A A swing cylinder, also called a rotary actuator, outputs torque and performs reciprocating angular motion instead of linear motion. It comes in single-vane, double-vane, and helical-swing types. In a vane type, a fixed stator block and a rotating vane are separated by seals; oil pressure causes the vane and shaft to rotate. Helical types use a piston and helical gears to convert linear stroke into rotary motion. Swing cylinders are used where limited-angle rotation with high torque is needed, such as crane slewing, marine steering, and indexing tables.

A A hydraulic cylinder consists of a cylinder barrel, end caps (gland and cap), a piston, a piston rod, seals, bearings or guide rings, and optional cushion devices and air bleed valves. The barrel houses the piston and pressurized oil. The piston divides the barrel into two chambers and carries seals. The piston rod transmits force outside the cylinder. End caps seal the ends. Guides support the rod. Cushions slow the piston at stroke ends. Bleed valves remove trapped air. All components must work together to ensure reliable, leak-free operation.

A The pressure rating must match the system's maximum working pressure with an appropriate safety margin. Common ratings are 16 MPa, 25 MPa, and 31.5 MPa. Selection depends on the required output force and the available installation space. Higher pressure allows a smaller bore cylinder to produce the same force, saving space and weight. However, higher pressure demands stronger materials, better seals, and may increase cost. The cylinder's rated pressure should always exceed the system's maximum operating pressure to ensure safety and long service life.

A Common mounting styles include tie-rod mounts for medium-duty applications, flange mounts for rigid alignment when the load is along the cylinder axis, clevis or eye mounts allowing pivoting movement, trunnion mounts for mid-body pivoting, and foot mounts for horizontal surface installation. The choice depends on load direction, whether the cylinder must pivot, available space, and structural support requirements. Proper mounting prevents side loading that can cause uneven seal wear, rod scoring, and premature failure.

A Hydraulic cylinders produce large forces due to Pascal's Law, where force equals pressure multiplied by piston area (F = P × A). Even a moderate pressure of 25 MPa acting on a piston with a diameter of 100 mm generates a force of approximately 196 kN. The incompressibility of hydraulic oil ensures immediate and stiff force transmission. By increasing either the system pressure or the piston diameter, extremely high forces can be achieved from relatively compact cylinders, making them ideal for heavy-duty applications such as presses, lifting equipment, and construction machinery.

A In a single-rod cylinder, the piston has a rod on one side only, so the effective area on the cap side (full piston area) is larger than on the rod side (piston area minus rod cross-sectional area). For the same oil flow, extension is slower but produces higher force, while retraction is faster but produces lower force. Conversely, for the same pressure, extension force is greater than retraction force. Double-rod cylinders have equal areas on both sides, providing equal speed and force in both directions, suitable for symmetrical motion requirements.