3 Common Causes of Hydraulic Overheating

HEAT is the dirty little “four letter word” that, in some form or fashion, affectsevery hydraulic system ever designed.

Learning what causes excessive heat, and how you can reduce its damaging effects on your hydraulic system, will extend your components' life expectancy far beyond its warranty period. Reducing heat can be as easy as adjusting a valve to performing a complete heat load analysis and adding the correct Air-Oil or Water-Oil cooling system.

Here are 3 Common Causes of Hydraulic Overheating:

User Improvisation

Common Question: “What is causing my hydraulic system to 'all of a sudden' start running hot when it has run fine for years?”

This is a common complaint we hear from our customers. Normally 9 times out 10 “something” has changed in their systems and it is usually an adjustment. We find that in pressure compensated variable volume pump systems, “someone” felt the need for the system to use more pressure. They make the common mistake of adjusting the pump compensator to move past the main relief valve setting. This causes the pump to come on stroke and dump wasted flow at the max pressure setting, inducing HEAT into the system.

Designer Shortcuts

Common Question: “Why is my machine getting hot just sitting there? Nothing’s is moving!”

Pressure Drop is another heat generator when components are not sized properly. When it takes too much pressure just to push the oil through all the valves, pipes, hoses, elbows, bends, and filters, this wasted energy shows up as heat. You can avoid this by simply upsizing your components and reduce the bends in your plumbing. If radical bends are unavoidable, try increasing the size of your hoses and fittings. You increase your flow capacity dramatically by increasing only one hose size.

For example, 10 gallons per minute (GPM) through #10 SAE hydraulic hose flows at a velocity of 10 feet per second (fps), while the same 10 GPM flows at 7.5 fps through #12 SAE hose. That’s a 25% decrease in flow restriction!

Your System's at a Point of No Return

Common Question: “I can’t change any components and I still have a heat problem. What do I do?”

When you hear this from your customers, the only thing you can do is add an external cooler to their system. Instead of reducing the cause, you just have to pull the excess heat out. You first determine the heat load and choose a cooler that will remove enough heat from the system to run at a normal temperature. Commonly, 120-140 degrees Fahrenheit (F) for industrial systems and 160-180 F for mobile applications are ideal. In heat removal, the general rule of thumb is to remove 1/3 of the input horsepower (or Prime Mover). Cooler selection is based on these factors and available flow. Proper selection can be made by any Cross Company account manager.

Heat is a hydraulic component killer and will indiscriminately attack each and every part of your system. Your oil can be as clean and pure as the wind driven snow, but if it gets hot, it will kill your machine. The mentioned methods, reduction tactics, or the addition of a oil cooler, will stave off this killer and help your components live a long and healthy life.

Contact an Expert

If you are having similar problems, or have questions about this topic, please do not hesitate to contact me or chat about your heat issues . Please have your system specifics on hand.