52nd North Carolina Industrial Ventilation Conference
Module MM-1-1 1
Monitoring & Maintenance of Monitoring & Maintenance of Ventilation Systems,Ventilation Systems,
P t I (MMP t I (MM 11 1)1)
NC Industrial Ventilation ConferenceNC Industrial Ventilation ConferenceRaleigh, NC Raleigh, NC –– April April 20102010
Part I (MMPart I (MM--11--1)1)
11MMMM--11--11
Have you ever heard this from Have you ever heard this from plant operations?plant operations?
“The new local exhaust “The new local exhaust ventilation system we started up ventilation system we started up a month ago doesn’t work!a month ago doesn’t work!EngineeringEngineering didn’t design it didn’t design it right!”right!”
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Tips to Prevent this Problem Tips to Prevent this Problem at Your Siteat Your Site
Where do you start?Where do you start? Why IVS failWhy IVS fail
Common failure modes forCommon failure modes for Common failure modes forCommon failure modes for HoodsHoods DuctsDucts FansFans Collectors Collectors –– TuesdayTuesday
Ventilation System MeasurementsVentilation System MeasurementsMMMM--11--11 33
Where Do You Start?Where Do You Start?
Broadly, are system problems due toBroadly, are system problems due to Original design?Original design? System modified without redesign?System modified without redesign? Poor operating practice? (Poor operating practice? (ieie, adjusting blast , adjusting blast
MMMM--11--11 44
p g p (p g p ( , j g, j ggates)gates)
Little or no system monitoring & Little or no system monitoring & maintenance?maintenance?
Getting startedGetting started Define the problem areas & symptomsDefine the problem areas & symptoms Gather visual and measurement data on Gather visual and measurement data on
systemsystem
Defining the ProblemDefining the Problem
Observable Symptoms?Observable Symptoms? Qualitative (visible, olfactory, etc.)Qualitative (visible, olfactory, etc.) Quantitative symptoms (air samples)Quantitative symptoms (air samples)
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Operator complaintsOperator complaints
Specific locations affected?Specific locations affected? Reasons, frequency of equipment entry?Reasons, frequency of equipment entry? One hood/enclosure?One hood/enclosure? Multiple hoods/enclosures?Multiple hoods/enclosures? Nowhere near a hood/enclosure?Nowhere near a hood/enclosure?
Data Gathering Data Gathering -- QualitativeQualitative
Original system design work as intended?Original system design work as intended? Design basis for each hood/enclosureDesign basis for each hood/enclosure System layout and schematicSystem layout and schematic
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System Baseline airflows and static pressuresSystem Baseline airflows and static pressures System IH Evaluation at startupSystem IH Evaluation at startup Problem area data today?Problem area data today?
52nd North Carolina Industrial Ventilation Conference
Module MM-1-1 2
Data Gathering Data Gathering –– Qualitative, 2Qualitative, 2
System modification without redesign?System modification without redesign? Site have a Change Management System with Site have a Change Management System with
IVS knowledgeable people part of the IVS knowledgeable people part of the ??
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process?process? Compare original schematic to as installedCompare original schematic to as installed Visual clues if no documentationVisual clues if no documentation Problem area data todayProblem area data today
Data Gathering Data Gathering –– Qualitative, 3Qualitative, 3
Operating practices?Operating practices? Designated system ownerDesignated system owner Operators (line and IVS) trainedOperators (line and IVS) trained Blast gates locked or adjusted whenever anyone Blast gates locked or adjusted whenever anyone
wantswants
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wantswants Monitoring & Maintenance?Monitoring & Maintenance?
System Baseline Documentation available as System Baseline Documentation available as reference for M&Mreference for M&M
Installed monitoring devices or routine system Installed monitoring devices or routine system wide data gatheringwide data gathering
Breakdown or predictive maintenanceBreakdown or predictive maintenance Recent maintenance on systemRecent maintenance on system
Data Gathering Data Gathering -- QuantitativeQuantitative
Hoods/enclosuresHoods/enclosuresMeasure area of openingMeasure area of opening
M f l itM f l it
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Measure average face velocity across Measure average face velocity across openingopening
Process at hood cause interference?Process at hood cause interference? External air currents?External air currents?
