Chapter 16 Conditioning and Distribution of Compressed Air Controlling Dirt, Moisture, Temperature, and Pressure

Chapter 16Chapter 16

Conditioning and Conditioning and Distribution of Compressed Distribution of Compressed AirAir

Controlling Dirt, Moisture, Controlling Dirt, Moisture, Temperature, and PressureTemperature, and Pressure

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.3

ObjectivesObjectives

Compare the various methods used to remove dirt from ambient air entering the compressor and in the final filtering of air distributed to the workstations.

Identify the benefits of controlling the temperature of compressed air and the methods used to remove excess heat.



Describe the problems caused by excess moisture in the compressed air of a pneumatic system.

Identify the source of moisture in a pneumatic system and various methods used to remove liquid water from a system.

Describe the functions of the pneumatic system receiver and identify construction features of typical designs.



Explain the factors that must be considered when establishing the size and location of a receiver for a pneumatic system.

Compare the various types of pipe, tubing, and hose used in pneumatic systems.

Identify and explain the factors that should be used when selecting a conductor for use in a pneumatic system.



Explain the design and construction of the various air distribution systems.

Describe the purpose, construction, and operation of the components used for the final preparation of compressed air at a pneumatic system workstation.


Conditioning and Conditioning and Storing Pneumatic Storing Pneumatic

System AirSystem Air Maximum pneumatic system operating

efficiency is achieved when system compressed air is:– Consistently clean– Free from moisture– At a relatively uniform temperature



System AirSystem Air Atmospheric air contains dirt under even the

best of operating conditions

DeVilbiss Air Power Company



System AirSystem Air Pneumatic systems need to carefully filter the

air taken into the compressor intake to extend the service life of– Compressor– Other system components



System AirSystem Air Correctly designed distribution system

IMI Norgren, Inc.



System AirSystem Air Filters used on the intake line of pneumatic

compressors may be– Dry element– Oil wetted– Oil bath

The filter used is based on the type of compressor, atmospheric conditions, and the final use of the compressed air



System AirSystem Air Air at construction sites is dirty

Atlas Copco



System AirSystem Air Painting requires

very clean air




System AirSystem Air The temperature of both the intake and

compressed air is important– Temperature changes are reflected in air pressure

and volume per the general gas law– Temperature influences the ability of air to retain

water vapor



System AirSystem Air Air in a pneumatic system may be cooled

before, during, or after compression– Intake air temperature usually depends on the

location of the compressor air intake– Intercoolers and aftercoolers are used to remove

heat of compression



System AirSystem Air Intercoolers cool compressed air between the

stages of a multiple-stage compressor Aftercoolers cool the air after the air has been

compressed Either air or water can be used as the cooling

medium in these devices



System AirSystem Air Water vapor in air is referred to as humidity

– Essential to our natural environment– Can cause problems in a pneumatic system when

the temperature of the compressed air drops to the dew point and the vapor condenses into liquid water



System AirSystem Air Free air at 70° Fahrenheit can hold 1.14 pounds

of water vapor per 1000 cubic feet By volume, this water is equal to approximately

one pint Retention of water vapor in compressed air is

based on the volume of air



System AirSystem Air Liquid water in a pneumatic system can:

– Wash away lubricants– Increase component wear– Cause inconsistent system operation– Lower the finished quality of products directly

using the air in the manufacturing process



System AirSystem Air Liquid water forms in system lines and

components whenever the air temperature decreases to the dew point

The first step in reducing the liquid water in compressed air is to locate the atmospheric air intake of the compressor in a protected area



System AirSystem Air Condensation of the water vapor in compressed

air can occur in:– Aftercooler units– Moisture separator– System receiver– Distribution system



System AirSystem Air Specific air driers can be used in pneumatic

systems to remove moisture– Chemical desiccant– Refrigeration units– Specialized membranes



System AirSystem Air The receiver is the storage unit for compressed

air Typically, the receiver is a metal, cylindrical tank

with domed ends In addition to air storage, the receiver:

