Transcript Compressed Air Technology
Natural Gas Engine Drive Air Compressor Training
Industrial Center, Inc.
Chicago, Illinois April 9, 1997 Industrial Center, Inc. / Air Compressor Consortium N.G.E.D.A.C. Training Ingersoll Rand
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Air Compressor Basics Presented By:
Allen L. Humphrey
Industrial Marketing Manager
Ingersoll-Rand Company Portable Compressor Division Air Compressor Group Mocksville, North Carolina Industrial Center, Inc. / Air Compressor Consortium N.G.E.D.A.C. Training Ingersoll Rand
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Hi !, I’m an expert in Natural Gas !
Isn’t all gas natural!!!
Gas Company Guy Industrial Center, Inc. / Air Compressor Consortium N.G.E.D.A.C. Training Air Compressor Guy Ingersoll Rand
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I’m an expert in compressed air,! Hot air, cooled, and dried I'm in trouble now, another guy full of hot air!!!
Air Compressor Guy Industrial Center, Inc. / Air Compressor Consortium N.G.E.D.A.C. Training Gas Company Guy Ingersoll Rand
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Outline:
I.
II.
Compressed Air Facts Compressed Air Technologies III.
Regulation & Controls IV.
System Location and Arrangement V. Compressor System Components The Basics
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Compressed Air Facts
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Compressed Air Facts
Most facilities consider compressed air a utility on par with electricity, gas, and water However, few operating people know the real operating cost of their compressed air system
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What is cost per CFM ?
A Good Approximation Typical Compressor produces 4 CFM per 1 Hp 1 Hp = 0.746/0.9 = 0.829kW
Therefore, 1 CFM = 0.207kW
@ 0.06 $/kw-hr, 1 cfm = $0.0124/hr 10 CFM over 8000 hours costs 10 x 8000 x 0.124 = $ 992.00
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Where are
NORMAL
savings ?
Fix System Leaks !!
Standard plant air system 8000 hrs per year operation Electrical costs = $ 0.06/kWhr Plant line pressure = 100 PSIG (1) 1/8th inch air leak = 26 CFM 26 x 8000 x $.0124/hr = $ 2,579.00
A typical plant can have air leaks = to 20% of total air usage.
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Air Basics
Three Main Parameters 1. Pressure 2.Capacity
3. Horsepower
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Pressure(PSI) = Pounds per Square inch Completely dependent on system, controls and safety valves An unregulated compressor will make ever increasing pressure until a failure occurs When plant capacity demand exceeds system capacity(CFM), compressor discharge pressure will drop
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Pressure - Capacity Relationship
P 1 x V 1 = P 2 x V 2
P 1
= Initial pressure
V 1
= Initial capacity
P 2
= Final pressure
V 2
= Final capacity If a system needs more capacity(CFM) than available, plant pressure
drops
in an
unsuccessful
trade of pressure for capacity
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The Cost of Pressure
Good Rule of Thumb Each # (PSI) of system pressure = 0.5% of system horsepower
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Pressure Cost Example
100Hp compressor set to discharge at 125 psig to plant system Plant system only requires 110 psig User resets compressor discharge pressure to 110 psig ( a 15 psi reduction) 15 PSI = 7.5 % of Hp = 7.5 Hp 7.5 x .746/.85 = 6.6kW x 8000 hrs x $.06/kWhr = $ 3,168.00 (Savings)
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Capacity(Flow) = CFM(ft 3 per minute) Basic measure of true compressor output A fixed value in most designs, for a given model Most all capacity measurements are referred back to inlet conditions. Capacity varies only slightly with a change in discharge pressure, for a given model
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Capacity Measurement
In the pneumatics industry,
ALL
capacities are measured referring back to inlet conditions Various formulae are used to define capacity(CFM): SCFM; ACFM; ICFM; FAD, etc. Require your vendor to define which and where ASME and CAGI-Pneurop have generally accepted testing standards Capacity tolerances may vary from vendor to vendor. Request definition
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Horsepower
Typically, electric motor nameplate HP or NG engine MCHP(Max Continous Hp) The work it takes to compress “X” CFM up to “Y” PSI Driver HP is usually fixed. If either CFM or PSI is increased, the driver may overload, unless regulation, a speed reduction, or a change in either CFM or PSI takes place.
