Ten common dust collection mistakes and remedies
By E.M. Phillips

1: Attitude

The tree from which many dust collection problems stem isn't mechanical, it's the attitude behind the system's purchase, says Rusty Angel, sales manager for DISA.

"People look at dust collection as a necessary evil," states Angel.

Kurt Corum, product application manager for Air Handling Systems, echoes those sentiments. "People put the cart before the horse," he says. "They purchase systems without having analyzed the plant's requirements."

A simple solution for this problem, according to all of the people FDM spoke with, is contacting an expert before you do anything in regards to your system - that includes setting your budget. And, the best part is that a lot of this expert advice can be gotten for free.

One low-cost option is reading one of the many preliminary design guides on the market. For the most part, these guides are easy to read and contain all of the equations owners need to figure out a plant's system requirements, says Corum.

If you don't want to do the math yourself, most large dust collection vendors have an engineering department that will do it for you if you supply them with floor plans and answer a simple survey.

"A little research up front can save consumers a lot of time, money and headaches," concludes Jeffery Hill, general manager, Air Handling Systems.

2: Buying from an unreliable vendor

Because dust collection is often viewed as a purchase to be made and gotten over with as quickly as possible, some buyers get stuck with lemons. "Buying a collection system is a lot like buying a car. You have to do the research and buy from a reliable vendor," says Angel.

Unfortunately, there are a handful of companies out there that have a sales force that isn't as knowledgeable about dust collection as they should be, says Corum. "If you combine an unknowledgeable salesman and an uneducated consumer, you have a recipe for catastrophe," Corum warns.

When buying a system, owners are advised to watch out for salesmen who walk into the plant and make collection recommendations without putting any type of machinery information or equations down on paper.

3: Not enough CFM

When it comes to CFM, or the system's overall air capacity, it is better to err on the side of caution and spend a few extra dollars on the larger system, says Jeffery Hill.

The general rule-of-thumb for CFM is to spend $4 per square foot of floor space, says Angel, with the price increasing to as much as $6 or $8 per CFM for systems with all the bells and whistles, such as automatic blast gates and spark detectors.

"A lot of owners will try to get by with less CFM than the equation calls for by saying, 'Well, we are really only running two-thirds of our machinery at one time,' but what happens is that they end up having two or three men or machines sitting idle," says Angel.

It is also important to have forethought, says Hill, who advises owners to think about how they plan to grow in terms of manpower and machinery in the years to come.

"The thing about dust collectors is that there isn't a switch you can turn from high to low when you need it. If you are going to need more capacity in the future, you have to build it into the front end," says Corum.

4: Noise

"Noise is something that needs to be considered inside and outside of the plant," says Angel, who gets a lot of calls from customers saying that their neighbors are complaining of the noise.

While some companies, such as DISA, advertise collectors with relatively low noise levels, other dust collectors come with no such guarantee.

If you find that noise is an issue, one relatively simple solution is to install silencers or enclose the fan, says Angel.

5: The wrong collector

While dust collection is naturally associated with a certain level of noise, a lot of noise can mean that you have a larger problem on your hands. Too much noise could be a sign that you have purchased the wrong collector altogether, says Corum.

When buying a collector, owners are advised to think not just about issues of horsepower and CFM, but about the types of materials that are being used and the waste those materials produce.

For machines such as large, multi-stage moulders that produce both large and small debris, a two-stage collector with a separator should be used. On the other hand, single-stage collectors should be used with machines that produce very light, fine dust and nothing coarse, such as sanders, says Corum.

"With a two-stage collector all of the large debris is spun out in a separator using centrifugal force and collected in the central area; with the use of a separator as little as 3 to 4 percent of the dust is left in the air stream to be filtered," explains Corum. With a one-stage collector all of the debris is sent directly to the fan.

"If you hook up a single-stage collector to the wrong machine, not only will the machine be very noisy from the fan being continually hit with large debris, but the fan's bearings will eventually be ruined," says Corum.

