DUST COLLECTORS

Common questions and answers

 

 

What size should I buy?

 

Until 1993, 95%+ of all mobile dust collectors being sold were rated at 15-20,000 CFM. Why this size? 20,000 CFM was a lot of air compared to using nothing. The 20,000 CFM units could be pulled by heavy pickup trucks. With negative air ventilation specified today, you want to have enough air so that the dust doesn't escape and cause problems. This was normally enough air to handle 2-4 men blasting with slag or steel grit.

 

With the new OSHA regulations, 30,45 and 60,000 CFM units are becoming the most popular sizes for a number of reasons. Engineers and contractors realize that it is better to have too much air than not enough. Extra CFM makes it easier to meet some of the new negative air performance requirements. Contractors are now seeing that extra air is less costly than trying to create a perfectly sealed enclosure.

 

Our recommendation:

Purchase the largest unit you can afford in the 30-60,000 CFM range. It costs less to purchase larger units (per CFM) than smaller ones. Too MUCH air is seldom a problem. Too LITTLE air can cause big headaches.

 

If I purchase a 30,000 CFM unit, how do I know that it will actually move 30,000 CFM?

 

The easiest way to determine how much air your dust collector is moving is to measure the air flow using a test gauge or our CFM flow guage (optional on our dust collectors). At Advantage SPS we rate our machines very conservatively assuming that ducting is attached and that the filters have dust in them. Most other companies measure their air flow assuming brand new conditions. Conditions that may only exist on the first day of operation. The 26,000 CFM dust collector may only deliver 26,000 CFM on the first day of operation. If you actually measure the airflow after 30 days on the job, you will probably be surprised how much air is actually being moved.

 

What can I ask for that will prove the performance?

 

You can ask for what is called the fan curve. This is a chart that shows what size the fan is (diameter) and what the RATED performance is. An organization called AMCA (Air Moving and Conditioning Association) certifies the ratings of fan manufacturers.

 

Is the fan rating the same as what I can expect to get?

 

The fan rating will tell you what the fan can do. If a fan is rated at 30,000 CFM at 13" SP (static pressure) that means it will produce that rating (30,000 CFM) with 13" of resistance. A typical dust collector might have 4-10" of resistance built in (from filters, elbows, etc.). If the filter is efficient, it will have a low SP which will mean you have more SP available for the resistance in the duct work.

 

If the total SP (dust collector AND ductwork) exceeds the rating of the fan, you WILL NOT get the rated performance if you measure the air flow at the end of the ductwork.

 

Why is this important?

 

It is important the day OSHA shows up and measures the velocity of air flow in your containment. If you made your calculations assuming a certain air flow and the collector isn't producing what you thought you purchased, all your calculations will be incorrect. All of a sudden the great deal you got on your dust collector isn't such a great deal when you add in the OSHA penalty. In the coming years, engineers will get more strict in their enforcement of ventilation requirements.

 

I see all the manufacturers are selling units with replaceable cartridges. What are these cartridges?

 

Filter cartridges are just like the big air filter on your compressor. They are made from a pleated material attached to a steel ring. The material is normally what is called "cellulose", which is really just wood fiber or paper. Other materials are also available that may include polyester and other synthetic fibers. These filters will typically cost more and last longer due to their resistence to absorb moisture.

 

Do all cartridges last the same amount of time?

 

Four paper manufacturers make virtually all the "paper" for all the companies that make cartridge filters. The "paper" is available in a variety of types. To get longer filter life, polyester fibers are added to the mix of paper. Advantage SPS uses a polyester blend (plastic fibers) or a spun-bond material which is all polyester. No filter will last forever. If the pulse cleaning system is set properly, they should last 1-6 years DEPENDING ON THE LEVEL OF DUST LOADING, MAINTENANCE, MOISTURE LEVELS, ETC. 

 

How long will the cartridge last?

 

Filters wear out for one or more of three reasons.

 

FATIGUE: The repeated pulses of air that clean the filter will cause the filter paper to fatigue and then rip open.

ABRASION:  If the dust collector is improperly designed, the dust coming into the filter will cause it to wear by abrasion. When this happens, the filter will begin to leak.

CLOGGING: Over time, the filter paper will become saturated with dust. If the dust is wet it can actually stick to the paper and not fall off when the pulse of air hits the inside of the cartridge.

 

How much will they cost to replace? How much work is it?

 

The typical cartridge will cost $60 to $120 each depending on the material that is used. Normally there is one cartridge per 100-500 CFM of fan capacity. Installation takes only a wrench and about 1-2 hours for a set. When you are buying a unit, check the cost of a full replacement set.

 

The "razor blade" concept.

 

Some manufacturers have designed dust collectors that are simply not engineered properly. If designed correctly, filters should last for years.  By design, some dust collectors will never work properly. They will never be able to get the filters "pulsed clean". You then have to purchase new sets of filters frequently. If filters are replaced (under the worst conditions) more frequently than once each 1-2 years, you may have a dust collector that was never designed properly. In most cases, the units were not designed to pulse improperly, rather it is a case of poor engineering.

 

Some manufacturers use vertical filters and others use horizontal. Which arrangement works best? Vertical or horizontal?