– Dampens system pressure pulsations– Removes water vapor from system air– In smaller systems, serves as the mount for the prime

mover and compressor



System AirSystem Air Formulas are available for calculating the

volume needed for a receiver These formulas consider:

– Cubic feet of free atmospheric air needed per minute

– Desired cycle time– Atmospheric, initial receiver, and final receiver

air pressures


Air-Distribution SystemAir-Distribution System

The air distribution system delivers high-pressure, conditioned air from the receiver to workstations with a minimum of pressure drop

The type of distribution system depends on the size of the facility and the level of demand for compressed air



Four general categories of air distribution systems are used with pneumatic systems– Centralized grid with fixed piping– Decentralized grid with fixed piping– Loop system with fixed piping– Flexible hoses for portable compressor systems



Centralized grid has one centralized compressor station and one line network for a facility

Decentralized grid has individual compressors in several locations providing air to smaller distribution networks



Centralized grid



Decentralized grid



Loop system has a main line that forms a continuous loop with compressors located at one or more locations

This design provides maximum airflow with a minimum of pressure drop between the compressors and the individual workstations



Loop system



Special attention must given to the setup of a hose air distribution in order to minimize pressure drop– Minimize hose length– Reduce the number of couplings– Eliminate kinks in the hose

Care must be taken to protect the hoses from abrasion in the work environment



Typical hose distribution system




Proper sizing of pipe for a fixed air distribution system is difficult

Most systems operate under a variety of work conditions:– Multiple workstations– Varying actuator loads– Intermittent actuator operation



Varying loads makes line sizing difficult




Sizing is based on:– Rated actuator air consumption– Estimate of the time actuators are actually operating– Estimate of the percentage of maximum load

delivered during actuator operation



The pipe in air distribution lines should be installed with a pitch of 1 per 10 of line– Allows liquid water to drain to water traps– Water can be remove from traps either manually

or with automatic drain devices



Drop lines lead from the main air distribution line to the workstations– Should be attached to the top side of the distribution

line– This prevents water in the distribution lines from

entering the workstation lines



Proper slope and drop line installation


Final Preparation of AirFinal Preparation of Airat the Workstationat the Workstation

Final preparation of air at a workstation is accomplished by an FRL unit– Air filter– Pressure regulator– Lubricator



Typical FRL unit



FRL air filter removes:– Airborne dirt remaining in the atmospheric air

compressed in the system– Rust and scale from the interior of the distribution

lines– Liquid water that has condensed in the drop line– Atomized oil from the operating compressor



Typical air filter uses centrifugal force and porous filter material to remove unwanted materials from system air– Inlet passageway swirls the incoming air, creating

a centrifugal force that separates air and contaminants

– Porous filter material traps other undesirable materials



Typical FRL air filter

IMI Norgren, Inc.



FRL filters typically have a drain



The pressure regulator in an FRL unit reduces system distribution line pressure to the level needed by workstation tools and circuit actuators

Unit is also necessary as air pressure in the distribution line fluctuates due to varying air demands and the characteristics of compressor-capacity control



Several regulator designs are available for use in a pneumatic system– Direct-operated regulator– Basic, diaphragm-chamber regulator– Relieving-type regulator– Balanced-poppet valve regulator– Pilot-operated regulator



Regulators commonly use a flexible diaphragm to sense outlet line pressure and provide the balancing force needed to control airflow through a poppet valve

Only sufficient airflow to maintain the selected workstation pressure is allowed to pass through the poppet valve to the outlet port of the regulator



Direct-operated pressure regulator



Many regulators have a diaphragm-control chamber to separate the regulator side of the diaphragm from direct contact with distribution system air– Sensing orifice connects the control chamber and outlet

port– This dampens the reaction of the diaphragm, providing

more sensitive and efficient workstation pressure control

– Protects diaphragm from contaminants



Diaphragm-chamber regulator



Some regulators contain a venting orifice located in the center of the diaphragm– Prevents pressure increase in the outlet port beyond

the regulator pressure setting– The relieving action automatically bleeds air from

the outlet port to the atmosphere– This design feature allows the regulator to act like a

small relief valve



Relieving-type pressure regulator

IMI Norgren, Inc.



