Designing Efficient Blower

Designing Efficient Blower
Packages and Systems Customers today are inundated by manufacturers who claim top quality products. However, customers also know that these claims are often untrue. Kaeser prides itself in giving great customer service and education: Through education, Kaeser can outpace all of the competition in customer service. Through education we empower more people to answers more questions, faster! Through education we give correct answers! Through education we make fewer mistakes which means it costs us less money to do business With this presentation we will discuss what efficiency means and how to improve the performance of a system and in turn increase the system efficiency.

Designing Efficient Blower Packages and Systems
Design the blower package and controls for maximum efficiency Life cycle costs consider all associated expenses for the entire life of a system Initial costs including purchase price, installation and startup Electrical energy for the life of the system Maintenance costs including parts, labor and rebuild charges Potential savings from: Blower efficiency Package design efficiencies In a diffused aeration plant, 75% of the electrical cost is to power the blowers. When all factors are considered (first cost, maintenance cost, and electrical cost), more than 90% of the life cycle cost is the electrical cost. Designing the blower package and system controls for maximum efficiency results in the lowest life cycle cost even if the first cost for the equipment is higher. This presentation discusses considerations to minimize the embodied energy of the installation. We will take a look at all of the factors that encompass the Life Cycle Costs of an entire system. Some salesman might focus on just the blower or maybe the efficiency of the motor and blower. We will look at these and also look at efficiency of the silencers, Enclosure design and cooling, and components that can effect pressure drop in the entire system.

Blower system design considerations: Motor efficiencies Blower design Blower lubrication Drive system efficiency Filter and silencer pressure drop Enclosure design and air flow Accessories Controls for multiple systems When looking at efficiency of the system there are several components that stand out that we should look at. Motor efficiency can effect a huge savings over the life of the blower. Saving one or two percent will add up to thousands of dollars. Blower design and efficiency. Every turn of the blower delivers a specific amount of air. The higher percentage of the air that is actually sent down the pipe will increase efficiency. We will discuss how to Maximize the blowers efficiency. The drive system can effect total energy costs by how much of the input energy is actually delivered to the blower. Having losses in the drive will effect the total cost over the systems life time. Filters, Silencers, And Accessories can have friction losses and thus cause pressure drops which effect how much air is sent down the pipe. We should consider these components carefully to make sure we have the best delivery possible with the smallest amout of wasted energy. Proper ventilation of the enclosure can effect the conditions at the inlet of the blower. Too high of an inlet temperature will reduce the inlet flow and performance.

Over an operating period of 40,000 hours, energy will have accounted for approximately 90% of the life cycle costs Electrical energy Potential savings Initial investment Maintenance costs In a diffused aeration plant, 75% of the electrical cost is to power the blowers. When all factors are considered (first cost, maintenance cost, and electrical cost), more than 90% of the life cycle cost is the electrical cost. Designing the blower package and system controls for maximum efficiency results in the lowest life cycle cost even if the first cost for the equipment is higher. This presentation discusses considerations to minimize the embodied energy of the installation. As indicated we will look at costs associated with Initial Costs, Energy consumption, Maintenance and other factors that can be reduced to lower the total Life Cycle Costs. - Blower package efficiency - Maintenance expenses - Motor/transmission losses - Installation costs

When evaluating blower systems the specific power of the entire package must be considered, not just the blower input shaft horsepower. ISO standard 1217: manufacturer agreed upon performance tolerances at specific conditions Verify that competitors adhere to the world standard ISO 1217 ISO 1217, Part 1, Annex C - Tolerances Volume (flow) at °F and maximum pressure [ft³/min] Air flow [ft³/min] Allowable manufacturing variance +/- 5 % +/- 6 % > 525 +/- 4 % This International Standard specifies methods for acceptance tests regarding volume rate of flow and power requirements of displacement compressors. This International Standard specifies the operating and testing conditions which apply when a full performance test is specified. For compressors manufactured in batches or in continuous production quantities and supplied against specified data, the tests described in Annexes B, C and D are considered equivalent alternatives. Detailed instructions are given for a full performance test, including the measurement of volume flow rate and power requirement, the correction of measured values to specified conditions and means of comparing the corrected values with the guarantee conditions. This International Standard specifies methods for determining the value of the tolerances to be applied to the measurement of flow, power and specific power. NOTE The tolerances to be applied to the measurement of flow, power, specific power, etc. for all acceptance tests carried out in accordance with this International Standard are agreed on by the manufacturer and the purchaser at the contractual stage or prior to the execution of the tests. *Free air delivery for complete package in accordance with ISO 1217, Appendix C, at 20°C ambient temperature and maximum pressure.

