What is the definition of "positive displacement compressor"?
A type of compressor that delivers a fixed volume of air at high pressures. Common types of positive displacement compressors include piston compressors and rotary screw compressors.

Learn more about positive displacement compressor in the class Pneumatic Power Sources 215 below.


Hydraulics and Pneumatics Training


Class Information
Hydraulics and Pneumatics Training Tooling U-SME classes are offered at the beginner, intermediate, and advanced levels. The typical class consists of 12 to 25 lessons and will take approximately one hour to complete.
Class Name:Pneumatic Power Sources 215
Description:This class describes different types of compressors and how they generate gas flow. It also describes prime movers and primary factors to consider when selecting a compressor for a particular application.
Prerequisites: 570125
Difficulty:Intermediate
Number of Lessons:14
Language:English, Spanish
 
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Class Outline
  • Objectives
  • Intro to Pneumatic Power Sources
  • Flow Rate
  • Positive Displacement and Dynamic Compressors
  • Piston Compressors
  • Single- and Multi-Stage Compressors
  • Rotary Screw Compressors
  • Vane Compressors
  • Lobe Compressors
  • Axial and Centrifugal Compressors
  • Air Receivers
  • Prime Movers
  • Compressor Selection
  • Summary
  
Class Objectives
  • Describe how a pneumatic system transmits power.
  • Describe the variables that determine gas flow rate.
  • Distinguish between positive displacement and dynamic compressors.
  • Describe the characteristics of piston compressors.
  • Describe staging.
  • Describe the characteristics of rotary screw compressors.
  • Describe the characteristics of vane compressors.
  • Describe the characteristics of lobe compressors.
  • Describe the characteristics of axial compressors.
  • Describe the characteristics of centrifugal compressors.
  • Describe the purpose of the air receiver.
  • List common types of prime movers.
  • Describe factors to consider when selecting a compressor.

Class Vocabulary

Vocabulary TermDefinition
air receiver A component that stores compressed gas and helps stockpile a constant supply of pressurized gas.
axial compressor A type of dynamic compressor in which gas flows parallel to the rotation of the axis.
blower The rotors of a lobe compressor. Common blowers have either 2 or 3 lobes.
centrifugal compressor A type of dynamic compressor that compresses air and expels it with a centrifugal force from a rotating wheel with radial vanes. Centrifugal compressors are often used for fans and cooling units.
centrifugal force A force directed outward and away from the center of a rotating object.
compressor A component that pressurizes ambient air and directs it into a pneumatic system.
crankshaft A rod that spins and drives a piston in a piston compressor. The crankshaft is powered by a prime mover.
cubic feet per minute A measurement of airflow that indicates how many cubic feet of air pass by a stationary point in one minute. Cubic feet per minute is abbreviated cfm.
diesel motor A type of internal combustion engine, controlled by a throttle, that is often used as a prime mover for mobile pneumatic applications.
diffuser A part of a centrifugal compressor that transforms the high-speed low-pressure gas into higher pressure.
double-acting compressor A pneumatic actuator that directs energy in both directions.
dry rotary screw compressor A type of rotary screw compressor that delivers air without the use of lubrication.
dynamic compressor A type of compressor that delivers larger volumes of air at lower pressures. Common types of dynamic compressors include centrifugal and axial compressors.
electric motor A machine that converts electricity into mechanical energy or motion. An electric motor is a type of prime mover for a pneumatic system.
flow rate A specification of a compressor that indicates how much air a compressor can move in a certain amount of time. Flow rate for pneumatic pumps is measured in cubic feet per minute.
fluid power Power derived from the motion and pressure of a fluid, such as water, oil, or air. Hydraulics and pneumatics are sources of fluid power.
gas turbine engine A type of rotary engine driven by high-speed gases that convert the chemical energy into mechanical energy by internal combustion.
horsepower A unit of power used to describe the strength of a pneumatic component. One horsepower equals 746 watts.
impeller The rotors of a lobe compressor. Common impellers have either 2 or 3 lobes.
intercooler A component that cools air inside a compressor. An intercooler is a type of heat exchanger that also removes moisture.
internal combustion engine A type of engine in which heat energy and mechanical energy is produced inside the engine. Internal combustion engines include gas turbines and types of diesel motors.
liquid ring compressor A type of vane compressor that expels liquid with a centrifugal force to create a liquid ring that forms a seal. Liquid ring compressors are dust and oil free but not very efficient compared to other compressors.
lobe The portion of a lobe compressor's impeller that interlocks and provides the ability to compress air.
lobe compressor A compressor that derives its pressurizing ability from two interlocking gear-type rotors called impellers or blowers.
multi-stage compressor A type of compressor that compresses air to the required pressure in multiple stages with cooling in between stages. Multi-stage compressors are often used for higher pressures.
NTP An abbreviation for normal temperature and pressure.
operating pressure The pressure at the actual operating point used to specify the valves, actuators, and other devices.
piston A rod inside a cylinder that is moved by pneumatic pressure.
piston compressor A pneumatic compressor that uses a piston driven by a rotating crankshaft to pressurize air in a pneumatic system.
pneumatic power Power derived from the motion and pressure of a gas, such as air.
positive displacement compressor A type of compressor that delivers a fixed volume of air at high pressures. Common types of positive displacement compressors include piston compressors and rotary screw compressors.
prime mover The component of a pneumatic system that powers the compressor.
psi A measurement of pressure. Pounds per square inch is abbreviated psi.
reciprocating compressor A compressor that derives its pressurizing ability from a component, usually a piston, that moves back-and-forth.
revolutions per minute The number of times a component rotates 360°, or in a complete circle, in one minute. Revolutions per minute (rpm) is a measurement of speed.
rotary screw compressor A compressor that derives its pressurizing ability from two interlocking threaded cylinders. The male-female thread interaction traps and compresses air.
rotor The main spinning portion of a rotary compressor.
single-acting compressor A pneumatic actuator that directs energy in one direction.
single-stage compressor A type of compressor that compresses air to the required pressure in a single operation. Single-stage compressors are often used for lower pressures.
staging A method that handles the various pressure requirements in a compressor. Compressors come in single and multiple stages.
stator A stationary component used together with a rotating part in an axial compressor.
STP An abbreviation for standard temperature and pressure. STP must be specified in a compressor before determining volume of flow.
vane A retractable spring-loaded mechanism that extends radially from the center of a compressor rotor. Vanes trap and move fluid to an outlet port.
vane compressor A pneumatic compressor that consists of a rotor mounted off-center in a circular cavity. As the rotor spins, vanes trap and compress air.
water trap A part of an air receiver that traps and drains away the condensation formed due to reducing the air temperature in the receiver.
wet rotary screw compressor A type of rotary screw compressor that delivers air with the use of oil to lubricate the screws.
working pressure The maximum pressure used to specifiy the compressor at the outlet.