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A Subject that Doesn't Suck
Mar. 17th, 2004 08:07 pm
As an Air Quality Guy I've picked up a few facts about air pollution control devices. If you're trying to control what we so quaintly term Particulate Matter ("particles" wasn't a good enough word for us, I guess) you have a number of options open to you, including cyclones and fabric filters.
By the way, the generic term people use-- "scrubber--" applies to a device that captures pollutants in some chemical solution or water. Water scrubbers were pretty big once upon a time, but due to their tendency to eat themselves (water at incredible pressures meets air at impossible velocities, in the presence of large amounts of abrasive grit) they're not much used any more. They're still big for certain specialized purposes, such as capturing hydrochloric acid (which mixes quickly and easily with water) or destroying certain other nasties by bubbling them through a neutralizing chemical brew. Other than that, they're pretty much a dead issue.
Anyhow, the cyclone was always the first thing the Honest Businessmen proposed as pollution control. It's cheap, it has no moving parts-- you just push the air through it at a high velocity, force the air to spin, and the grit gets thrown against the sides of the cyclone and slides down to the bottom, where it's collected. Very simple, and it causes very little "pressure drop" in the air stream, which means it dosn't take much fan power to drive one of these things.
The current king of particle control devices is the fabric filter, and its most common type is called a baghouse. It's a metal box, sometimes huge, containing a few or a few hundred vertical, cylindrical fabric bags-- more like tubes than bags in shape, really. Air blows up through them, the dust stops on the fabric. There's some mechanism to clean the dust from the bags, a few at a time, so it falls to the bottom of the baghouse into hoppers for disposal.
Baghouses come in two varieties, positive pressure and negative pressure. The positive pressure baghouses have the fan upstream of the baghouse, and push the air through. The disadvantage is that the fan has to 'eat' all the grit, filth, and corruption before it gets collected-- tough on the blades and motor. The negative pressure kind has the fan downstream of the bags and pulls the air through by suction. Its advantage is the fan is on the clean-air side, but the baghouse itself has to be much stronger to handle the vacuum.
Both of them are good, though, and either of them is far more efficient than a cyclone.
You've probably realized by now that what I'm describing is God's own vacuum cleaner. The positive-pressure is an old fashioned upright, the kind which had the fabric bag instead of a hard shell. The negative pressure is a cannister vac or the newer (but not improved) hard-shell uprights. And you probably understand why I'm slightly amused at the current crop of "bagless, cyclonic" vacuums, since I know that bags are far more efficient at capturing grit than any cyclone ever was.
Lately the manufacturers seem to be outdoing themselves at making bigger, bulkier, heavier, more angular vacuum cleaners. After years of trying to make them light and polished in form, now heavy and crude is the deal. It's a return to 1950s design. Which is appropriate, I guess, because it's a return to 1950s pollution control technology too.
Then there's rating the motor in amps. You want to rate the motor in horsepower. Amps is fuel consumption, and if you really want a motor to use a lot of amps you make it as inefficient as possible. I guess the manufacturers couldn't make one horsepower sound all that impressive. So they tell you how much electricity the thing uses, and say nothing of what you GET for the cost of all that electricity.
Nevertheless, I'd bet all these new vacuums work pretty well. If only because they still have a HEPA fabric filter on the exhaust. And because the chief thing that helps a vacuum clean isn't the suction. It's the agitation of the carpet brush beating the dust out of the carpet. The suction only pulls the dust away after it's been loosened.
Which is fine as long as you're working on carpets. But my vacuum, at least, doesn't do squat on bare floors. For bare floors you turn the beater brush off, leaving you with pitiful suction only fit to collect dirt that's already been beaten into the air. It doesn't pick up a thing. So you turn the brush on, and you discover that without carpet fibers to hold the filth in place, the brush just scatters all the dirt over an approximately two-acre area. You should be wearing safety goggles and a dust mask when you try this little stunt, trust me.
These days I'm stripping carpet out of my house, planning to put more and more bare floors. I'm facing a world of bare floors, and vacuum cleaners suck on bare floors. Oops, I mean they DON'T suck on.. no, I mean.. oh, to hell with it.
The ideal for bare floors would be a cannister, but darned if I can find any-- except for a Hoover or two I found online. Last Hoover I had destroyed itself in record time. That's especially because they give them such things as powered beater heads, to try to make them work on carpets the way an upright does. It does work pretty well, for about a week until all the extra hoses, belts, motors, cables, and plugs start to go south.
I was thinking of a ShopVac, but something designed to catch sawdust and small bolts isn't going to have HEPA filtration. And HEPA is amazing. With it, my existing vacuum fills its bag in about one pass across the carpted parts of the house. They also make non-HEPA bags, and those take three or four passes to fill. Obviously, if you want to COLLECT the dust instead of just blowing it out again, you want the HEPA.
I suppose I could buy a cannister for bare floors only, track down a simple one at Sears or something, and have an upright for the carpets. But since I gave up the huge closet in the center of the house to become the furnace room it should always have been, I don't have any place to put two vacuums, really.