Ducts & FansDucts & Fans Duct layout Duct layout –– diameters, lengths, types of transitions diameters, lengths, types of transitions
at junctionsat junctionsD t i l it d t tiD t i l it d t ti
Data Gathering Data Gathering –– Quantitative, 2Quantitative, 2
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Duct conveying velocity and static pressuresDuct conveying velocity and static pressures Fan shaft speed, motor ampsFan shaft speed, motor amps
Air cleaning deviceAir cleaning device Differential pressureDifferential pressure Operating at base condition?Operating at base condition?
Causes of IVS FailuresCauses of IVS FailuresSudden Failure ModesSudden Failure Modes –– major airflow reductionmajor airflow reduction
Broken fan beltBroken fan belt Water in baghouse Water in baghouse
cleaning compressed aircleaning compressed air Bag sucked into ductBag sucked into duct
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Bag sucked into ductBag sucked into duct Baghouse dust removal Baghouse dust removal
system backs up into system backs up into baghousebaghouse
Explosion vent opensExplosion vent opens
Causes of IVS Failures Causes of IVS Failures Gradual Failure ModesGradual Failure Modes
Dust buildup in elbowsDust buildup in elbows Dust erodes holes in ductsDust erodes holes in ducts Increasing filter differential Increasing filter differential
pressurepressure Bag cleaning systemBag cleaning system
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Bag cleaning systemBag cleaning system Moisture sensitive dustMoisture sensitive dust
Slipping fan beltsSlipping fan belts Dust visible in exhaustDust visible in exhaust Duct gaskets or access door seals Duct gaskets or access door seals
leaking audiblyleaking audibly
52nd North Carolina Industrial Ventilation Conference
Module MM-1-1 3
Causes of IVS Failures Causes of IVS Failures –– Gradual Gradual FailureFailureCollector High Differential PressureCollector High Differential Pressure
High bag differential pressure due to improper bag conditioning (seeding) at startup of new bags
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at startup of new bags
Scrubber venturi plugging another example
Causes of IVS Failures Causes of IVS Failures –– where where in the system?in the system?Branch versus System failure?Branch versus System failure?
Branches Branches -- Localized impactLocalized impact Dusting at some hoodsDusting at some hoods Poor suction some hoods, harder suction at Poor suction some hoods, harder suction at
th h dth h d
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other hoodsother hoods Filter and fan not obviously affectedFilter and fan not obviously affected
SystemSystem--widewide No or low airflowNo or low airflow Similar effects seen at all branchesSimilar effects seen at all branches
Causes of IVS FailuresCauses of IVS FailuresChange Change -- Add a duct branch/hoodAdd a duct branch/hood
AA
IDID D,inches
Q,CFM
V,fpm
VP/ 100’
AA 88 1500 4200 3.4
BB 88 3000 8400 13
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BB
CC
BB 88
CC 88 4500 16800 350
Impossible conveying velocity Impossible conveying velocity requirements that fans cannot requirements that fans cannot deliver. Only option with this deliver. Only option with this duct is branch ON/OFF duct is branch ON/OFF procedure procedure –– good luck!good luck!
Rough Rule of Thumb:
Downstream duct diameter2 ~ sum of squares of upstream duct diameters
82+82 = 128 ~ 112 or 121
112+82 = 185 ~ 142 or 196, ~ 132 or 169
Causes of IVS FailuresCauses of IVS FailuresChange Change –– Remove Remove a duct branch/hooda duct branch/hood
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Don’t blank a branch like these. It starves airflow and velocity downstream causing dust dropout.
Unless duct changed, bleed air equivalent on removed branch.
