Common Faults of Hydraulic Systems: Causes, Elimination Methods And Daily Maintenance for High Oil Temperature in The Hydraulic Station

Hydraulic oil is the working medium of the hydraulic transmission system. Generally, it works best within the range of 35-60℃. During the operation of the hydraulic system, pressure loss, solvent loss and mechanical loss will all be converted into heat energy, causing the oil temperature to rise. Changes in oil temperature will lead to changes in the viscosity of the oil, thereby causing unstable movement speeds of the mechanical system.

If the oil temperature of the hydraulic system is too high, the equipment will break down:

1. It affects the lifespan of the hydraulic oil and hydraulic components, accelerating the oxidation of the oil and causing it to deteriorate;

2. High oil temperature will seriously affect the stability of the hydraulic oil, thereby affecting the sealing, lifespan and transmission efficiency of the entire hydraulic system.

Therefore, while monitoring the normal temperature rise of the hydraulic system, it is necessary to be able to promptly detect abnormal temperature rise in the hydraulic system and promptly find the cause to eliminate the fault.

I. Causes and Elimination Methods of Abnormal Oil Temperature

Causes of abnormal oil temperature 1. Hydraulic system design

The hydraulic system has excessive power, resulting in significant energy loss during operation, causing the oil temperature to rise excessively; the specifications of hydraulic components are improperly used, with the capacity of the components being too small and the flow rate being too high; the design of the system circuit is poor, with low efficiency and the presence of redundant components and circuits; the throttling method is improper; during non-operational periods of the system, there are no effective discharge measures, causing a large amount of pressure oil to be lost and converting into heat for the oil; the hydraulic system is pressurized too high, resulting in significant pressure losses during non-operational cycles, causing the oil temperature to rise excessively. Improvements and refinements can be made based on the above unreasonable designs.

Reasons for abnormal oil temperature 2. Loss causes pressure to convert into heat

The most common cause is improper design and installation of the pipeline, as well as insufficient timely maintenance and cleaning of the pipeline, which leads to increased pressure loss. This should be improved during commissioning and maintenance. If the viscosity of the oil selected is too high, replace it with oil of the appropriate viscosity; if the pipeline is too thin and long, causing excessive resistance of the oil and excessive energy loss, select appropriate-sized pipes and valves, shorten the pipeline length, appropriately increase the pipe diameter, and reduce the bending radius of the pipe.

Abnormal oil temperature reason 3. Heat generated by large volume loss of oil

After air enters the circuit, it will circulate with the oil in the high-pressure and low-pressure areas, being constantly mixed into, dissolved in, or released from the oil, causing pressure shock and a sharp increase in oil temperature, resulting in oil oxidation and part erosion. Therefore, at the connection points and clearance of the hydraulic pump, measures should be taken to prevent internal and external leakage, reduce volume loss, and completely remove the air from the circuit.

(1) To prevent air from being brought in when the return oil pipe returns oil, the return oil pipe must be inserted below the oil surface.

(2) After the inlet filter is clogged, the suction resistance increases significantly, and the air dissolved in the oil is separated out, causing the so-called cavitation phenomenon.

(3) At places lower than atmospheric pressure such as the inlet fittings and pump shaft sealing parts, be careful not to let air in.

(4) The liquid level of the oil tank should be as large as possible. Use a partition to separate the suction side and return oil side, and select an oil return filter with a liquid flow diffuser to achieve the purpose of eliminating bubbles.

(5) At the highest parts of the pipeline and hydraulic cylinder, there should be air holes. During startup, the air in them should be released.

The reasons for abnormal oil temperature: 4. Excessive mechanical wear causing the oil to heat up

Mechanical wear often results from poor processing accuracy and assembly quality of the hydraulic components, poor installation accuracy, and excessive frictional heat between relative moving parts. If the sealing components are installed improperly, especially if the compression amount of the sealing components is inappropriate, it will increase the friction resistance.

Abnormal oil temperature reasons: 5. Excessive pressure setting

In non-optimal working conditions, increasing the system pressure to ensure normal operation cannot be used to solve the problem. This will increase energy loss and cause the oil to heat up. Try to set the system pressure as low as possible under the condition of meeting the working requirements.

II. System failures caused by oil overheating

1) Damage to the relief valve: This results in inability to discharge pressure. If the discharge pressure is increased, the pressure loss will be too high. In this case, the relief valve needs to be replaced and adjusted to the normal working pressure.

2) Decreased performance of the valve: For example, if the valve is prone to vibration, it may cause abnormal overheating.

3) Wear of pumps, motors, valves, cylinders and other components: At this time, the worn components should be replaced.

4) Overload of the hydraulic pump: Check the support and seal conditions, and check if there is a load exceeding the design requirements.

5) Dirty oil or insufficient oil supply: If the oil deteriorates, clean or replace the filter; replace the hydraulic oil and add oil to the specified level.

6) Poor performance of the cooler, the oil passing through the cooler cannot reach the specified temperature. If the cooling water supply is lost or the fan does not work, check the cooling water system, replace, clean the solenoid valve and fan. If there is sediment or scale in the cooling water pipeline, clean, repair or replace the cooler.

III. Daily Maintenance

During the daily operation and maintenance of the hydraulic system, the following points should be particularly noted:

1) Regularly maintain the oil level in the oil tank to ensure that the system has sufficient conditions for oil circulation and cooling;

2) Check and ensure that the water volume in the cooler is adequate and the pipeline is unobstructed;

3) When the system is not in operation, the hydraulic pump must be unloaded.