Blower efficiency questions you might be asked?
What is the difference between an energy efficient and premium efficient motor? What effect does the blower design, speed and drive system have on efficiency? What is the designed pressure drop through the filters and silencers? How does the enclosure and accessories effect overall efficiency? What are the most efficient methods to control a system with multiple blowers? These are a few of the questions you might encounter when it comes to Efficiency. We will discuss each of these questions and determine how to sell Kaesers features to overcome these questions.

Drive Motor Considerations
Minimizing blower motor life cycle cost: Use premium efficiency motors Use inverter ready motors for variable frequency drive (VFD) applications Use isolated motor bearings or shaft grounding for VFD applications (large motors) Properly lubricate the motor bearings Incorporate thermistors to protect the windings from running too hot The use of a premium Efficient motor will reduce your total Life cycle costs. If the blower only runs a few hours a day it will take a long time to over come the added cost but for a system that runs 24/7 then it the added cost will be overcome rather quickly. Thermistors embedded into the windings will Monitor winding temperature and if connected will protect the motor from over temperature of the windings and motor. When it comes to a motor that will be operated by a VFD drive you need to lok at shaft grounding to prevent Electro Discharge Machining. This seems to be a bigger problem in motors over 100hp. Using a premium Efficient motor will increase the efficiency of your motor and thus reduce the amount of energy needed to drive the motor. It is the same as a car that has a more efficient engine will use less gas to do the same work. A premium efficient motor will drive the motor using less input power. If we have winding thermistors they can be connected to your control panel and in the event they see a high temperature they will trigger your panel to shut down the motor. This will protect the motor from over temperature and damage to the windings.

Nominal Full Load Efficiency
Drive Motor Efficiencies NEMA full load efficiency comparison for 60 Hz electric motors rated 600 volts or less (random wound) Nominal Full Load Efficiency Horsepower 5 7.5 10 15 20 25 30 TEFC 3,600 rpm (2 pole) Energy Efficient 87.5 89.5 91.0 92.4 Premium Efficient 91.7 93.0 93.6 40 50 75 100 150 200 300 94.1 94.5 95.0 95.4 95.8 96.2 The values are average full load efficiency This is a chart that indicates the differences in efficiency between standard motors, Energy Efficient and Premium Efficient motors. This is just a sampling of motors at a certain horse power and motor speed. Use these numbers as a general guideline to indicate what the difference in efficiency might be. To find the efficiency of a specific motor you can refer to the name plate and/or the motor manufacturer. Source: Baldor “The Energy Independence and Security Act of 2007”

Calculating a Motors Input Power (kW)
Input power equals the required output power divided by the motors efficiency Equation for calculating a motors input power: bhp x kW / hp ηmotor Where: bhp = full load brake horsepower ηmotor = motors full load efficiency kWin = Powerin = kWin This slide shows you the formula for calculating a motor’s input power. As the formula shows, kW input equals the brake horsepower (bhp) x kW / hp. (Note: This is just a mathematical way of saying that is equal to 1 kW per input horsepower) The number you get by multiplying those 2 numbers together is divided by the motor’s full load efficiency. That funny looking “n” symbol is once again just a mathematical way of expressing motor efficiency. This number will be stamped on the nameplate of the motor. Simply put, this formula is used to determine how much input power (kW) is required to operate the motor at full load. Does all of this make sense so far? If you have any questions, now is the time to ask before we move. Let’s try doing a calculation to put it all together. Powerout = bhp

Calculating a Motors Input Power (kW)
Example: Compare the required input power (kW) for 50 hp energy efficient and premium efficient motors operating at full load Energy efficient motor: Premium efficient motor We just plug the numbers in to the equation to get the answer. However, it is often not easy to get the bhp (brake horsepower). It’s easy to get the nameplate (rated) horsepower and usually the motor efficiency is also right there on the nameplate. But, how do you know if the manufacturer is actually using some of the motor’s service factor when the compressor is running at it’s rated full-load capacity? Simple, look at the engineering data sheet. If you don’t have the engineering data sheet, you may need to make an educated guess. Motor manufacturer’s typically are allowed a +/- 5% tolerance. So, a responsible manufacturer would not typically exceed the motor’s nameplate power by more than 5% LESS than the motor’s service factor. The first step is to calculate the bhp so you know exactly what is being felt on the shaft of the motor. To get this number simply multiply the nominal horsepower of the motor that is stamped on the nameplate by the estimated percentage of the available service factor being used. Bhp = 60 hp X 1.10 = 66 bhp After we get the bhp it’s simple, just plug the numbers into the equation. There are only 2 numbers we have to plug in at this point…the bhp and the motors efficiency. So the calculation should look like what we see here on the slide. We are looking for our answer to be in kW so we have to make sure the hp units cancel out. We see that they do so our formula looks like this… hp x kW / hp ηmotor kWin = (50 hp) x (0.746 kW / hp) .93 = = 40 kW (50 hp) x (0.746 kW / hp) .945 = = 39.5 kW bhp x kW / hp ηmotor kWin = = (66 hp) x (0.746 kW / hp) .92 / = 53 kW

