Can a dust collector be over worked?

[SpiderDave]

Okay, I've got a hair brained idea I'd like to run past the vast knowledge of fellow Woodnet members. I'd like to occasionally use my Dust Collection system for welding exhaust fume extraction. My system's a cyclone and then a Shop Fox W1687 - 8", 3 HP, 2,800 CFM Dust Collector vented outside. I'm in the process of installing it now actually. This is the time for changes and modifications if there are going to be any. Rather than purchase another blower, running circuits, making another hole in the wall, etc. Why can't I just make a 2-way valve type switchable blast gate and divert it from the wood particle cyclone to the 18 ft Fume extraction arm I built? I can build a cyclone for it to separate debris, which it's only smoke so that seems over kill when a screened box filter would likely be more practical - we'll see. In other words, I wouldn't be mixing (hot) metal and wood. As for the occasional particles that will inevitably make it through, it will have to travel 50 ft wind tunnel to get where it's going and be cooled plenty by that time. The weld fumes would just bypass the wood system directly to the Dust Collector and vent outside like it would anyway. Only sharing the Dust Collection Blower and the outward vent pipe. 

My welding fume exhaust arm has internal workings and structure within the pipe - lots of friction/drag. It typically requires a centrifugal or inline type fan which I didn't count on being so expensive when I built it. I'd like to limit the holes I put in the shop and save some money as well. No running new circuits or remodeling to do it. If I have both systems individually in the same work shop, I'd of course need blast gates or one way valves on each ducting system to avoid pulling the exhaust back from that side of the shop. So why not join them together to solve many issues? Only one would be used at a time.

Unless I misunderstood. I read in a thread earlier that if there was reduction or constriction in the air flow the DC would just being working that much less, rather than harder. Since a DC is about air flow rather than vacuum. My system will be a straight forward one machine at a time hook-up. Roll tool out, hook up hose, use tool & then put it back sort of process. I'm concerned about the drag in the exhaust arm. If I hook it up temporarily and it sucks up enough welding fume to be satisfactory (around 350-400 cfm's), would that reduction be working the motor hard and draw more amps? Or the other way around? If it's not going to hurt it, then why not? If need be, I have considered plan-B which is to take the arm apart and mount the 6" hose it uses on the 'outside' of the arm where air can flow more freely. Another thing to consider, as the arm is bent or turned it will increase or decrease friction/drag. Will this change or mess with the motor too much or is there more leeway and freedom with it than that?  Whether I use those exhaust arm piping on the outside or not, I think the question still applies. If done properly, do you think this would be a good multi-use of my Dust Collector? Does anyone have any input, suggestions or ideas here?

My apologies if this is too long. It's a hard to ask a question like this, without going into detail and explaining. I'd like to get it right the first time while I still have people's interest. Thanks for your time!

[TDKPE]

Restricting the flow will reduce the motor load in a centrifugal blower or pump.  Like blocking the end of your vacuum cleaner hose - the motor speeds up because the load has been reduced, and being a universal motor, speed changes with load is very obvious.

In the case of a DC with induction motor, your best bet is to simply check the current with a clamp-on ammeter, and if it's higher than the nameplate current "FLA" number, restrict the flow until it's not.  That would be true for any installation, including your normal cyclone system, by the way.

But yes, you certainly can overload a DC blower motor, mostly by having too little restriction on either/both end/s, which includes the bags or filters.

Oh, and a welding fume extractor is nothing more than a centrifugal blower with a long hose. Just like a DC, absent the bags, though some have filtration of course. We use them to ventilate tight spaces the welders are working in, and blowing the fumes into the main area isn't an issue.

[SpiderDave]

Restricting the flow will reduce the motor load in a centrifugal blower or pump.  Like blocking the end of your vacuum cleaner hose - the motor speeds up because the load has been reduced, and being a universal motor, speed changes with load is very obvious.

In the case of a DC with induction motor, your best bet is to simply check the current with a clamp-on ammeter, and if it's higher than the nameplate current "FLA" number, restrict the flow until it's not.  That would be true for any installation, including your normal cyclone system, by the way.

But yes, you certainly can overload a DC blower motor, mostly by having too little restriction on either/both end/s, which includes the bags or filters.

Oh, and a welding fume extractor is nothing more than a centrifugal blower with a long hose.  Just like a DC, absent the bags, though some have filtration of course.  We use them to ventilate tight spaces the welders are working in, and blowing the fumes into the main area isn't an issue.

Thanks TDKPE! That answered a lot! I was concerned about the back pressure or the lack of.

I kept the filter bags for the same reason you specified, just in case - glad I did now Or considered using a damper to adjust flow. Even considered locating the filter bags outside the shop in their own enclosure. It'd be more favorable if I made that bit of dust emptying the bags outside, rather than inside.  I was trying to cover my bases but didn't have a real sense of direction with it, so thank you. This makes sense to me now.

