What Is the Function of A Poppet Valve in Compressors - Samco

What Is the Function of A Poppet Valve in Compressors?

A poppet valve is generally linked with applications and pressure control equipment. They play a crucial role in compressors. This article covers the primary function of this vital component or its working principle in a compressor.

A poppet valve is a specific type of valve designed to regulate the timing and amount of vapor or gas flow into an internal combustion engine or pneumatic system. This mushroom-shaped, directional control valve rises perpendicularly from its seat and effectively replaces the standard spool with a seat and ball.

Poppet valves are controlled via solenoids and, in their de-energized state, can be set to normally closed or normally open when desired. The high-flow, fast-acting valves are usually employed as check valves to prevent one-way flows and relief valves to prevent overpressure.

A poppet or engine valve – is usually placed adjacent to spool valves as an alternative for pneumatic/hydraulic systems. Due to its design, a poppet valve has a large flow path that allows media to pass through its main body.

How a Poppet Valve Works in a Compressor

As established earlier, a poppet valve is shaped like a mushroom and uses rounded stem tips or balls, often called poppets, to seal or shut off passageways by pressing the poppets right onto seats.

This action often occurs through a combination of fluid pressure and spring force and is in the normally-closed position.

The valve can be operated manually, mechanically – i.e., via a limit switch – or electrically through a solenoid. Pilot air can also open this valve pneumatically, pushing the stem and efficiently drawing the poppet off its seat. This gives room for fluid to flow, and this is known as the normally-opened position.

A popular valve design is usually a 3-way, 2-position valve permitting fluid to flow, for instance, into a cylinder as soon as the valve is initiated. It expels all emitted fluid straight into a reservoir through an exhaust port or when the valve closes.

Poppet Valves vs. Spool Valves

Poppet valves are far different from spool valves. The latter uses cylindrical elements and often comes fitted with several O-rings that work linearly in a bored valve body.

As soon as the spool shifts, the O-rings open and close the ports alternately, thus promoting seamless movement among the valve ports.

Spool valves also remain in position, i.e., they can’t be displaced, making them very balanced unless an external force via manual operation or from a solenoid acts on them. Most poppet valves are available in highly balanced designs that never fail to meet operators’ expectations during daily operations.

What You Should Know About Poppet Valve Design

Poppet valves are usually constructed with a valve stem and a flat metal disk. A poppet valve has an open-ended chamber or hole, usually oval or round in cross-section. The valve stem pushes down on the valve to open it, while a spring is adopted for closing the valve whenever the stem is no longer in operation.

This makes the poppet valve fundamentally different from oscillating and slide valves. The most significant benefit of a poppet valve is its non-existent movement on the seat. This means no lubrication is necessary to facilitate its smooth operation or performance.

The working end of the valve stem is known as the valve face and is usually ground at a 45-degree angle to seal against a corresponding valve seat ground into the rim of the chamber that is getting sealed. The shaft moves through a valve guide to maintain its alignment.

Pressure differentials on both sides of the valve impair or assists its performance. For instance, in intake applications, lower pressure helps open the valve, while in exhaust applications, higher pressure – against the valve – helps seal it.

A wide range of actuators moves the stem, including mechanical, manual, pilot, or solenoid operators. However, this depends significantly on the application.

The Benefits of Using Poppet Valves in Daily Operations

Poppets valves are best known for their considerable use in steam and internal combustion engines. But they are also employed in several industrial processes, including isolating sterile air within the semiconductor industry to control milk flow in industrial dairy communities.

Spool valves do not offer users the same benefits poppet valves provide. Some of the most significant benefits poppet valves offer to include the following:

  • Faster response times
  • Lower costs
  • Longer or extended lifespans, thanks to lower friction during operation
  • Closed crossovers
  • Higher flow rate
  • Not prone to severe damage that contaminants usually cause

Regarding crossovers, poppet valves take the upper hand, as crossovers usually involve opening a single port right before another port gets fully closed. This crucial consideration is necessary because precise control is highly essential.

Poppet Valve Applications

Poppet valves are primarily used for load holding and lowering with single-acting cylinders. The relief valves in air tanks are made of poppet valves. They are also utilized as unloading components in the majority of displacement pumps.

Poppet valves also offer appropriate systems of flow reversal prevention in fluid circuits. They are also used extensively to prevent contamination of different media in mixing systems.

A handful of poppet check valves are fashioned to allow reverse flow. An excellent example is its extensive use in hydraulic lifts. Poppet valves in this capacity must allow fluid flow into the cylinder to hold the piston in place.

The fluid must reverse its path through the valve to reduce the load. External pilot pressure assists in lifting the poppet valve off its seat, allowing the fluid to return swiftly to the valve through the outlet.


Poppet valves are one of the most vital components used extensively across various industries. They are used in compressors, steam, and internal combustion engines. They offer numerous benefits to users, such as faster response times, closed crossovers, lower costs, etc.

Moreover, poppet valves are preferable to their counterparts, such as spool valves, being less expensive to fabricate.