What is Hydraulic Pressure and Why is it Important?
Hydraulic pressure provides one of the simplest and most powerful forms of producing considerable amounts of force within a confined space, using hydraulic fluid pressure to generate a force. Since the early inventions of low pressure and heavy hydraulic lifting jacks through to the latest state of the art high pressure hydraulic systems of today, hydraulic power has remained an extensively used and widely respected assistant to mankind’s drive for even greater power and knowledge.
The Hydraulic System
A hydraulic system uses compressed fluid to transfer force applied at one point to another point. The basic components that make up a hydraulic system are: Reservoir, Pump, Valves, Fluid, Motor, Hose, Filter, and Cylinder.
The hydraulic reservoir stores the non-pressurized hydraulic fluid, typically hydraulic oil which travels through a filter that collects its impurities.
The hydraulic pumps transfer the fluid from the reservoir to the hydraulic system. In which this transfer then raises the energy level of the fluid. The motor provides the power for the pump.
The high-pressure fluid acts upon the rod and piston within the hydraulic cylinder. Each stroke the cylinder converts the fluid power (pressure) into work (mechanical force). The reservoir oil level falls while the rod and piston extend.
Then when the rod and piston retract, the fluid returns to the reservoir. The reservoir has metal walls which cool the fluid by allowing the heat to escape. With the reduced pressure in the reservoir now it allows trapped or dissolved air to escape from the fluid. Remember if the cylinders must compress air bubbles, the efficiency of the system is reduced.
There are two types of valves, directional control valves and pressure relief valves. The Directional control valves manage the flow path of the fluid. The pressure relief valves protect the systems plumbing and components against occurring pressure overloads. They also limit the output force exerted by rotary motors and cylinders. These values will open whenever the pressure goes beyond the set value, allowing oil to flow back into its reservoir.
The fluid travels from one component to the next within a hydraulic system through a hydraulic hose.
Now that you understand what hydraulics are, you can explore how to control that hydraulic pressure and keep you and your machinery safe.
How to Control Hydraulic Pressure
To achieve hydraulic pressure control the hydraulic systems meter the flow of a fluid. The rule of thumb here is:
Pressure= force to move the load
Flow= how fast the load moves
The actual fluid pressure involved here plays a crucial role in this ‘Multiplication of Force’ and in this context there are two features of hydraulic pressure which is important to remember:
1. Hydraulic pressure is measured as a force per unit of area e.g. Bar (Kg/cm2) or PSI (Pounds per square inch).
2. The Hydraulic pressure at any point within the fluid is the same in all directions provided of course that the fluid is static.
The accepted international standard for maximum working pressure in the high-pressure hydraulic tools industry is 700 Bar (10,000 PSI). The criteria for establishing the maximum output force of a hydraulic cylinder at 700 Bar pressure is the size of the effective area of the cylinder bore.
Dangers of Overpressurization
Overpressurization can result in hose and seal failure, and mechanical failure of certain parts in pumps, motors, cylinders, and valves. Valve plate separation is often characterized by vibration or pulsation in the pressure line of the pump of motor combined with erratic machine movement as the cylinder barrel separates and re-couples to the valve plate.
It is extremely important to not set your hydraulic system’s pressure too high. The logic behind if you have higher pressure, the faster the machine will run is not true. To avoid mistakes that in turn can damage your hydraulic system and cause serve damage to yourself- refer to your manufactures guide or ask a professional.