Hydraulic fluid is the lifeblood of any hydraulic system, and is responsible for power transmission, lubrication and heat transfer. Due to component and design efficiencies, as well as external factors, oil temperature can increase and reach a point outside of optimum operating range. This can result in decreased system performance, increased maintenance and damaged components.
While selecting the proper fluid for an application is immensely important (and a topic all its own), I am going to focus on the selection of temperature switches for a typical industrial installation. A “typical industrial installation” is located indoors with an ideal oil temperature range of 110 °F to 130 °F.
Liquid Level Sensors
Factory pre-set temperature switches that are installed directly through the tank top into the fluid tend to be the most popular type of temperature switches. As temperature rises, the switch contacts open or close (depending on the ordered configuration). I have been using this type of switch with a setting of 158 °F for the last 20 years as a high-temperature warning or system shutdown. While inexpensive insurance, this particular switch only indicated if the fluid is above or below the 158 °F setting, and not the exact temperature.




Temperature Controllers
Temperature controllers are a step up from simple switches and combine the functions of temperature switches, temperature sensors and displays in a single instrument. With temperature controllers, you will know the exact temperature of your fluid, and will be able to make educated decisions regarding how quickly your oil temperature increases, and by how much.
Regardless of how you monitor your fluid’s temperature, it is vitally important to ensure your are in the proper range.
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