Pr-pyr P06-16 V1-1 How To Measure Fan Efficiency 4c2y1f
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How to measure the fan efficiency of the main fans Pyroprocessing
PR PYR P06-16 V1.1
1/8
Introduction ƒ This procedure explains how to measure the efficiency of a fan. ƒ Improving fan efficiency and / or reducing damper pressure loss will lower the power consumption of the plant.
ƒ Improving the ID fan efficiency (when in limit) will maintain the kiln feed at the highest level. ƒ Indeed, poor fan efficiency wastes kW, lowers the gas flow available for the kiln and consequently reduces the kiln feed to maintain the level of O2 kiln inlet.
Where to begin ƒ Give priority to 20% of the fans making up 80% of the global power consumption. ƒ Special attention should be given to the fans where dampers or louvers operate in a closed position (>50% closed). Their efficiency may be good but they could be wasting power unnecessarily.
ƒ In the long term, the profitability of the optimization of each fan >36 kW should be evaluated.
What is a good result? ƒ A good result is when the measurements are within 5% of the fan performance curve. ƒ If the results are not within this tolerance it indicates there is something wrong with the fan, provided the measurement accuracy is within this tolerance. anomalies.
It is necessary to inspect the fan to check for
1 How to improve fan efficiency by internal inspection (false air, internal build up, bad gaps)
ƒ When an optimised fan(*) is operating with an efficiency level less than 72%, an opportunity study
should be made to see if replacement of the impellor or complete fan could be justified economically, by power savings (and / or by production increase if appropriate).
ƒ In the case of a fixed speed fan normally operating with a high damper pressure loss, an opportunity study should be made to determine if either
ƒ 1/ reducing fan speed, or ƒ 2/ application of a variable frequency drive, or ƒ 3/ replacement of the damper by a more efficient one could be financially viable. (*) optimized fan is when false air, internal build up, bad gaps are solved after applying the procedure “How to improve the efficiency of a fan by internal inspection?”
How to measure the fan efficiency of the main fans Pyroprocessing
PR PYR P06-16 V1.1
2/8
Safety aspects ƒ In the course of working in and around a fan, persons can be exposed to several hazards, depending on the fan in question. It is necessary to conduct a full risk assessment for each case.
ƒ Possible hazards are: ƒ Confined spaces ƒ High speed shafts ƒ Hot dust ƒ Hot gases ƒ Negative / positive pressure ƒ Access difficulties ƒ Hot surfaces ƒ Noise ƒ Inform and be in with the control room (two way radio…) ƒ Use suitable Personal Protective Equipment (PPE). If hot gas, use a fire resistant balaclava, safety helmet with visor, high temperature gloves.
Prerequisites ƒ Measurement conditions: process has to be as stable as possible. For example, for measuring ID fan, disconnect Lucie and freeze the fan speed.
ƒ Measurements are generally conducted at normal operating conditions to avoid the need to extrapolate. ƒ Measuring points installed for fan gasflow, and for pressure and temperature at fan damper inlet, fan inlet and fan outlet
ƒ Known duct areas at measuring points and fan inlet and outlet flanges, confirm with site measurements, if possible.
ƒ Measurement accuracy of fan power from control system and or motor control centre verified by electrical department portable test equipment.
ƒ Obtain the fan performance curves and design data from the fan supplier ƒ The performance curves normally consist of two curves: - a graph of volume against pressure. The type of pressure used to draw the curve can vary from supplier to supplier and even country to country, so make sure that the type of pressure used for the curve is known (fan static pressure, fan total pressure or static pressure rise across the fan). - a graph of volume against fan shaft power - the volume used for these curves usually relates to the fan inlet conditions.
ƒ Sometimes fans have inlet louvers or variable inlet vanes, which suppress the pressure and power curve. In this case it is normal for the supplier to provide a series of volume vs pressure and volume verses power for a range of damper positions up to 100%.
