What is a poppet valve and what does it do

What is a poppet valve and what does it do

The poppet valve is used to control the flow, it could use a disc, ball, or cone to control the flow. Poppet valves are directional control valves and these valves would act very quickly. These valves are composed of movable poppet which would close against a valve seat. The ball, cone or disc in the poppet valve is used to close the seating area. In a certain type of poppet valve, the actuation force is depended on the pressure and area so in order to avoid this pressure compensation is done. Most of the poppet valves have this problem and poppet valves cannot be constructed for pressure compensation, because of this the actuation of the poppet valve is done by high switching force. So the actuation is done with the help of pilot control or lever transmission.

What is the difference between the Poppet valve and spool valve

Poppet valves are able to cover the internal passage by using a ball or disc and it is held by using air pressure and a spring. So when the poppet valves are actuated the poppet will be pushed away by the stem from the seat so that the flow could occur. While in case of a spool valve a spool is used to block the flow so when the spool valve is actuated then the spool will move and that could cause the seal to be close to the bore and the ports will be opened for the airflow

How does a poppet valve work

The poppet valve has a poppet that is movable and it would close against a valve seat the valve would be tightly closed by the pressure from the inlet. When we apply a small force to the poppet stem then the poppet would open. The stem of the poppet valve has an O-ring seal so that it can reduce the leakage. In most of the poppet valves, the poppet is held down with the help of a spring. According to the purpose of the valve, the number of poppets will vary.

How to do the selection, installation, and maintenance of a poppet valve

  • Check if the disk is centered within 3mm on the seat
  • During the stroke, we must check the shaft alignment and the valve must be straight between the cylinder and guide by 1mm, if it is more than this then it would cause problems
  • During the closed position, the valve disc must not have more than 1mm clearance to seat
  • Cylinder end stroke must be varied to soften final seat speed so that hard hit to the seat can be avoided
  • The disc deflection must be checked when it touches the seat, it must not be in the range of 4-6mm and this will provide proper pressure for the seal
  • Check the center hole of the disc, it should be cut, round with no edging or rough cuts
  • The washers used in the top and bottom part of the disc and nut must be checked and the diameter of the washer should be proper for the disc
  • Check if the PRV is installed and the pressure setting is correct
  • Check the solenoid and air tubing
  • Exhaust air pressure must be checked
  • Check if the poppet valve shaft guides have Teflon bushing
  • Check if dry air is used for poppet air supply

What are the types of the poppet valve

Mostly there are two poppet valves and they are ball seat poppet valve and disc seat poppet valve

Ball seat poppet valve

In this type, a ball is used to stop the flow poppet valves are normally closed valves the ball valves are normally 2/2 directional control valves. The sealing characteristics of this valve are very good hence it can be used as a shut-off valve. The ball will move from its position while pressing the push button. The ball will be lifted from its seat and the flow will take place. If the push button is released then the ball will block the flow with the help of air pressure and spring.

Disk seat poppet valve

In this type of poppet valve, a disk is used to stop the flow and this valve is a 3/2 way directional control valve. So in this type when the push button is released then the port R and P will be connected. So if the push button is pressed then the port R would be blocked by the valve stem and pushes the disc down and thus the valve would open. So the P and R port made a connection by this. In order to close the valve the push button is released then the port P will be closed by the spring and thus closes the valve.

How ball seat poppet valve is different from disk seat poppet valve

Ball seat valves are not expensive and they are small, it can resist dirt and it can be operated manually or mechanically. While the disk seat poppet valve requires more area but a small lift is needed. Quick response time and they are resistive to dirt, and these valves can be actuated manually, mechanically, electrically and pneumatically.

What are the advantages of the poppet valve

  • It has a high flow rate because of the larger internal surface
  • The controlling of the positions can be done properly because the exhaust port is covered by the poppet before the flow
  • The product life would be high because of less wear
  • The response time of poppet valve is really fast, during the actuation the port will open quickly
  • We would get a larger opening in a small stroke
  • These valves are resistive to dust and dirt
  • Less maintenance and economical

What are the disadvantages of the poppet valve

  • These valves are unbalanced and pressure compensation is required
  • It is not used with vacuum
  • Actuation is done by higher force because the spring and air pressure must be overcome for the flow
  • If there is no supply pressure then the back pressure may open the valve, so these valves cannot be used to hold the pressure downstream.
  • Pitting can happen due to the opening impact
  • Because of buckling, the spring could wear

What are the applications of the poppet valve

  • It can be used for gas transport because it has a low opening impact, high lift, and good efficiency
  • They are also used for process applications

Check the following links to get more info about control valves

News Reporter
post-graduate in Electronics & communication