degrees, the bore becomes perpendicular to the flow path, meaning the valve is
closed and the fluid cannot pass through.
