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α Chapter-6 Design Concept and Calculation
6-1
Chapter-6 Design Concept and Calculation
α-α α α compressed air system
α.α Compressed Air System α
(storage tank size) gallons α cubic feet α
Electrical cost
α α (α α) (50 hp) air compressor α (8 hours per day α α (5 days a week) α 1kWh ($0.06 per kWh) α efficiency αα%
50 hp x 0.746 x 2080 hours x $0.06 / 0.90 = $5,172.27 per year α 5,172.27 α
Compressor RPMα Motor RPMα Motor Pulley Diameter Compressor Pulley Diameter α
Required Piston Displacement
α
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Compressed Air(ft3)
Free Air(ft3)
Gallons
Up Time
α - α (α α) (50 hp) air compressor 24 CFM (αα)(80 gallon) (receiver) 100 psi α compressor α α compressor α Up Time (minute)
Up Time (minute) 1.51 minutes 100 psi α 150 psi α compressor (α.α )α α α compressed air α )
α.α.α Specific Power Specific power compressor efficiency α electrical input (kW)
Free Air Delivery(FAD) m3 (Free Air Delivery (FAD)) 1 m3/s α (kW)α α α α Compressor α specific power
α (Energy Costs Calculation)
BHP = motor full load horsepower Hours = annual hours of operation HP = 0.746 x kW Electricity rate = electricity cost in $/kWh motor efficiency = motor full load efficiency
α Chapter-6 Design Concept and Calculation
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α.α.α Volumetric Efficiency (%)
α-α Pressureβ Swept Volume Induced Volume
Volumetric efficiency (%) piston displacement α Free Air Delivery(FAD)
α.α.α Compression Ratio
Pa= average atmospheric pressure at your elevation P= line pressure (psig) αα discharge pressure
Compressed air system (required pressure) α (pressure) α tool α α α α Process α α α α α α equipment α α α (leak) α (operation cost) α α α Compressed air system α α α α ) (pressure)
Compression ratios at gauge pressures psig Compression ratio 60 5.05 70 5.76 80 6.44 90 7.12 100 7.80 110 8.48 120 9.16 130 9.84 140 10.52 150 11.20 200 14.50
α α α α α α 7 bar(700kPa) compressed air system (pressure) 500kPa(5bar) αα 600kPa (6bar) α tool α equipment α α α
α
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Systemα α α α (pressure drop)α α α (leak)α α system pressure α
α α tool α process α (pressure) α α α α tool αα equipment compressed air system α α (h α α α α (high pressure) equipment αcompressor α compressed air system (pressure) α α α α α
α-α High pressure Band Low pressure Band
α.α Working Pressure working pressure α pipingα valves α dryers filter α α System α (pressure) α α α α α α equipment α regulator αα valve α working pressure α Demand side α α (system pressure) α α α α (filter)α α α α α α (filter)α α (pressure drop)
α.α Compressed Air System (Sizing)
air compressor (under ) (System pressure) (flow rate) α α α
Compressor α (pressure) α α compressed air system α α (energy conssumption) α% α
air compressor α (size) efficiency α part load α ( ) efficiency
α Chapter-6 Design Concept and Calculation
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Compressed air system (over ) ( ) oversize αα α α
α.α.α α (Air Demand Calculation) Pneumatic Equipment
Paint Spraygun @ 1.5mm flat jet
Paint Spraygun @ 3mm flat jet
Blowgun @ 2mm
Screwdriver
Air Demand 5 SCFM 12 SCFM 8 SCFM 14 SCFM Working Pressure 40 psig 90 psig 90 psig 90 psig
Number 2 1 1 1 Utilization Factor 50% 25% 10% 20%
Effective Air Demand
2 x5 x 0.5=5 SCFM 12 x 0.25 = 3 SCFM
8 x 0.1= 0.8 SCFM
14 x 0.2= 2.8 SCFM
Total Demand: 5 SCFM + 3 SCFM + 0.8 SCFM + 2.8 SCFM = 11.60 SCFM
The following should be added to Total Demand: for leakages +10% = 1.16 SCFM For errors +15% = 1.74 SCFM As a reserve +20% = 2.32 SCFM Total Delivery: = 16.82 SCFM
( ) Operating pressure requirements α ( ) Compressed air requirements ( ) Duty cycle of existing equipment αα new system α α α (average) flow demand αα
α (air flow) 16.82 SCFM (11.6 SCFM + 1.16 SCFM + 1.74 SCFM + 2.32 SCFM) Screw compressor α duty cycle ααα% Compressor α duty cycle
α α screw compressor α (capacity) 110 psig 16.82 SCFM α α (other pressure losses)
α - compressed air α
Equipment A B C
Air demand (FAD) 5 SCFM 3 SCFM 12 SCFM
