Variable Volume Dust Collection System
Dust Collection System: Variable Volume vs. Constant Speed
A ventilation system using automated variable speed fans and motorized gates to reduce energy use in fume and dust collection systems.
Item ID: 12
Process Loads & Appliances--Industrial Processes
Technical Advisory Group: 2010 HVAC TAG (#3)
Average TAG Rating: 2.3 out of 5
TAG Ranking Date: 06/29/2010
TAG Rating Commentary:
- Usually end of life replacement.
- This is well accepted in other industries. Not a very wide application.
- "It will be important to evaluate the narrow market potential, as described; i.e. battery manufacturing facilities. Sounds pretty limited. Variable speed control is good to do in dust collection systems, and in product transport systems, but the applications are all unique and will require custom analysis. It will not be easy for BPA to turn this into a simple "program.""
- This one needs to be renamed I think. Variable flow dust transport systems. The minimum velocity that's most critical isn't in the space; it's in the ducts. When the velocity in any of the duct segments drops below critical, the duct becomes blocked rapidly, bringing down that part of the system... a very undesirable situation.
- If it works well this should find its way into design standards for these types of facilities.
- Limited applicability outside of specialist industries.
- Application is too limited.
Technical Advisory Group: 2009 HVAC TAG (#2)
Variable volume dust or fume collection systems have been demonstrated in laboratory hoods, welding booths, forest products plants (sander dust), and battery plants. The technology consists of automated gates in strategic locations of the ductwork, a computer control system, and variable speed drives to control fan motor speed to provide enough flow for the number of open gates. Analysis must identify the required flow rates for each ventilation configuration. Minimum flow velocities are necessary so collected particulates do not dis-entrain from the flow stream, accumulate, and plug ducts.
This technology is appropriate for any pneumatic conveying system with multiple pickups. In wood products plants, fan speed is regulated to maintain a constant pressure in the main duct system. Seldom-used machines are fitted with automatic gates that open when the woodworking machine operates and close when the machine is shut down. Fan zoning using multiple small fans instead of one large fan might be employed to provide the flexibility and scalability needed to meet changing requirements. Reducing airflows provides for reductions in space heating and cooling costs. Studies show that blower systems can account for 25% to 35% of the electricity use in secondary wood products facilities. Energy use by pneumatic conveying systems in the Northwest wood products industry alone is estimated at 365 million kWh/year (Shinn, 2002).
This technology provides significant energy savings but may require expensive fan relocation, redesign and replacement of poorly designed duct systems, or, further, sectionalizing the fume collection or pneumatic dust collection system may be necessary. The Ecogate system has been installed in over 125 large industrial plants and is generally designed for use in large factories with more than 20 workstations. Installers of Ecogate's Smart Dust Collection Systems obtain an average dust collector fan energy savings of 68% (see www.ecogate.com). A case study at Trojan Battery in the Southern California Edison service territory resulted in 1,330,793 kWh saved with a total project cost of $778,000 (Southern California Edison, 2007).
Baseline Description: Cabinet Manufacturing Plant
Baseline Energy Use: 325000 kWh per year per unit
Consider a cabinet manufacturing plant with a dust collection system consisting of 28 pickups powered by a continuously operating 200 hp motor. Given single-shift operation and a 75% load on the motor, this constant speed system will consume about 325,000 kWh per year of electrical energy.
Manufacturer's Energy Savings Claims:
"Typical" Savings: 68%
Savings Range: From 18% to 80%
The Ecogate Smart Dust Collection system (www.ecogate.com) is designed for use in large factories with more than 20 workstations and dust collection pickups. The system requires the installation of sensors at all dust producing production machines. The system monitors machine activity and, with an adjustable speed drive (including load reactors/dV-dt filters, and a new dust collector inverter-duty motor); automatically closes the gates to any non-operating machinery and continually optimizes the amount of power supplied to the dust collector fan. Ducts may need to be resized and a controller is used to activate motorized gates as required. The system control may open additional gates when necessary to maintain minimum airflows in the ducting system and avoid product (sawdust) settling. Early systems required wiring to be installed between sensors, controllers and gates. An average energy savings of 68% has been reported with over 125 large industrial systems in operation. Additional savings have been reported due to increased filter media life. The Ecogate approach is suitable for allowing future dust collection system expansion, and can improve the performance of undersized dust systems. In contrast, lower energy use reductions (37%, 23%, 36%) were found in the Northwest's timber products plants due to reducing fan speeds.
Best Estimate of Energy Savings:
"Typical" Savings: 40%
Low and High Energy Savings: 18% to 80%
Energy Savings Reliability: 2 - Concept validated
The Northwest Energy Efficiency Alliance (NEEA) "Just Enough Air" project investigated energy savings associated with pneumatic conveying systems at forest products plants in the Northwest. Measures employed ranged from changing out pulleys to adjusting fan speeds to complete equipment upgrades including variable frequency drives. Energy savings from fan speed reductions alone ranged from 23% to 39%. Results from projects involving system retrofits and comprehensive capital upgrades ranged from 18% to 50% (Shinn, 2002).
Ecogate systems are designed for use in large factories with more than 20 workstations. In many such facilities, as few as 50% of dust or fume-creating machinery may be in operation at any given time, but the extraction plant usually runs at full capacity, with fixed fan speed all of the time. The result is an extraction system which is likely to be consuming more electricity than necessary. The Ecogate system solves that problem by automatically closing ports to non-operating machines, and by regulating the speed of the extraction fan accordingly. Energy savings obtained by using motorized gates and a variable speed drive average 68% with savings up to 80%. A "typical" savings equivalent to 40% of the baseline energy use will be used in this analysis.
