Pulse Jet Pointers
Vol. 1, No. 3

If you are "part of the herd", you will soon, if not already, buy ceiling fans for your workplace. Everybody's doing it, so it must be right, right? No, only about 10% right! We have no argument with commercial and institutional applications (unless recycled sweat bothers you), but when it comes to industrial fumes, mists, and gases — look out! The one thing the ceiling fan can never be is an air purification device. Our forefathers built plants with saw tooth roofs. A few of them remain. lf the windows on the vertical part of the saw don't leak enough on their own, they can be opened. The processes which create the contaminated air also usually heat it up. It then rises into the saw tooth area and is released to the great outdoors. Replacement air comes in where it can, is heated by whatever means is there, and hopefully does not create too many drafts on the workers. Modern plants have flat roofs, gravity or powered ventilators, and heated make up air systems. If the air going out does not meet air pollution standards, roof vents are replaced with dust or fume collectors. Similarly, replacement air is filtered to a degree acceptable for human environments. Suddenly, enter the ceiling fan salesman; sometimes even armed with a "computer analysis." He turns off the exhaust; he turns off the supply; and he turns on his windmills. He also "turns on" the comptroller with big reductions in fuel bills. But what about the air that was up in the trusses? It was, of course, leaking out or being powered out by ventilators originally installed for that very purpose. Now it is right back down in the breathing zone of the worker, lacking in oxygen, but high in CO, COs, aldehydes, oil vapors, fine particulates and noxious odors. Because there is a new and often very welcome circulation of air, the worker feels that for once the boss did something right. But look out for more respiratory ailments and lower productivity. We believe there is no substitute for good dust and fume control. There is also no way to handle odors and gases within the average plant's budget, except to exhaust and replace. Then, when you know that the air at the ceiling is only warm and otherwise uncontaminated, some properly sized industrial grade ceiling fans are in order. Despite what all of the above sounded like, we do sell them. Our brand is the Mirage Awesome 60 by Leading Edge, Inc. A truly industrial grade ceiling fan. Ask us for a bulletin and prices. We have been making good air for industry since 1921.

Pulse jet type bag 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. Bag material
7. Air stream density, temperature, dew point, or properties of gas if other than air.

Most users of pulse jet bag 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.

1. Most dust is plus one micron in size.
2. Most of our bag collectors are 99.9% efficient on
   all particles one micron and over.
3. Most bags see less than one grain/CFM inlet load. Even though inlet dust loading may be considerably higher, decantation in the hopper seldom allows more than one grain per CFM into the bag area.
4. Therefore, at 99.9% efficiency most outlet loadings are .01 grains per CFM or less.

To help you with the conversation of grain load to other common units:

Firstly, never while the pollution inspector is on site! However, to be serious, there are times when efforts to save heat and reduce pollution can be very futile. All of us have studied energy saving propositions when even the study is futile. How can one quickly grasp the economics of air cleaning? Here are the factors we use in selling air pollution control devices (remember that, with sales calls costing $134.00 each according to McGraw-Hill, we are not anxious to waste time either).

1. Can the contaminates be concentrated? (Hood pick up vs. general ventilation)
2. Is the contaminate a dust? (Gases and odors are absorbed or neutralized only at great expense).
3. Will "State of the Art" methods suffice, or will hot (over 500° F) and sticky contaminates make collection equipment exotic and experimental in nature?

If you have two or three yes answers, there is good reason to proceed with the project (inviting us in to quote, we hope). If the answer is one yes, or three no's, let us recommend a good fan! If effluents exceed legal limits, "see your industrial hygienist and avoid excessive use". Maybe the process can be changed to one which does not create "uncollectibles."

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Since 1921, Industrial Dust Control, Ventilation and Process Equipment

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