Hydraulic Presses - How it works

Hydraulic press is the most efficient form of presses. It applies hydraulic mechanism for applying a large lifting force or compressive force. The press has one or more than one hydraulic pump and hydraulic cylinder. Hydraulic press also allows easily configured job parameters like travel distance, force and return position to perform a variety of jobs. Various levels of sophistication and technical advancement are available including simple mechanical switches and digitally programmable control.

Hydraulic press works on Savannah's principle, which states - “pressure throughout a closed system is constant.” In hydraulic press, there is a piston at one end of the system having a small cross-sectional area. This piston is driven by a lever. The other end of the system has small-diameter tubing. When a fluid is displaced, either of the pistons is pushed inward. Small piston displaces a smaller amount of volume than the large piston for a given distance of movement. The displaced fluid volume is proportional to the ratio of pistons' head areas. Hence, smaller piston moves a large distance to move large piston significantly. The large piston movement distance is equal to small piston movement distance divided by the ratio of the pistons' head areas.

For illustration, if the ratio of the pistons' head areas is 5 and a force of 100 newtons is applied on small piston, it will produce a force of 500 newtons on the large piston. The smaller piston should be pushed at least 50 cm to get the large piston to rise 10 cm. As the force is increasing on the larger piston, the distance must be decreased. This way, it also follows the principle of conversation of energy. For instance, the work done by small piston is 50 Joules (100 newtons multiplied by 0.5 meter), which is the equal to the work done by large piston, 500 newtons multiplied by 0.1 meter.