[SpiderDave]

Restricting the flow will reduce the motor load in a centrifugal blower or pump.  Like blocking the end of your vacuum cleaner hose - the motor speeds up because the load has been reduced, and being a universal motor, speed changes with load is very obvious.

In the case of a DC with induction motor, your best bet is to simply check the current with a clamp-on ammeter, and if it's higher than the nameplate current "FLA" number, restrict the flow until it's not.  That would be true for any installation, including your normal cyclone system, by the way.

But yes, you certainly can overload a DC blower motor, mostly by having too little restriction on either/both end/s, which includes the bags or filters.

Oh, and a welding fume extractor is nothing more than a centrifugal blower with a long hose.  Just like a DC, absent the bags, though some have filtration of course.  We use them to ventilate tight spaces the welders are working in, and blowing the fumes into the main area isn't an issue.

Okay, I think I have a grasp on this. But that little voice of 'don't ruin your new DC Unit' is still tapping me on the shoulder, buggin' me.  

One thing I would like to get my brain around, is the lack of load vs amps. I'm understanding this so much better than I was before. Allowing the dust collector to run naked is a bad idea. It needs some back pressure or friction/drag in order to not over draw amps. It took me a bit to grasp that the motor's doing nothing and speeding up for that reason. Like most people I was stuck on the idea/misunderstanding that when a vacuum is plugged up with your hand and you hear the pitch of the electric motor ramp up. It's because it's working harder. Now I understand it's the opposite. 

With this fume extraction arm. If the amps are below the FLA, does it matter how much air is being moved? Can you move too little air and burn it up that way also? I read a lot of articles about people downsizing an 8" hose to 6' or 4" like many tools have. My mind asks if having some relief with a another tools blast gate to balance things out a bit and provide more flow? Both to move particles and to allow the machine to breathe a bit? I am wondering in that same sense if I need to be concerned about balance or just make sure the amps are where they should be and everything else if fine and more about preference?  And do I want the amps at that mark, slightly below or well below the FLA? How do I know where the sweet spot is?

Bottom line, if the amps are lower that the FLA or running amps. Should I even bother being concerned about anything else at all? If the fumes are sucked up nicely (with no real concerns over wood debris, particles or chips needing flow to move them), then is it okay? The drag or static pressure that the arm structure creates inside of the piping, will reduce air flow. Does this mean my DC isn't working as hard, therefore it will not harm it? Can you see what I'm getting at? If I'm happy with the performance of the fume exhaust arm, and the amps are in a safe range, then all is well?  

My thinking is I can measure amps with the extraction arm straight. Then measure it when it's folded as much as I would ever realistically use it (not much difference really). And make sure both don't go above the FLA. And as long as it's sucking up fumes, I'm fine? Amps are my concern, not air flow when it comes to the 'health' of my Shop Fox Dust Collector motor? Or both? 

I do want to say. When it's in the budget, I plan to have another method to suck up fumes. I'd like to keep and use this arm for removing fine dust in areas where I do hand work (like sanding etc.) or where I may need extra dust removal. When that happens I'll likely be putting the hose/ducting on the outside of the arm. Just wanted to point that out because this is a wood working site, not metal. And I don't want to cross any lines here. But it isn't about metal in my mind. It's about the health of my Shop Fox and making sure it's being taken care of properly so when I get where I'm gong with it. It'll still be there, dependable and running smooth as always. Such a nice machine, I'm proud of it. It took me a great deal to acquire one. So I'd like to take care of it, like I do all of my tools. :-) So i really appreciate any and all help in my education here. Thanks as always!

[TDKPE]

Okay, I think I have a grasp on this. But that little voice of 'don't ruin your new DC Unit' is still tapping me on the shoulder, buggin' me.  

One thing I would like to get my brain around, is the lack of load vs amps. I'm understanding this so much better than I was before. Allowing the dust collector to run naked is a bad idea. It needs some back pressure or friction/drag in order to not over draw amps. It took me a bit to grasp that the motor's doing nothing and speeding up for that reason. Like most people I was stuck on the idea/misunderstanding that when a vacuum is plugged up with your hand and you hear the pitch of the electric motor ramp up. It's because it's working harder. Now I understand it's the opposite.  Correct.