Calculating a Motors Electrical Costs
We just plug the numbers in to the equation to get the answer. However, it is often not easy to get the bhp (brake horsepower). It’s easy to get the nameplate (rated) horsepower and usually the motor efficiency is also right there on the nameplate. But, how do you know if the manufacturer is actually using some of the motor’s service factor when the compressor is running at it’s rated full-load capacity? Simple, look at the engineering data sheet. If you don’t have the engineering data sheet, you may need to make an educated guess. Motor manufacturer’s typically are allowed a +/- 5% tolerance. So, a responsible manufacturer would not typically exceed the motor’s nameplate power by more than 5% LESS than the motor’s service factor. The first step is to calculate the bhp so you know exactly what is being felt on the shaft of the motor. To get this number simply multiply the nominal horsepower of the motor that is stamped on the nameplate by the estimated percentage of the available service factor being used. Bhp = 60 hp X 1.10 = 66 bhp After we get the bhp it’s simple, just plug the numbers into the equation. There are only 2 numbers we have to plug in at this point…the bhp and the motors efficiency. So the calculation should look like what we see here on the slide. We are looking for our answer to be in kW so we have to make sure the hp units cancel out. We see that they do so our formula looks like this… Comparing the annual power cost of efficient and premium efficient motors Annual power cost = (kW) (hours) (Cost per kwh) Energy efficient motor: Annual power cost = (40 kW) (8,000 Hrs) ($0.12 /kWh) Annual power cost = $38,400.00 Premium efficient motor Annual power cost = (39.5 kW) (8,000 Hrs) ($0.12 /kWh) Annual power cost = $37,920.00 bhp x kW / hp ηmotor kWin = = (66 hp) x (0.746 kW / hp) .92 / = 53 kW

Calculate Payback on Initial Cost Difference
We just plug the numbers in to the equation to get the answer. However, it is often not easy to get the bhp (brake horsepower). It’s easy to get the nameplate (rated) horsepower and usually the motor efficiency is also right there on the nameplate. But, how do you know if the manufacturer is actually using some of the motor’s service factor when the compressor is running at it’s rated full-load capacity? Simple, look at the engineering data sheet. If you don’t have the engineering data sheet, you may need to make an educated guess. Motor manufacturer’s typically are allowed a +/- 5% tolerance. So, a responsible manufacturer would not typically exceed the motor’s nameplate power by more than 5% LESS than the motor’s service factor. The first step is to calculate the bhp so you know exactly what is being felt on the shaft of the motor. To get this number simply multiply the nominal horsepower of the motor that is stamped on the nameplate by the estimated percentage of the available service factor being used. Bhp = 60 hp X 1.10 = 66 bhp After we get the bhp it’s simple, just plug the numbers into the equation. There are only 2 numbers we have to plug in at this point…the bhp and the motors efficiency. So the calculation should look like what we see here on the slide. We are looking for our answer to be in kW so we have to make sure the hp units cancel out. We see that they do so our formula looks like this… Energy efficient motor 50 hp list price: $4,268.00* Premium efficient motor 50 hp list price: $4,842.00* Cost difference: $4, $4, = $574.00 Annual power cost difference: = $38,400 - $37,920 = $480.00 Power cost savings per month: = $ ÷ 12 = $40.00 /month Payback period = Initial cost difference Power cost savings /month Payback period = $ = months $40.00 * Online price - 1/05/2010 bhp x kW / hp ηmotor kWin = = (66 hp) x (0.746 kW / hp) .92 / = 53 kW

