EnergyEcon

Dust collecting equipment manufacturers, installers, distributors, factory owners, technical universities, OSHA inspectors, and workstation producers will all play a role in redefining DUST COLLECTING.

At present, dust collection technology retains outdated modes of operations. In a technologically progressive world the old world designs may cost users tremendous amounts of time, money, and environmental problems.
New technology available today will force us to ask ourselves:

Will factories continue expending energy on evacuating dust from all workstations all the time when generally less than 50% are running at any one time?
Why, during the second or third shift in a factory, is a large dust collector used when only a small percentage of equipment is operational?
Will manual blast gates continue to be installed when they are usually left open on machines not in use?
Will employees be able to avoid the extra noise and fine dust from "add-on" dust collectors designed as a "quick fix" for the ever-changing workplace environment?
Will factories continue to have abandoned ductwork terminating randomly and openly in the upper reaches of their infrastructure?

Unfortunately, dust collecting is an afterthought for some factories. We feel that the dust collecting industry can now take a more cost-effective approach to addressing these health and energy-waste concerns. This article features the new technology necessary to address these concerns. Dust collection requirements are more lax here in America than in Europe. Even so, most American factories are challenged to meet even the basic standards.

Previously, if OSHA regulators enforced the regulations it may have had an adverse impact on the factories. The end result is that factory workers often work in an overly noisy (due to oversized dust collectors) environment with tremendous amounts of potentially hazardous particulate in the air (from ineffective evacuation). There is no argument as to the detrimental health effects of airborne particulates from the manufacturing processes.

As the world enters a new electronics-oriented, 24-hour per day workday, energy becomes a critical component. So even while people are sound asleep, the energy demands of all working automation is taxing our ability to generate enough low cost power. This is especially evident in California where rolling blackouts are becoming a necessity for dealing with power shortages. Fortunately NEW ECONOMY, demands can be met with NEW DUST COLLECTING technologies that have the capability to reduce industrial dust collecting costs by as much as 80% while greatly reducing air-pollution within factories.

Old technologies forced dust collection system designers to develop a "balanced" system with minimal ability to conserve energy consumption. The aim of this paper will be to show that new technologies will allow system designers the ability to evacuate the greatest possible amount of sawdust at minimal cost.

Today manufacturers assume greater flexibility to constantly modify their operations to meet changing customer demands. This is a "must" for every industry that would like to remain profitable. This will also require dust collection systems to be more modular in nature. Quick coupling, or clamp-together duct systems need to replace soldered or welded systems. This measure will improve airflow management, a topic that we will explore further.

The data from one Californian factory using new dust collection technology will show ways to effect savings in dust collection. Presented in TABLE 1 (in Appendix) is workstations use (WS#1 to WS#7) and consequent CFM (air volume) demand. Based upon the table we have graphed out the vacuum requirements. These data are typical of most factories (low percentage of use of the workstation). Note the constant red line across the top of the table. This is the constant and wasteful vacuum in CFM employed by their existing "unregulated" design.

The average air volume demand of this factory works out to 10,666 CFM. Peak air volume demand is 21,292 CFM (for only a six minutes per day!). Air volume demand should all machines hypothetically be working at the same time is 25,415 CFM. Classic "unregulated" designs take this hypothetical demand and add at least a 20% safety margin. In this instance the factory's cyclone motors and dust system were designed to maintain a constant airflow of 30,498 CFM (i.e. 25,415 CFM + 20%). With manual blast gates installed the system could be designed for peak demand at 21,292 CFM. But because workers tend to "forget" to close the blast gates on non-operating machinery, the factory could be left in clouds of sawdust. This is a readily apparent example of where factories can start improving on their design.

Common sense would say that a dust system should be designed to reflect the actual requirements of the manufacturing plant. This would mean creating a system whereby only the required CFM is actually demanded of the vacuum. To do this would take advantage of the Fan Affinity Laws. These state that for a linear decrease in CFM, there is an corresponding exponential decrease in required Horsepower that says, for example, that if you use only 50% CFM, you use only 12,5% Horsepower.

Applying the Fan Affinity Laws to the previous CFM demand example, we get:

Power (HP) requirements (0 to 160 HP) unregulated design (HP1), NEW design (HP2).The RED line indicates the power (in Horsepower) requirements of an "unregulated" design while the BLUE curve demonstrates potential power requirements if only actual CFM requirements are satisfied. The rectangular graph below illustrates the system power requirements of an "unregulated" design:

This illustration area represents the power consumption of the new, "regulated" design:

Today's new technology dramatically reduces the new system's power requirements (a 90% savings). To create this NEW DUST COLLECTING system a new form of airflow management is also required. A blast gate installed in the ductwork to each machine needs to open and close depending on whether or not the machine is working. Vacuum thus goes only where it is required.