No Documented Proof of No Documented Proof of PerformancePerformance
BaselinePerformance Criteria:•Airflow: + 10 % design•Pressure: + 20% baseline•All duct branches
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Turnover document -engineering to operations along with air monitoring results
ISOMETRIC VIEW - OPERATOR FRIENDLY
Causes of IVS Failures Causes of IVS Failures -- Changes to Changes to Calculated System Resistance :Calculated System Resistance :
Dust plugs ducts, elbows first - more resistance Baghouse filter media blinds - poor startup seeding Bags bridge in filter - dust removal failure or filter design
incorrect for particulate collectedA d l ft b d t t k
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Access door left open – bypass duct network Fan belts wear and slip Balancing orifices or blast gates removed/changed Unauthorized changes to system Design not robust enough to minimize duct plugging Proof of performance not measured or documented
52nd North Carolina Industrial Ventilation Conference
Module MM-1-1 4
Lack of management ownership and support No one accountable for system operation No trained personnel on site
C t t d ti t l / i t i t
Causes of IVS Failures Causes of IVS Failures –– Lack of Lack of Management SupportManagement Support
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Cannot get downtime to clean/maintain system No system in place to ensure changes done by
competent resources Breakdown rather than predictive maintenance –
Working Harder, Not Smarter
IVS Operating Skills IVS Operating Skills NeededNeeded
5 functional levels of increasing skill General Awareness User Operator
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p Troubleshooter Change Reviewer
Site complexity and risk assessment determines job description and number of people trained at each level
SummarySummary
IV Systems degrade and stop performing without maintenance due to Physical reasons Management reasons
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Management reasons Predictive M&M is “Before the Fact” control of
exposures Staff for success, but keep looking for the best
value Best to work with Baselined IVS
Hood/Enclosure Failure Hood/Enclosure Failure ModesModes
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Open Faced HoodsOpen Faced HoodsOBJECTIVE: CAPTURE Dust source between
person and hood Protection is general air
movement into hood Low air velocity must pull
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Low air velocity must pull dust into hood
Airflow requirement increases with distance
Welding hoods, simple “elephant trunk” hoods
Key Principle for Open HoodsKey Principle for Open HoodsFlow Rate as Distance from HoodFlow Rate as Distance from Hood
X ti 2 Q ti 4
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X times 2 Q times 4
(move hood away and performance drops)
52nd North Carolina Industrial Ventilation Conference
Module MM-1-1 5
Capture VelocitiesCapture Velocities
Dispersion Conditions
Example Capture Velocity, ft/min
Release with practically no velocity into quiet air
Evaporation from tanks; degreasing, etc.
50 -100
Released at low velocity Spray booths; intermittent 100 - 200
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yinto moderately still air
p y ;container filling; welding; plating; pickling
Active generation into zone of rapid air motion
Spray painting in shallow booths; barrel filling; conveyor loading
200 – 500
Released at high initial velocity into zone of very rapid air motion
Grinding; abrasive blasting; tumbling
500 - 2000
Table 6-1: From American Conference of Governmental Industrial Hygienists (ACGIH®), Industrial Ventilation: A Manual of Recommended Practice for Design, 26th Edition. Copyright 2007. Reprinted with permission.
Capture Velocities Capture Velocities –– factors to factors to decide upper or lower end of rangedecide upper or lower end of range
Lower End of Range Upper End of Range Room air currents minimal
or favorable to capture Disturbing room air
currents
Contaminants of low toxicity or of nuisance
Contaminants of high toxicity
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toxicity or of nuisance value only
toxicity
Intermittent, low production
High production, heavy use
Large hood-large air mass in motion
Small hood-local control only
Table 6-1: From American Conference of Governmental Industrial Hygienists (ACGIH®), Industrial Ventilation: A Manual of Recommended Practice for Design, 26th Edition. Copyright 2007. Reprinted with permission.
Hood Shape and Distance Hood Shape and Distance Determine Required AirflowDetermine Required Airflow
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Fig. 6-11: From American Conference of Governmental Industrial Hygienists (ACGIH®), Industrial Ventilation: A Manual of Recommended Practice, 26th Edition. Copyright 2007. Reprinted with permission."
Hood Calculations Hood Calculations -- Math Math ReviewReview
Continuity Equation: Q = VxA = V1xA1 = V2xA2Q-ft3/min, V-ft/min, A-ft2
Duct Area:
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A = pi x radius2 = pi x (diameter/2)2
A=3.14x(D/2)2x(1 ft/12in)2 = pi x D2/576
Velocity-Velocity Pressure:V = 1096x(VP/df)1/2 = 4005x(VP)1/2 (sea level)or VP = (V/4005)2 (VP-inches water column)
Calculate Hood Face VelocityCalculate Hood Face Velocity
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Hood Face Velocity SolutionHood Face Velocity Solution
Find VductVd = 4005x(1.1)1/2 = 4200 ft/min
Find AductAd = pi x (4)2/576 = 0.087 sq.ft.