Calculating a Motor’s Electrical Costs
Motors operate most efficiently at or near full load A small motor operating at or near full load will likely be more efficient than a motor operating a 35% load As you can see from this diagram as you increase the load on a motor the efficiency of the motor increases. Why is this? Well think about a car and modern technology. Some of the new cars and trucks have a method of only running on fewer cylinders at lower power demands. Why would they do this? Instead why not just supplying less fuel to the big 8 cylinder engine to do the required work. Well as it turns out a large engine operating at less than maximum power will be less efficient. So what do they do? They reduce the number of cylinders that are supplied with fuel and in essence make the engine smaller and a smaller engine will be more efficient that a large V-8 with reduce demand. The same goes for an electric motor. As you can see on this chart as the load is increased on a motor the efficiency will increase to a point. At that point we go beyond the maximum efficiency point and the motor efficiency starts to fall off a bit. If you are riding a bicycle you shift the gears to reach a comfortable peddling speed. As you come to a hill if you do not shift down you will start to work harder and eventually your efficiency will fall off and you might not be able to make it over the top. But on the other hand if you shifted down and stayed in your sweet spot you will of course slow down but you will be able to maintain efficiency in peddling and make it over the top.

Variable speed applications for drive motor Motor should be inverter ready to reduce the possibility of insulation failure Larger variable speed motors need to be protected from electrical discharge machining (EDM) Shaft grounding systems will help prevent EDM (eddy) currents Kaeser recommends shaft grounding for motors larger than 100 hp (4 pole) and 125 hp (2 pole) The protection provided to the motor offsets the additional expense associated with a bearing failure When motors are used in variable speed applications the should be inverter ready to reduce the possibility of insulation failure due to overcharging. Another phenomenon that occurs with all motors driven through a variable frequency drive is electric discharge machining. The use of isolated motor bearings or shaft grounding mitigates this problem. The value of the motor offsets the additional cost in larger sizes. We recommend motor bearing isolation in motors larger than 100 hp (4-pole) and 125 hp (2-pole).

Proper motor maintenance is essential to long life Use the recommended lubricant (brand of grease) Correct quantity of grease Grease at proper interval (roller bearings require greasing twice as often as ball bearings) Lubricate bearings while rotating motor Refer to motor name plate for greasing information Kaeser Com-paK Plus™ motors should be greased according to TI bulletin - No USA Proper greasing of a motor will increase the life span of a motor. Just as with your car you need to use the proper lubricant. You would not put general purpose oil in your finely tuned race car engine. Neither would you put gasoline engine oil into a diesel engine. They have different needs and requirements for engine oil. Well an electric motor is the same. We need to use the proper type of grease per the manufacturers specification. The name plate will indicate the proper brand of grease, the correct amount of grease and the correct greasing interval. Pay attention to these specifications and you will get maximum life from your motor.

Efficient Blower Selection
Blower design and selection criteria Rotary-lobe blowers are a non- contacting design No sealing strips No liquid sealing Leakage (slip) occurs between rotor and block At a given pressure, slip is constant With constant pressure, as blower speed is increased volumetric efficiency increases The rotary-lobe blowers is a non-contacting design. There are no sealing strips or liquid injection so there is internal leakage. At a given pressure, the leakage is constant. The throughput can be adjusted by changing the speed. As the blower speed is increased, the effect of internal slip is minimized and the volumetric efficiency increases.

The “leak area” clearances in all blowers are about the same Manufacturing tolerances are the difference between blowers Leak area includes the clearances all the way around the rotor Rotor tip to block Rotor to rotor Rotor end to block The leak area (or slip) includes all the clearances around a rotor. Of course the rotor tip to block will have a clearance and thus slip. Also the ends of the rotor between the rotor and the housing will have clearances and some slip. The other area that we sometimes forget is the clearances between the rotors. This area between the rotors has a certain clearance and will allow for some slip. Leak area around rotors