ƒ Design data can vary from supplier to supplier, but would normally include the impellor diameter, fan speed, gas density, dust content in gas stream, mechanical design temperature, inlet and outlet pressure, shaft power, installed motor power, inlet and outlet duct areas, plant altitude and operating point (volume, pressure, shaft power and efficiency). In any case, the fan speed and gas density relating to the curves will be required as a minimum.
How to measure the fan efficiency of the main fans Pyroprocessing
PR PYR P06-16 V1.1
3/8
ƒ There should be a set fan curves for all large fans ƒ The dust concentration affects the power consumption of the fan and therefore the power curve should
be adjusted by the density effect of the dust, e.g. with a gas density of 1,4 Kg/Nm3 and a dust concentration of 50 g/Nm3 would increase the effective density to 1,45 Kg/Nm3.
Tools ƒ ƒ ƒ ƒ
Pitot tube standard or “S” type for dusty gases, with known factor. Manometer, digital or Hg column Thermocouple and digital thermometer Any instrument required to determine gas density:
ƒ Combustion gas analyser ƒ Hygrometer, wet bulb indicator ƒ Tachometer / stroboscope for checking fan speed
1 Lafarge standard spreadsheet for re-drawing the fan curves at different speeds and gas densities.
1 Fan efficiency calculation spreadsheet (Pyroprocessing Tools) In this procedure you may find references to other information (tools, other “How to” procedures, knowledge documents, etc) which are available from their respective domain of the Web Cement Portal (e.g. Grinding, Pyroprocessing..) or from the BRS database / indicators section.
How to measure the fan efficiency of the main fans Pyroprocessing
PR PYR P06-16 V1.1
4/8
Action Steps 1.
Measure the gas flow ƒ Measure the fan gas flow in a suitably straight section of duct, preferably on the inlet side of the fan. Also measure the static pressure, gas temperature and duct area at this location.
1 How to measure air flow by Pitot tube
2.
Measure system pressures & temperatures ƒ Damper ƒ Measure temperature, damper inlet and outlet pressure, noting any physical or local indication of
damper position for comparison with the control system indication. When a damper is located close to the fan inlet, the space for a good measuring point may be limited.
ƒ Fan inlet ƒ Measure the static pressure, the temperature and duct section at the inlet of the fan according to the available fan curve.
ƒ It should be clarified if this static pressure measurement is before or after the damper. This depends whether the damper is included in the fan curve or not.
ƒ Fan Outlet ƒ Measure the static pressure, the temperature and duct section at the outlet of the fan. The measurements at the inlet, outlet and airflow should be done at the same time. If it is not possible, try to correct them with the help of on-line sensors. Use a Pitot tube for measuring static pressures.
3.
Measure fan power ƒ Record the indicated fan power in the CCR, if available. ƒ Measure the fan power ideally using a clip on power recorder (connected to the by electric department), from the power meter or from an ammeter.
ƒ Calculate shaft power by taking into the efficiency of the drive components ƒ If the losses from the drive components are not available from the supplier, assume the following standard values:
ƒ for std. 3 phase induction motor and transmission losses: direct drive
flat belt drive
v-belt in good condition
assume 3%
assume 3.5%
assume 6%
ƒ losses will be higher with poor tensioning of belts. Losses will differ for wound rotor motors, or DC motors. VFD losses not included – depends on meter location – before or after VFD box.
4.
Measure fan speed ƒ Using a tachometer or stroboscope check the speed of rotation of the fan. ƒ In the case of a stroboscope the approximate speed needs to be known, since the pulsation of the strobe at multiples of the shaft speed will also be able to ‘stop’ the shaft.
How to measure the fan efficiency of the main fans Pyroprocessing
PR PYR P06-16 V1.1
5/8
Action Steps ƒ In the case of a variable speed fan, compare the measured speed against that shown in the control room ƒ For a fixed speed fan compare with the design speed.
5.
Determine the gas density ƒ Determine the gas density according to the gas composition. In the case of air, this can easily be done,
however, for combustion products additional measurements are necessary, at least oxygen and humidity plus combustion calculations to be able to calculate the gas density.