Horsepower tolerances may vary from vendor to vendor. Request definition
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Air Basics Translations
Capacity(CFM) does the work; Pressure effects the rate at which the work is done A trending decrease in plant air pressure typically indicates a requirement for more capacity(CFM), not pressure Increasing or decreasing the existing compressor discharge pressure will normally have negligble effect on the compressor capacity
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II. Compressed Air Technologies
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Compressor Technology
Air Compressors Positive Displacement Dynamic Displacement Reciprocating Rotary Screw Single Acting Double Acting Oil Flooded Centrifugal Oil Free
Lower Technology
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Higher Technology
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Dynamic Displacement
180 160 140 120 100 80 60 40 20 0 0% FL
“Performance Curve”
20% 40% 60% 80% Percent of Full Load 100% 120% Industrial Center, Inc. / Air Compressor Consortium N.G.E.D.A.C. Training Ingersoll Rand
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Centrifugal Compressors
Advantages Only real option over 600+ Hp High air quality- 0 PPM oil carryover Moderate to high efficiency Longer design life than Rotaries Disadvantages Higher initial cost Fluid cooled only Power reduction down to 70% flow Constant speed operation
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Positive Displacement
“Performance Curve”
180 160 140 120 100 80 60 40 20 0 0% FL 20% 40% 60% 80% Percent of Full Load 100% 120% Industrial Center, Inc. / Air Compressor Consortium N.G.E.D.A.C. Training Ingersoll Rand
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Positive Displacement
Reciprocating or Rotary Screw Designs Constant cfm; Variable pressure Adaptable to variable speed drive Variable speed and unloading provide close alignment with system demand
Oil Flooded Rotary Screws
--The design of choice for NGEDAC’s
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Rotary Screw
Oil Flooded- Single Stage
Advantages
Low 1st cost; Low maintenance $ Simple packaged design Adaptable to variable speed drive
Disadvantages
Somewhat lower efficiency Moderate durability - 10 15 years on average
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Rotary Screw
Oil Free
Advantages
High air quality- 0 PPM oil carryover Moderate efficiency Packaged design
Disadvantages
Higher initial cost Higher maintenance cost
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Compressor Selection Criteria
Evaluated First Cost Efficiency Controls Maintenance Cooling Air Quality Durability
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General Guidelines- First Cost
Single-stage rotary screw Typically lowest first cost Greatest market growth, largest population Typically lowest efficiency Possible Alternatives Two-stage rotary screw Oil free rotary screw * Centrifugal *
*Dependent on air quality requirements
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General Guidelines- Maintenance
Capabilities of on site maintenance personnel ? Contract maintenance ?
Oil flooded rotaries typically require lowest maintenance “Air-in-the-box” design enables on site overhauls of both compressor system and engine
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General Guidelines- Cooling
Fluid-Air cooled - less expensive Most designs have fluid or fluid air cooled design options available Closed evaporative cooling towers; open towers and external fluid to air coolers are viable cooling options
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III. Regulation & Controls
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Regulation/Controls Applications
Average number of compressors = 2.5 per facility Typical system controls: manual/ none Each incremental 1 PSIG of unnecessary pressure cost 0.5% of compressor horsepower Each electric motor driven compressor running unloaded = 35-50% of the full loaded electrical costs
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Regulation Basics
Do not run compressors unnecessarily Evaluate current regulation parameters Consider upgrading substandard controls The most efficient operating point is 100% full load.