Slip speed for a 2” gear, short impeller blower may be 400 rpm compared to an 8” gear, long impeller blower might be 60 rpm The efficiency of a blower increases as rpm increases For example: A Kaeser 21P blower operating at 3,000 rpm and 5psi = 70 scfm Efficiency = 77% * A Kaeser 21P blower operating at 6,000 rpm and 5 psi = 162 scfm Efficiency = 88% * Typically blowers must turn at higher speeds to achieve good volumetric efficiencies The rotary-lobe blowers is a non-contacting design. There are no sealing strips or liquid injection so there is internal leakage. At a given pressure, the leakage is constant. The throughput can be adjusted by changing the speed. As the blower speed is increased, the effect of internal slip is minimized and the volumetric efficiency increases. The clearances in all blowers are about the same. The ratio of leak area to displacement is closer in a small blower than in a large blower. For example, the slip speed in a 2” gear, short impeller blower may be 400 RPM where the slip speed of a large 8” gear blower with a long impeller may be less than 60 RPM. What this means is that small blowers must turn at higher speeds to achieve good volumetric efficiencies. This is a hard concept to understand. It seems as you speed up the blower the slip would either increase or possibly become less. The rotors are spinning faster so the slip should change. Think about it this way. The clearances between the rotor and housing is a fixed dimension. Do we all agree on that? This fixed dimension can be thought of as being a fixed leak and does not change. Think about a pipe with a hole in it or fixed orifice. At a constant pressure the amount of air the escaping is constant and does not change regardless of how much air passes through the pipe. Do we agree with that? Well then think about the blower as a fixed hole (orifice) in a pipe. At a constant pressure only so much air will escape (slip) past the rotors. The fact that the rotor is turning does not effect the size of the fixed orifice so the amount of air that escapes will be constant as long as pressure remains constant. Of course if you increase pressure the amount of air that escapes will increase. If we agree with this concept then we can understand that as a blower speed increases the volume of air delivered will increase but the slip will remain the same. This means the percentage of air delivered compared to the slip will increase thus the blower is more efficient. Lets try an example a blower operating a 10 psi and 100 cfm might slip 10 cfm this make the efficiency at 90% If you speed up the blower to operate at 10 psi and 200 cfm the slip is still 10 cfm. Efficiency will rise to 95% Any questions? * Taken from Kaeser Omega selection program

Selecting smaller blowers will: Minimize components (motors, bases, silencers, etc.) Reduce initial cost and operating costs Are less expensive to replace Lower replacement costs will reduce the life cycle cost Larger packages increase capital expense, power requirements and maintenance costs When we select smaller blowers to do the same job we find that the other components that compliment the package can be smaller also. This means less cost and a lower Life Cycle cost.

Well maintained “process quality” blowers can have run time of 200,000 hours between repairs Low-quality blowers often have design service lives of only 30,000 hours Features to look for in a high value (process quality) blower: Roller bearing construction Large shaft diameters Heavy-duty rotor shaft seals Casing wear rings Shaft protection sleeves Oil lubrication There are several different blowers out there and among these different blowers there is a difference in quality. Some blowers are made as a throw away blower or a lower quality which comes with a lower price tag. What we refer to as a Process quality blower is a blower that is made to a high standard and can be used in a critical process where it is essential that the blower operate properly. We have listed a few of the differences between a standard blower and a process quality blower.

Advantages of oil lubricated bearings over grease lubricated bearings: Reduced friction Cooler running bearings Oil flushes contaminants out of bearing races Contaminants are flushed from blower sump Site glass for easy oil level checks Allows for visual inspection of lubricant condition Lets look at lubrication for the blower bearings. Some of the advantages of having an oil sump to lubricate the bearings are listed. Blower Lubrication Oil lubricated blowers always last longer than grease lubricated blowers. Synthetic lubricants reduce friction and have longer run-times than petroleum lubricants reducing the maintenance cost. The first is oil will provide the proper lubrication to the bearing constantly. And the proper oil will reduce friction in the bearings which in turn reduces power requirements and also heat. Which brings us to the next point cooler running bearings. The oil will carry away the heat from the bearings and the bearings will run cooler. Oil constantly flushes contaminates from the bearings and when changed removes them from the oil sump. My question is why is this better than having greased bearings? Or why is an oil sump better since the motor has greased bearings? In a blower there is air, moisture and contaminates passing through the blower. These contaminates are contained as best as possible but they can still migrate into the bearing area. By changing the oil we can remove the contaminates and put in fresh oil. If you had greased bearings you are simply putting in more grease and not removing the old stuff. In a motor we have greased bearings because they are contained within the motor and do not come in contact with as much moisture and contaminates. So grease in a motor bearing is just fine but in a blower which is a much dirtier condition oil is the best lubrication option.

Blower Drive System Most rotary-lobe blowers are V-belt driven Belt drives should be selected with at least a 1.50 service factor The most common drive system uses a motor slide base This requires the blower be tagged out of service to check the belt tension Labor and maintenance costs are increased The drive system of a blower can effect overall efficiency. The type of system can effect simple maintenance check and the amount of time it takes to perform these tasks. Typically blower packages use a slide base belt tensioning system. How do you check the tension with this type of system? You have to shut down the blower to be able to properly tension the belts. Then you have to have the proper tool to measure tension. I think what happens in most cases is the belts are check by pressing with your thumb. But how do you know if the belts are tight enough and probably how do you know if they are too tight. Too tight puts undo stress on the belts but also on the motor and blower bearings.

