A valve is a mechanical device used for controlling fluids
and gases in most pipe conveying systems. A valve is a control part of the
pipe, which is used to change the passage section, to minimise the pressure of
the flow or to check the flow of liquid, slurries or molten solids in only one
direction.
Valves carry out other functions like a diversion, cut off, throttling, check back, or overflow relief. Based on the
structure and mechanism of functioning various types of valves are available in
the market that includes ball valve, duckbill valve, gate valve, globe valve
and different types of disc check valve like diaphragm check valves, swing check valve, stop check valves,
lift check valve, in-line check valve and pneumatic valve.
The check valve is one of the most important types of
valve that allows fluid to move through it in only one direction. It consists
of only two openings in the body; one is used for inflow of the fluid and the
other is used for the outflow of the fluid. Swing check valve is a
butterfly-style valve perpendicular to the centreline between two parts. Swing
check valve comes in a variety of sizes. Check valve impedes the backflow by
placing a barrier to the normal flow of the liquid that can only be opened in
one direction by pressure.
Swing check valve has a disc inside that covers the
opening of the valve. The opening of the valve has to be very clear for the
passage of the liquid or gaseous material. The disc of the valve is attached to
a hinged so that the disc can swing open or closed when liquid hits the disk.
It is like a circular door. The direction of the flow is the most important thing
when using these valves. When enough pressure is applied in one direction of
the pipe, the flap swings open allowing the flow of liquid or gas to pass
easily through it. Once the pressure decreases, the flap automatically falls
back into place. In case the pressure is applied from the opposite direction,
the flap is pressed firmly against the valve seat stopping the overflow of
liquid.
On the contrary, globe valve is spherical in shape, separating the two parts of the valve with an
internal baffle. It is different from ball valve and used for regulating the
flow in the pipeline.
The globe valve
consists of a movable disk-type element that can be screwed in the manual and a
stationary ring seat. Its design offers good regulation characteristics, but it
causes a more pressure drop owing to a high disturbance in the flow path. The
pressure can be dropped by increasing the opening area to bring the cross
sectional area closer to the pipe. The flow across the partition gets smoother
and reduces the level of pressure. This type of valve is used by numerous
industries such as oil systems, cooling water systems, boiler vents drain,
turbine seal, main steam vents, and drains.
