Heat can take a toll on outdoor equipment and heavy machinery. The heat damage done to the machinery or components, like a rotary union isn't always immediately noticeable. For example, elastomeric hydraulic seals within the rotary union will start to 'take a set' if they are overheated, meaning that they will become brittle, losing their elastomeric properties. Once they start taking a set, they no longer function properly. Many times, heat damage will show up when the temperatures begin to get colder and can be the first indication is often not sealing correctly.
Due to the nature of rotary unions, it typically is the one place within the hydraulic system where all the hydraulic lines and functions come together. With all the hydraulic lines converging within the component, heat build-up can occur. If a function is held over relief, or if hydraulic fluid never circles back to the tank, heat can build up in the rotary union. The system temperature probes may not notice an overheating situation within the rotary union.
Many OEM manufactures of hydraulic-powered equipment do temperature testing. They perform a Limiting Ambient Temperature (LAT) test. This effectively indicates an upper limit in the ambient temperature that the equipment can safely operate in without overheating.
The upper limit of the ambient temperature is directly related to the health of the cooling system. If debris or improperly mixed coolant enters the cooling system, it can negatively affect the health of the system. Another variable is altitude, as higher attitude results in less efficient cooling. Properly maintained engine coolant and hydraulic cooling system can help keep the LAT near the same level as a new machine.
In addition to maintaining the cooling system, steps can be taken to make the rotary union outlast other components in the hydraulic system. This typically involves using more PTFE-based sealing components and high-temperature rated elastomeric elements such as FKM (also known as Viton). PEEK plastic backup rings can also be added.
Higher temperature-rated components usually have a higher cost associated with them. Customers should communicate operating conditions to UEA engineers when designing a new rotary union for a new application to keep costs in control. Not all situations require higher-priced seals, nor do end customers want to pay for the best if the application doesn't require it. UEA can help design the right-sized rotary union and performance specifically for your needs.
Are you interested in starting a new rotary union project with UEA? Contact us today!