Compressed Air System Maintenance:Achieving Maximum Performance with

Minimal Investment

Ultrasound World IIIClearwater Beach, Florida

November 5-8, 2006

COMPARISON OF COSTSELECTRIC vs. AIR MOTOR

Approx. $200/year Approx. $1,500/yearPower Cost Power Cost

* Air motors require about 7hp of compressor capacity or 27-30cfm per hpoutput.

Based on 5,000 hours/year at $0.05/kWh

Why is Compressed Air so Inefficient?

• Less than 20% of input energy available for work• Pressure drops and regulators reduce useable energy•Typical air tool has typical 12-15% overall efficiency

A How Much ?!?!A Question of Initial Cost

@ $0.06/kwh, a single stage rotary screw compressorcosts about $10,000/year per 100 cfm to operate!

A How Much ?!?!A Question of Initial Cost

When selecting a compressor,the following should be taken into consideration:

• What is the total cost of ownership?

• What type of controls will best suit my operation?

• Two stage compressors will likely save money in the long run.

5.0 to 5.3 cfm/hp• H/D 2 Stage Water Cooled Recips.

4.5 to 5.0 cfm/hp• Multistage Centrifs.• 2 Stage Rotary Screw• Higher Speed 2 Stage Recips.

4.25 to 4.5 cfm/hp• Low Rotor Speed Single Stage Oil FloodedScrew

4.0 to 4.25 cfm/hp• Most Single Stage Oil Flooded Screw

3.5 to 3.8 cfm/hp• 80% of compressors at 230 BC Hydro andOntario Hydro Customers had delivery I thisrange on compressors with modulating air inletcontrols.

Plant Air Compressor DeliveriesDesign vs. Actual

What Price is Efficiency?

Plant Air Compressor DeliveriesDesign vs. Actual

* Based on 8500 hours per yearand $0.05/kWh and $7 / kW

$40,000 per year Difference

5.25 cfm/hp

3.5 cfm/hp

Matching Compressors to Production DemandsHow does your facility stack up?

• Operating multiple rotary screw or centrifugal compressors, ALL featuring some form ofinlet throttle modulating control.

• When production ends and maintenance takes over, are compressors just left running?

• No means of compressor performance testing. Output is assumed based on power draw orreferencing OEM curves.

• Addressing air leaks is not a priority because of lack of manpower, lack of education, orattitude that leaks are not a high concern.

• Mentality is evident that “air is free”, it is used for menial applications such as blowing dustor water off of product, machine bearing cooling, optical scanning equipment cleaning,cooling personnel, etc.

Matching Compressors to Production DemandsHow does your facility stack up?

THIS IS WHERE YOU WANT TO BE!

• Multiple compressor installation under control of a programmed PLC sequencer orequivalent.

• Air Leak monitoring is part of PM (Preventive Maintenance) program and maintenanceand planning departments see that leaks get monthly attention and the process hasACCOUNTABILITY.

• Performance under load tests are utilized to measure actual compressor performance toconfirm compressors are producing rated air and controls are allowing proper delivery ofair into the system.

• Heatless desiccant air dryer purging is under full control of a RELIABLE dew pointmonitoring system.

An Example of Multiple Compressor Sequencing

Time Days/Week Required Flow Leak Volume CompressorsOn

1st Shift 5 2,500 - 2,800 400 A & B & C

2nd Shift 5 2,000 - 2,200 400 A & B

3rd Shift 5 700 400 B

Weekends 2 400 400 C

Current Operation:

400 hp

250hp

125hp

A

CB

400 hp

250hp

A

CB125hp

400 hpA

CB250hp

125hp

400 hpA

CB250hp

125hp

53% of the time there is little or no air use in the system

Leak costs: 400cfm is roughly equivalent to 100hp which over a yearwill cost:

100hp * .746kW/hp * 8760 hrs/yr * $.06/kWh = $39,200 per year

An Example of Multiple Compressor Sequencing

Time Days/Week Required Flow Leak Volume CompressorsOn

1st Shift 5 2,500 - 2,800 400 A & B & C

2nd Shift 5 2,000 - 2,200 400 A & B

3rd Shift 5 700 400 B

Weekends 2 400 400 C

Current Operation:

400 hp

250hp

125hp

A

CB

400 hp

250hp

A

CB125hp

400 hpA

CB250hp

125hp

400 hpA

CB250hp

125hp

Annual Electric Energy Cost: $109,781

An Example of Multiple Compressor Sequencing

400 hp

250hp

125hp

A

CB

400 hp

250hp

A

CB125hp

400 hpA

CB250hp

125hp

400 hpA

CB250hp

125hp

Recommendations:

• Repair Half of the System Leaks

• Install Dedicated compressor (5hp) for SprinklerSystem

• Install PLC Multi-compressor Sequencer ~ $3,500

An Example of Multiple Compressor Sequencing

Time Days/Week Required Flow Leak Volume CompressorsOn

1st Shift 5 2,300 - 2,600 200 A & B

2nd Shift 5 1,800 - 2,000 200 A & C

3rd Shift 5 500 200 C

Weekends 2 200 200 None

400 hpA

CB

400 hpA

CB250hp

125hp

250hp

125hp

400 hpA

CB 250hp

125hp

A

CB 125hp

400 hp

250hp

Annual Electric Energy Cost: $80,687

Proposed Operation:

An Example of Multiple Compressor Sequencing

Time Days/Week Required Flow Leak Volume Compressors On

1st Shift 5 2,500 - 2,800 400 A & B & C

2nd Shift 5 2,000 - 2,200 400 A & B

3rd Shift 5 700 400 B

Weekends 2 400 400 C

Current Operation: $109,781

Time Days/Week Required Flow Leak Volume CompressorsOn

1st Shift 5 2,300 - 2,600 200 A & B

2nd Shift 5 1,800 - 2,000 200 A & C

3rd Shift 5 500 200 C

Weekends 2 200 200 None

Proposed Operation: $80,687

Energy Savings = $ 29,094

Compressed Air Flow Volumes for Various Sized Orifices

In reality, you will probably never come across a perfect, round, sharp edged orifice leakanywhere in your plant facility. Leaks occur in joints, couplings, slits or gashes in pipes and lines,and other types of fittings. Thus, the tables presented here can only be used as a guideline.

Common Air Leaks and Misapplication

• Optical scanning equipment clean off – use small blower• Air hoses – loose or frayed clamps• Air lances and fittings• Pressurized computer and electrical rooms/panels• Belt cleaning – use a small blower• Cooling machinery bearings- use a fan• Worn cylinder packing, “O“ rings, faulty PR valves orbroken diaphragms, bleed off vent holes in valves.

CompressedAir Leakage (cfm) Rolling Average

Target LeakVolume

Tracking Compressed Air Leakage

Even with consistent program leaks will reoccur

SummaryTable of TestingResults

Compressor Compressor Expected flow(cfm) Actual peak flow(cfm)Location hp and pressure andpressure

Main Mill Comp. Room 350 1,400 1,290@100psig @84psig

Main Mill Comp. Room 300 1,200 990@100psig @80psig

Stacker/Sorter 150 600 495@100psig @80psig

Planer 100 400 330@100psig @80psig

Totals 900 3,600 3,105

Note: Compressorsareunderperformingby1600cfm-Equiv. to400hp compressor

SummaryTable of Air LeakTest Results

Leak Volume %of EquivalentLeakLocations (cfm) Peak Flow Compressor hpMain Mill 670 29% 191RemanOperation 450 20% 128Sorter 0 0% 0Stacker 150 30% 45Planer 215 65% 65Totals 1,485 48% 430

Note: Half of thecompressedair producedis beinglost directly to atmospherewithno useful work beingdone!

