Hydraulic Power Variables 301
Hydraulic Power Variables provides users with a foundational knowledge of variable factors in hydraulic power and how the variables affect hydraulic systems. Hydraulic power variables are measurable or quantifiable characteristics of a hydraulic system or system component. The two most integral variables are fluid flow and pressure. Additional power variables include speed, horsepower, and torque. Changing any variable impacts the system's operation.
After taking Hydraulic Power Variables, users will understand how the variables of a hydraulic system contribute to the manipulation of pressurized fluid in order to transmit power. Understanding the power variables allows hydraulic system operators to predict the performance of a system and select compatible components.
Number of Lessons 16
- Hydraulic Power
- Hydraulic Power Variables
- Volume Flow Rate
- Types of Fluid Flow
- Fluid Flow Variables Review
- Pressure Ratings
- Hydraulic Horsepower
- Torque and Horsepower
- Hydraulic Power Variables Review
- Final Review
- Describe hydraulic power.
- Describe hydraulic power variables.
- Describe volume flow rate.
- Distinguish between laminar flow and turbulent flow.
- Describe fluid displacement.
- Describe pressure in a hydraulic system.
- Explain pressure ratings.
- Describe speed.
- Describe hydraulic horsepower.
- Describe torque.
- Describe efficiency ratings.
- Describe effects of extreme temperatures.
- Describe hydraulic system noise.
actual flow rate
The flow rate that a pump delivers during operation. Actual flow rate is measured when determining a pump's volumetric efficiency.
actual operating torque
The amount of torque required to power a hydraulic pump. Actual operating torque is used to calculate mechanical efficiency.
An active fluid system component at the end of the hydraulic circuit. Actuators, such as cylinders or hydraulic motors, convert hydraulic energy into mechanical energy.
A-weighted decibel scale
A scale for measuring noise production that reflects the exclusion of frequencies that humans do not normally hear. An A-weighted decibel scale is commonly used to measure workplace noise levels.
A layer of mostly stationary liquid that forms in the fluid closest to the inside wall of a conductor. A boundary layer forms during fluid flow.
A pressure rating that indicates the pressure at which a conductor fails during a pressure rating test. Burst pressure is higher than the working pressure.
A condition caused by excess air that creates bubbles in hydraulic fluid. Cavitation can damage various system components, but it commonly affects the hydraulic pump because it results in an inadequate amount of fluid being delivered to the pump.
centimeters per second
cps. The number of centimeters that an object travels in one second. Centimeters per second is a unit used to measure the speed of linear components, such as a cylinder actuator.
The small space between components that allows for movement and lubrication. Clearances are necessary for the successful operation of many fluid system components.
Noise produced by the normal operation of a hydraulic component. Component noise is generated throughout a hydraulic system, particularly by the pump.
A passive fluid system component that conveys liquid through a hydraulic system. Conductors include pipes, tubes, and hoses.
A value or number that does not change. The mathematical constant 1714 is used when calculating hydraulic horsepower requirements.
An active fluid system component that controls fluid flow, direction, and pressure. Control valves function within given temperature and pressure ratings.
An active fluid system component that controls hydraulic fluid flow, direction, and pressure. Control valves include pressure relief valves and needle valves.
cm³ A metric unit of measurement used to measure volume. Cubic centimeters are used to measure the fluid displacement of a hydraulic pump.
in.³ An English unit of measurement used to measure volume. Cubic inches are used to measure the fluid displacement of a hydraulic pump.
One complete revolution or rotation of a rotary component. A cycle may also be one complete extension and retraction of a linear component.
An actuator that directs force in a straight line. Cylinder actuators may be single- or double-acting.
A noise level designation that indicates decibels measured on an A-weighted decibel scale. A dBA scale indicates the decibel output of a device.
dB. A unit of measurement that describes the intensity of a sound wave. Decibels below 80 are acceptable for a hydraulic system.
The difference in pressure measurements between any two points of a system or a component. Differential pressure is measured in pounds per square inch (psi) or pascals (Pa).
A constant ratio between two values in which one value changes in the same way as the other. The directly proportional values of hydraulic horsepower and flow rate mean that one increases or decreases as the other increases or decreases.
A hydraulic system's work output divided by the pump's energy input. Efficiency ratings are used to determine the condition of a pump.
The amount of power output a hydraulic system produces compared with the amount of power input. Efficiency ratings are used to determine operating conditions.
A hydraulic pump with a fluid displacement value that stays the same from cycle to cycle. Fixed-displacement pumps are not as common in industrial settings as variable-displacement pumps.