1 How to measure air flow by Pitot tube ƒ In addition, dust concentration may be taken into consideration if above 10g/m3.
6.
Redraw fan curves ƒ Using the ‘Fan Laws’ – redraw the curves for the measured fan speed and at the measured density
1 Vade-mecum / Fluid flow / Fans / Fan laws ƒ Redraw the design system curve corrected for gas density
7.
Plot the measurements on the fan curves ƒ Correct the measured airflow to the temperature and pressure at the fan inlet. ƒ Determine the fan pressure difference from the inlet and outlet pressure, according to the pressure drawn on the curve.
ƒ Plot the corrected gas flow and pressure difference on the same graph as the corrected curve ƒ Using the relation PV2 (P – pressure difference, V gas volume) calculate the pressure difference for a range of gas volumes and plot the ‘system resistance curve’ on the same graph.
ƒ Determine the shaft power of the fan and together with the fan inlet gas flow plot this point on the
graph For detailed analysis also use the fan inlet and outlet areas at the appropriate flanges for correction of pressures. Fan curves are given for the fan from inlet to outlet flanges, although we seldom measure right at the flange. For approximate estimates – this level of precision is not needed. For very precise measurements e.g. Performance guarantee testing, it is recommended.
8.
Determine the fan efficiency η% ƒ
The fan efficiency can be determined from the following formula:
ƒ η = 100 x ΔP x Q W
ƒ ƒ ƒ ƒ
Q is the measured fan inlet volume in m3/s. ΔP is measured pressure difference across the fan kPa W is the measured fan shaft power kW Read off the pressure difference and shaft power from the fan curve at the measured fan inlet volume and, using the same formula above, calculate the “theoretical efficiency”.
How to measure the fan efficiency of the main fans Pyroprocessing
9.
PR PYR P06-16 V1.1
6/8
Treatment of results
ƒ
Compare this ‘theoretical efficiency’ with the measured efficiency.
ƒ
Compare the measured previous results.
ƒ
Evaluate the damper pressure drop.
ƒ
If the efficiency is not within 5% of the curve value:
efficiency
with
1 How to improve fan efficiency by internal inspection ƒ
If after modification (elimination of false air and build-up, adjusting gaps at nominal…), the efficiency is still low, investigate the options to increase efficiency, by fan or by impellor replacement.
ƒ
If high damper pressure loss check normal operating range and investigate potential options to reduce.
10. Write the Report Discuss it with the plan management team. Your report should include: ƒ ƒ ƒ ƒ ƒ ƒ
fan efficiency measurements measuring error estimation comparison with previous measures comparison with design comparison of field measurements with control room indications and clear proposal for an action plan justified by :
ƒ potential savings in power consumption ƒ potential increase in production ƒ e.g. it may be that you recommend to stop the preheater fan for cleaning, so have to justify the savings gained against the losses from the stoppage.
For an ID fan prone to build up, it is recommended to evaluate the efficiency systematically before and after a long kiln stop to evaluate the impact of the precise internal cleaning of the fan. A thorough clean-up of the build-up inside the impeller or between the impeller and the inlet cone, can improve the efficiency of 5 percent.
1 Annex 2: Fan efficiency after cleaning internal parts
How to measure the fan efficiency of the main fans Pyroprocessing
PR PYR P06-16 V1.1
7/8
11. Summary of measurements ID Fan : well prepared, the operation should take less than 4 hours.
Preheater
Kiln
Preparation work : •
•
Determine Gas analysis (O2, CO, CO2, H2O) for the normal gas density calculation: ρN (kg/Nm3) Fan set of curves
Qv by Pitot, T°, Ps, altitude
Damper
Outlet Ps, T°, Section
Inlet Ps, T°, Section
ID fan
kW
How to measure the fan efficiency of the main fans Pyroprocessing
Appendix 1.