BLAST GATES The gates cannot be of a manual type for two reasons. First, workers tend to forget to open and close gates. More importantly, a central processor needs to be aware of which gates are open and closed in order to control power to the fan motor. Also, the gates cannot be of a hydraulic type as they are logistically and technically difficult to deal with, and expensive.

The best alternative is an electronically controlled, motor driven blast gate. These gates are available to fit all industrial ductwork ranging from 4" and up.

A central computer controller (industrial PLC) that has several capabilities is needed. It needs to be able to:

Detect which machines are in operation
Selectively open the blast gates to these machines
Closing blast gates to all non-operating machinery
And regulate the power of the dust collector

How control computer (PLC) works?

The computer will have a table of both minimum airflow and negative pressure requirements for each workstation. Minimum airflow requirements from selected open gates will be added for a total required CFM. Negative pressure will be set by selecting the greatest required negative pressure (i.e. from the furthest away gate). Power (RPM) delivered to the dust collector will be calculated as a function of these two values.

Appropriate negative air pressure sufficient to overcome losses in the ductwork as caused by distance from the dust collector needs to be maintained. For each workstation this value depends mainly on its distance away from the dust collector and on diameter of ducts.

Also, a minimum airflow needs to be maintained in order that particulate does not drop out of the vacuum flow (and settle in the ductwork) before it reaches the dust collector. The main duct has a minimum value of air velocity depending on the diameter. Furthermore, the negative pressure requirement will be checked against a negative pressure sensor located just ahead of the dust collector. If this value is less than the largest negative pressure requirement, dust collector power will be increased to correspond.

NEW Design of the duct system

The NEW DUST COLLECTION SYSTEM designs can incorporate narrower ductwork due to reduced total CFM demands as previously mentioned with a partially different layout. The system design will have to take into account both peak and average workstation usage periods. A good way to visualize this is through the example of home heating. The heating system is not most efficiently designed to heat the uncommonly cold day (in that case system will be too expensive); rather it heats for the lowest average day. Your house may be few degrees cooler for one day. You probably won’t even notice. Mathematically, this is a min-max probability problem, the parameters of which will be set according to the manufacturer’s needs. Likewise, as the installer has no problem selecting the right heater size for home installation, the manufacturer will have no problem selecting the right size of duct system and dust collector.

These new dust-collecting concepts have been tested on many systems in factories and proven by ECOGATE, Inc. (www.ecogate.com) with verified test results. It has been demonstrated that in a factory with two 100 HP dust collectors, this new design saves $55,289 in electric costs yearly. According to a study by the Public Library of Los Angeles, the United States has approximately 50,000 such woodworking factories. If this system were implemented in all these factories, savings in electric costs alone would total $2,764,450,000, or roughly the value of the power output of twenty major power plants.

Given these important new facts we ask the following of friends and colleagues in the dust collecting industry.
From dust collecting equipment manufacturers: embracing this system reflects a desire for and drive toward improved product lines.

From installers and distributors: offering customers this automated, money saving system allows you access to new installation and distribution opportunities.

From factory owners: require that this latest generation of dust control system is installed so as to reduce dust collecting energy costs up to 80% and total energy expenditures by over 20%.

From technical universities: help us redefine both dust collection system design theory and industrial energy usage levels. Future systems will have a smaller initial design and operate more efficiently.

From OSHA inspectors: because such a cost effective system exists, OSHA regulations can now be enforced without being a financial liability on manufacturers.

And from workstation producers: hydraulic blast gates are presently included in all CNC machines to facilitate dust collection and hence improve the product. The low cost of new motorized blast gates now allows all workstation producers to integrate them into even their least-expensive products (table saw, routers, etc.).

The described system is neither a "miracle" nor a "perpetual-motion machine", but just the combination of motorized blast gate and the latest industrial PLC control system. It brings the dust collecting industry up to a new, hi-tech industrial level.

Los Angeles, December 16, 2000

Appendix, TABLE 1: workstations use (WS#1 to WS#7) and consequent CFM (air volume) demand. Zero (0) indicates that the machine is OFF, and one (1) indicates that the machine is ON. The following is a 30-minute sampling (from 1:00 PM to 1:30 PM) from one week's data collection. Data are based on data loggers installed by SC EDISON on the woodworking machines.

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