Hydraulic cylinders are a widely used structural component in hydraulic systems. To ensure their proper operation, it is essential to understand their key characteristics.

　　(1) Single‑rod hydraulic cylinders have a piston rod only on one side, resulting in unequal effective areas on either side of the piston. The larger the diameter of the piston rod, the greater the difference between the effective areas on the two sides. Under equal supply pressure, the thrust generated on the rodless side is greater than that on the rod side. When the flow rate is constant, introducing pressurized oil into the rodless side causes the piston rod to extend at a slower speed than when pressurized oil is supplied to the rod side to retract the piston rod.

　　(2) Double-rod hydraulic cylinder: This cylinder has piston rods on both sides of the piston. When the diameters of the two piston rods are identical and the supply pressure and flow rate remain constant, the reciprocating speed and the force acting on the piston are equal. Moreover, with two piston rods, the cylinder exhibits improved rigidity and stability.

　　(3) Single-acting hydraulic cylinder: This is the simplest type of hydraulic cylinder. It can supply pressurized fluid to only one side of the piston, generating a unidirectional force. The return stroke is achieved by external load forces, spring force, or the self-weight of the piston rod or plunger—there is no hydraulic force acting in the opposite direction. Its advantages include reduced hydraulic power consumption and a simplified hydraulic circuit.

　　(4) Double-acting hydraulic cylinders are more widely used than single-acting hydraulic cylinders. Pressurized oil can be alternately supplied to both sides of the piston, driving it in a reciprocating motion, and allowing control over the speed of movement in both the extension and retraction directions as well as the supply pressure. Double-acting hydraulic cylinders come in two types: single‑rod and double‑rod.

　　(5) Plunger hydraulic cylinders are typically single‑acting. They feature a simple structure and are easy to manufacture and maintain. The plunger in such cylinders is thick, large, and heavy, offering superior rigidity compared to a piston rod. Consequently, this type of cylinder is preferred for applications requiring long strokes. Since the cylinder bore does not come into direct contact with the plunger—guidance is provided solely by the guide sleeve—the inner wall of the cylinder can be left unground or subjected only to rough machining, resulting in excellent manufacturability and low production costs.

　　(6) Telescopic hydraulic cylinders, also known as multi‑section cylinders, multi‑stage cylinders, or composite cylinders, come in both single‑acting and double‑acting configurations. These cylinders offer a long total stroke while maintaining a short retracted length, making them particularly well suited for applications where installation space is limited but a long stroke is required. Moreover, the more stages a cylinder has, the shorter its retracted length will be.