Nor the money for some gadget-ridden, over-featured, under-powered monster that's going to eat itself in a year or two, no matter what it costs.
I told you this subject didn't suck. And that's just the problem.
By the way, the generic term people use-- "scrubber--" applies to a device that captures pollutants in some chemical solution or water. Water scrubbers were pretty big once upon a time, but due to their tendency to eat themselves (water at incredible pressures meets air at impossible velocities, in the presence of large amounts of abrasive grit) they're not much used any more. They're still big for certain specialized purposes, such as capturing hydrochloric acid (which mixes quickly and easily with water) or destroying certain other nasties by bubbling them through a neutralizing chemical brew. Other than that, they're pretty much a dead issue.
Anyhow, the cyclone was always the first thing the Honest Businessmen proposed as pollution control. It's cheap, it has no moving parts-- you just push the air through it at a high velocity, force the air to spin, and the grit gets thrown against the sides of the cyclone and slides down to the bottom, where it's collected. Very simple, and it causes very little "pressure drop" in the air stream, which means it dosn't take much fan power to drive one of these things.
The current king of particle control devices is the fabric filter, and its most common type is called a baghouse. It's a metal box, sometimes huge, containing a few or a few hundred vertical, cylindrical fabric bags-- more like tubes than bags in shape, really. Air blows up through them, the dust stops on the fabric. There's some mechanism to clean the dust from the bags, a few at a time, so it falls to the bottom of the baghouse into hoppers for disposal.
Baghouses come in two varieties, positive pressure and negative pressure. The positive pressure baghouses have the fan upstream of the baghouse, and push the air through. The disadvantage is that the fan has to 'eat' all the grit, filth, and corruption before it gets collected-- tough on the blades and motor. The negative pressure kind has the fan downstream of the bags and pulls the air through by suction. Its advantage is the fan is on the clean-air side, but the baghouse itself has to be much stronger to handle the vacuum.
Both of them are good, though, and either of them is far more efficient than a cyclone.
You've probably realized by now that what I'm describing is God's own vacuum cleaner. The positive-pressure is an old fashioned upright, the kind which had the fabric bag instead of a hard shell. The negative pressure is a cannister vac or the newer (but not improved) hard-shell uprights. And you probably understand why I'm slightly amused at the current crop of "bagless, cyclonic" vacuums, since I know that bags are far more efficient at capturing grit than any cyclone ever was.
Lately the manufacturers seem to be outdoing themselves at making bigger, bulkier, heavier, more angular vacuum cleaners. After years of trying to make them light and polished in form, now heavy and crude is the deal. It's a return to 1950s design. Which is appropriate, I guess, because it's a return to 1950s pollution control technology too.
Then there's rating the motor in amps. You want to rate the motor in horsepower. Amps is fuel consumption, and if you really want a motor to use a lot of amps you make it as inefficient as possible. I guess the manufacturers couldn't make one horsepower sound all that impressive. So they tell you how much electricity the thing uses, and say nothing of what you GET for the cost of all that electricity.
Nevertheless, I'd bet all these new vacuums work pretty well. If only because they still have a HEPA fabric filter on the exhaust. And because the chief thing that helps a vacuum clean isn't the suction. It's the agitation of the carpet brush beating the dust out of the carpet. The suction only pulls the dust away after it's been loosened.
Which is fine as long as you're working on carpets. But my vacuum, at least, doesn't do squat on bare floors. For bare floors you turn the beater brush off, leaving you with pitiful suction only fit to collect dirt that's already been beaten into the air. It doesn't pick up a thing. So you turn the brush on, and you discover that without carpet fibers to hold the filth in place, the brush just scatters all the dirt over an approximately two-acre area. You should be wearing safety goggles and a dust mask when you try this little stunt, trust me.
These days I'm stripping carpet out of my house, planning to put more and more bare floors. I'm facing a world of bare floors, and vacuum cleaners suck on bare floors. Oops, I mean they DON'T suck on.. no, I mean.. oh, to hell with it.
The ideal for bare floors would be a cannister, but darned if I can find any-- except for a Hoover or two I found online. Last Hoover I had destroyed itself in record time. That's especially because they give them such things as powered beater heads, to try to make them work on carpets the way an upright does. It does work pretty well, for about a week until all the extra hoses, belts, motors, cables, and plugs start to go south.
I was thinking of a ShopVac, but something designed to catch sawdust and small bolts isn't going to have HEPA filtration. And HEPA is amazing. With it, my existing vacuum fills its bag in about one pass across the carpted parts of the house. They also make non-HEPA bags, and those take three or four passes to fill. Obviously, if you want to COLLECT the dust instead of just blowing it out again, you want the HEPA.
I suppose I could buy a cannister for bare floors only, track down a simple one at Sears or something, and have an upright for the carpets. But since I gave up the huge closet in the center of the house to become the furnace room it should always have been, I don't have any place to put two vacuums, really.
Nor the money for some gadget-ridden, over-featured, under-powered monster that's going to eat itself in a year or two, no matter what it costs.
I told you this subject didn't suck. And that's just the problem.
