What is the purpose of Thermal Protection on constant fill fluid couplings?
Thermal protection on a fluid coupling provides safety to a fluid coupling and directly to the driver and driven machine. Fusible plug is most common thermal protection. If the temperature of fluid in the coupling increases due to any reason (which includes overloads) than the fusible metal in plug melts & all the fluid in the coupling drains out thus stopping power transmission & reloading the prime mover.