Fan efficiency after cleaning internal parts Practical example (Port-La-Nouvelle plant, ) :
PR PYR P06-16 V1.1
8/8
PR PYR P06-16 V1.1
1/8
Introduction ƒ This procedure explains how to measure the efficiency of a fan. ƒ Improving fan efficiency and / or reducing damper pressure loss will lower the power consumption of the plant.
ƒ Improving the ID fan efficiency (when in limit) will maintain the kiln feed at the highest level. ƒ Indeed, poor fan efficiency wastes kW, lowers the gas flow available for the kiln and consequently reduces the kiln feed to maintain the level of O2 kiln inlet.
Where to begin ƒ Give priority to 20% of the fans making up 80% of the global power consumption. ƒ Special attention should be given to the fans where dampers or louvers operate in a closed position (>50% closed). Their efficiency may be good but they could be wasting power unnecessarily.
ƒ In the long term, the profitability of the optimization of each fan >36 kW should be evaluated.
What is a good result? ƒ A good result is when the measurements are within 5% of the fan performance curve. ƒ If the results are not within this tolerance it indicates there is something wrong with the fan, provided the measurement accuracy is within this tolerance. anomalies.
It is necessary to inspect the fan to check for
1 How to improve fan efficiency by internal inspection (false air, internal build up, bad gaps)
ƒ When an optimised fan(*) is operating with an efficiency level less than 72%, an opportunity study
should be made to see if replacement of the impellor or complete fan could be justified economically, by power savings (and / or by production increase if appropriate).
ƒ In the case of a fixed speed fan normally operating with a high damper pressure loss, an opportunity study should be made to determine if either
ƒ 1/ reducing fan speed, or ƒ 2/ application of a variable frequency drive, or ƒ 3/ replacement of the damper by a more efficient one could be financially viable. (*) optimized fan is when false air, internal build up, bad gaps are solved after applying the procedure “How to improve the efficiency of a fan by internal inspection?”
How to measure the fan efficiency of the main fans Pyroprocessing
PR PYR P06-16 V1.1
2/8
Safety aspects ƒ In the course of working in and around a fan, persons can be exposed to several hazards, depending on the fan in question. It is necessary to conduct a full risk assessment for each case.
ƒ Possible hazards are: ƒ Confined spaces ƒ High speed shafts ƒ Hot dust ƒ Hot gases ƒ Negative / positive pressure ƒ Access difficulties ƒ Hot surfaces ƒ Noise ƒ Inform and be in with the control room (two way radio…) ƒ Use suitable Personal Protective Equipment (PPE). If hot gas, use a fire resistant balaclava, safety helmet with visor, high temperature gloves.
Prerequisites ƒ Measurement conditions: process has to be as stable as possible. For example, for measuring ID fan, disconnect Lucie and freeze the fan speed.
ƒ Measurements are generally conducted at normal operating conditions to avoid the need to extrapolate. ƒ Measuring points installed for fan gasflow, and for pressure and temperature at fan damper inlet, fan inlet and fan outlet
ƒ Known duct areas at measuring points and fan inlet and outlet flanges, confirm with site measurements, if possible.
ƒ Measurement accuracy of fan power from control system and or motor control centre verified by electrical department portable test equipment.
ƒ Obtain the fan performance curves and design data from the fan supplier ƒ The performance curves normally consist of two curves: - a graph of volume against pressure. The type of pressure used to draw the curve can vary from supplier to supplier and even country to country, so make sure that the type of pressure used for the curve is known (fan static pressure, fan total pressure or static pressure rise across the fan). - a graph of volume against fan shaft power - the volume used for these curves usually relates to the fan inlet conditions.
ƒ Sometimes fans have inlet louvers or variable inlet vanes, which suppress the pressure and power curve. In this case it is normal for the supplier to provide a series of volume vs pressure and volume verses power for a range of damper positions up to 100%.
