Pneumatic Spool Valves



Pneumatic directional control valves with O-ring spools (usually 3way & 5 way) come in two types  - Dynamic and Static.

The Dynamic design has the O-rings mounted in grooves on the spindle (bobbin) which moves inside the valve cavity directing the air though the ports when actuated.

The Static design has the O-rings or lip seals clamped between spacers inside the valve cavity and fixed in place. The spool (bobbin) moves inside the seal spacers directing the air though the ports when actuated.

Actuation of the spool comes from various mechanisms depending on the valve (lever, plunger, button, roller, toggle, foot, solenoid etc) but the internals are usually of the above designs.


Both designs require maintenance - usually on an annual basis depending on the frequency of operation. If the valve has been in storage for a long time this may be done prior to installation as the lubricate can dry out. 

Using a clean workbench the spool is carefully removed after the end caps / operating mechanisms have been unscrewed. A suitable grease or mineral oil that is compatible with the NBR O-rings seals is lightly applied to the O-rings (Dynamic) or the spool (Static).

Reassemble and test.