Severe Consequences of Improper Hydraulic Pump Operation

Many operators and maintenance manufacturers of sanitation vehicles, loaders and heavy-duty construction machinery tend to operate hydraulic pumps in a rough manner with inadequate routine maintenance. This not only causes rapid wear and scrapping of hydraulic pumps, but also subjects the matched hydraulic cylinders to overload damage, greatly shortening the service life of the entire hydraulic system.

If you are purchasing heavy-duty hydraulic cylinders compatible with construction machinery, sanitation vehicles and loaders, choose Jiangsu Youjiaxin. We specialize in customized production of lifting cylinders for sanitation dump trucks, boom and bucket cylinders for loaders, and non-standard cylinders for all types of heavy-duty construction machinery. We have thorough knowledge of the matching working conditions of complete hydraulic pump-cylinder assemblies, and can avoid linked damage to pumps and cylinders at the source of hydraulic system matching. Below is a detailed explanation of standardized operation, disassembly and assembly key points for hydraulic pumps to protect your full set of hydraulic equipment.

I. Key Specifications for Standard Hydraulic Pump Operation (Mandatory for Sanitation Vehicles & Heavy-Duty Loaders)

Sanitation vehicles perform frequent lifting and tilting movements, while loaders endure continuous impact during shoveling. Their hydraulic pumps operate under alternating high pressure for long hours. Improper operation easily causes cavitation and severe pump wear, which in turn leads to barrel bulging or burst of matched hydraulic cylinders. All operators of heavy-duty construction machinery must comply with the following standards:

1. Hydraulic Pump Startup Standards Before startup, check the hydraulic oil tank level via the oil level gauge. Insufficient oil will cause pump air intake and cavitation; high-pressure cavitation abrades both internal pump components and cylinder inner walls. Monitor oil temperature with a thermometer — never start the pump when oil temperature is below 0°C.

If oil temperature is lower than 10°C, run the hydraulic pump under no-load for more than 20 minutes for preheating. Use electric startup with jog test runs. Judge the pump flow by changes in operating noise and pressure gauge readings. If the pump runs for over 1 minute with zero flow, its vanes and rotor are prone to seizure. Instant high-pressure shock will transfer to matched cylinders, exceeding their rated pressure of 16 MPa and resulting in cylinder barrel deformation.

All supporting cylinders manufactured by Jiangsu Youjiaxin are produced with barrel wall thickness compliant with the 16 MPa standard. However, even the most durable cylinders will develop bulges and oil leakage if instantaneous peak pressure occurs due to misoperation of the front-end hydraulic pump. Standardized pump startup is the first line of defense to protect hydraulic cylinders.

2. Inspection Points During Operation & Shutdown Monitor the running status of the hydraulic pump throughout operation: harsh abnormal noise, drastic pointer fluctuation on the pressure gauge and excessively high oil temperature indicate severe internal pump wear. Unstable output pressure from the pump subjects the seals of sanitation lifting cylinders and loader boom cylinders to continuous alternating high-pressure impact, triggering frequent oil leakage.

Compare the temperature of the pump housing and oil tank. A temperature difference over 5°C means the pump has extremely low volumetric efficiency, accompanied by higher energy consumption and disordered pressure output. Pay extra attention to oil leakage at pump shafts and pipeline joints. Sanitation vehicles and loaders work under long-term high temperature and high pressure; minor leaks will gradually cause out-of-control system pressure and indirectly lead to cylinder damage from overpressure.

3. Monitoring Vacuum Degree of Suction Pipeline Regularly check the reading of the vacuum gauge installed on the pump suction pipeline. The reading shall stay below 127 mmHg during normal operation. If the reading exceeds the limit, immediately inspect the suction filter element and cleanliness of hydraulic oil. Clogged filter elements and impurities in hydraulic oil cause poor pump oil supply and pressure pulsation. Long-term pulsating pressure scratches the inner walls of heavy-duty construction machinery cylinders and accelerates seal aging.

II. Standard Disassembly & Assembly Procedures for Hydraulic Pumps

Maintenance of sanitation and heavy-duty construction machinery often requires hydraulic pump disassembly. Non-standard disassembly and assembly directly result in abnormal pump oil supply and unstable pressure, which continuously damage matched hydraulic cylinders. This section covers special disassembly/assembly steps for double-acting vane pumps and general management specifications for all hydraulic pumps:

(1) Disassembly & Assembly of Double-Acting Vane Pumps

1. Disassembly Sequence Remove the fixing bolts on the front cover and take off the front cover; detach the front pump housing; take out the two valve plates, stator, rotor, vanes and drive shaft as an integrated assembly and separate them from the rear pump housing.

Important Reminder: The two valve plates, stator, rotor, vanes, drive shaft and bearings form a pre-matched integrated unit. Do not forcibly separate inseparable components. Forced disassembly damages matching precision, causing fluctuating pump output pressure after reassembly and continuous impact on supporting construction machinery cylinders.

2. Core Assembly Requirements Thoroughly clean all parts with dedicated cleaning fluid before assembly. Vanes have a fixed installation direction — never install them upside down (swap top and bottom). Reassemble strictly in reverse order of disassembly to ensure uniform stable sealed volume inside the pump, steady pressure output within rated limits, and effective protection of matched cylinders for sanitation vehicles and loaders.

(2) General Management Rules for Hydraulic Pump Disassembly & Assembly

1. Implement the "disassembler-assembler accountability system": assign one staff member to fully handle disassembly and reassembly of a single component.

2. Keep detailed written records during disassembly; draw simple assembly diagrams for complex pump units to avoid misinstallation of parts.

3. Store small easily-lost parts (springs, positioning pins, sealing rings, etc.) in dedicated small storage boxes to prevent missing parts that cause pressure leakage after assembly.

4. Prohibit arbitrary removal of pump parts from other groups during cross-shift maintenance. Mixing parts from different pump models will lead to unbalanced pressure.

5. Fully analyze the internal sealed volume and oil distribution structure of each pump before assembly to predict post-assembly pressure output performance.

6. Sort out the complete assembly sequence before disassembly and assemble step-by-step following the workflow to avoid missing or misinstalled parts.

7. Forbid rough disassembly and assembly with violent knocking or prying. Collision damage to precision parts such as pump housings, rotors and valve plates leads to disordered pump pressure output, which easily triggers instant overpressure and cylinder burst on downstream cylinders.

8. Perform no-load trial operation immediately after full assembly. Inspect noise, oil temperature and pressure stability; only put the pump into heavy-duty service after confirming normal operating status.

Most hydraulic failures of construction machinery are caused by two interrelated issues: mismatched operating parameters of hydraulic pumps and incompatible pressure-bearing standards of hydraulic cylinders. Whether you need tilting and lifting cylinders for sanitation garbage trucks and road sweepers, boom and bucket cylinders for loaders, or special cylinders for mining, dump trucks and other heavy-duty construction machinery, choose Jiangsu Youjiaxin.

Our technical team can select hydraulic cylinders with appropriate barrel wall thickness and rated pressure resistance based on the rated output pressure, flow rate and operational impact load of customers’ existing hydraulic pumps, ensuring the operating pressure of the entire system never exceeds the cylinder’s design standard of 16 MPa. We also provide professional guidance on hydraulic system matching and standardize the startup, shutdown, maintenance, disassembly and assembly operations of hydraulic pumps. We help prevent overpressure, component wear, cylinder burst and oil leakage throughout the whole hydraulic circuit from pump to cylinder, significantly cutting maintenance costs for sanitation vehicles, loaders and heavy-duty construction machinery, and extending the service life of complete hydraulic equipment.