Blower Drive System Dynamic belt tensioning systems
Motor swing frame designs utilize the weight of the motor to tension the belts Adjustable spring tensioner allows the belt tension to be tuned for the specific motor and drive Spring tension prevents motor bounce on startup Proper belt tension reduces drive losses and increases belt life Blower package designs which utilize swing frames with an adjustable spring and a belt guard can be checked and adjusted without shutting down the blower package reducing the maintenance cost. The belts are always at the proper tension to provide the highest efficiency and longest belt life.

Blower Package Design Considerations
Wire-to-air analysis should incorporate all system components Consider air friction losses through the entire blower package: Filter Silencer Blower Check valve Added components Enclosure design and cooling The efficiency of the blower is important but it is equally important that the blower package is designed to minimize air friction losses and designed for easy maintenance. The scope of supply for the blower package may be different for each manufacturer so it is important to make sure that all of the system components are included in the wire-to-air analysis. Inlet air filter: The inlet air filter is needed to protect the blower from contaminants as well as downstream components.

Rotary-lobe blowers are impervious to small volumes of particulates An inlet air filter is needed to protect the blower from larger contaminants Fine filters are not required Initial pressure loss should be less than 1 inch of water column Maximum differential is 17 inches of water column or 0.62 psi Using a low cost element and changing it frequently minimizes operating cost Inlet air filter: The inlet air filter is needed to protect the blower from contaminants as well as downstream components. Rotary-Lobe blowers are impervious to reasonable volumes of particulates (smaller than the clearances in the blower) so filters with very high retention characteristics are not required. The initial pressure loss across the media should be less than 1 inch of water and the recommended maximum differential is 0.62 PSI. Using a low cost element and changing it frequently minimizes the operating cost of the package. Some manufacturers of pleated elements recommend more than 1-2 psi dP across the filter. This added pressure drop will decrease the efficiency of the package. The filter housing and associated pipe fittings have pressure losses so designs which incorporate the inlet filter inside of the inlet silencer result in lower inlet losses.

Inlet and discharge silencers: Consider the coefficient of friction of a silencer Chambered type silencer is 4.2 Absorptive silencer is 0.8 The silencers should be connected directly to the blower to minimize inlet losses Some designs have an expansion joint and fittings between the blower and silencer Added piping connections increases turbulence and pressure loss Inlet and Discharge Silencers: Absorptive silencers have a lower pressure loss than chambered or combination type silencers. The coefficient of friction of a chambered type silencer is 4.2 where the coefficient of friction of an absorptive silencer is only 0.8. The silencers should be designed to connect directly to the blower to minimize inlet losses. Some silencer (and blower) designs require an expansion joint between the silencer and the blower inlet and discharge ports.

Typical Discharge Silencer Losses
Blower Package Design Considerations Typical Discharge Silencer Losses This chart indicates the typical pressure losses through a silencer. As you can see there is a big difference between the typical silencer and the silencer we utliize on Kaesers Com-paK Plus packages.

Blower Enclosure Design Considerations
Silencers are effective in controlling pulsation noise A full enclosure will control all sources of noise: Blower mechanical noises (gears and bearings) Motor mechanical noises (fan and bearings) Blower discharge pulsations Inrush air noises Enclosure cooling fans Relief valve blow-off Piped oil drains with valves reduce maintenance time and help to prevent spills. Sound Enclosures Silencers are effective for controlling the pulsation noise from blowers but full enclosures control all of the sources of noise: Blower discharge pulsations Inrush air noises Blower mechanical noises (gears and bearings) Motor mechanical noises (motor fan and bearings) Enclosure cooling fans Relief valve blow-off

Blower Enclosure Cooling
A fan removes the heat inside the enclosure Either mounted on the blower shaft or a separate unit A blower shaft mounted fan will speed up and slow down with a VFD The fan must be sized for the slowest VFD operating speed As the blower speed increases the fan moves more air and wastes energy Separately driven fans are properly sized and always move the correct amount of air Enclosures require ventilation. If the package design uses a fan mounted to the blower shaft make sure the fan is sized for the actual blower speed and motor heat load. In variable speed applications, the fan must be sized for the lowest frequency. This means that at all other conditions of service, the fan is wasting energy. Separately driven fans always operate at the design speed so there is adequate ventilation at all conditions of service without over-producing.

