Definition of hydraulic oil

hydraulic oil overheat
Hydraulic oil overheat

First of all, it is important that you know what hydraulic oil is. Hydraulic oil is a type of oil that has a thickness and classification like engine oil. The difference is that the viscosity level of hydraulic oil is not referred to as SAR or by API service code.

To become more familiar with hydraulic oil, it is a good idea to learn about the properties of this type of oil, including

  1. Hydraulic oil is fluid (liquid) or easy to flow.
  2. It is incompressible, or means that it cannot be compressed.
  3. Stable physical and chemical properties.
  4. Endowed with properties to lubricate the machine.
  5. Prevents rust because it protects engine parts.
  6. Capable of separating dirt.

Damage to hydraulic oil can be caused by two main factors, namely deterioration and contamination. Deterioration is a damage of the oil whose cause comes from the interior of the oil. Meanwhile, pollution is damage caused by factors other than oil.

You should not ignore or underestimate oil problems because when there is a problem, the engine can experience problems because the oil has a great influence on various components of the engine.

The various properties of hydraulic oil mentioned above can only be fully utilized if the oil does not experience problems, including the problem of hot hydraulic oil.

Hydraulic fluid temperature

Hydraulic fluid temperatures above 180°F (82°C) damage most sealing compounds and accelerate oil degradation. While operation of any hydraulic system at temperatures above 180°F should be avoided, fluid temperature is too high when viscosity falls below the optimum value for hydraulic system components. This can occur well below 180°F, depending on the viscosity grade of the fluid.

Causes of hot ( Overheat ) hydraulic oil

There are several things that cause hydraulic oil to get hot, including:

  1. Cooling circulation system
    One of the causes of hot hydraulic oil is a cooling circulation system that is not working properly. Cold plugging and dirty passages result in lower cooling efficiency and higher oil temperature.
  2. Hydraulic system working pressure
    Hydraulic oil heats up when the working pressure of the adjusted hydraulic system is much higher than the actual requirement.
  3. There are components that are worn
    Such as gear pumps, piston pumps, engine cylinders, valve plates, bores, and plungers. This can lead to increased internal leakage and thus cause the hydraulic oil to overheat.
  4. High load usage
    Using high loads for a long time and too high ambient temperature can also be the cause of hot hydraulic oil.
  5. Air circulation
    A hydraulic system may not have enough flow to dissipate the heat generated when the hydraulic fuel tank is too small, causing the oil temperature to rise.
  6. Hydraulic oil grade
    The difference in quality and viscosity, as well as different levels of hydraulic oil, can cause the viscosity index of the hydraulic oil to be too low or too high.
  7. Other factors
    Various factors, such as severe contamination, poor construction environment, and contaminated hydraulic oil entering the pump, motor, and valve bores, can increase friction, wear, and leakage, leading to high temperatures. of the oil.
  8. filter plug
    Hot hydraulic oil can also be caused by a filter plug resulting in oil resistance and increased power consumption.

hydraulic oil overheat

Beat the heat

There are only two ways to solve overheating problems in hydraulic systems:

  1. Decrease heat load or
  2. Increase heat dissipation
    Hydraulic systems dissipate heat, albeit a relatively small amount, through the reservoir. Therefore, check the fluid level in the reservoir and if it is low, fill it to the correct level. Check for obstructions to airflow around the reservoir, such as a buildup of dirt or debris.

How to maintain hydraulic oil

So that the Hydraulic oil does not heat up easily and can be used for a long time, there are several proper maintenance methods that you can perform, including

  1. Try to keep the hydraulic oil drum under the roof.
  2. Always clean the top of the drum before opening the drum so dirt does not get into the oil when the drum is opened.
  3. Be sure to use a clean pail or container and hose.
  4. Before putting the oil in the tank, please filter the oil first.
  5. Prevent the oil from becoming contaminated by condensation.
  6. Make sure the circuit parts remain firmly attached and the filter system is in good condition to prevent oil contamination.
  7. Before it is completely damaged, you should schedule an oil change.

Well, that is information on the causes of hot hydraulic oil.


What happens if hydraulic pressure is too high?
If the pressure is found to be too high, the system will use excessive input energy and the fluid may overheat. In addition, excessive pressure may stress components and create a very real danger to humans.

Can hydraulic pressure be adjusted?
Adjust the relief valve by turning the adjuster clockwise until the reading on the gauge builds to the pressure called for on the machine drawings. This is what is known as the valve “cracking” pressure, which is the pressure at which the relief valve starts to open.

What happens if hydraulic oil is too thick?
If you use oil that is too thick, then the pump may not be able to draw it efficiently from the reservoir and cavitation may occur. If the oil is too thin then internal slippage may occur within the system’s components making it operate less efficiently.

What will happen if very high viscosity oil is used in hydraulic circuit ?
When a hydraulic oil is too thick (high viscosity), the fluid will be more difficult to pump through the system and may reduce operating efficiency.

All hydraulic fluids must be able to retain optimum viscosity during operation in cold or hot temperatures, in order to consistently and effectively transmit power.

Is hydraulic oil better 32 or 46?
46 is medium and No. 68 is thicker. Generally speaking, if the temperature is low in winter, use #32 & #46 hydraulic oil with a lower viscosity, and use #68 hydraulic oil with a higher viscosity in summer.

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By Aditya

Hi, I’m Aditya Sharma, a professional blogger from Gurgaon, India and I launched this blog called aadityacademy on July 2021. is a mechanical Project-oriented platform run by Aditya sharma and I got the motivation to start aadityacademy blog after seeing less technical education information available on google.

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