Hot Systems

Whenever I check out a hydraulic system my first reaction is to cautiously touch the side of the tank.
If I can comfortably keep my hand on the side I know that the system is running at a good temperature 20-30C (50-60Cmaximum). If my hand recoils due to the high temperature I know straight away that there is a potential problem.
Hot oil causes all sorts of problems and affect, seals, oil viscosity, oil degradation and the danger of scalding.
Ensuring that the system is running at the right temperature should be done at the drawing board stage and not tagged on later as an afterthought.
Things to consider are:
Installed Power
Duty cycle
Ambient temperature
Size of tank
Heat comes from the inefficiency of the system. If we do not use all the energy we are generating in doing work the rest will be converted into heat. Conversely, you will not generate any more heat than the maximum power of the prime mover.
Relief valves are the prime source for heat generation and if possible the system should be designed to minimise the length of time oil passes over this valve. Open centre control valves, pressure compensated pumps and unloading valves can help.
Some heat is radiated by the tank and can often remove the need for a cooler.
This is a huge subject, ranging from the damage heat can cause to the best types of coolers and I know that there are many in our group who will have some very interesting views on this subject.
Cheers
Bob