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Basic Types of Regulation
This information will be covered in detail later in the seminar presentation
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IV. System Location and Arrangement
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#1
Possible Locations
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Outdoors
Advantages
Zero floor space Zero heat load
Disadvantages
Potential weather damage (Freezing, water, etc.) Potential lack of maintenance (Out of sight, out of mind)
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#1
Possible Locations
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Indoors Centralized
Advantages
Protected from elements Potentially easier access
Disadvantages
Greatest floor space Potentially long piping runs
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#1 #2
Possible Locations
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Indoors Decentralized
Advantages
Possible to install closest to large air users Least amount of pressure drop through air lines
Disadvantages
Highest probability of incorrect regulation Potential to spread noise and heat complaints to broadest number of employees
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Environmental Factors
Temperature Ventilation Conditions Atmosphere Personnel
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Temperature - Low
Below 35
0
F
Possible control freeze problem Possible condensate freeze problem Possible fluid misapplication
Recommendations
Heaters Heat tracing key elements Relocate
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Temperature - High
Above 100
0
F
Possible unit shutdown Increased engine maintenance Possible decreased lubricant life
Recommendations
Improved ventilation/relocate Higher performance lubricant More suitable equipment design
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Ventilation
Insufficient Ventilation
Possible unit shutdown Increased maintenance Possible decreased lubricant life
Requirements
Air-cooled Water-cooled
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Ventilation - The High Air Temperature (HAT) Vicious Cycle
Compressor Generates Heat Insufficient Ventilation Causes Heat To Remain Around Unit Unit Temperature Spirals Upward This Heat is Ingested By Engine-Compressor Increasing Operating Temperatures Of Unit Industrial Center, Inc. / Air Compressor Consortium N.G.E.D.A.C. Training Ingersoll Rand
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Miscellaneous Conditions
Atmosphere Personnel These important subjects will be covered later in the Seminar
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V. Compressor System Components-The Basics
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Basic Selection Criteria
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Real World Systems
Design Criteria Air Quality required by User Moisture content ?
Oil carryover ?
Contaminants Pressure Drop Demand Characteristics Energy profile
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Ideal Components For a Compressed Air System
Compressor Aftercooler Wet Receiver Pre-Filter Dryer After Filter Dry Receiver
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Ideal Components Layout
Compressor After-Cooler Pre filter Dryer After filter “Dry” Receiver “Wet”Receiver Industrial Center, Inc. / Air Compressor Consortium N.G.E.D.A.C. Training Ingersoll Rand
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Air Compressor
Dryers - Moisture Content
“Rule of Thumb” Aftercooler 100ºF 80ºF 60ºF 100% RH 100% RH 100% RH Effect of Compressed Air Temperature on sizing of drying equipment.
A 20º F reduction in temperature condenses 50% of the water vapor in saturated air.(Collect it; trap it; dispose of it) A 20º F. rise in temperature doubles (200%) the moisture holding capacity of the air.
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After Filter (Recommended)
Purpose Reduce oil carryover Benefit Improved air quality Improved product quality Instrument air applications Painting
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Dry Receiver (Recommended)
Purpose Provide a reservoir of clean dry air to meet fluctuating system demands Benefit When sized and installed correctly can minimize airline pressure fluctuations Prevents short term capacity requirements from overloading cleanup equipment
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Real World Systems
Moisture Content Pressure Dewpoint - Temperature at which water vapor condenses into liquid in a compressed airline
Rule of thumb:
Select a dewpoint 10-20 0 F below the lowest temperature the compressed airlines will see
Real World Systems WARNING:
This applies only to general industrial application. Specific applications have specific dewpoint requirements (i.e., paint booths, instruments, etc.) Contact equipment OEMs
Real World Systems
“Typical” Real World System A 1000 CFM system with lowest plant ambient temperature of 60 0 F sensitivity to lubricant fairly steady plant demand
Real World System
After Cooler “Wet” Receiver Dryer After filter Compressor
1000 CFM Compressor Air Cooled 1000 gallon receiver oil coalescing filter Refrigerated air dryer with a 40 0 dewpoint F
Real World Systems
Pressure Drop Pressure Drop is the cost of air quality Every air clean up device will utilize 2-10 PSI to perform its function Air dryers typically 3-5 PSI Air filters typically 2-10 PSI (dependent on how long the element has been in place)
Remember @ 1/2% energy for each PSI, additional filters may become needlessly expensive
Real World Systems
Demand Characteristics Receiver size and placement varies depending on plant demand cycle and receiver size Possible to supply a new intermittent large air user with a properly sized and installed receiver tank
Real World Systems
Typical Compressor Carryover Values: Oil Flooded
Real World Systems
Oil Content Requirements Whether the oil is removed at the compressor, or at the point of use, should be determined by overall plant requirements
Real World Systems WARNING:
Although some equipment may benefit from (or even require) lubricant in compressed air, many other applications (paint booths, instrumentation) cannot tolerate it Again overall system requirements should dictate system design
Air Compressor Basics
Thank you for your kind attention
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