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A MEDIUM-SIZE MANUFACTURER MAY BE UNDECIDED ABOUT WHETHER TO GO WITH A PORTABLE DUST COLLECTION SYSTEM vs. A CENTRAL SYSTEM. WHAT ARE THE PROS AND CONS OF BOTH? WHAT ABOUT A COMBINATION OF THESE TWO TYPES OF DUST COLLECTION METHODS?

Niels Haugaard, West region sales manager, Dantherm Filtration, Inc.: There are uses for both portable dust collectors and central dust collection. A large shop could potentially have a need for both.

Portable Dust Collectors: Portable dust collectors are usually used in a cell manufacturing situation. This is where a small unit or portable collector is used in a specific area, usually for a few pieces of equipment, but also sometimes as a dedicated source of collection. When using interior collectors it is very important to make sure you are aware of the codes. For instance NFPA guidelines states that an interior collector has to be at a maximum of 5,000 cfm and have to be located a minimum of 20 apart if more than one is used. They also have to be located 20 feet away from any operating personnel. This type of collection system that includes these units can be less expensive per cfm because you only need to run the units as the machine it is connected to is needed, and they do not have some of the features available for central units, such as airlocks and automatic cleaning. Portable dust collectors can also be moved to locations where only intermittent collection is required.

The cons for portable dust collection systems include a small waste capacity, and they take up valuable space — you would prefer money generating machines on the floor. They cannot handle the dust collection requirements of large machines; a moulder or planer could easily fill their waste capacity in less than 15 minutes. They are used indoors only — which can mean more dust and heat in your inside environment vs. a central system which can be located outside.

Central dust collection: Central dust collection systems have ONE place where you collect all the dust. They are normally located outside the work environment. They can be sized for any air volume requirement. Central collectors can handle a large volume of waste. They can utilize large Dumpsters or trailers to make disposal easier, less frequently needed and allow for continuous operation. Central systems can have online cleaning to make sure that your media are properly conditioned and run more consistently. They can be set up to exhaust or they can recirculate the air to help with cooling and heating your shop.

With central dust collection, if you do not utilize blast gates or fan zoning, you can be using more dust collection than needed if collection is being used on idle machines. Central systems can be less flexible. Adding or relocating equipment or redesigning your floor layout can be costly if you have a rigid ducting configuration.

A properly designed, energy-efficient central system would rarely require the use of portable units. However, they are an ideal way of adding extra dust collection if a few machines are added to the shop after a central system has been installed.

Curt Corum, sales manager, Air Handling Systems Manufacturers Service Co., Inc.: The pros for portable dust collectors include:
• Ideal for machinery that is quite a distance from the central system. Collector cost is far less than the ducting required, and the additional resistance level will add to the central system.
• Suitable for job shops that are consistently rearranging production equipment.
• Optional cartridge filter for fine dust particles.
• Less costly than central system if floor space is not an issue.
• Advantageous for shops with overhead cranes where overhead ducting is an obstruction.

There are also some cons to portable dust collection to keep in mind, such as:
• Requires substantial amount of floor space.
• Extremely high-maintenance labor for discarding waste collected.
• High deflagration hazard if dust bags are not secured properly.
• All waste material collected enters fan unit first. There’s a danger of collecting debris that may cause a spark or damage the impeller.
• Typically supplied with 5-micron dust bags, which cannot retain very fine dust particles.
• Mostly run on single phase-power.
• Are not capable of providing proper air volume for large production machines.
• Higher noise level than central system collector when several are running simultaneously
• It’s not suitable for a sound attentuator/silencer.
• Require additional wiring all throughout the shop.
• Highly prone to misapplication.

Central system pros include:
• All waste is deposited in one location.
• Require substantially less floor space than portable collectors.
• Can be located outside of the building with clean air return back to the work environment.
• Suitable for sound attenuation on return air noise.
• Necessary for implementation of spark detection/suppression system.
• Ultra-fine micron filtration of fine dust options.
• Automatic shaking or pulsing of filters.
• Explosion vents.
• Waste collected does not enter blower unit first.
• Belt-driven blowers allow for change in pulley arrangement.
• Necessary for large production machinery.
• Operate on three-phase power.
• Require extremely less maintenance than portable collectors.
• Must adhere to NFPA regulations.

There are also a few cons to central systems, including:
• Require permits for installation.
• Need concrete pads for outside installations.
• Purchase and installation are costly.
• Overhead ducting requires additional ceiling height.

Dick Cowan, president, Rees-Memphis, Inc.: There are many things that must be considered first before making a decision for either type of system:
• The type of manufacturing processes and machinery in place.
• The characteristics of material being collected and potential for explosiveness.
• The amount of overall air required for the various machines.
• The volume of waste being collected.
• The handling of waste and how it is to be disposed.
• Whether or not the manufacturing areas are individual workcells.
• How many machines are being run at one time.
• How spread out the machines are throughout the building.
• Whether or not there is space availability for inside dust collectors or an outside central system — and many other considerations that must be explored.

Prior to installing any type of dust collection system, local building codes, OSHA regulations, local fire codes and EPA standards must always be explored. The owner should also check with his insurance carrier for its recommendations or requirements.

Smaller, portable-type collectors, 1 to 20 hp, are very popular and somewhat less expensive overall than larger central systems in most cases. They serve a great solution when machines are remotely located from each other; the manufacturing process works in “cell groups” that run independently from each other and have varying schedules. They also can be moved with less labor required if the plant expands or moves machinery often. They keep the filtered, clean air in the work space, thus reducing overall heating or cooling costs. However, regulations are varied on inside units depending on your state and local codes. The frequency and labor required to change out the bags of waste can be costly in some situations, especially when large sawdust producing machines are involved.

Larger, central systems are also a good solution for medium to large manufacturers. They most often provide one central location for all of the sawdust to be collected and either stored in a bin for boiler fuel, future load-out or immediately discharging into a truck or other waste container, thus eliminating the required labor for handling the waste collected by inside type collectors. Also, central systems can provide easy future air requirements for additional machinery for which you have planned or future expansion without additional work other than a small amount of piping to the new machines. Usually, a central system is located outside of the manufacturing area, freeing up costly and often needed inside space.

A combination of both of these types of systems is quite often utilized in larger manufacturing facilities, especially when future air requirements were not included or not known when the original central system was installed. Also, even though the manufacturer has a central system, quite often there are several small machines or processes that are remotely located within a building that are better served by small portable-type units to keep the power requirements and expense down when making long runs of pipe to serve these machines.