Applied Industrial Technology

Hydraulic Technology

The basic idea behind a hydraulic system is simple:

Force that is applied at one point is transmitted to another point using an incompressible fluid.

Hydraulic Multiplication

The piston on the right has a surface area ten times greater than the piston on the left. When force is applied to the left piston, it will move ten units for every one unit that the right piston moves, and the force is multiplied by ten on the right-hand piston.

To determine the multiplication factor, start by looking at the size of the pistons. The piston on the right is 10 times larger than the piston on the left. What that means is that any force applied to the left-hand piston will appear 10 times greater on the right-hand piston. An input force of 10 pounds on a 1-square-inch piston develops a pressure of 10 pounds per square inch throughout the container. This pressure will allow a 10-square-inch piston to support a 100-pound weight. The forces are proportional to the piston areas. So if you apply a 100-pound downward force to the left piston, a 1000-pound upward force will appear on the right. The only catch is that you will have to depress the left piston 10 inches to raise the right piston 1 inch.

In most hydraulic systems, valves, hydraulic cylinders, and pistons are connected to a pump supplying high-pressure hydraulic fluid through schedule 80 pipe or special hydraulic hoses, with pressures reaching between 1000 to 2000 psi (pounds per square inch). Unlike pneumatic systems which exhaust the air to the atmosphere, hydraulic systems must return the oil back to the tank to be reused. A hydraulic tank reservoir usually holds between 100 and 1000 gallons of hydraulic fluid, but on very large and complex hydraulic systems the tank could hold much more. Notice the white filter hanging from the connecting pipes next to the reservoir. The filter is used to capture contaminants and metal particles in the fluid. If the system is kept clean the fluid may never need to be changed.

One of the most well known hydraulic systems is the automobile brake system. This is a perfect example of how a basic hydraulics system works. A small cylinder pushes hydraulic fluid pressure through a small tube to the brake cylinder where a large amount of pressure is applied to the brake pads, stopping your vehicle. A pneumatic system would not be able to generate the amount of pressure necessary to stop a vehicle quickly. For this type of application, hydraulics works better than pneumatics because hydraulics is more effective at higher pressures.

A typical Hydraulic System includes the following components:

	A Hydraulic pump which converts mechanical power to fluid power.
	A Cylinder or motor, which converts fluid power to linear or rotary mechanical power.
	Valves, which control the direction, pressure and rate of flow.
	Filters, regulators and lubricators, which condition the fluid.
	Manifolds, hose, tube, fittings, couplings, which connect the fluid to other components.
	Sealing devices, which help contain the fluid.
	Accumulators and reservoirs, which store the fluid.
	Instruments such as pressure switches, gauges, flow meters, sensors and transducers, which are used to help monitor the performance of a fluid power system.

Industrial

Here fluid power is used to provide power transmission and motion control for the machines of industry. End use industries range from stamping facilities to paper production. Applications include metalworking equipment, controllers, automated manipulators, material handling, and assembly equipment.

Fluid power is used to transport, excavate, and lift materials as well as control power equipment in other industries including construction, agriculture, marine, and the military.

Hydraulic systems use components which are very similar to pneumatic components. Cylinders are usually used as output components to provide movement and valves are used to control them. Hydraulic cylinders have one big advantage over pneumatic cylinders. They can be stopped and held in any part of their travel. It is possible to equalize the pressure on both sides of the cylinder because the oil does not exhaust in the same way as air.

Pneumatic systems are fine for low force requirements, but if large forces or equalization of pressure on both sides of a cylinder are required, a hydraulic system is much more efficient.

Click here to see other Hydraulic symbols.

This is the basis of "how" Hydraulics works in modern manufacturing processes.