ƒ Design data can vary from supplier to supplier, but would normally include the impellor diameter, fan speed, gas density, dust content in gas stream, mechanical design temperature, inlet and outlet pressure, shaft power, installed motor power, inlet and outlet duct areas, plant altitude and operating point (volume, pressure, shaft power and efficiency). In any case, the fan speed and gas density relating to the curves will be required as a minimum.
How to measure the fan efficiency of the main fans Pyroprocessing
PR PYR P06-16 V1.1
3/8
ƒ There should be a set fan curves for all large fans ƒ The dust concentration affects the power consumption of the fan and therefore the power curve should
be adjusted by the density effect of the dust, e.g. with a gas density of 1,4 Kg/Nm3 and a dust concentration of 50 g/Nm3 would increase the effective density to 1,45 Kg/Nm3.
Tools ƒ ƒ ƒ ƒ
Pitot tube standard or “S” type for dusty gases, with known factor. Manometer, digital or Hg column Thermocouple and digital thermometer Any instrument required to determine gas density:
ƒ Combustion gas analyser ƒ Hygrometer, wet bulb indicator ƒ Tachometer / stroboscope for checking fan speed
1 Lafarge standard spreadsheet for re-drawing the fan curves at different speeds and gas densities.
1 Fan efficiency calculation spreadsheet (Pyroprocessing Tools) In this procedure you may find references to other information (tools, other “How to” procedures, knowledge documents, etc) which are available from their respective domain of the Web Cement Portal (e.g. Grinding, Pyroprocessing..) or from the BRS database / indicators section.
How to measure the fan efficiency of the main fans Pyroprocessing
PR PYR P06-16 V1.1
4/8
Action Steps 1.
Measure the gas flow ƒ Measure the fan gas flow in a suitably straight section of duct, preferably on the inlet side of the fan. Also measure the static pressure, gas temperature and duct area at this location.
1 How to measure air flow by Pitot tube
2.
Measure system pressures & temperatures ƒ Damper ƒ Measure temperature, damper inlet and outlet pressure, noting any physical or local indication of
damper position for comparison with the control system indication. When a damper is located close to the fan inlet, the space for a good measuring point may be limited.
ƒ Fan inlet ƒ Measure the static pressure, the temperature and duct section at the inlet of the fan according to the available fan curve.
ƒ It should be clarified if this static pressure measurement is before or after the damper. This depends whether the damper is included in the fan curve or not.
ƒ Fan Outlet ƒ Measure the static pressure, the temperature and duct section at the outlet of the fan. The measurements at the inlet, outlet and airflow should be done at the same time. If it is not possible, try to correct them with the help of on-line sensors. Use a Pitot tube for measuring static pressures.
3.
Measure fan power ƒ Record the indicated fan power in the CCR, if available. ƒ Measure the fan power ideally using a clip on power recorder (connected to the by electric department), from the power meter or from an ammeter.
ƒ Calculate shaft power by taking into the efficiency of the drive components ƒ If the losses from the drive components are not available from the supplier, assume the following standard values:
ƒ for std. 3 phase induction motor and transmission losses: direct drive
flat belt drive
v-belt in good condition
assume 3%
assume 3.5%
assume 6%
ƒ losses will be higher with poor tensioning of belts. Losses will differ for wound rotor motors, or DC motors. VFD losses not included – depends on meter location – before or after VFD box.
4.
Measure fan speed ƒ Using a tachometer or stroboscope check the speed of rotation of the fan. ƒ In the case of a stroboscope the approximate speed needs to be known, since the pulsation of the strobe at multiples of the shaft speed will also be able to ‘stop’ the shaft.
How to measure the fan efficiency of the main fans Pyroprocessing
PR PYR P06-16 V1.1
5/8
Action Steps ƒ In the case of a variable speed fan, compare the measured speed against that shown in the control room ƒ For a fixed speed fan compare with the design speed.
5.
Determine the gas density ƒ Determine the gas density according to the gas composition. In the case of air, this can easily be done,
however, for combustion products additional measurements are necessary, at least oxygen and humidity plus combustion calculations to be able to calculate the gas density.