The Ecogate controller responds when a production machine is turned on. A remote sensor signals the control unit to open a motorized gate and provide extraction for that particular machine. The controller then determines the optimum fan speed, which is achieved using variable speed technology. When the machine is turned off, the gate automatically closes and fan speed is again adjusted accordingly. This means power is only used when needed. The system is also designed to maintain minimum airflow in the duct system, by opening additional gates when necessary, delivering good system balance and preventing dust settling in the duct system.
Many case studies are available that illustrate both savings potential and achieved savings. The existing dust extraction system at a kitchen cabinet manufacturer is designed to deal with dust and chips from all production lines and uses fans that run at a constant speed, irrespective of the number of machines operating or the amount of dust to be extracted. The cabinet manufacturer installed the Ecogate control system which monitors the 28 motorized gates and shows status, provides negative pressure readings, electricity savings and input kW levels for each fan. Collection system energy savings in excess of 56% were achieved, with a return on the investment in approximately two years. Plant staff indicated that the extraction system was by far the biggest power user on site and the Ecogate system deployment provided a savings of 23% of overall facility electricity usage.
Energy Use of Emerging Technology:
195,000 kWh per unit per year
Energy Use of an Emerging Technology is based upon the following algorithm.
Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
The Ecogate systems work by automatically closing electronically controlled gates (pickups) at systems that are turned off, then adjust airflow and air velocities with an adjustable speed drive to meet system requirements. Each dust collection system is different, with greater energy savings available for the more complex systems with multiple pickups. NEEA funded the preparation of a number of "Just Enough Air" case studies. Generally these studies are for relatively simple dust collection systems at forest product-related plants. Canyon Creek Cabinet Company is a cabinet making shop that uses particleboard, plywood and hardwood. Residues are produced by machining, edgebanding, and sanding. Their existing collection system consisted of a 300 hp motor driving a backward inclined fan. The initial energy use of 837,200 kWh/year was reduced by 312,468 kWh/year, resulting in an energy savings of 37%-- simply through reducing the fan speed by 26% (from 1,001 RPM to 741 RPM). Duct velocities were above the minimum requirements.
A 60 hp fan at the PrecisionCraft Log and Timber Homes facility in Idaho showed a 23% annual energy use reduction (from 113,400 kWh/year to 87,000 kWh/year) simply through reducing the fan speed by 10%. A manufacturer of display partitions (Synsor Corporation in Everett) obtained an energy savings of 243,000 kWh/year, equivalent to 36% of the baseline dust collection system use, through using a variable frequency drive to control a 200 hp dust collection fan motor. Closure caps were also installed on previously open ducts. At the end of a period of testing, Synsor removed the variable frequency drive and achieved the desired 15% fan speed reduction by changing a sheave.
Potential number of units replaced by this technology:
This technology only makes sense in industrial facilities that have multiple work stations that can be served by a single dust or fume collection system. Accurate information has not been located on the number of multi-station dust collection systems in the Northwest. The estimated number of systems is based on numbers found or estimated for forest products mills, furniture and cabinet manufacturers and woodworking shops.
Numbers used in this analysis are in the table below.
Multi-Station Dust Collection Systems in the Northwest
Regional Technical Potential:
Dust Collection Systems per Bldg.
Timber and Plywood Mills
Furniture, Cabinet and Woodworking Shops
Current Technology Penetration
Total Collection Systems
0.15 TWh per year
Regional Technical Potential of an Emerging Technology is calculated as follows:
Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)
Installed first cost per: unit
Emerging Technology Unit Cost (Equipment Only): $60000.00
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $0.00
Baseline Technology Unit Cost (Equipment Only): $0.00
Costs of installing automatic gates on pickups, a controller that senses when gates are turned off and automatically closes gates, and an adjustable speed drive vary depending upon the complexity of the ducting system(s), the number of controlled gates and the size of the fan or blower drive motors. An Ecogate greenBOX can control up to twelve gates with a 20 hp blower drive motor. Cost is $250 to $500 per workstation. The Ecogate Pro can serve up to 22 work stations with a dust collector sized between 20 and 500 hp. Costs range from $10,000 to $40,000 for the system. The Ecogate Master can control 22, 44 or 88 work stations with installed costs ranging from $50,000 to $130,000 (Source: Ecogate web site). Dust collection system energy savings average between 60% and 70%.
Simple payback, new construction (years): 5.1
Simple payback, retrofit (years): 5.1
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
Reference and Citations:
Low Pressure Blower Systems Best Practices Guide
Northwest Energy Efficiency Alliance
Best Practices Guide, Low Pressure Blower Systems
Optimizing Airflow on Dust, Mist and Fume Collection Systems
Southeastern Air Works
Variable Dust Collection System--Trojan Battery, Emerging Technologies Final Report
Southern California Edison
Optimizing Airflow on Dust, Mist and Fume
Author is a Technical Training Manager for Donaldson Torit, a company that manufacturers dust collectors and filters.
Variable Dust Collection System - Trojan Battery
Southern California Edison
Washington Mill Survey 2012
Washington Dept. of Natural Resources
Number of Firms, Number of Establishments, Employment, and Annual Payroll by Enterprise Employment Size for States, NAICS Sectors: 2011
US Census Bureau