 

The first cartridge filter systems were sold in the late 70's. These were referred to as "up flow" systems because the dusty air had to flow "up" into the cartridge. The pulse air burst would then blast "down" causing the dust to fall down into the hopper. In the 80's the "down flow" systems become popular because they could be built to take up less space on large industrial installations.  Additionally, the filters were placed in the housing horizontally and were easier to remove. With the "down flow" approach, the dusty air MUST come from the top and flow DOWN over the filters. When the air blast pulses the filter, the dust would jump up from the filter and get pulled down to the hopper with the "down flow" air. On mobile collectors, there usually isn't room to have a big air duct bringing the air from the top downward over the filters. The manufacturers of these mobile systems have cheated and pulled the air in from the sides. The result, shorter filter life.

 

Advantage SPS uses only "up flow" systems because they have proven to be reliable under the toughest conditions. When the "pulse" air blasts into the filter, the dust falls down into the hopper. Gravity can always be relied upon to work.

 

How important is particle size efficiency? 1 micron or 2 micron?

 

VERY IMPORTANT. A dust collector was specified to collect the hazardous dust in a filter and deposit it into a hopper. The goal is to catch the dust particles, NOT let them pass. Regulations are becoming very strict about filter efficiency. Advantage SPS systems are designed to the following  specification using the  ASHRAE 52-76 test procedure:

 

100%  particle efficiency by weight on particles 5 micron (large particles)

100%  particle efficiency by weight on particles 2 micron

99.9% particle efficiency by weight on particles 1 micron

99.8% particle efficiency by weight on particles .5 micron (very small particles)

 

State DOT and consulting engineers are very concerned that the money they spend to specify dust collection GETS THEM COLLECTION OF THE HAZARDOUS DUST. They don't want to find that the fan is exhausting a steady steam of small dust particles. Expect to see filter efficiency specified on projects.

 

What is HEPA? Do I need it?

 

HEPA (High Efficiency Particulate Assimilator) was developed during in the 40's to address very high levels of filtration. Addition of a HEPA stage to a typical dust collector will increase the static pressure by 1" of water. These are typically used in situations where a hazardous material such as asbestos is being vacuumed. When escape of ANY material could present health hazard, HEPA is the solution. HEPA is not commonly used for dust collectors in the 10-70,000 CFM range.

 

What size do I want to use for ducting?

 

The biggest you can handle and afford. The smaller the duct the more friction loss. Just like blast hose, the bigger the hose, the less pressure you lose. For 20,000 CFM two 20" flexible ducts are the minimum. Smooth bore tubing has a lot less friction than flexible ducting. Whenever possible, use smooth tubing to reduce friction.

 

Advantage SPS dust collectors are designed to deliver their rated CFM assuming 100 feet of straight tubing off each inlet. We recommend that you analyze the length of smooth tubing, length of flexible tubing and number of bends before you select a hose size.

 

When long vertical runs are required, 24” is a common size. When the duct must be handled daily, 20” is the most common because it is about the largest size that can be handled by one person. Over that size, it gets hard to handle because you can’t get your arms around the duct.

 

What do I need to pull this dust collector to jobs?

 

You must look at the trailer rating of the vehicle you intend to use. It will have an indication of the weight that it can safely pull. As dust collectors get bigger, it is very important to use a truck that has the braking ability to match the weight of the collector.

 

In addition to determining the ability of the truck, it is important to check the ability of the hitch to pull and hold up the tongue.

 

How much maintenance does it take to keep a machine going?

 

Mobile dust collectors don't require a great deal of maintenance. As long as the pulse cleaning system is working properly, the filters will work as they should. Over time, timer boards, diaphragm valves and filters will require some attention.

 

When Advantage SPS dust collectors don't work properly, it is usually as simple problem. Failure to run the augers to remove the dust from the hopper, failure to turn on the pulse timer, failure to turn on the pulse air and other oversights are the most common reasons for problems. Before you start the new season, it is best to have the entire unit checked over.

 

Is hopper size important? 

 

In fact it is perhaps the single most important element in allowing long filter life. A large hopper allows the air velocity to slow down as it comes in from the ducting. This reduces the chance of abrasion as the cause of filter failure.

 

 

 

A BETTER DUST COLLECTOR:

 

Largest hopper for long filter life

 

A large hopper will allow the incoming air to drop to a lower velocity as the dust laden air hits the filters. If the velocity is too high, the dust can actually wear holes in the filter units. The lower the velocity, the less filter abrasion.

 

Lightest weight for easy pulling

 

Without sacrificing performance, we have reduced the overall weight to make the unit easier to pull.

 

Largest pulse reservoir for high power pulse cleaning

 

The number one cause of filter clogging is insufficient pulse cleaning pressure. An 8" diameter reservoir provides maximum volume for high impact pulse cleaning.

 

Top removal of cartridge filters

 

Top removal means you can stand on a safe platform while you easily loosen and lift filters out. Dust is contained within an area that can easily be vacuumed.

 

Vertical cartridge filters clean better and last longer than horizontal filters

 

The vertical design makes it much easier to pulse clean more dust off the filters. Dust just drops straight down into the hopper. Horizontal systems were designed to be used with dusts like welding fumes, not heavy lead paint dust.

 

Lowest center of gravity improves pulling and reduces chance of rollovers

 

If you expect to pull your dust collector onto the shoulder or grass area WATCH OUT. Some machines on the market are very top heavy and can easily roll.

 

Many types of filters available

 

Full polyester, blended polyester, Gore-Tex, Teflon, cellulose and treated cellulose are just some of the options available from Advantage SPS.