Good Supplier presents the Pneumatic Needle Valves,
which are used to reduce the flow rate in a leg of a pneumatic circuit,
consequently slowing actuator speed.
Unlike a Flow Control, a Needle Valve is bi-directional,
meaning it controls flow in both directions instead of only one direction.
In addition, a finely threaded stem allows the gradual adjustment
of the amount of controlled flow passing through the valve.
Flow enters the input port,
travels through an orifice sized by the tapered stem, and out the output port.
A needle valve features a small port and threaded needle-shaped plunger
and can allow precise flow regulation at lower flow rates.
The best way to control the speed of either a pneumatic or hydraulic actuator
is through the use of flow control on either the control valve or the actuator itself.
Flow control works by controlling the rate at which you allow the exhaust air to escape
out of the cylinder when you want to actuate it.
You generally use a knob or screw adjustment to set the exhaust rate
at the appropriate level for the speed that you want to achieve.
The slower the speed, the lower the flow,
the further in you will turn the knob or screw.
Therefore, to control the speed as accurately as possible,
you will want to locate the flow control as close to the actuator as possible.
Most valves have flow control options,
but a flow control fitting mounted right
in the actuator port will give you the best control.
Flow controls are directional and will have free
flow in one direction and metered flow in the other.
Needle valves are very similar to flow controls,
but they meter in both directions.
A needle valve is used to control flow rates of clean gasses or fluids accurately.
The adjustments are gradual and smooth to prevent the flow rate.
However, they can also be used as a reliable shut-off valve.
They are generally only used for low flow rates
and have a relatively significant pressure drop from the inlet to the outlet.
Standard port sizes for needle valves range from 1/8” up to 2”.
The most common application is to control the flow of gas like a propane needle valve does.
How needle valves work?
Needle valves open and close an orifice with a tapered
end that raises and lowers with the spin of a handle.
The handle is connected to the plunger, also called a stem.
When you turn the handle, the plunger moves up or down based on the threads.
The locking nut prevents it from fully unscrewing.
As the plunger moves down, the tapered,
pointed end comes into contact with the valve seat to fully seal the orifice.
Often, the valve seat is also tapered.
Various options and sizes can connect it to a pipe
or hose through the port connection on the input and output.
The bonnet is connected to the valve housing,
which can be made of different brass or stainless steel materials.
Based on the threads, you can very precisely locate the plunger’s tapered
end away from the valve seat to control the flow rate accurately.
Therefore, by varying the plunger location,
you will maintain the flow rate between maximum and zero.
What are the different types of needle valves?
A manually operated threaded needle valve is the most common type of needle valve.
However, two additional variants are motorized and angle.
Motorized Needle Valve:
These needle valves don’t have a handle for manual operation
but instead use an electric or pneumatic actuator to connect to and turn the plunger.
These can be remotely controlled, used in a closed-loop system,
and put on a timer to control the flow rate remotely accurately.
Angle Needle Valve:
These needle valves turn the output from the inlet by 90 degrees instead of in-line.
The same operation concept applies, but the 90-degree angle can allow for better system integration.
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