Introduction to Basic Hydraulics

Understanding Basic Hydraulics

Hydraulics operates on a fundamental principle: liquids are incompressible. When a liquid is confined within a sealed system and pressure is applied at one point, this pressure is uniformly transmitted throughout the liquid, reaching every part of the system without losing intensity.

Illustrating Force and Pressure

When force is applied to a piston (A1) that compresses a confined fluid, according to Pascal’s Principle, the resulting pressure (F2) is transmitted to a larger piston (A2). This allows a small initial force to be magnified, producing a much larger force on the other side.

Automotive Lift Repair Florida Hydraulic Principles

Pressure is defined as the uniform stress exerted equally in all directions. When force is applied to a specific area within a confined liquid, it is evenly distributed across every square inch of the vessel’s interior. If a second piston is present, this force is transmitted to every square inch of the piston’s surface.

For example, if a pump piston A moves downward by 12 inches, the piston in cylinder B will rise by 1 inch. If the pressure is 2,000 PSI, and piston A has an area of 1 square inch, it will exert a force of 2,000 lbs. Meanwhile, piston B, with an area of 12 square inches, will exert a force of 24,000 lbs.

Automotive Lift Repair Florida Cylinder Terminology

The force applied to each square inch of a confined liquid’s area is transmitted uniformly to every part of the vessel’s interior. For example, if a chamber is subjected to 1,000 PSI, and piston. 

Basic Physics in Hydraulics

In Automotive Lift Repair Florida hydraulic systems, we can exchange force for distance by adjusting the relative sizes of the pistons at each end of the system. A small piston moving over a long distance (e.g., a foot) can generate sufficient pressure to move a larger piston over a shorter distance, enabling the movement of a heavy weight.

Engineers calculate the required piston sizes and travel distances to move specific weights efficiently. This principle enables small cylinders to handle very heavy loads.

For example:

– If the distance (D) is 2 ft, the Force = 500 lbs.

– If D = 10 ft, the Force = 100 lbs.

– If D = 20 ft, the Force = 50 lbs.

Hydraulic Formulas

The basic hydraulic principle is that pressure applied to a fluid is transmitted equally in all directions, according to Pascal’s Law. The force generated by a hydraulic cylinder equals the hydraulic pressure multiplied by the cylinder’s effective area (the surface area of the piston face in square inches).

Flow rate refers to the volume of fluid that moves through a system over a specific period.

Flow velocity, on the other hand, describes the distance a specific volume of fluid travels within a given time frame. Unlike flow rate, flow velocity is not measured directly but is calculated using the flow rate and the cross-sectional area of the hose. Flow velocity depends directly on both the flow rate and the hose size.

Altering the flow rate of the pump while keeping the hose size constant changes the flow velocity. Similarly, modifying the hose size while maintaining a consistent pump flow rate will also affect the flow velocity.

As Automotive Lift Repair Florida flow velocity increases, so does heat, due to friction. Friction occurs when fluid molecules rub against the inner surface of hoses and pipes. Although we often think of fluid as flowing as a single mass, it actually moves in distinct parallel layers at low velocities, a state known as laminar flow. However, as fluid velocity increases, tiny imperfections in the hose or pipe disrupt the flow path, leading to turbulent flow. Turbulent flow, caused by friction, generates additional heat and is often found in hydraulic systems where there are bends or restrictions. To minimize turbulent flow, using larger hoses and fittings is beneficial.

Pressure in Hydraulic Systems

Pascal’s law states that any pressure applied to a confined fluid is transmitted equally in all directions. However, this holds true only when the fluid is trapped.

Pressure in a Automotive Lift Repair Florida hydraulic system is created either by resistance to flow, known as dynamic pressure, or by the potential energy of an object under the influence of gravity, referred to as static pressure. Static pressure occurs when fluid wants to flow but is unable to, as in the case where gravity is pulling a cylinder rod down, but the valve is closed, preventing the fluid in the cylinder from escaping. This trapped fluid gains energy due to the force pulling the cylinder rod down, and this energy is reflected in the pressure gauge reading.

Dynamic pressure, in contrast, is related to the kinetic energy of the fluid. As resistance to flow increases, so does the pressure. When fluid passes through a restriction, there is a pressure drop due to energy conversion, with friction causing heat. Bernoulli’s principle states that within a system, total energy remains constant. Thus, if kinetic energy (fluid velocity) decreases, there must be a corresponding increase in potential energy (pressure).

Surface Area in Automotive Lift Repair Florida Hydraulic Systems

Surface area refers to the total exposed area of a solid object. In hydraulic systems, the surface area of components that interact with the fluid is crucial, as it can significantly impact the system’s capability. There is a direct mathematical relationship between the force a hydraulic system can transfer, the pressure within the system, and the surface area of the component being driven. This relationship is often represented by the FPA Triangle.

By knowing the pressure and the surface area of a piston, we can calculate the force generated. Conversely, if we know the required force and the available pressure, we can determine the necessary piston surface area. Additionally, if the force and surface area are known, the system’s pressure can be calculated. By using a smaller surface area on one side of the Automotive Lift Repair Florida system, it’s possible to amplify the force exerted by the other side.