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Frequently Asked Questions

Was it the Dust Collector, or was it the Dust?
What kind of Efficiency questions should  you ask?
How do I choose the correct filter media?
Regarding Water Pressure; How does it relate to what I am familiar with?
How do Trickle Valves Work?
Pulse Jets--How Do They Work?

Was it the Dust Collector, or Was it the Dust?

We Often Hear:

"Can you find me something that will work?"

"Sure" we say, "but it's not the dust collector's fault." At this point we can be charitable to the competition. After all, it is hardly the manufacturer's fault that the customer picked one out of a catalog, based his selection on price and delivery, and bought it over the phone from an order taker who doesn't know what the important questions needing to be asked are.

A lot of things about a dust collector are the same: a bag, a box and a fan. If the bag or bags are big enough, the box strong enough and the fan powerful enough, it will work in most any environment, but you must also keep in mind that there are more than 144 kinds of dust. Answering the questions below will help us determine the correct unit for your particular needs.

Wendell Hiester and I are in our second half century of building dust, smoke and fume collection units. We consider the first fifty years as being on the learning curve and at this point we don't really see the curve getting any flatter.

There are three dusts which form a baseline: sawdust, cement, and flour. Sawdust is disgustingly easy to collect, but is explosive, especially if it is fine. Cement won't explode or burn, but can be very hard to deal with otherwise. Flour is both difficult and explosive. So, in describing a dust, customers will often say it is like one of the three above.

You should answer these seven questions:

  • Explosive? (do you know the Kst number)

  • Hygroscopic? (and humidity of airstream expected)

  • Sub-Micron? (particle size distribution)

  • How Abrasive? (Moh's scale)

  • Static Charge? (will it stick to an inverted foam cup?)

  • Angle of Repose? (put it in a pile on a piece of cardboard and then tip the cardboard and see what the angle is when it starts to roll off.)

  • Settling rate? (throw a handful off a tall ladder and see how long it takes to float to the ground).

Now that we have the dust identified, how about the physical requirements for the dust collector.

Again, seven questions:

  1. Is the dust collector to be indoors or outdoors?

  2. What is the maximum allowable height of the dust collector?

  3. Do we furnish a fan, and if so what is the external system pressure drop?

  4. How is the area electrically classified? (voltage, phase, hertz, NEMA 4, 12, 7 or 9)

  5. Is compressed air available and at what pressure?

  6. How do you want the dust removed? (drum, airlock, slide valve or screw conveyor)

  7. How many other auxiliary items do you want us to furnish? (Leg structure, ladder, service platform, motor starter, wiring, sound attenuator, after-filters, ductwork, emission monitor and start-up service)

Answers are best obtained face to face. The phone will work too, if you give the answers thoughtfully.
--Bruce A. Beckert, President

Regarding Water Pressure; How does it relate to what I am familiar with?

Regards plus or minus 17" water gauge (abbreviated W.G.), this is a measure of pressure (about 0.6 psig). Our ordinary dust collectors are made to withstand this pressure. 28" water gauge = 1.0 psig (your car tires are at 35 psig). So this 17" W.G. is a very small amount of pressure. On the other hand if there were 17" of water gauge, plus or minus, in the room you are now in, you would not be able to get the door open to go home. The door has about 2100 square inches of surface area, so unless you lift weights at the gym, it would take more than you could muster to pull that hard on the door knob (1275 lbs).

 

Efficiency Questions Answered
A. Pulse jet type cartridge dust collector efficiency is a function of the following parameters:
1. Particle size
2. Particle shape, stickiness, hydroscopic or static charge properties
3. Particle specific gravity
4. Bulk density of particles
5. Dust collector inlet grain loading
6. Filter material
7. Airstream density, temperature, dew point, or properties of gas if other than air

B. Many users of pulse jet cartridge collectors cannot answer, or sometimes even guess at the parameters above. Even if they can, we, as manufacturers, can only use prior knowledge and some rules of thumb to determine efficiency from this data. Volumes have been written and millions have been spent, but existing technology simply cannot substitute for a stack analysis. Furthermore, an efficiency taken today is only an efficiency for today, as tomorrow the parameters will, in all likelihood, change.

C. All of this aside, we do offer the following:
1. Most dust is plus one micron in size. (One notable exception - metallurgical fumes.)
2. Most of our collectors are 99.9% efficient, by weight, on all particles one micron and over.
3. If the inlet load is five grains per CFM, at 99.9% efficiency, outlet loading is .005 grain per CFM.

D. To help you with the conversion of grain load to other common units:
1. 7000 grains = 1 pound
2. 1 gram = 15,4324 grains
3. 1 grain per cubic foot = 2288. 1 micron-grams per cubic meter
4. 1 pound per 1000 cubic feet = 16,017 micrograms per cubic meter
5. Air at standard conditions weighs .075 pounds per cubic foot
6. 44 micron size = 325 mesh (one mesh is one inch x one inch)

Choosing the Correct Filter Media

Fiber Air to
Media
Range
Maximum
Continuous
Operating
Temps
Resistance
to Acids
Resistance 
to Alkalis
Flex &
Abrasion
Percent
Expected
Efficiency on
One Micron
Approx
No. of
Sq.Ft
per
Cartridge**
Polyester 10-15 275F Fair to Good Fair to Good Good 99.90 33
Acrylic 10-15 240F Good++ Fair to Good Fair 99.90 33
Polypropylene 10-15 200F Very Good Very Good+ Good++ 99.90 33
TFE 10-15 425F Very Good Very Good Fair 99.99 33
Felted Glass 5-10 550F Good Poor Poor 99.90 33
Aramid 10-15 425F Poor* Fair Good 99.90 33
Aromatic
Polyimide
10-20 500F Very Good Fair Fair 99.99 33
Cotton 20-30 180F Poor Fair Good 90.00 55
Cartridge Standard 1-3 140F Fair Fair Good 99.90 226
Cartridge "U" Paper 1-3 140F Fair Fair Good 99.95 226
*Acid resistance is generally fair in environments above acid dew point.
**Applies to standard cartridge.
+Not to be used with aromatics and chlorinated hydrocarbons.
++Affected by aniline, glyoxal, phenol and pyridine.

        

How do Trickle Valves Work?
Pulse Jets--How Do They Work?

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                 Since 1921, Industrial Dust Control, Ventilation and Process Equipment

  

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Beckert & Hiester, Inc.
P.O. Box 1885
Saginaw, MI  48605-1885
Local and International - 989-792-3443 or 989-793-2420
Toll Free - 800 332-4031
Fax - 989-793-2971 or 989-791-4781
 

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