Working pressure 40 psig 60 psig 90 psig
Quantity 2 1 2
Utilization factor 50% 30% 20%
Free Air Delivery αα α (leakage) αα%
α
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Equipment A B C Air demand (FAD) 5 SCFM 3 SCFM 12 SCFM Working pressure 40 psig 60 psig 90 psig Quantity 2 1 2 Utilization factor 50% 30% 20% Effective air demand 2x 5 x 0.5= 5 SCFM 1x 3 x 0.3= 0.9 SCFM 2 x 12 x 0.2 = 4.8 SCFM
α (Total Demand) = 10.7 SCFM (=5 SCFM + 0.9 SCFM + 4.8 SCFM) 20% = 2.1 SCFM = 12.8 SCFM α 12.8 SCFM 90 psig α compressor
Utilization Factor
Utilization factor α α α (actual consumption) (αα) (
α.α.α α (Air Requirement Calculation)
α (air requirement) α System (tool)α α α process α α (air consumption) system α (air requirement)
Utilization factor α α α α α α α (leak)α compressor α α α α α α
(present air requirement) α α α (air consumption) αα βU Factorβ αα α Hand Book α α (Standard Value) Tool α βU F β αα α α sand blasting grinder α α (α)α α (αα)α α α
α α αα ( α α (compressed air requirement) compressor capacity compressor
α Chapter-6 Design Concept and Calculation
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α (capacity) α (reliability) α (flexibility)
α-α Load profile compressor
α.α.α (Design Sequence) (α) Compressed air α α α α process α α workstation α
Compressed air α βair consumerβ α
(α) Air consumer α (air volume) α
(α) Air consumer (pressure range) α
(α) Air consumer α (air quality) α
(α ) Duty cycle α αα α α compressed air α α α
(α) Branch α main header system α α air consumer αα
(α) α α α (allowable leakage) αα
(α) α α αα (future expansion)α α α αα
(α) layout α (preliminary piping layout) α α (preliminary pressure drop) αα
(αα) Air compressor α (type) α α α (air inlet location)α filtrationα treatment α electrical panel α α
(αα) Piping network α piping layout
α
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α.α Compressor Rating α α Compressor α (performance) α α (α) α (maximium working pressure) (α) α (capacity) (α) α α (power consumption) (α) α (cooling method and requirement) α
αα α α data sheet α ( ) α (sea level) α
(ambient pressure) ( ) (Ambient temperature)
( ) (Humidity) (α) Coolant (temperature) ( ) Compressor α ( ) α α α
α.α.α (Inlet Air Temperature) Compressed air system α
(inlet air temperature) compressor α α α% α compressor α (hot air)α (inlet air) α d compressor α (power consumption)
Effects of Ambient Condition on Compressor Ratings
α-α (ambinent condition) α SCFM
(inlet air temperature) 3Β°C α 4Β°C compressor α α (power consumption) α% α
α Chapter-6 Design Concept and Calculation
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α Temperature Correction Factor α - Chapter-1
α.α.α α (Elevation Correction Factor)
Compressed air system α α
(pressure variation) α α (sea level) α compressor α (sea level) α α (αααα) α α presssure ratio 11.1 ( working pressure α α ) α α Elevation Correction Factor α - -
α.α α (Pressure Regulation) α (pressure regulation) α
α α α Pneumatic cylinder load
volume ( ) α (αα) α (10 cycle per minute) α Compression ratio 5.08 at 4.1 α α (Minimum pressure) 4.1bar α-α production line pneumatic
4.1 bar α α production line α (αα )
(operate )α α (αα α) α (operate)α $0.1/ 4.1 bar α α α α (kWh)
Pressure (bar)
Air (m3/min)
Power (kW)
Energy use (kWh/year)
Lost (kWh/year)
Lost (β¬/year)
4.1 1.64 10.80 40,564 0 0 4.8 1.86 12.30 6,019 5,455 545 5.5 2.08 13.70 1,404 10,840 1,084 6.2 2.30 15.20 6,859 16,295 1,630 6.9 2.52 22.30 62,314 21,750 2,175
α (sea level) α α α α
α
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α α α (7 bar compressed air system) α 2.52 m3 α 22.3 k α 62314 kWh α β¬2,175 α α 21,750 kWh α α α α α
α.α Plant Room Ventilation and Intake Air Compressor α βPlant Roomβ (plant
room) compressor α α α α α α Compressor α α ventilation α (hot air)α ventilation Ventilation α α compressor α α compressor (air cooled) αα compressor (water cooled) compressor α compressor α α
Air cooled compressor α ventilation α α (kW or HP) α α α α α (Heat energy) α Water cooled compressor α ventilation α α α (kW or HP) αα% α
α α compressor α α α α α Compressor α (plant room) (information)α compressor α α