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Find AhoodAh = 4”x10”x(1 ft/12”)2 = 0.278 sq.ft.
Calculate VhoodVh = Vd x (Ad/Ah)
= 4200 x (0.087/0.278) = 1315 ft/min
52nd North Carolina Industrial Ventilation Conference
Module MM-1-1 6
Calculate Hood SPCalculate Hood SP
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Included angle = 90o
Calculate Hood SPCalculate Hood SP
1. Find duct VP
2 Find entry loss coefficient for shape
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2. Find entry loss coefficient for shape
3. Find acceleration loss
4. Calculate Hood SP
Hood Entry Losses Hood Entry Losses –– ShapesShapes
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Fig. 9-a: From American Conference of Governmental Industrial Hygienists (ACGIH®), Industrial Ventilation: A Manual of Recommended Practice for Design, 26th Edition. Copyright 2007. Reprinted with permission.
Hood Entry Losses Hood Entry Losses -- TransitionsTransitions
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Fig. 9-a: From American Conference of Governmental Industrial Hygienists (ACGIH®), Industrial Ventilation: A Manual of Recommended Practice for Design, 26th Edition. Copyright 2007. Reprinted with permission.
1. Duct VP = 1.1”w.c. (diagram)2. Entry loss = 0.25 x VP3 Acceleration loss = 1 x VP
Calculate Hood SPCalculate Hood SP
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3. Acceleration loss = 1 x VP4. Hood SP
= acceleration loss + entry loss = 1VP+0.25VP=VP(1+0.25)=1.1x1.25 = 1.4”w.c.
Using Hood Static Pressure (Using Hood Static Pressure (SPSPhh) for ) for MonitoringMonitoring
Every hood has a specific SPh based on its shape and the airflow through it.
SPh values can be found in Industrial Ventilation, A Recommended Practice
MMMM--11--11 3636
A Recommended Practice SPh values can be measured in the field at
startup Local SPh indication (Magnehelic or manometer)
provides operator warning of IVS problems
52nd North Carolina Industrial Ventilation Conference
Module MM-1-1 7
Open EnclosuresOpen Enclosures
OBJECTIVE: CONTAIN Person in front of cabinet, dust
inside cabinet Protection: low velocity inward
i t
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air movement Avoid giving particle escape
velocity from process or manual handling procedure
Bag dumps, super sack dumps, dump cabinets
Uniform Velocity Profile Techniques to Uniform Velocity Profile Techniques to Get Equal Air Path LengthsGet Equal Air Path Lengths
Internal baffle
Bag dump open face enclosure
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Air inlet from top – unequal air paths => poor face velocity profile (arrow length)
Baffle moves air inlet to back wall – equal air path lengths & velocities
Air inlet from back – equal air path lengths also possible – decide based on layout
Uniform Velocity ProfileUniform Velocity ProfileSlotsSlots
Hood opening: 60” x 60”
3 slots, 2”x 36”
Duct diameter 12”
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Duct diameter 12
Rectangular to round duct transition 120 degrees
Sealed EnclosuresSealed Enclosures Contaminant totally surrounded by
enclosure Protection: negative pressure and
inward air movement Low air velocity at access openings
A id l i i
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Avoid enclosure positive pressure -dusting
Examples: belt conveyor housings, bins, Loss In Weight bins
Need air bleed to maintain duct conveying velocity
Air Bleeds Air Bleeds –– Maintain Duct Conveying Maintain Duct Conveying Velocity with Sealed EnclosuresVelocity with Sealed Enclosures
Good Air Bleed Design
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How does air get How does air get into the duct?into the duct?
Biggest Hood & Enclosure FailureBiggest Hood & Enclosure FailureCause: Room Air CurrentsCause: Room Air Currents
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Open windowsPedestal fans
High velocity HVAC diffusers
52nd North Carolina Industrial Ventilation Conference
Module MM-1-1 8
Face Velocity Impact:Face Velocity Impact:Unauthorized ChangesUnauthorized Changes
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Other Hood/Enclosure Failure Other Hood/Enclosure Failure ModesModes
Open hood moved out of position Excessive particle momentum
Face velocity too low to stop high energy particles Process design steps to slow particles
Poor face velocity profile
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Poor face velocity profile Unequal air paths External air currents
Changing hood airflow Physical changes to hood (ie, dust buildup inside, etc.) Connected IVS degrades
No air bleed on sealed enclosure HVAC Supply insufficient
Hood MaintenanceHood Maintenance
Visual Checks React to visible emissions to room Check for hood modifications
First line of defense – monitor air flow
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Install Hood Static Pressure gauges with action limits (+ 20% Baseline)
OR take routine Face Velocity
measurements
Hood Maintenance, cont.Hood Maintenance, cont.
