Differences between poppet and spool valves

Differences between poppet and spool valves

There are two valves to consider when working with different applications: poppet valves and spool valves.

This raises the question as to what the differences are between these valves.


What differentiates poppet from spool valves?

Depending on its position in the housing (the switching position), it creates and/or blocks connections between ports.

One of the characteristic parts of a hydraulic valve is the moving control element.

Hydraulic valves are characterised as spool valves or poppet valves depending on the design version of the control element.


Spool valves

These valves have a control element that is a control piston or 'spool' that is pushed inside the housing borehole. The spool blocks or opens the connection between the channels in the valve body depending on its position in the body.

The control piston is guided in the housing bore with little clearance, only a few microns. A fluid film forms between the two parts and the control spool 'floats' on this film, reducing friction forces.


Poppet valves

As a moving control element, poppet valves use a ball, cone, or plate.

The control element blocks or closes the valve channel by being pressed onto the valve seat by a spring. The channel is opened against the spring force.

These valves have greater leak tightness than spool valves.

Poppet valves are therefore the valve of choice in applications where components or hydraulic systems need to be shut off without any leakage.

There needs to be awareness, however, that flow capacity ratings of all hydraulic valves are greatly affected by their mechanical design.

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