A rating that indicates how much fluid a hydraulic pump moves into the system in a given amount of time. Flow capacity, also known as flow rate, is measured in gallons per minute (gpm) or liters per minute (lpm).
An instrument used to measure the volume of fluid moving through a pipe or component. Flow meters are used to measure the actual flow rate of a pump.
A rating that indicates how much fluid a hydraulic pump moves into the system in a given amount of time. Flow rate, also known as flow capacity, is measured in gallons per minute (gpm) or liters per minute (lpm).
A pump rating that indicates the total volume of fluid a hydraulic pump moves into the system in one reciprocating or rotating cycle of the pump. Fluid displacement is measured in cubic inches or cubic centimeters.
The motion of a liquid or gas subjected to unbalanced forces or stresses. Fluid flow in a hydraulic system is subjected to resistance, which causes pressure to develop.
Noise produced by pressure surges in a hydraulic system. Fluid noise is produced by a hydraulic pump.
ft.-lbs. An English unit of measurement used to measure work. One foot-pound indicates the amount of energy needed to move one pound a distance of one foot.
The push or pull that gives energy to an object. Force results from an object's interaction with another object.
The proportional increase in available power associated with hydraulic systems. Force multiplication allows a hydraulic system to produce an output force that is proportionally larger than the input force.
A force that resists motion between two objects that are in contact with each other. Friction generates heat and increases wear in components.
gallons per minute
gpm. A unit used to measure the volume flow rate of fluid in a hydraulic system. Gallons per minute is an English unit of measurement.
A fixed-displacement hydraulic pump that uses meshing gears that rotate to move fluid. Gear pumps are relatively inexpensive and compact.
gallons per minute@revolutions per minute. A term often used to describe a pump's flow rate. gpm@rpm describes how many gallons per minute of fluid a pump can move into the system at a specific driven speed.
Any source of potential damage, harm, or human health risk in the workplace. Hazards include noise pollution and extreme heat.
hp. A unit used to measure power. One horsepower is equivalent to 33,000 ft.-lb. per minute.
HHP. The power required to drive a pump at a known flow rate and system pressure. Hydraulic horsepower is directly proportional to pump flow rate and system pressure.
Energy derived from the movement of a liquid, such as oil or water, under pressure. Hydraulic power is converted into mechanical power when it leaves a hydraulic system.
hydraulic power variables
Any characteristic of a hydraulic system or component that can be measured and quantified. Hydraulic power variables include pump displacement, motor speed, and system efficiency.
A mechanical power source that generates fluid flow. Hydraulic pumps receive energy from a prime mover, such as a motor or engine.
A type of power transmission system that uses oil or another liquid under pressure to transmit mechanical power. A hydraulic system can transmit large amounts of power using a small input force.
inches per second
ips. The number of inches that an object travels in one second. Inches per second is a unit used to measure the speed of linear components, such as a cylinder actuator.
A constant ratio between two values in which one value changes in the opposite way as the other. The inversely proportional values of hydraulic horsepower and system efficiency mean that if hydraulic horsepower decreases, the system efficiency increases.
J. A unit in the International System of Units (SI units) used to measure work. One joule equals 0.737 ft.-lb.
A type of fluid flow in which fluid particles move in continuous and parallel flow paths within fluid layers. Laminar flow minimizes friction.
Movement that takes place along a straight line. Linear motion produces mechanical energy.
liters per minute
lpm. A unit used to measure the volume flow rate of fluid in a hydraulic system. Liters per minute is a metric unit of measurement.
The force that acts on an object and provides resistance. The load in a hydraulic system is pressurized fluid.
maximum allowable operating pressure
MAOP. A pressure rating that indicates the maximum amount of pressure a hydraulic system component can safely tolerate. The maximum allowable operating pressure is less than the maximum allowable working pressure (MAWP).
maximum allowable working pressure
MAWP. A pressure rating that indicates the pressure required for a component to overcome the resistance of the applied load. Maximum allowable working pressure may be referred to as the working pressure.
An efficiency rating that describes the amount of energy loss in a hydraulic pump. Mechanical efficiency can decrease due to friction between mechanical and fluid components.
N-m. A metric unit used to measure torque. Newton-meters may be used to express the torque of an electric motor.
A sound that is typically unpleasant and interferes with a person's ability to hear. Noise is measured in decibels.
The pressure at which a system or component normally runs. Operating pressure is often used to specify the capabilities of specific hydraulic system components, such as control valves and actuators.
