Fluid Systems

A fluid system is something that makes use of a gas or liquid to perform tasks. If the fluid is a liquid, the system is hydraulic. If the fluid is a gas, the system is pneumatic.

Most hydraulic systems apply a force on a liquid that fills a closed space, such as a tank or a pipe. The applied force creates pressure that moves the liquid through a series of tubes, pipes, or hoses. This causes motion at the other end of the system. You use a hydraulic system when you turn on a hose or a water tap. When you squeeze a tube of toothpaste, you are using a hydraulic system, too.

Many hydraulic systems use a pump to give the force that pushes the liquid. Pumps put the liquid under pressure. Automobile mechanics use hydraulic systems to lift cars and other heavy objects through hydraulic multiplication.

Pascal's law states that when there is an increase in pressure at any point in a confined fluid, there is an equal increase at every other point in the container. So the pressure on the left equals the pressure on the right.

Many pneumatic systems use a device called a compressor to compress the air so pressure builds up. When the pressure is released, the gas exerts a strong, steady force. This force can be used to fill tires, drill teeth and bring trucks to a safe stop through the use of air brakes.

Problems with Hydraulic and Pneumatic Systems

These systems cannot work if they lose pressure. A crack or hole in a closed-filled container will let fluid leak out and reduce pressure. These systems cannot work if they become blocked.

For example, if a vacuum cleaner filter becomes clogged with dust the vacuum will not work well.

The fan creates low pressure inside the vacuum. Air moves from an area of high pressure to low pressure, so the higher air pressure in the room rushes into the vacuum. The air rushes into the vacuum and through a filter before exhausting back into the room. If the filter becomes clogged, the air flow out of the vacuum is blocked.

If the air cannot escape, the air pressure rises inside the vacuum. Rising air pressure inside defeats the purpose of the vacuum, as there is no longer a strong pressure difference to force air into it.