Pv =Quantity of ventilation air (m3/s) Q = heat flow (kW) ΞT=
Ventilation air α duct α α (inlet) α α α α α α α α α α
α-α Compressed air plant Electrical cabinets compressor α (α (1500 mm) α
α Chapter-6 Design Concept and Calculation
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α-α Double independent system
(α-α) double independent system 100% reserve system Compressor α receiver α dryer α compressed air system α α
α (exhaust fan) air intake α Compressor α Compressor α α α exhaust fan α α α air velocity 4 m/s αα
control α α α α control α (outdoor temperature) 7Β°C α α
ventilation α
Option(1) Option(2)
Option(3) Option(4)
α-α Compressed air plant room α α ventlation
α
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α-αα α (exhaust fans) α α α (plant room) α α α
α.α Compressor α (Selection of Compressor Types) α compressor α (selection
of compressor type) compressed air system α compressor α
(α) α α
(α) α α (Noise limitations)
(α) Compressor α (Compressor pressure capability)
(α) Compressor α α α (Maximum flow rate)
(α ) α (Availability, cost, and quality)
(α) α α (Need for oil-free air)
(α) α α α αα α α (Electrical power limitations)
(α) (Initial cost and long-term cost) α
α.α.α Compressor System Compressor α System (Centralization or Decentralization) Compressor αα compressor α α α α 6-7 α (α-α) load profile compressor ( ) Compressed air α α α α (cost of a
production stoppage)
( ) α α (availability of electricity)
( ) α (loading variations) (α) Compressed air system ( ) α (available floor space) α
α Chapter-6 Design Concept and Calculation
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Based Compressor
Base load α compressor βBase Compressorβ α Base load α α α constant load
Trim Compressor Base load α load α
compressor βTrim Compressorβ α
α-αα load compressor α
Computer-based air system management α (flow) (pressure) highest overall efficiency Compressor α multiple compressor system compressor single compressor systems α
α-αα High Pressure Air System
(High Pressure βBooster Compressorβ )
α.α Centralized Compressor Installations Compressor α (plant room) β Systemβ α α Compressor α e
α
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α monitor Filter α cooler auxiliary equipment α αα α α α compressor α β β compressor α sequence efficiency Decentralized Compressors compressor α αα α Control α
α-αα Single Compressor System
α-αα Multiple Compressor System
α-αα Multiple Compressors System with redundant clean air treatment
α Chapter-6 Design Concept and Calculation
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α.α.α Power Source α (Electric Motor)
α α α (sea level)α (αααα) α α 40ΒΊC(104Β°F) α α α α α α α (Combustion Engine) (atmospheric pressure) α α α humidity αα α α α
α-αα Schematic of Plant Air System with Booster
α-αα System Pressure Flow(SCFM)
α - α compressed air system actual demand flow pattern α Flow (pressure) α (inversely related) Point 1
Point 2 (Point 1, system pressure)α (Flow[SCFM]
Point 3 α desired low pressure set points 100 psig α 90 psig
Point 4 Point 4 actual demand flow α α α system pressure
α
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Point 5 (hatched area) (flow) α α
(system pressure) actual demand flow flow α αα α actual demand flow α (system pressure)α storage capacity αα α (receiver tank) (receiver tank) peak demand α
α.α.α Annual Electricity Cost( )
BHP = motor full load horsepower (1 HP = 0.746 kW) Hours = Annual hours of operation( α )
Cost = electricity cost in $ / kWh( ) Motor Efficiency = motor nameplate full load efficiency α α (ααα) (200 HP) compressor motor full load efficiency αα (αααα α α (1 kWh) ($0.05/1 kWh)
Compressor modulation α Compressed air system α ( ) Reciprocating Compressors 1, 2, 3, 4, 5 compressor
Compressor Reference
Measured Capacity CMM (@ 7 kg/ cm2)
'On' Load kW
'Unload' kW
Load Time Min.
Unload Time Min.
Compressor 1 13.17 115.30 42.3 Full time* Nil
Compressor 2 12.32 117.20 51.8 Full time* Nil
Compressor 3 13.14 108.30 43.3 Full time* Nil
Compressor 4 12.75 104.30 29.8 Full time* Nil
Compressor 5 13.65 109.30 39.3 5.88 min. 39.12 min.
