Hydraulics Flashcards

Vocabulary flashcards based on lecture notes about hydraulics.

Mass

The amount of material in an object. Units: Imperial - pound and slug; Metric - gram (g, kg).

Orifice

A device used to provide a restriction to liquid flow, creating a pressure drop.

Power

The amount of work done in a given period of time. Units: Imperial - horsepower (hp); Metric - watt (W).

Pressure

Force per unit area. Caused by resistance to liquid flow. Units: Imperial - pound per square inch (psi); Metric - newton per square metre (Pascal).

Pump

A device that converts mechanical power into hydraulic power (pressure and flow).

Torque

A twisting force caused by force acting through a radius. Units: Imperial - pound foot, pound inch (lb-ft, lb-in); Metric - newton metre (N·m).

Vacuum

The absence of pressure. A perfect vacuum is the total absence of pressure; a partial vacuum is less than atmospheric pressure.

Velocity

The rate of motion (speed). Linear Velocity Units: Imperial - feet per second (ft/sec); Metric - metres per second (m/sec). Rotational measured in revolutions per second (RPS).

Volume

The internal capacity of a space or chamber. Units: Imperial - cubic inches, gallons (in³, gal.); Metric - cubic centimetres, litres (cm³, L).

Work

The product of force acting through a distance. Units: Imperial - foot pounds, inch pounds (ft-lb, in-lb); Metric - newton metres (N·m).

Actuator

A device that converts hydraulic power (pressure and flow) into mechanical power. Examples: hydraulic motors and cylinders.

Flow rate

The amount of liquid that a pumped delivers in a given period of time.

The volume of a fluid passing a given point in a given period of time. Created by a difference in pressure. Units: Imperial - gallons per minute (GPM); Metric - litres per minute (L/min).

Fluid

Any substance that flows (gases and liquids). Gases are compressible, while liquids are virtually incompressible.

Force

A push or pull. Units: Imperial - pound (lb); Metric - newton (N).

Hydraulics

The engineering science that pertains to the transmission of force and/or motion through a fluid medium.

Hydrodynamics

The area of hydraulics that pertains to the transmission of force and/or motion using liquid motion (high flow rate, low pressure).

Hydrostatics

The area of hydraulics that pertains to the transmission of force and/or motion using confined liquids (high pressure, low flow rate).

International System of Units (SI)

The present form of the metric measurement system adopted by most countries as the primary measuring system.

Pump Displacement

The volume of liquid that a pump delivers when the pump input shaft rotates one revolution.

Volumetric Efficiency

Is a comparison of a pump’s theoretical delivery and its actual delivery at a rated pressure and RPM.

Mechanical Efficiency

Is an expression of the amount of power required to overcome the pumps, internal friction.

Unidirectional pumps

Operate in One Direction only

Cavitation

1-The amount of restriction to oil flow in the pump inlet line.

2-The speed at which the pump is driven.

Viscosity

Is a measure of its internal resistance to flow.

Viscosity index

Is a measure of the amount of viscosity change oil will experience as ambient temperature changes.

Boundary lubrication

When minute imperfections on the surfaces of moving parts are in contact

Pipe is sized by?

Nominal inside diameter and wall thickness.

Steel tubing is sized by?

Outside diameter and wall thickness.

Hydraulic hose is sized by?

Inside diameter

Emulsion

A mixture of oil and water

Pour point

The lowest temperature at which oil will flow.

Orifices main function

To create a pressure drop

Simplest form of a directional control valve?

A check valve

true or false

Viscosity is a measure of liquids slipperiness.

False

Relative viscosity

The amount of time required for a given quantity of oil to flow through a standard orifice while being held at a specific test temperature.

SAE

Society of Automotive Engineers

Ideal reservoir size is

2 to 3 times the flow rate of the pump

ISO is the acronym for?

International Standards Organization

Common signs of oxidation

Varnish and sludge formation

True or false?

Pressure reducing valves are normally open

True

They close off when pressure increases downstream