Things that can change airflow: Dirty screens Deposited
contaminants in plenum behind
MMMM--11--11 4646
plenum behind hood opening
Bypassing thru open access doors
Hood face modifications
Duct & Fan Duct & Fan Failure ModesFailure Modes
4747MMMM--11--11
Key Duct Design Key Duct Design PrinciplesPrinciples
Round ducts preferred Smooth duct interior, not spiral wound Adequate conveying velocity - ALL BRANCHES – target +
10% design
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10% design Elbow radius 2.5 R/D mitered or 2.0 R/D smooth is best
to minimize duct fouling Merge two dusty streams at angle appropriate for dust
properties Balance and Baseline systems to prove you got what you
paid for
52nd North Carolina Industrial Ventilation Conference
Module MM-1-1 9
Design Principles Design Principles -- Duct Duct SizingSizing
Size Ducts for Conveying Velocity Range Dust Control Systems: 3500 to 4500 fpm. Aerosol or other small particle Control Systems:
2500 to 3500 fpm.
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(ft/min)duct in ty air veloci V
min)/(ft airflow Q
(inches)diameter duct D
)(ftduct of area sectional-crossA
: where 576/)144/1)(4/(
3
2
22
V
QDDA
Range of Minimum Duct Design Range of Minimum Duct Design Velocities Velocities
Nature of Contaminant
Examples Minimum Design Velocity, fpm
Vapors, gases,
k
All vapors, gases, smoke Any desired velocity (economic optimum
l it ll )
MMMM--11--11 5050
smoke velocity usually)
1000 - 2000 Fumes Welding 2000 – 2500
Very fine light dust
Fine rubber dust, Bakelite molding powder dust, jute lint, cotton dust, shavings (light,) soap dust, leather shavings
3000 – 4000
Table 3-1: From American Conference of Governmental Industrial Hygienists (ACGIH®), Industrial Ventilation: A Manual of Recommended Practice, 25th Edition. Copyright 2004. Reprinted with permission.
Nature of contaminant
Examples Minimum transport velocity, fpm
Average industrial
dust
Grinding dust, buffing lint (dry), wool jute, coffee beans, shoe dust, granite dust, general material handling, brick dust, clay dust, foundry (general,) limestone dust
3500 - 4000
Range of Minimum Duct Design Range of Minimum Duct Design VelocitiesVelocities
MMMM--11--11 5151
limestone dust
Heavy dusts Sawdust (heavy & wet,) metal turnings, foundry tumbling barrels and shake-out, sand blast dust, wood blocks, hog waste, brass turnings, cast iron boring dust, lead dust
4000-4500
Heavy or moist
Lead dusts with small chips, moist cement dust, asbestos chunks from transite pipe cutting machines, buffing lint (sticky,) quick lime dust
> 4500
Table 3-1: From American Conference of Governmental Industrial Hygienists (ACGIH®), Industrial Ventilation: A Manual of Recommended Practice, 25th Edition. Copyright 2004. Reprinted with permission.
Duct Conveying Velocity Changes with Duct Conveying Velocity Changes with Diameter Diameter
Find V & VPQ=VA=VAAA=VBAB, VB=VA(AA/AB)Remember duct area A=Pi D2/4
V =V (D /D )2 = 1000(8/4)2
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VB=VA(DA/DB)2 = 1000(8/4)2
= 4000 fpmV = 4005(VP)1/2, VP=(V/4005)2
VPA = (1000/4005)2 = 0.062” w.c.
VPB = (4000/4005)2 = 0.998” w.c.
Pressure Loss Pressure Loss ––Overcoming Straight Duct FrictionOvercoming Straight Duct Friction
Smaller ducts have greater resistance per length. They create high system pressure
MMMM--11--11 5353
create high system pressure drop on the governing leg of the system.