6: Poor ducting

"What a lot of people forget is that the duct system is as critical as the dust collector itself," says Corum. "If your duct system is wrong, you are only going to get 60 percent, maybe less, of what the system is capable of collecting."

Generally, bad duct design is the result of two things: machinery additions and the use of improper materials, says Angel.

ä First: Changes in your machinery layout or machinery additions need to be accompanied by the same modifications to your ducting systems, says Angel. "Often the original duct design is fine, but then machines are added or moved around and the original design no longer applies," he says.

When this happens, Angel says bringing in the original planner or another expert to make a few modifications to the ducts will often cure the problem.

ä Second: Professionals should handle the system's ducting.

"A lot of people just don't know that there are right and wrong pipes to use," says Corum. "They think that a pipe is just a pipe and they end up using heating ducts with 90 degree intersections, short elbows or the corrugated black-plastic pipe used for gutters."

While improper ducting is a large problem, Corum notes that there are bigger mistakes that can be made. "If you do your own duct work and make a big mistake, you are out $500 or $600. If you buy the wrong collector, you can easily be out $10,000."

7: Poor zoning

Dust collection has to start at the dust's source. "You need to pick up the dust as you are making it, and nine times out of 10, people piecemeal things together and then the dust is escaping the hood, or, even worse, it isn't getting collected at all," says Jeffrey Hill.

One way to make sure that dust is collected at the source is to zone the machines, says Angel. For example, if a business has 20 machines, rather than have one fan and one blower, an owner can install multiple smaller blowers connected to one central dust collector with two or three fans. Since it is common to have different areas of the shop for finishing, assembly, sanding, etc., it can be a very good idea to group the system's blowers and fans as you group your machines, says Angel.

Done this way, rather than turning on one huge system, an operator can turn on just one or two smaller machines.

"Zoning gives the owner much more flexibility with the system, and it also increases efficiency while decreasing operating costs," concludes Angel.

8: Bad filtration

Air-to-cloth ratio, that is, the total air volume divided by the square footage of cloth, should not exceed 10- or 12-to-1, says Angel.

When purchasing a machine, Corum advises people to ask themselves if the machine is going to contain the material the system is collecting?

"If the filters are wrong and everything is just going back into the shop, you have achieved nothing. If an inspector walks in I guarantee you are going to be in violation of minimum exposure limits," says Corum.

To avoid improper filtering, Angel says to find out what the suggested air-to-cloth ratios are for the different machines you are running and err on the side of caution. "The rule-of-thumb might be 6-to-1 for a sander and 10-to-1 for a moulder, so a shop that is running both should have an 8-to-1 or 9-to-1 ratio overall," says Angel.

Owners are also advised to check on how full their filters are and to change them when the time comes. "These filters are just like the ones in your vacuum at home only larger. When they get full the system won't suck anymore," says Angel.

9: Leaky airlocks

A popular trend in dust collection over the past 10 to 15 years is a break away from traditional engineering, says Joe Hill, president of Southern Pneumatics, a division of Joe Hill Co. Inc.

One of the most common of these breaks has been the introduction of a negative system in which the blower is put on the clean-air side of the collector. However, when this is done, it is important to make sure that the flex-tip blades in the airlocks are changed on a regular basis, sometimes as much as twice a year, says Joe Hill.

"A leaky airlock will cause dust to suspend above the airlock, making for a corrupt situation," he says. "A major shutdown of this type can take up to four hours to fix."

If your dust collection system is negative and discharging material into a relay system that is experiencing bridging, Hill recommends checking your airlock vanes.

10: Penny-wise, dollar-foolish

"Most of the mistakes I see are because people were penny-wise and dollar-foolish when buying their dust collection system," says Angel. "They think that it is no big deal because in their mind dust collection is just something they have to do, and, in the end, it ends up costing them more than it should."

When purchasing a system, owners are encouraged to take their time and answer the necessary questions of manpower, equipment and waste before committing to anything.

"The biggest thing I hear from people is that if they had only known up front that there is a right and a wrong way to do things, they would have done things very differently," concludes Joe Hill.

Have something to say? Share your thoughts with us in the comments below.