The horsepower a prime mover provides to a hydraulic pump. Output horsepower requirements determine prime mover selection.
A pump rating that compares the total horsepower output to the total horsepower input. Overall efficiency is determined by multiplying volumetric efficiency by mechanical efficiency.
Pascals. A metric unit used to measure pressure. Pa units are used to express the pressure requirements for a hydraulic system.
A physical law stating that pressure applied to a confined fluid at rest is transmitted equally throughout the fluid. Pascal's Law describes the relationship between force, pressure, and area.
Pa. A metric unit used to measure pressure. Pascal units are used to express the pressure requirements for a hydraulic system.
The point at which horsepower and torque are highest. After peak value is reached, speeds increase and horsepower and torque decrease.
personal protective equipment
PPE. Any clothing or device worn to minimize exposure to hazards and prevent injury. Personal protective equipment includes hearing protection and safety goggles.
A hydraulic pump with a fixed fluid displacement per cycle or revolution. Positive-displacement pumps are used with a pressure relief valve on the outlet side.
lb.-ft. An English unit of measurement used to measure torque. Pound-feet may be used to measure the torque of an electric motor.
pounds per square inch
psi. An English unit used to measure pressure. Pounds per square inch units are used to express the pressure requirements for a hydraulic system.
The rate of work performed by a system. Power is expressed in units of horsepower.
The amount of force exerted upon a fluid or object per unit area. Pressure is commonly expressed in pounds per square inch (psi) or pascals (Pa).
The exertion of force upon a fluid. Pressure is measured in pounds per square inch (psi) or pascals (Pa).
A mechanical instrument that measures the internal pressure of a vessel or system. Pressure gauges may have a dial display or a digital readout.
The range of pressure a hydraulic component can withstand during normal operation. Pressure ratings apply to various components of a hydraulic system.
The component in a hydraulic system that provides mechanical energy to the hydraulic pump. Prime movers for hydraulic systems include electric motors and internal combustion engines.
The amount of work performed in a particular time. Productivity rates depend on system variables such as flow rate and pressure.
pounds per square inch. An English unit used to measure pressure. Psi units are used to express the pressure requirements for a hydraulic system.
The opposition to a force. Resistance can be created by friction.
revolutions per minute
rpm. A unit that indicates the number of rotations a cylindrical component completes in one minute. Revolutions per minute is a measurement of speed.
Spinning or turning movement that takes place around a fixed axis, without a change in linear position. Rotary motion produces mechanical energy.
revolutions per minute. A unit of measurement that indicates the number of rotations a cylindrical component completes in one minute. Rpm is a measurement of speed.
The rate an object travels measured over a given period of time. Speed is used to measure both linear and rotational movement.
A temperature range assigned to hydraulic components. The temperature rating of a hydraulic system is typically between 100°F and 125°F (38°C to 52°C).
theoretical flow rate
A pump's rated operating flow rate. Theoretical flow rate is higher than actual flow rate.
theoretical operating torque
The amount of torque a hydraulic component is capable of delivering. Theoretical operating torque is used when calculating the mechanical efficiency of a pump.
A control used to vary the speed of a mechanical device, such as a diesel engine. A throttle on an engine may be used to change the driven speed of a pump.
A force that produces rotary motion. Torque is measured in pound-feet in the English system and newton-meters in the metric system.
A type of fluid flow in which fluid particles move roughly and erratically within fluid layers. Turbulent flow can result from abrupt changes in the direction or diameter of a conductor.
A hydraulic pump that can be adjusted to change the amount of fluid that is moved in one pump cycle. Variable-displacement pumps are generally more expensive than fixed-displacement pumps.
The speed with which fluid flows through a hydraulic conductor. Fluid velocity is measured in inches per second (ips) or meters per second (mps).
Noise produced in response to pressure surges. Vibration noise is produced by the hydraulic pump.
The amount of space that a substance or object occupies within a container. Volume is measured in cubic inches or cubic centimeters.
volume flow rate
The total volume of hydraulic fluid that moves through a hydraulic system component in a given period of time. Volume flow rate is measured in gallons per minute (gpm) or liters per minute (lpm).
An efficiency rating that describes the amount of leakage in a hydraulic pump. Volumetric efficiency is the most commonly used efficiency rating when determining the condition of a hydraulic pump.
The result of a force applied to an object and the distance through which the force travels. Work is expressed in foot-pounds or joules.
A pressure rating that indicates the pressure required for a component to overcome the resistance of the applied load in a system component. Working pressure is sometimes referred to as the maximum allowable working pressure (MAWP).