To prevent the piston from striking the cylinder head at either end of its stroke—causing noise, compromising workpiece accuracy, and potentially damaging machine components—hydraulic cylinders in hydraulic pump‑station systems are often equipped with cushioning devices at both ends. These devices operate on the principle of throttling oil to decelerate moving parts. Common types of cushioning devices include annular‑gap type, adjustable‑flow valves, and variable‑throttle valves.

　　Impact Hydraulic cylinder The factors affecting the piston are as follows:

　　1. Annular‑gap type: When the cushioning piston enters the inner bore of the mating cylinder head, hydraulic fluid is discharged through the clearance, thereby reducing the piston’s speed. Since the mating clearance remains constant, the cushioning effect is non‑adjustable. As the piston speed decreases, the cushioning action gradually diminishes.

　　2. Adjustable flow valve: When the cushioning plunger enters the cylinder head’s internal bore, hydraulic fluid must pass through the throttle valve to be discharged. Because the throttle valve is adjustable, the cushioning effect can also be adjusted; however, this adjustment must be made prior to cushioning, and the cushioning characteristics remain fixed during the cushioning phase.

　　3. Variable throttling orifice: A triangular groove is machined axially in the piston, with its flow cross-section progressively decreasing. As the rotational speed declines, the cushioning effect is enhanced. This design provides uniform cushioning, low cushioning pressure, and high positioning accuracy, thereby addressing the issue of weak cushioning in the latter part of the stroke. Cushioning devices include clearance-type buffers, throttling buffers, and axial‑groove buffers.

　　Drain the hydraulic fluid from the hydraulic pump station system. For hydraulic cylinders that have been idle for an extended period or are newly purchased, air can easily accumulate in the upper portion of the cylinder. The presence of air can destabilize the hydraulic pump station system, leading to vibration or creep. Therefore, hydraulic cylinders should be equipped with venting devices. These devices typically come in two forms: one involves drilling a vent hole at the highest point of the cylinder and connecting it via a long pipe to a remote vent valve; the other is to mount the vent valve directly on the top of the cylinder head. Hydraulic cylinders in double-acting hydraulic pump station systems should be fitted with two vent valves.

　　Hydraulic cylinders primarily consist of a cylinder barrel, a piston rod, a cylinder head, and a piston. The material used for the cylinder head varies depending on the operating pressure: cast iron is typically employed at low pressures, HT300 gray cast iron is suitable for medium and low pressures, and steels 35 and 45 are used for medium and high pressures. When the cylinder head itself serves as a guide sleeve for the piston rod, it is made of cast iron; in such cases, the guide‑rail surface should be surfaced with brass, bronze, or other wear‑resistant materials. If the guide sleeve is press‑fitted into the cylinder head, it should be made of wear‑resistant cast iron, bronze, or brass.

　　Common materials used for pistons include wear-resistant cast iron, gray cast iron, steel, and aluminum alloys. The concentricity tolerance with the piston rod is 0.03 mm. Cylinder barrels are typically made from seamless steel tubes of grades 20, 35, or 45, which are ground or rolled to achieve a surface roughness of no more than 0.4 μm; low-pressure cylinders may use grade 20 steel tubing, while high-pressure cylinders generally employ grade 45 steel tubing.

　　Piston rods come in two types: solid and hollow. The hollow piston rod must have a vent hole at one end to facilitate welding and heat treatment. Solid piston rods are made from 35 and 45 steels, while hollow piston rods are manufactured from seamless steel tubes of grades 35 and 45. After rough machining, the piston rods are quenched and tempered in India to a hardness of 229–285 HB; following high-frequency quenching, their hardness reaches 45–55 HRC.

　　Hydraulic oil is also crucial for hydraulic cylinders. It serves as the working fluid in hydraulic systems that harness hydraulic power. For proper operation, cylinders must be supplied with hydraulic oil, making its use of utmost importance. However, it is essential to verify the oil level and ensure that all hydraulic lines are in proper standby condition before starting up.