Hydraulic Systems: Components, Functionality, and Maintenance

Hydraulic Systems

Storage

Fluid storage tanks are constructed of steel plates and brackets to contain fluid, sediment, and contaminants, and to dissipate generated heat. These tanks are typically coated with water-resistant paint. The bottom of the tank should be sloped with a drain plug for vacuum cleaning. Lids, vents, and air filters prevent the entry of impurities. Baffles within the tank prevent turbulent flow, allowing sediment to settle, separating air from the fluid, preventing foaming, and dissipating heat. Tank capacity should be 2-3 times the pump supply group capacity. Tanks should also have a sight glass, suction line, return line, and drainage.

Filtration

Filtration is the mechanical or physical process of separating materials using a filter. A filter uses a porous material for retention. A strainer is a coarser filter, typically a metal mesh. The filter's pore size determines its fineness.

Types of Filters

• Pressure Filters: Located upstream of pumps and valves, these filters prevent particles from reaching sensitive components.
• Return Filters: These filters capture particulate contamination from the fluid before it returns to the tank, preventing tank pollution.
• Suction Filters: These remove coarser particles before they reach the pump.

Filter Materials

• Mechanical Filters: Retain particles between closely interlocked metal discs and meshes.
• Absorbent Filters: Retain fine particles (typically paper or cotton) and are usually protected by metal mesh.
• Adsorbent Filters: Not often used in hydraulics due to potential fluid contamination.

Magnetic Sensors

Magnetic sensors, installed inside tanks, use a permanent magnet in direct contact with the fluid to capture metallic contaminants.

Air Coolers

Fluid is pumped through finned tubes, often with a fan to enhance heat transfer and cooling.

Hydraulic Pumps

Hydraulic pumps deliver the required flow to move actuators.

Gear Pumps

Gear pumps provide flow by transporting fluid between the teeth of meshing gears.

Hydrostatics

Hydrostatics is the study of fluids at rest. Pascal's principle states that force applied to a confined fluid is transmitted equally in all directions.

Hydro Power Transmission

Hydraulic power transmission involves a pump delivering flow, which transmits power.

Pressure Drop

Pressure drop is the difference in pressure between two points in a hydraulic system.

Fluid Velocity

Fluid velocity is the distance traveled by fluid particles per unit of time.

Flow Rate

Flow rate is the volume of fluid passing a point per unit of time.

Laminar Flow

In laminar flow, fluid particles move in straight, parallel paths.

Turbulent Flow

In turbulent flow, particles cross paths, increasing friction. This occurs with sudden changes in direction or pipe section.

Hydraulic Fluid (Oil)

Hydraulic fluid provides work force, dissipates heat, lubricates valves and components, and helps detect leaks. Key properties include stickiness, extreme pressure lubrication, viscosity, and high wear resistance.

Additives

Additives enhance the performance of hydraulic oils.

Hydraulic Piping

Iron, steel, and seamless steel pipes are commonly used. Wall thicknesses include standard, extra thick, and double extra thick.

Pipe Joining Methods

• Threaded (conical, cylindrical)
• Welding
• Flanged

Couplings include tapered, cylindrical, ring, compressive, reducing gearbox, straight, plug, elbow, and spherical joints. Flanges on large pipes are welded or threaded (lap joint, standard, ring). Flexible hoses, used for moving parts, are made from layers of rubber and braided fabric or steel wire mesh. Steel mesh reduces hose elasticity. The inner layer must be compatible with the hydraulic fluid.

Sealing

Effective sealing is essential to maintain pressure within the hydraulic circuit.