Sawmill Example. Cost of CompressedAir

AnnualLoaded Unloaded Hoursof %of Time Annual Cost of energy Cost of Demand Total Cost

Compressor kW kW Operation Loaded kWh @$0.0386/kwh @$5.43/kW of electricitySorter/Stacker 100 75 8500 70% 786,250 30,349$ 6,516$ 36,865$Planer 74 64 8500 90% 618,694 23,882$ 4,806$ 28,687$MainMill 300hp 217 195 8500 75% 1,797,750 69,393$ 14,140$ 83,533$MainMill 350hp 273 243 8500 75% 2,256,750 87,111$ 17,789$ 104,899$Totals 5,459,444 210,735$ 43,250$ 253,984$

Sawmill Example. LeakAnalysisand AchievableSavings

Current kWhto kWh Cost Acceptable kWh Savings kWhCost SavingsCompressor %of Leaks Leaks of Leaks %of Leaks Achievable AchievableSorter/Stacker 30% 255,000 9,843$ 10% 170,000 6,562$Planer 65% 407,469 15,728$ 10% 344,781 13,309$MainMill 300hp 49% 903,805 34,887$ 15% 627,130 24,207$MainMill 350hp 49% 1,137,045 43,890$ 15% 788,970 30,454$Totals 2,703,319 104,348$ 1,930,881 74,532$

Using the LP Load Flow Meter, to determine compressor performance:

• Isolate compressor from system

• Open meter orifices until compressor can just keep up at test pressure

• Open and close valves to test at other pressure/flow combinations

Performance Testing an Air Compressor

Leak Testing an Air System

1. Perform a compressor capacity test at system pressure

2. Pressurize the System without plant operating

3. Perform a second flow test at the same system pressure

4. The difference in measured flow volumes is the leak volume in thesystem

Provides very accurate leak quantities which can be converted into annualcosts.

Any equipment or segemnt of the system thhat can be isolaed can be tested

Focus maintenance efforts to areas of high leaks

Other Applications: Check leaking block valves, leak test underground pipe,and check complex piping or process for total leak volume.

Purge cycle on a desiccant dryer can be tested just as if it were a leak.

Procedure:1. Perform standard performance test with dryer isolated (or bypassed)2. Put dryer into purge mode and perform a second test3. The difference in measured flow volume at the meter is the purge volume

Any piece of equipment or process which can be isolated can be tested

Typical purge volumes: 15-17% for heatless dryers4-8% for heated regenerative dryers.

Testing Purge Volume on a Desiccant Dryer

Performance Curves

Modulating valve prematurely throttling

325 cfm

Performance Test - Theory Vs. Reality

Inlet Throttle Control

Modulating Air Inlet Controls

Modulating Control Valve Cutaway

Dirt, oil, water, or other contaminants can foul the valve causing pre-mature modulation

Centrifugal Compressor Performance Curve

100%

100%0%

BlowOff

Range

ThrottleRange

Capacity (ICFM)Dis

char

gePr

essu

re

Surg

e Lim

itAir FlowMeasurement

ConstantSpeed Drive

Air Inlet

Vent Valveto Atmosphere

Check Valve

Centrifugal Compressor Diagram

Constant Speed Centrifugal Compressor

Centrifugal Instrumentation

Inlet, outlet, and inter-stage temperaturesand pressures are the quickest method todetermine compressor health.

Gauges or control points should beinstalled and monitored for :

Air and water temperatureAir and water pressurePower consumption (amps, kW,

kWh)Flow

Make sure gauges or control points:

1. Exist2. Calibrated regularly3. Accessible4. Logged (maintenance sheets ordatalog)

Commonly Found Centrifugal Compressor Problems

Moisture Carryover - Improper moisture removal by trap- Leak in intercooler

Electrical - Improper motor grounding- Residual magnetism (static)- Welding (improper ground)

Improperly set clearances

High Vibration - Unmatched rotor assemblies- Shaft Misalignment- Worn or damaged bearings

Ingestion of particles - Surge induced- Poor filtration

Performance Diagnostics: Examples from the Field

1. Nuclear Power Plant – Centrifugal compressor testingSurging problem blamed on compressor traced to stuck valve on dryerSaved critical equipment downtime and 2 man weeks of labor

2. Pet Food Company – Previous air study recommended expensive modifications

• Testing revealed serious deficiencies in compressors performance• After repairs (~$920), intermediate control project was cancelled ($15,000 cost)

3. Sawmill Operation – 300hp Compressor tested at 60% of rated flow• 4 hours of maintenance found coil spring problem• Output increased 47%

4. Wood Products Plant –•50 hp at 211 cfm, 75 hp at 160cfm•16kW in energy savings at a zero implementation cost

Knowledge is power - be a TYRANT. The more you know about yourcompressor operation, the quicker you can solve the root problems!