1 How to measure air flow by Pitot tube ƒ In addition, dust concentration may be taken into consideration if above 10g/m3.
6.
Redraw fan curves ƒ Using the ‘Fan Laws’ – redraw the curves for the measured fan speed and at the measured density
1 Vade-mecum / Fluid flow / Fans / Fan laws ƒ Redraw the design system curve corrected for gas density
7.
Plot the measurements on the fan curves ƒ Correct the measured airflow to the temperature and pressure at the fan inlet. ƒ Determine the fan pressure difference from the inlet and outlet pressure, according to the pressure drawn on the curve.
ƒ Plot the corrected gas flow and pressure difference on the same graph as the corrected curve ƒ Using the relation PV2 (P – pressure difference, V gas volume) calculate the pressure difference for a range of gas volumes and plot the ‘system resistance curve’ on the same graph.
ƒ Determine the shaft power of the fan and together with the fan inlet gas flow plot this point on the
graph For detailed analysis also use the fan inlet and outlet areas at the appropriate flanges for correction of pressures. Fan curves are given for the fan from inlet to outlet flanges, although we seldom measure right at the flange. For approximate estimates – this level of precision is not needed. For very precise measurements e.g. Performance guarantee testing, it is recommended.
8.
Determine the fan efficiency η% ƒ
The fan efficiency can be determined from the following formula:
ƒ η = 100 x ΔP x Q W
ƒ ƒ ƒ ƒ
Q is the measured fan inlet volume in m3/s. ΔP is measured pressure difference across the fan kPa W is the measured fan shaft power kW Read off the pressure difference and shaft power from the fan curve at the measured fan inlet volume and, using the same formula above, calculate the “theoretical efficiency”.
How to measure the fan efficiency of the main fans Pyroprocessing
9.
PR PYR P06-16 V1.1
6/8
Treatment of results
ƒ
Compare this ‘theoretical efficiency’ with the measured efficiency.
ƒ
Compare the measured previous results.
ƒ
Evaluate the damper pressure drop.
ƒ
If the efficiency is not within 5% of the curve value:
efficiency
with
1 How to improve fan efficiency by internal inspection ƒ
If after modification (elimination of false air and build-up, adjusting gaps at nominal…), the efficiency is still low, investigate the options to increase efficiency, by fan or by impellor replacement.
ƒ
If high damper pressure loss check normal operating range and investigate potential options to reduce.
10. Write the Report Discuss it with the plan management team. Your report should include: ƒ ƒ ƒ ƒ ƒ ƒ
fan efficiency measurements measuring error estimation comparison with previous measures comparison with design comparison of field measurements with control room indications and clear proposal for an action plan justified by :
ƒ potential savings in power consumption ƒ potential increase in production ƒ e.g. it may be that you recommend to stop the preheater fan for cleaning, so have to justify the savings gained against the losses from the stoppage.
For an ID fan prone to build up, it is recommended to evaluate the efficiency systematically before and after a long kiln stop to evaluate the impact of the precise internal cleaning of the fan. A thorough clean-up of the build-up inside the impeller or between the impeller and the inlet cone, can improve the efficiency of 5 percent.
1 Annex 2: Fan efficiency after cleaning internal parts
How to measure the fan efficiency of the main fans Pyroprocessing
PR PYR P06-16 V1.1
7/8
11. Summary of measurements ID Fan : well prepared, the operation should take less than 4 hours.
Preheater
Kiln
Preparation work : •
•
Determine Gas analysis (O2, CO, CO2, H2O) for the normal gas density calculation: ρN (kg/Nm3) Fan set of curves
Qv by Pitot, T°, Ps, altitude
Damper
Outlet Ps, T°, Section
Inlet Ps, T°, Section
ID fan
kW
How to measure the fan efficiency of the main fans Pyroprocessing
Appendix 1.
Fan efficiency after cleaning internal parts Practical example (Port-La-Nouvelle plant, ) :
PR PYR P06-16 V1.1
8/8
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