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How They Work
Poppet valves are a very robust and resilient construction for use in industrial directional control valves. They are usually very tolerant of typical air line contaminants (rust, scale, etc) when used in compressed air service. This type of valve construction is typically characterized as being a high flow, fast acting design due to the large flow paths through the body that can be opened quickly. Think of a poppet valve very much like a stopper or plug in a bath tub drain. When the plug is pulled, the flow path opens quickly and the area that opens is quite large. The large opening of a poppet allows particulate to pass through the valve easily.
Poppets are only one of several different types of construction used in the manufacture of industrial directional control valves. Poppet valves are characterized by having a movable element (the poppet) that is used to direct the flow of a fluid or a gas through the valve body. The poppet inside is moved via a stem that pushes the poppet off its seat allowing a flow path (in the case of a 2-way, normally closed valve), or closing off a flow path by pushing the poppet onto a seat (in the case of a 2-way normally open valve). The stem is moved by some sort of actuator (typically a pilot, manual, mechanical or solenoid operator). In the case of a pilot actuator, a piston chamber is pressurized by a fluid or gas, causing a piston to push down on the stem. In the case of manual operation, some sort of device such as a knob, lever, or pedal is actuating the stem via human force. Valves actuated by manual force are often referred to as "human interface" devices. Mechanical operators such as a stem extension, roller, or a cam roller are actuated by the actual process in which the valve is installed. Actuation of the stem via a solenoid can be achieved in one of two ways. When using a direct solenoid, the actual electro-mechanical force pushes directly on the stem to open the poppet. In the case of a solenoid/pilot actuator, the solenoid only controls the flow of a gas (typically compressed air) or liquid into and out of a pilot chamber (previously discussed above) which moves the stem.
When the operator force is removed from the stem on a normally closed valve, a spring pushes the poppet towards the seat in the body and is assisted by the flow through the valve. Once the poppet reaches the seat, the inlet pressure assists in keeping the poppet seated bubble tight. On normally open valve models, the flow through the valve assists a spring in pushing the valve off its seat to return it to the open condition.
Poppet valves such as illustrated here feature a design that incorporates a seal that is crimped into the poppet's sealing face. The seal materials that are used include various types of rubber, plastics or other exotic polymers which are chosen based upon various operating conditions. Parameters that affect seal material choices would include operating pressure, temperature extremes, chemical composition of the gas or liquid passing through the device, environmental concerns, etc. In some cases, the entire poppet may be made from exotic polymers rather than just the seal insert.
Typical models of poppet valves would include 2-way (either in a normally closed or normally open configuration) and 3-way operation for filling and exhausting frunctions from one device.
Poppet valves have many applications, including:
Lexair, Inc. offers a complete line of poppet valves, including: