Miscellaneous Mechanical Components
When using oil as a fluid in a high pressure hydraulic system, the possibility of fire or an
explosion exists. A severe fire hazard is generated when a break in the high pressure piping
occurs and the oil is vaporized into the atmosphere. Extra precautions against fire should be
practiced in these areas.
If oil is pressurized by compressed air, an explosive hazard exists if the high pressure air comes
into contact with the oil, because it may create a diesel effect and subsequent explosion. A
carefully followed preventive maintenance plan is the best precaution against explosion.
The important information in this chapter is summarized below.
The relationship between pressure and force in a hydraulic piston
is expressed mathematically as:
P x A
Oil from a tank or reservoir flows through a pipe into a pump. The
pump can be driven by a motor, turbine, or an engine. The pump
increases the pressure of the oil.
The high pressure oil flows in the piping through a control valve. The
control valve changes the direction of the oil flow. A relief valve, set at
a desired safe operating pressure, protects the system from an over-
pressure condition. Oil entering the cylinder applies pressure to the
piston, developing a force on the piston rod.
The force on the piston rod enables the movement of a load or device.
The oil from the other side of the piston returns to a reservoir or tank
via a filter, which removes foreign particles.