Balanced-poppet valve regulators have a design that subjects both ends of the valve poppet to equal air pressure– Allows the valve to be more accurately positioned – Produces better pressure control and improved

response to system load variations



Balanced-poppet valve pressure regulator



Pilot-operated regulators have a sealed pilot-air chamber in place of a control spring and adjustment screw– A second, small, remotely located regulator is used

to control air pressure in the pilot-air chamber– The air pressure in the pilot-air chamber acts as an

air spring to establish the setting of the pilot-operated regulator



Pilot-operated pressure regulator



Installation of a pilot-operated pressure regulator with a secondary regulator

IMI Norgren, Inc.



Factors to consider when selecting a system regulator are:– Regulator style– Pressure range– Airflow range– Conductor connection size



The lubricator in an FRL unit meters oil into pressurized system air at the workstation

This provides lubrication for system valves, actuators, and air-powered tools



Typical FRL lubricator

IMI Norgren, Inc.



Rapidly moving system air passing through a lubricator breaks up droplets of oil, forming a mist or fog

This mist is transported through the workstation lines to system components


Distribution System Distribution System Conductors and Conductors and

FittingsFittings Effectively moving compressed air through a

distribution system requires appropriate conductors and connectors

Conductors can be classified as– Rigid– Flexible



FittingsFittings Pipe is the most common rigid conductor Hose is the most common flexible conductor Conductors must be properly sized and

assembled for compressed air to be transported from the compressor to actuators with minimal pressure drop



FittingsFittings Conductors and the associated fittings must

be properly sized

IMI Norgren, Inc.



FittingsFittings Tables are available that provide data on air

pressure loss in standard rigid and flexible conductor sizes using various flow rates



FittingsFittings Various types of hose are available

Atlas Copco



FittingsFittings Hose selection, application, and maintenance

are critical to assure air distribution with a minimum loss of pressure– Hoses should be no longer than necessary– Hoses should be no larger than necessary– Use a minimum number of fittings– Layout lines to eliminate kinks and reduce the

number of bends



FittingsFittings Proper hose selection is important


Review QuestionReview Question

Name five materials that may be used to make the element in a dry filter for use in pneumatic systems.

A. Paper, B. plastic, C. cloth, D. metal, and E. ceramic.



_____ is the temperature at which water vapor in the air begins to condense to form liquid water.

Dew point



Name five places where liquid water may form in the pneumatic system.

A. Intercooler, B. aftercooler, C. moisture separator, D. receiver, and E. system distribution lines.



Name two things that occur when warm, humid, high-pressure air cools in the distribution lines of a pneumatic system.

A. The pressure of the air reduces according to the general gas law, and B. liquid water forms when the dew point of the air is reached.



In addition to air storage, the receiver dampens air _____ caused by compressor operation.

pulsations



What can be used to supply compressed air to a section of the distribution system that contains equipment using a large volume of air on an intermittent basis without increasing the size of the system?

An auxiliary receiver.



What is the most common rigid conductor for major pneumatic systems?

Pipe.



Identify two factors that are critical to selecting the actual sizes of the lines used in an air distribution system.

A. Anticipated airflow rate through the lines, and B. pressure drop caused by the lines and fittings.



The _____ compressed-air-distribution system distributes air from a single location to all workstations in a facility.

centralized grid



Why is it necessary to use a pressure regulator in the final air preparation unit at a system workstation?

Air pressure in the distribution lines is higher than what is needed for operation of the workstation actuators. Also, the pressure in the distribution lines varies considerably because of the way the compressor-capacity control system functions.

Documents

Chapter 16 Conditioning and Distribution of Compressed Air Controlling Dirt, Moisture, Temperature, and Pressure