In the majority of applications a reservoir immersion heater is not the recommended solution to keep the hydraulic oil at the proper operating temperature in an extremely cold weather application. In addition to being a high priced accessory immersion heaters are not energy efficient.
Hydraulic dock lifts are operated using a power unit which is a combination of an electric motor, a gear pump, valving and a hydraulic reservoir. The hydraulic oil is pumped from the reservoir to the lift table cylinder(s) causing the dock lift to rise and the oil is then routed back to the reservoir through a valve assembly allowing the dock lift to lower.
In an extremely cold environment the viscosity of the hydraulic oil thickens. When lifting the thick hydraulic oil can put a strain on the power unit pump assembly causing internal friction and premature wear or even pump failure. When lowering the thicker hydraulic oil does not flow as freely through the hoses and valve assembly resulting in a slower lowering speed.
In the majority of installations the dock lift is installed outside and used intermittently. The hydraulic oil that is present in the cylinders and hydraulic hoses does not get warm because it is not exposed to the heater in the reservoir.
To avoid these detrimental operating characteristics the power unit should always be located in an area with a warm ambient room temperature up to approximately 30C. In an extremely cold operating environment there are specialty hydraulic fluids available to provide optimum performance. There may be a requirement for hydraulic fluid changes during seasonal temperature fluctuations.
In summary the most effective solution for extremely cold environments is the combination of an internally stored power unit and lower temperature rated hydraulic fluid.