Relevant data show that about 80% of construction machinery hydraulic system failures are caused by hydraulic oil contamination, which not only seriously affects the normal operation of construction machinery but also causes great economic losses to engineering construction. Therefore, in order to ensure the normal operation of hydraulic systems in construction machinery, systematic engineering methods should be adopted in light of the characteristics that hydraulic oil in construction machinery is prone to contamination, and the three main links of “purchase, management, and use” should be carefully handled to effectively prevent hydraulic oil contamination.

　　1. Purchase correctly and control the purchase of hydraulic oil

　　(1) First, hydraulic oil should be purchased reasonably, and it is best to purchase hydraulic oil consistent with the brand and grade specified by the original manufacturer. At present, there are many manufacturers and suppliers of hydraulic oil at home and abroad; hydraulic oil varies in quality and there are also counterfeit and inferior products. Therefore, hydraulic oil should be purchased from suppliers designated by the manufacturer or from specialty stores of large manufacturers. Equipment management departments must change the past management approach of only purchasing without regard to quality status, and strictly control the entry of hydraulic oil.

　　(2) Hydraulic oils of different brands and grades must not be mixed. The physical and chemical indicators of hydraulic oils of different brands are different; if mixed, they may produce chemical reactions, corrode hydraulic components, and damage the hydraulic system.

　　(3) If other hydraulic oil is to be used to replace the original hydraulic oil, the substitute hydraulic oil must be tested by an authoritative department, and its main technical indicators must be consistent with or close to those of the original hydraulic oil. In addition, the substitute hydraulic oil must not be mixed with the original hydraulic oil.

　　2. Manage strictly and control the purification of hydraulic oil

　　(1) An oil use management card should be set up in the equipment management ledger, clearly indicating the oil brand and grade, oil consumption quota, and oil change records of the construction machinery.

　　(2) Hydraulic oil should be sampled and tested before being put into storage, and only qualified oil may be stored; hydraulic oil in storage should be sampled and tested periodically, and unqualified oil must not be used; oil entering the warehouse should be stored and kept according to brand sequence, and mixing must be strictly avoided. Oil products must not be stored in the open air. If unavoidable, rainproof measures should be strengthened or oil drums should be placed obliquely to prevent rainwater from seeping in through the drum openings and contaminating the hydraulic oil.

　　(3) Establish the concept that “new oil is not clean.” When adding new oil, the oil filling tools must first be cleaned, and then the new oil must be strictly filtered. When the oil filter machine is not in use, the oil pipes should be kept clean.

　　(4) Periodic cleaning or replacement of filters should be established as a system to enhance the “immunity” of the hydraulic system. Replace or clean filter elements periodically or according to indicator instructions to ensure filtration accuracy and prevent secondary contamination of hydraulic oil.

　　(5) When changing to new oil, the residual liquid in the oil tank should be drained completely, sediment should be cleaned out, and the interior of the oil tank should be carefully flushed with an appropriate amount of the oil to be added. Old oil remaining in components can be discharged by jogging operation.

　　(6) When repairing and maintaining the hydraulic system of construction machinery at the construction site, attention should be paid to the cleaning of all parts. Disassembled hydraulic components must not be placed randomly. During assembly, the components should be strictly cleaned with gasoline (or diesel) and hydraulic oil before assembly to prevent impurities from entering the hydraulic system.

　　3. Use reasonably and control correct use

　　(1) Strengthen hydraulic technology training for management personnel, drivers, and maintenance workers, improve their quality and quality awareness, and enable them to master basic knowledge of hydraulic oil and use hydraulic oil correctly.

　　(2) Strengthen the purification and monitoring of hydraulic oil during the use of construction machinery, and clarify the monitoring responsibilities of drivers. Drivers should pay attention to changes in hydraulic oil temperature during use; if the oil temperature is too high, they should immediately stop the machine and find the cause. During daily inspection and routine maintenance of machinery, attention should be paid to changes in oil level and oil quality, so as to “add oil according to quantity, filter according to need, and change oil according to quality.”

　　(3) When refueling, drivers should pay attention to the cleanliness of the oil drum opening, the oil tank opening, and the inlet and outlet of the oil filter machine.

　　(4) Construction machinery should be prevented from operating while faulty and from overload operation, so as to avoid excessively high oil temperature and prevent hydraulic oil deterioration and abnormal wear of hydraulic components that generate relatively large solid particles.