Heat is generated in a hydraulic system as a byproduct of inefficiency. Coolers are used to remove this heat load from the hydraulic system to ensure a long system life. Coolers come in a variety of styles, including air cooler and water cooled, tube and plate, industrial and mobile. They can use AC motors, DC motors, or hydraulic motors to power the fan. Hydraulic Controls Inc stocks many varieties, please contact us for you cooler needs.