FX Series fans are designed to be installed on heavy equipment, including excavators, grinders and haul trucks. Fan is 20 to 78 inches in diameter. Replaces the existing OEM fan assembly. A hydraulic actuator inside the fan assembly controls blade pitch on the FX Series. A solenoid pressurizes either side of this double-acting actuator, which drives the blades into a blower or sucker position. The air dam effect is created when oil pressure is relieved from both sides of the piston, and centrifugal force keeps the blades in the neutral position. The piston has a 1-inch stroke length and requires a hydraulic pressure between 300 and 1,200 psi. This pressure is usually taken from the hydraulic pilot system, however other sources may be used. Higher or lower pressures can be accommodated but will require a few design alterations.