Maintenance Saver Maintenance Saver ––Long Radius ElbowsLong Radius Elbows
MMMM--11--11 5454
52nd North Carolina Industrial Ventilation Conference
Module MM-1-1 10
Branch Entries:Branch Entries:Merge angle based on contaminant characteristicsMerge angle based on contaminant characteristics
MMMM--11--11 5555
15 degree15 degree30 degree30 degree
Branch Entries:Branch Entries:Do not use TDo not use T--ConnectionConnection
MMMM--11--11 5656
Pressure Loss Pressure Loss –– Branch EntriesBranch Entries
Very sticky
MMMM--11--11 5757
Mildly sticky
Dry, free flow
NO, don’t do this!!!!
Fig. 9-f: From American Conference of Governmental Industrial Hygienists (ACGIH®), Industrial Ventilation: A Manual of Recommended Practice for Design, 26th Edition. Copyright 2007. Reprinted with permission.
Balancing Airflows Balancing Airflows Between BranchesBetween Branches
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1. w/o balancing devices, airflow takes path of least resistance
2. Change in one branch affects entire system balance
Note: 11” S.P. to fan, 7” just to get to bag
house inlet
Which Method to Balance Systems Is Which Method to Balance Systems Is Used at Your Site?Used at Your Site?
Balance by Design Size ducts to restrict flow or
add flow Adds 10-20% more airflow to
system
l b l
MMMM--11--11 5959
Balance by Blast Gate Adjustable (both advantage
and disadvantage)
Balance by Fixed Orifice Pre-calculate orifice size
based on actual duct construction – most accurate balance
At a glance, duct design At a glance, duct design principles met?principles met?
KEY PRINCIPLES1. Size duct for
conveying velocity in all branchesM i t i
1133
44
MMMM--11--11 6060
2. Maintain conveying velocity through merge of two dusty air streams
Good, Bad, & Ugly all in one photo!
22
33
52nd North Carolina Industrial Ventilation Conference
Module MM-1-1 11
Duct MaintenanceDuct Maintenance
Visual Damage-dents, holes? Open duct access doors? Local gauges with action
limitsR ti it i
MMMM--11--11 6161
Routine monitoring Duct network static pressures Strategic airflows
Take Troubleshooting action > + 20% Baseline static pressure
Maintenance Access Maintenance Access
Fittings & elbows should be flanged (or have quick disconnect couplings) at both ends.
For frequently removed section or complex sections -match mark adjoining duct sections for efficient re-assembly
MMMM--11--11 6262
assembly. Provide quick opening access door in large diameter
ductwork (18” dia. and above). Consider permanent platforms for hard to reach duct
section requiring frequent cleanout.
Monitoring Monitoring -- Test Test PortsPorts
Remote sensing of duct static pressure saves climbing ladders
Use single piece of tubing
MMMM--11--11 6363
Use single piece of tubing Need to wait for reading
to equalize Check for plugging if
reading doesn’t change
Courtesy Dwyer Co.
Belts lose or worn?Pulleys aligned?Bearings lubed?Vibration?
Fan Failure Modes Fan Failure Modes -- Fan Fan Drive SystemDrive System
MMMM--11--11 6464
Fan Design PrinciplesFan Design Principles
Match the fan performance curve with the system Oversizing for possible future need may be inefficient operating
point for current need Consequence – major energy costs
For long term reliability
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o o g te e ab ty Heavy duty industrial exhausters Optimal shaft alignment and balance Don’t exceed fan mfr’s maximum shaft speed recco.
Avoid fan performance degradation (system effects) due to poor fan inlet and discharge duct design
Design Operating PointDesign Operating Point
System balance calculations determine fan requirement
Fan Performance TablesFan
Pressure
MMMM--11--11 6666
Fan Performance Tables locate the vendor’s fan that can deliver requirement
SystemSystem
OperatingPoint
Flow
52nd North Carolina Industrial Ventilation Conference
Module MM-1-1 12
Fan LawsFan Laws
•First Law: Airflow
•Second Law: Static Pressure
Q QN
N3 23
2
SP SPN
N3 23
2
2
MMMM--11--11 6767
•Third Law: Power
rough approximation:
N2
PWR PWRN
N3 23
2
3
268.2)(
3
PaSPh
mairflow
kWPWR
Calculation Calculation –– Fan Capable of Fan Capable of Change?Change?