* Compressors running in load conditions and not getting unloaded during normal operations. α compressed air system
Compressor 5 α cycle time (α) Compressed air α (generated in m3)
α Chapter-6 Design Concept and Calculation
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Measured Capacity (m3/min) (air volume) capacity (m3/min) α (45 min) α α = 45 (13.17) + 45 (12.32) + 45 (13.14) + 45 (12.75) + 5.88 (13.65) = 2392.36 m3
(α) Power consumption (kWh) Compressor 1 α Compressor 4 unload time α Compressor 5 load time (5.88 min) α = 45/60 (115.3) + 45/60 (117.20) + 45 / 60 (108.3) + 45/60 (104.3) + 5.88/60 (109.30) + (39.12) / 60 ) 39.3 = 370.21 kWh/ 45 Minutes
(α) Compressed air (actual generation capacity - m3) = 45 [ 13.17 + 12.32 + 13.14 + 12.75 + 13.65 ] = 2926.35 m3
(α) Compressed air (consumption rate) = 2392.36 / 45 = 53.16 m3/minute
(α ) Compressed air (consumption rate) (% of capacity = [2392.36 / 2926.35 ]/100 = 81.75%
(α) Specific power consumption Specific power consumption = 370.21 / 2392.36 = 0.155 kW/m3
(α) Unload α α Idle power consumption due to unload operation = 25.62 kWh in every 45 minutes cycle i.e., 34.16 kWh every hour.
(α) Unload α α (loss)α compressor compressor α (A suitable smaller capacity compressor can be planned to replace the compressor with highest unload losses.)
α.α Rule of Thumbs
βRule of Thumbβ α α αα α α α α α Rule of Thumb α α α α ( Rule of Thumb α
(α) Air compressor α (discharge pressure) 4 CFM αα 5 CFM α (1HP)
(α) Compressed air system α 1000 CFM α (αα ) α (αα) α (maintenance cost)
(α) (pressure) 2 efficiency α α (emergy consumption) α α α
α
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(α) 4 CFM α 5 CFM 100 psig α α α α α $750 α ( (kWh) (αα) (10 cent/kWh)
(α ) α (α α) (50 HP) compressor α 126,000 Btu α α (Heat rejection α )
(α) (ααα) (100ΒΊF) saturated compressed air α(water vavpor content)α 100 CFM compressor α α α α α (6 gallons per day)
(α) α compressor α compressed air (water-cooled after cooler ) 100 CFM α (3 GPM per 100 CFM)
(α) Saturated compressed air α 20ΒΊF compressed air α α (water vapor content) α α% α α α α α
(α) compressed air α α α α
(αα) Compressed air system compoment α ( α ) α (pressure drop) 15 psi αα 15 psi α
(αα) (storage tank) demand profile System α (storage tank) α (storage tank) system α (Performance) ( )
α.αα Air Demand Analysis (ADA) Point 1 compressor α α (capacity) Total
capacity αα total air available from
Point 2 peak production demand (available capacity) αα
Point 3 Leaks α artificial demand other non-productive factor α air consumption α non productive load α
α Chapter-6 Design Concept and Calculation
6-19
α.αα Air Demand Analysis (ADA)
α.αα Compressed Air System Reference Code α Compressed air system α α
α α α α α Code α α α ANSI/ISA S7.0.01 Quality Standards for Instrument Air API 617 Centrifugal Compressors for Petroleum, Chemical and Gas Industry Services API 618 Reciprocating Compressors for Petroleum, Chemical and Gas Industry Services API 619 Rotary-Type Positive Displacement Compressors for Petroleum, Chemical and Gas Industry Services API 672 Packaged, Integrally Geared Compressors for Petroleum, Chemical and Gas Industry Services ASME ASME Boiler and Pressure Vessel Code, Section VIII, Div.1 ASME/ANSI B16.5 Steel Pipe Flanges and Flanged Fittings ASME/ANSI B31.1 Power Piping ASME/ANSI B31.3 Chemical Plant and Petroleum Refinery Piping ANSI/CAGI B19.1, Safety Standard for Air Compressor Systems CAGI B186.1 Safety Code for Portable Air Tools ISO 11148 Series
α
6-20
Safety related regulations and standards EN 1012-1 Compressors and vacuum pumps β Safety demands EN 1012-2 Compressors and vacuum pumps β Safety demands Pressure safety EN 764 Pressure equipment β Terminology and symbols - Pressure, temperature. EN 286-1 Simple unfired pressure vessels designed to contain air or nitrogen β Part 1: Design, manufacture and testing EN 286-2 Simple unfired pressure vessels designated to contain air or nitrogen EN 286-3 Simple unfired pressure vessels designed to contain air or nitrogen EN 286-4 Simple unfired pressure vessels designed to contain air or nitrogen ISO 3857-1 Compressors, pneumatic tools and machines - Vocabulary - Part 1: General ISO 3857-2 Compressors, pneumatic tools and machines - Vocabulary - Part 2: Compressors ISO 5390 Compressors - Classification ISO 5941 Compressors, tools and machines SS-ISO 1217 Compressed air technology β displacement compressors β delivery tests ISO 5389 Turbo-compressors β Performance test code ISO 7183-1 Compressed air dryers - ISO 7183-1 Compressed air dryers - Part 2: Performance ratings ISO 8010 Compressors for the process industry - Screw and related types ISO 8011 Compressors for the process industry - Turbo types
-End-
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