This article mainly introduces the maintenance points of hydraulic power units and related equipment, including: lubricating the motor according to the manufacturer's instructions; cleaning and replacing filters as indicated or in the manual, ensuring the use of the appropriate type and proper cleaning; the suction filter is usually cleaned for the first time after 10 hours of use, and then every 100 hours (the specific time may vary by manufacturer); regularly check the oil level in the reservoir, especially when first used, ideally every 100 hours; replace the hydraulic oil within the 1000-2000 hour usage range according to the manufacturer's requirements and factors such as the usage environment and application; and check if the oil is overheated, as overheated oil is darker in color and may have a burnt smell compared to new oil.

Hydraulic power units (HPUs) are widely used in industrial manufacturing, construction machinery, aerospace, ships, and agricultural equipment, providing efficient power support for various heavy machinery. In the manufacturing industry, HPUs drive presses and automated production lines, significantly enhancing production efficiency, but they face the problem of high energy consumption. In the construction sector, excavators and cranes rely on hydraulic systems to complete high-intensity operations, with their load adaptability being outstanding, but the maintenance costs are relatively high. In aerospace and ship applications, the reliability and precise control of HPUs are extremely demanding, and custom solutions are usually required. In agricultural machinery, hydraulic systems are used to complete farming and harvesting operations, with their durability being suitable for harsh environments, but the energy efficiency differences can affect operating costs.

This article provides key maintenance points for hydraulic cylinders, including checking the condition of the piston rod, seals and valves, hydraulic oil and filtration system, cylinder barrel status, regular replacement of the cylinders, as well as maintenance of accessories such as fork heads and ball joints. It emphasizes the importance of thorough inspection and prompt handling of issues in each step to prevent failures.

This article outlines the key steps in hydraulic cylinder selection. The first step involves determining the mass of the moving object and calculating the required force to overcome resistance (e.g., gravity, friction), with an additional safety margin. Next, the load's geometric distribution must be analyzed, as asymmetric loading or lever effects significantly influence the cylinder's force requirements. The minimum bore size is then calculated based on system pressure and required force to ensure sufficient thrust. Subsequently, the piston rod diameter is selected according to stroke length, with critical consideration given to buckling strength to prevent failure. Finally, for high-speed applications, internal cushioning can be incorporated to reduce impact forces at stroke ends without altering the cylinder’s external dimensions.

Hydraulic cylinders are the core components of construction machinery and are widely used in various fields such as construction, mining, and agriculture. In the construction industry, hydraulic cylinders provide power for equipment like excavators and bulldozers, ensuring construction efficiency. Mining equipment relies on hydraulic cylinders to complete heavy material handling and maintenance tasks. Agricultural machinery uses hydraulic cylinders to achieve precise operations, enhancing farming and harvesting efficiency. These applications fully demonstrate the crucial role of hydraulic cylinders in modern industry.

Hydraulic power units are widely used in various industries such as construction, manufacturing, mining, and agriculture. They possess advantages such as compact size, high power density, high energy efficiency, precise and stable control, excellent power-to-weight ratio, strong durability, the ability to achieve immediate and smooth shifting, and are equipped with safety devices like pressure relief valves. These features enable them to provide reliable power while also considering economy, safety, and efficiency, making them suitable for various working conditions.

Hydraulic cylinders can generate powerful force due to the incompressibility of hydraulic oil and the surface area of the piston. They are easy to maintain, operate smoothly and can adjust precision through flow control. They come in various sizes and configurations to suit different scenarios, and are highly reliable (able to withstand certain lateral loads and undergo strict quality inspection). They can also efficiently convert hydraulic pressure into linear motion and, combined with energy-saving design, achieve efficient energy utilization.

The hydraulic cylinder assembly must be performed in a controlled environment (20–25°C, dust-free, low noise) with dedicated equipment (assembly machines, cleaning systems, pressure testers). Proper tools (torque wrenches, non-metallic hammers) and lifting methods (hoisting belts) ensure part safety. Workshop cleanliness (organized workflow, oiled floors) is critical to maintaining quality standards.

Hydraulic cylinders are essential in various industrial applications, converting fluid power into linear mechanical motion. This article outlines the four main parts of a hydraulic cylinder—cylinder barrel, cylinder head, cylinder base or cap, and piston—detailing their functions, construction, and sealing mechanisms. Understanding these components ensures efficient design, maintenance, and operation of hydraulic systems.

This paper focuses on the application of hydraulic cylinders in the propulsion system of shield machines and discusses the optimized design measures to prevent cylinder leakage. Through overall structural adjustment, integrated valve block design, vibration reduction control, sensor optimization and reliability analysis, the stability and operational efficiency of the hydraulic system have been effectively enhanced. The technical solution proposed in the article has practical guiding significance for the leakage control and fault prevention of hydraulic equipment.