Performance of existing fan 12,546 ACFM @ 8” FSP Fan shaft speed 875 RPM and 23.2 BHP.Increase flow at the system hoods to
MMMM--11--11 6868
Increase flow at the system hoods to 14,000 CFM without changing any of the system duct. The Determine new operating volume, pressure and horsepower if the change is made by only a fan speed increase.
Fan Laws CalculationFan Laws Calculation
1. Calculate new fan shaft speed
2 Calculate new static pressure required
MMMM--11--11 6969
2. Calculate new static pressure required
3. Calculate new brake horsepower
Fan Laws CalculationFan Laws Calculation
Speed change N2=N1(Q2/Q1)=875(14000/12546)=976 RPM
Static pressure change P2=P1(Q2/Q1)2 =8”(14000/12546)2= 9.95”
MMMM--11--11 7070
2 1(Q2/Q1) ( / )
Brake horsepower change HP2=HP1(Q2/Q1)3=23.2(14000/12546)3
=32.2 BHP (versus 25 HP motor) fan motor upgrade to next size, 40 HP MCC & wiring upgrade size 2 size 3
Effect of Fan Speed ChangeEffect of Fan Speed Change
(1.1)2=1.21
(1.1)3=1.33
MMMM--11--11 7171
(1.1)
No Fan System EffectsNo Fan System Effects
No loss stack4 x (D+1”)
Inlet duct- 5D or greater
System effects can add several inches Fan Static Pressure to overcome poor inlet conditions
MMMM--11--11 7272
52nd North Carolina Industrial Ventilation Conference
Module MM-1-1 13
Stack Weather Head Stack Weather Head –– Critical to DispersionCritical to Dispersion
MMMM--11--11 7373
DON’T USE THESE!
Recommended “No Loss” Stackhead – bird’s eye view!
Fan MaintenanceFan Maintenance
Visual Overheated bearings? Unusual noises or vibrations (belts aligned?, impeller
out of balance-erosion/buildup?) Air leaks on flexible connections?
MMMM--11--11 7474
Routine Maintenance Lubricate shaft bearings – fan, motor Check mechanical components (belts, bearings, fan
impellor & housing clean) Check vibration isolators Vibration analysis Motor condition & electrical current draw
Useful Fan ReferencesUseful Fan References
AMCA Publication 201 – Fans & Systems Publication 202 – Troubleshooting Fans
ACGIH
MMMM--11--11 7575
ACGIH Industrial Ventilation, A Manual of Recommended
Practice for Design, 26th edition Industrial Ventilation, A Manual of Recommended
Practice for Operation and Maintenance, 1st edition
Your Fan Manufacturer’s literature
Key Issues for Any CollectorKey Issues for Any Collector
Meeting environmental emission permit requirements contaminant collection efficiency collected contaminant recycle or disposal
Operating the collector within its designOperating the collector within its design
MMMM--11--11 7676
Operating the collector within its design Operating the collector within its design differential pressure (DP) rangedifferential pressure (DP) range DP high DP high –– acts like a damper & reduces airflow in acts like a damper & reduces airflow in
rest of systemrest of system DP low DP low ––
bypassing of collector and DC System?bypassing of collector and DC System? cause higher than desired airflow in DC System?cause higher than desired airflow in DC System?
Types of CollectorsTypes of Collectors
Particulate Collectors (dusts/mists/fumes) Fabric Filters or
Baghouses
Vapor/Gas Collectors Absorbers Gas Scrubbers
Thermal & Catalytic
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Cyclones Particle Scrubbers Electrostatic Precipitators Mist Eliminators
Thermal & Catalytic Oxidizers
Bio Filters
SUMMARY SUMMARY ––RELIABLE IVS PERFORMANCERELIABLE IVS PERFORMANCE
Reliable Hood/Enclosure Exhaust Airflows Interference by room air currents Modifications that degrade performance
Keep duct conveying velocities within range
MMMM--11--11 7878
Keep duct conveying velocities within range Air flow balanced between all branches Design systems with maintenance in mind Fan inlets and exhausts – avoid fan system effects Keep air cleaning device differential pressures within Base
Condition range