Improvements do not need to be expensive.

Operations and maintenance savings can amount to 50% or more of projectsavings.

From experience, most facilities do not need expensive new equipment, theyjust need to make the equipment and system they have work correctly.

Sample Project Savings

Desiccant Dryer Overview

Prefilter - removes dirt, oil, and water

Dryer – Removes water vapor

After Filter – Removes fines to protect the system from contamination

Oil contamination reduces the effectiveness of desiccant to adsorb water.

Oil contamination increases chances of fire hazard

Drain Trap Types

Timer Drains• Open based on time and duration• Waste energy by blowing air

Float Traps• Use float to open valve• No air loss• Maintenance concerns

Inductive Traps• Use inductive sensor• No air loss• Higher reliability• Higher cost• Can include alarms

Receiver Placement in Compressor Rooms

Compressor - Receiver - Dryer ?

Compressor - Dryer - Receiver ?

Locating and Sizing Air Receivers

Receiver helps smooth out demand and allows compressors to react tochanges in Demand. Essentially to give the system capacitance.

One receiver should be located in or near the compressor room.

As a Rule of Thumb, receiver volume should be at least 5% of totalcompressor(s) output in cu. ft.

Locate receivers in the plant at high use locations. This will help resolvelocal pressure/velocity issues and help reduce the overall pressuresetpoint.

Receiver

Receiver

Air Piping Considerations

Pressure Drop Rule of Thumb - Max. 3 psig drop between supply pointof use.

High Air Velocities – undersized piping = high velocity and highpressure drop. Rule of thumb = velocity should be under10,000’/minute (5-7,000 better).

Velocity = CFM*144/Pipe Area

Corrective actions include:1. Increase the section of undersized piping2. Install an air receiver at the point of air usage.

Pipe Diameter vs. Flow – If you double the pipe diameter, the crosssectional area will increase by 4 times.

*** Use long radius elbows and “Y” connections

Air Piping Considerations

Maintenance Consideration – Blow out scale periodically. Open a large valveand purge air system every 6 months for an hour.

1. Less particulate load on filters2. Air dryer may be bypassed during flushing

Loop Piping – Where possible use loop piping layout instead of branchlayout. The loop system will often result in a more stable system airpressure.

Comp.

Air Piping Considerations

Maintenance Consideration – Blow out scale periodically. Open a large valveand purge air system every 6 months for an hour.

1. Less particulate load on filters2. Air dryer may be bypassed during flushing

Loop Piping – Where possible use loop piping layout instead of branchlayout. The loop system will often result in a more stable system airpressure.

Note: Increasing the system setpoint pressure tocompensate for other deficiencies is NOT the way to go.

AIR PRESSURE : low pressure air holds more liquid (oil or water)1. Demand exceeds compressor delivery output,2. Compressors with load/no load control where unload pressure is toolow3. High air velocity due to dirty separator element.

TEMPERATURE :1. Over cooled compressor can have saturated air entering separator.2. Can lead to water condensation with cooling affect throughseparator.3. This condition can be accentuated with a dirty separator filter.

Reasons for High Oil Carryover

Energy Efficient Alternative Solutions to Common AirUses

Specialty Regulators – Pilot regulators on a receiver for low pressureapplications.• Receiver charged at line pressure, flow controlled for low pressureapplications.

Blowers – Low pressure, high volume: as little as 3 psig can be affective• Dust/debris removal• Drying

Vortex Amplifiers – blast or jet of air: entrain ambient air with compressedair.• 20:1 amplification possible• Spot cooling• Dust removal• Air assist

Boosters – Limited volume at higher pressure pressure• Can use line pressure or ambient air• Process• Air assist• Air jet

Thank You!

Questions?