Hi Industrial Energy Management - Fans & Blowers (Section 1).

Complete this questionnaire to better characterize the energy savings opportunities from Energy Management Systems. If an energy savings opportunity is identified, the results will appear immediately below the question.

Yes / No ?

• Have you considered automatic on-off fan controls to reduce energy consumption?
• Significant energy savings can be achieved by using an automatic fan control system to stop the fan when the ventilation is not required. Typical savings range from 10-50%. In addition to energy savings, this approach will reduce maintenance costs and increase equipment life.
• Have you checked to see if all of your fans are properly sized?
• Significant savings can often be achieved by selecting efficient fans that are sized as accurately as possible to work near their point of most efficient operation at the correct air flow. Fans that are properly sized for a particular application result in optimal energy consumption. However, it may often be more cost-effective to simply reduce the speed of the fan than to replace it. The rotation speeds on belt-driven fans can be changed by adjusting or changing the size and shape of the sheaves (pulleys). In this way, the fan speed can be optimized for fan efficiency and airflow, thereby reducing energy consumption. Typical savings range from 5-30% of fan energy consumption.
• Have you considered improved controls and adjustable speed drives for fans that experience highly variable demand conditions to match the fan speed to the ventilation demand?
• Ventilation demand often depends on the level of activity in the plant. As ventilation demand changes, an automatic controller can adjust the airflow rate to meet this demand, thereby saving energy that would otherwise be lost. The airflow rate can be adjusted using by using an adjustable speed drive (ASD) or variable pitch fan blades. Adjustable speed drive is just one of several terms used to describe a motor-driven system that rotates at variable speeds, such as variable speed drives (VSDs), adjustable frequency drives (AFDs), and variable frequency drives (VFDs). ASDs provide energy savings by matching the rotation speed to fan load requirements and thereby ensuring that motor energy use is optimized to a given application. ASDs can provide significant energy savings on fans that experience highly variable demand conditions. ASDs are best on fan systems that occasionally operate at low flow but do not operate for extended periods under low-flow conditions. For larger axial fans, adjusting the pitch of the blades is an alternative method for adjusting the airflow rate.
  Savings from ASDs and pitch controls can be as high as 30%. The resulting energy and maintenance cost savings can often justify the investment costs for the ASD. However, where there is no need to adjust the airflow rate, installing an ASD could increase energy consumption by 5%.
• Have you considered straightening or turning vanes upstream of the fan inlet?
• Significant savings can be achieved by making the airflow entering the fan more uniform across the fan. If there is swirl at the inlet that is moving in the opposite direction to the fan rotation, then fixed inlet vanes will straighten out the flow and provide fan energy savings. If there is a duct bend close to the inlet, then turning vanes installed in the duct bend will provide the fan with more uniform flow and provide energy savings. Typical energy savings is 5-15%.
  Similarly, it is generally good practice to not have ductwork bends close to the outlet. If there must be bends in the ductwork close to the outlet, use radius bends with splitters.
• Is your ducting tubular with a large cross-sectional area?
• Fan energy savings can be achieved by installing tubular ducting instead of standard rectangular ducting and ensuring that the cross-sectional area is as large as possible. The combination of large diameter and circular cross section will produce a low velocity system with a low pressure drop, thus maximizing efficiency. A duct that is too small for the required air velocity can significantly increase the amount of fan energy consumption. Where possible, duct diameters can be increased to reduce energy requirements, but the energy savings due to increased duct diameters must be balanced with increased costs for ducting system components. Increasing duct diameters is likely to be cost effective only during major system retrofit projects. Typical energy savings is 7%.
• Have you checked to see if any of your fan motors are oversized?
• Losses are often caused by the selection of a safety margin that is too large during the design and installation stages, resulting in the specification of a motor that is too large. Motors give good performance from 50-100% of rated load. Selection of the right motor is important. Typical energy savings range from 5-10%.
• Has your company implemented a comprehensive fan maintenance program?
• A comprehensive fan maintenance program will lead to fan system energy savings of anywhere from 2% to 7%. Inadequate maintenance can lower fan system efficiency and increase fan energy costs. The implementation of a fan system maintenance program helps to avoid these problems by keeping fans running optimally. A solid fan system maintenance program generally includes the following tasks:
  1. Cleaning dirty fan blades (dirt increases air drag which increases energy use and reduces the airflow rate, which requires higher fan speeds to maintain airflow rates and thereby increases energy use)
  2. Bearing inspection and repair
  3. Bearing lubrication replacement, on an annual or semiannual basis
  4. Inspection of motor condition, including the motor winding insulation
• Have you installed high-efficiency belts (cog belts) where possible?
• Belts make up a variable, but significant portion of the fan system in many plants. Cog belts are more efficient than standard V-belts. Standard V-belts tend to stretch, slip, bend and compress, which lead to a loss of efficiency. Replacing standard V-belts with cog belts can save energy and money, even as a retrofit. Cog belts run cooler, last longer, require less maintenance, and have an efficiency that is about 2% higher than standard V-belts. Payback periods range from less than one year to three years.
• Have you considered adjustable speed drives on combustion air fans?
• Often the cooling air and stack blowers run continuously, while variations in demand are either not met or they are met by using variable inlet vanes. The application of ASDs on the fan systems may be an opportunity for energy savings if there are variations in demand for air from the furnace. The savings (and hence payback period) will depend on the operating conditions of the fan system and the size of the furnace. One plant audit found electricity savings by installing ASDs on the furnace air blowers to have a payback period of 1.7 years. With large variations in heating demand (e.g., in small-scale intermittently used furnaces), installing an ASD may lead to savings in fuel use as well, as it reduces excess combustion air.
  The U.S. DOE’s Fan System Assessment Tool (FSAT) helps quantify the potential benefits of optimizing fan system configurations that serve industrial processes. FSAT requires only basic information about your fans and the motors that drive them. With FSAT, you can calculate the amount of energy used by your fan system; determine system efficiency; and quantify the savings potential of an upgraded system.
  
  

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