Positive Displacement (PD) blowers have a fixed amount of slip at a given pressure With less through-put air to remove this heat, the blower and enclosure will become hotter For this reason, the fan must be sized to provide the required cooling at the blowers slowest speed Enclosures require ventilation. If the package design uses a fan mounted to the blower shaft make sure the fan is sized for the actual blower speed and motor heat load. In variable speed applications, the fan must be sized for the lowest frequency. This means that at all other conditions of service, the fan is wasting energy. Separately driven fans always operate at the design speed so there is adequate ventilation at all conditions of service without over-producing. In this chart you can see that as the speed of the blower is increased with constant pressure the discharge temperature become lower. Hopefully we have explained this enough so you understand why this is. In our previous example we had a blower with 100 cfm and 10 cfm slip so we had 90 cfm to remove the heat. In the second we had a blower with 200 cfm and 10 cfm from slip so we have 190 cfm to carry away the heat. Granted turning faster we will create more heat in the bearings and drive but this is a small increase and the added air will far out weigh the added heat.

Separate enclosure fans should run for 15 minutes after the blower package is turned off to remove latent heat from inside the enclosure The drive motor insulation, lubricant, seals, and belts will last longer reducing maintenance costs Separately driven enclosure ventilating fans should be wired to allow the fan to run for 15 minutes after the blower package is turned off. In this way, latent heat is removed from inside the enclosure. The result of the additional ventilation is that the motor insulation, lubricants, seals, and belts last longer reducing maintenance costs.

Incorporate separate intakes for cooling air and process air Process air taken from inside the enclosure will be preheated Preheating process air will reduce blower efficiency Rule of Thumb: An increase of 10°F results in ~2.% less mass flow 100 icfm at 68°F would require icfm at 78°F The sound attenuating enclosure ventilating air and the process air must be separate circuits. If the process air is heated by radiation from the blower, motor and belt drive, the wire to air efficiency is reduced. An increase of 7° Kelvin results in 2.5% less mass flow. FYI 310° Kelvin = 99° F 317° Kelvin = 110° F

Com-paK Plus™ units can be installed side-by-side reducing infrastructure and piping expenses The sound attenuating enclosure ventilating air and the process air must be separate circuits. If the process air is heated by radiation from the blower, motor and belt drive, the wire to air efficiency is reduced. An increase of 7° Kelvin results in 2.5% less mass flow. FYI 310° Kelvin = 99° F 317° Kelvin = 110° F

Blower Discharge Check Valves
All blowers should have a discharge check valve Check valves have pressure drops Consider this pressure drop when evaluating check valves Two types of check valves are used: Center pivot Swing gate Generally, full-bore (swing) check valves will have a lower pressure drop Swing check Discharge Check Valve All blowers should have a discharge check valve. This helps to prevent reverse flow and/or siphoning when the system is turned-off. There are different types of valves available and all of them have pressure losses. Consider the coefficient of friction and the design flow when evaluating check valves. Generally, full-bore check valves will have a lower pressure loss. Another consideration is the check valve design. In a center hinge design, the valve elements can be conveyed downstream and possibly damage components. Swing check valves utilize fully-retained elements within the body and will not be conveyed down stream where they could damage components. These reduce the potential for damage to downstream components. Center pivot

Blower Package Summary
Specify premium efficient motors Blower design and tolerances effect blower efficiencies Blower efficiency will increase with higher speeds (constant pressure) Proper belt tension will increase belt life and reduce slip Blowers do not require high quality filters Silencer design will effect pressure drop in a blower system Enclosures should have separate cooling and process air intakes Choose blower accessories for minimum pressure drop Conservative system design provides for redundancy in the system. In large systems and systems with varying capacity, it is common to use multiplex blowers on a common header. In constant pressure systems it is common to use variable speed drives to match the blower capacity to the system demand.

Large Blower Systems Conservative system design provides for redundancy in large systems Large or varying demand systems commonly use multiple blowers Constant pressure systems commonly use variable speed drives to match flow to demand Control strategies can have a major effect on power costs An efficient control system will reduce life cycle costs Conservative system design provides for redundancy in the system. In large systems and systems with varying capacity, it is common to use multiplex blowers on a common header. In constant pressure systems it is common to use variable speed drives to match the blower capacity to the system demand.

Large Blower Systems Multiple units with VFD’s could create a situation where all units are operating at less than 60 Hz At frequencies < 60 Hz efficiencies will be reduced including the: Frequency drive Motor efficiency Blower and drive efficiency All too often, we find blower rooms with four identical blowers with four identical variable frequency drives and all four blowers are operating at 18 hz. This is not efficient because the efficiencies of the blower, the motor, and the variable frequency drive are all less as the speed is reduced As you can see in this diagram as the speed is reduced the efficiency of all 3 components is reduced.

