How Hydraulic Cylinder Works? Explained

Everyone related to the hydraulic industry knows the importance of hydraulic cylinders. These cylinders are required for converting the pressurized hydraulic fluid flow to useful force/energy. Almost all hydraulic applications will use these cylinders for moving, holding, or lifting operations. Different types of hydraulic cylinders are available for performing various tasks. Single acting and double acting cylinders are two important hydraulic cylinder types.

A hydraulic cylinder is an actuating device used for creating linear motion. They appear simple in construction but are powerful based on performance. Cylinder housing, pistons or piston rods, seals and valves are some important components required for cylinder construction. The cylinder housing will contain one or more ports and polished bore (for piston operation). The piston connected with the piston rod will move according to the extension and retraction of the cylinder. The diameter and hardness of piston rods are important for preventing bending of rods under heavy loads. The commonly used ports are used for filling and draining hydraulic oil, and removing trapped air (bleed off port). The hydraulic cylinder uses check valves and throttle valves for cushioning. Cushioning is the process of reducing shock as a result of high pressure. A piston requires a piston seal for maintaining the required pressure. Different seals like O-Rings, piston seals, and wiper seals are also used for preventing leakage.

How does a hydraulic cylinder works?

Similar to all other hydraulic applications, Pascal’s law is the working principle behind the working of the hydraulic cylinder. Larger the cylinder size, greater will be the force generated. The diameter of the piston (also, the inside diameter of tubing’s) is known as the bore. A piston is located inside the cylinder for pushing fluids. So, according to Pascal’s principle, larger bore cylinders will have a higher lifting capacity.
Now, we can discuss the design of the hydraulic cylinder and how it works. Hydraulic cylinder design will contain two cylinders with different diameters parallelly connected with a pipe. The cylinders will have two separate ports for fluid intake and removal. The assembly is then filled partially using suitable incompressible hydraulic oil. A piston appears as a flat solid disk with a rod attached to its center. While applying force on the smaller piston, it will try to compress the fluid present in the smaller cylinder. This will result in the flow of fluid from a smaller cylinder to the larger cylinder through the tube connected and the piston of the larger cylinder will move upwards with this generated force.
The pressure difference inside the cylinder is the key factor that makes the piston move. When you apply continuous pressure and the cylinder reaches its maximum space. Then, the pressure release valve will relieve this pressure and make it possible to move further.
For purchasing, you just need to consider some important hydraulic cylinder specifications like operating conditions, type of fluids, constructing materials, seals, etc. Hydraulic cylinders have applications in marine, aerospace, construction equipment, industrial machines, etc… Operating conditions for all these applications will be different. Due to varying operating conditions (like temperature, fluid pressure, humidity, etc.), a hydraulic cylinder needs to be selected in such a way that the cylinder will adapt to those changes. Fluid selection is important for every hydraulic cylinder. Not all hydraulic cylinder will use the same fluid, it will vary depending on the application, operating condition and constructing materials. The material used for constructing cylinder head, base and bearing will affect the performance and durability of hydraulic cylinders.