Large Blower Systems Efficient control scheme with VFD:
Operate base load units at full speed Use one VFD for varying trim loads Or without a VFD: A master sequencer can operate base and trim blowers in dual control (load/unload and on/off) It is more efficient is to operate as many blowers as needed at their design speed to provide the base load and then vary the speed of one VFD controlled package to provide the trim load A master sequencer can be used to operate the base load blowers in dual control (load/unload and on/off) This system control scheme (load splitting) is more efficient than using multiple VFD controlled machines

Example of Different Control Strategies
A customer requires 3,000 cfm at 10 psi with varying demand between 2,000 and 3,000 cfm Customer wants backup in the event of a blower failure Supplier A is quoting 1 large blower with Omega Frequency Control (OFC) panel and an identical unit for back-up Supplier B is quoting 2 base machines with Wye-Delta Start Control (STC), 1 OFC trim unit and 1 additional back-up unit with STC Which scenario do you think will have the lowest initial cost? Which scenario do you think will have the lowest life cycle costs? In this example we are going to compare two different approaches to a customers needs. One supplier wants to use a large blower o cover the demand and have an identical blower for backup. The other supplier wants to use multiple blowers with different controls to provide a base load and then a trim unit.

Large Blower Systems Supplier A:
1 – HB 950C – 200 hp – 3,199 icfm $ 55,500.00 hp OFC control panel $ 60,000.00 Back-up unit 1 – HB 950C – 200 hp – 3,199 icfm $ 55,500.00 1 – 200 hp OFC control panel $ 60,000.00 Total initial cost $231,000.00 Load splitting by using more machines with less capacity has a lower first cost, provides for more turndown range and the cost of redundancy is reduced. Get Stephen to help with an example like this: 3, PSID system example: Two 200 HP blowers with VFD control: $, minimum flow:, Max flow: Four blowers (3=3,000 ICFM and 1 spare) one with vfd and others with wye delta control:$, Minimum flow:, max flow:

Large Blower Systems Supplier B: Base units:
2 – FB 440C – 60 hp – 1,034 icfm - $27, $ 54,000.00 hp STC control panel - $4,000 $ 8,000.00 Trim unit: 1 – FB 440C – 60 hp – 1,034 icfm $ 27,000.00 1 – 60 hp OFC control panel $ 22,500.00 Back-up unit: 1 – 60 hp STC control panel $ 4,000.00 Total initial cost $142,500.00 Load splitting by using more machines with less capacity has a lower first cost, provides for more turndown range and the cost of redundancy is reduced. Get Stephen to help with an example like this: 3, PSID system example: Two 200 HP blowers with VFD control: $, minimum flow:, Max flow: Four blowers (3=3,000 ICFM and 1 spare) one with vfd and others with wye delta control:$, Minimum flow:, max flow:

Large Blower Systems System cost comparison:
Supplier A total initial cost $231,000.00 Supplier B total initial cost $142,500.00 Total initial cost saved with Supplier B $ 88,500.00 Life cycle cost (based on operating 8,000 hrs per year) Supplier A - 5-Year life cycle cost $898,000.00 Supplier B - 5-Year life cycle cost $800,000.00 Total LCC savings with Supplier B $ 98,000.00 Load splitting by using more machines with less capacity has a lower first cost, provides for more turndown range and the cost of redundancy is reduced. Get Stephen to help with an example like this: 3, PSID system example: Two 200 HP blowers with VFD control: $, minimum flow:, Max flow: Four blowers (3=3,000 ICFM and 1 spare) one with vfd and others with wye delta control:$, Minimum flow:, max flow:

Designing Efficient Blower Packages Summary
Life cycle costs reflect all expenses Strategies to ensure efficient systems Achieving the lowest life cycle costs Effect of blower sizing on volumetric efficiency Effect of blower design on life cycle cost Package design will effect efficiencies System splitting strategies to minimize the initial cost Life cycle costs for multiple blower systems In this presentation we discussed strategies to ensure efficient systems and achieve the lowest life cycle cost for the application. We discussed the effect of blower sizing on volumetric efficiency and the effect of blower design on life cycle cost. We discussed the design of blower packages and how good design can improve the wire to air efficiency while simultaneously reducing maintenance cost. Finally, we discussed system splitting strategies to minimize the first cost, the cost of redundancy, and the power cost of variable capacity systems.

Designing Efficient Blower

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