With this fume extraction arm. If the amps are below the FLA, does it matter how much air is being moved? Can you move too little air and burn it up that way also? Some vacuum cleaners used to use the air stream for motor cooling, so you could damage them by blocking all of the air flow, but that's not the case with a DC motor, which is self-cooled and completely independent from the blower unit.  Larger ones are usually belt driven in fact, which puts the motor nowhere near the blower.  I read a lot of articles about people downsizing an 8" hose to 6' or 4" like many tools have. My mind asks if having some relief with a another tools blast gate to balance things out a bit and provide more flow? Both to move particles and to allow the machine to breathe a bit? I am wondering in that same sense if I need to be concerned about balance or just make sure the amps are where they should be and everything else if fine and more about preference?  And do I want the amps at that mark, slightly below or well below the FLA? How do I know where the sweet spot is?  Motor life is dependent on the winding temperature, which is designed for some maximum based on winding insulation class, and on the overall quality of the motor.  The hotter it runs, the shorter its life will likely be; 'likely' because it's the statistical likelihood of failure at some number of hours at design load they're designing to, based on 100+ years of motor design and operation experience in the industry.  If it's designed for 20,000 hours at full load, you'll (likely) get more life out of it at less than full load.  In fact, every 10 deg. C you drop the winding temperature by reducing the load will double the life of the motor, or so the accepted paradigm goes.  Where the sweet spot is depends on what you want it to be, but for the typical home woodworker or metal worker, it should last nearly a lifetime at or below rated current.  Frequent starts will put more thermal stress on the windings than just running at or below rated load, by the way.  A current wallop of 4-8 times rated current every time it starts, without sufficient time for the internal winding and hot spot heating to dissipate, will suck the life out of it faster than just running it.  If you need to start/stop frequently, it would be better just to block the suction when you would stop it, as that unloads the motor almost completely.  And your electric meter will spin slower.   

Bottom line, if the amps are lower that the FLA or running amps. Should I even bother being concerned about anything else at all? If the fumes are sucked up nicely (with no real concerns over wood debris, particles or chips needing flow to move them), then is it okay? The drag or static pressure that the arm structure creates inside of the piping, will reduce air flow. Does this mean my DC isn't working as hard, therefore it will not harm it? Can you see what I'm getting at? If I'm happy with the performance of the fume exhaust arm, and the amps are in a safe range, then all is well?  The motor has no idea what's going on at the other end of the shaft; all it knows is the torque load it's driving, and as that load slows the shaft (slightly in the case of an induction motor, but a lot in the case of universal motors like vacuum cleaners and routers), it will continue to drive the torque load but will allow more current to pass in order to do that.  From a no-load current value, it will draw an increased current more or less in proportion to the applied torque.  Increasing flow resistance anywhere in the system will reduce the load on the motor.  So if it's pulling fumes the way you want it to, and the motor current is no higher than the nameplate FLA, then you're golden.

My thinking is I can measure amps with the extraction arm straight. Then measure it when it's folded as much as I would ever realistically use it (not much difference really). And make sure both don't go above the FLA. And as long as it's sucking up fumes, I'm fine? Amps are my concern, not air flow when it comes to the 'health' of my Shop Fox Dust Collector motor? Or both?  As long as you stay at or below the nameplate FLA value, it'll be fine.  It'll be fine above that value, but won't live as long, so maybe that's not being fine.  A lot above that value and it'll stop being fine real soon, though (see above about winding temperature).  Well below the FLA figure and it might live forever (in human terms).

I do want to say. When it's in the budget, I plan to have another method to suck up fumes. I'd like to keep and use this arm for removing fine dust in areas where I do hand work (like sanding etc.) or where I may need extra dust removal. When that happens I'll likely be putting the hose/ducting on the outside of the arm. Just wanted to point that out because this is a wood working site, not metal. And I don't want to cross any lines here. But it isn't about metal in my mind. It's about the health of my Shop Fox and making sure it's being taken care of properly so when I get where I'm gong with it. It'll still be there, dependable and running smooth as always. Such a nice machine, I'm proud of it. It took me a great deal to acquire one. So I'd like to take care of it, like I do all of my tools. :-) So i really appreciate any and all help in my education here. Thanks as always!  A true fume extractor is nothing more than a centrifugal blower with a hose, maybe with a filter.  Our big fabrication shop has used cheap DC blowers as fume extractors and they're fine.  The only thing that makes it a woodworking DC is that the impeller is usually designed for wood bits and chips and such to hit it at speed, while a fume extractor may have a more efficient impeller design that's not intended to get hit with stuff, though I don't know that for fact.  But the common single-stage DC impeller most certainly is designed to move debris through itself without damage or clogs.  Other than the task of switching from wood to fume mode and back, I don't see any reason you shouldn't use it for both.  Or get a cheap Harbor Freight 1 hp DC on rollers, like this one, and dedicate it to fume extraction.  Maybe pipe the exhaust out a window to keep the air clear.  

https://www.harborfreight.com/13-gal-1-h...61808.html

One other comment on current: low line voltage will cause an increase in current draw through the motor, as will an increase in motor torque load, so the real indicator of motor "loading" is the current.  Loading because even if the motor load is within the nameplate load (say 1 hp, for talking sake), but the voltage is very low due to (for example) very long wiring and/or a long/small extension cord, the motor will draw more current to maintain speed and can exceed the nameplate rating.  The heating from the current is what ages them, so a shorter life can be expected.  So no matter what else is going on with that motor, the current through it is the best single indicator that it's operating within design parameters.  

[SpiderDave]

One other comment on current: low line voltage will cause an increase in current draw through the motor, as will an increase in motor torque load, so the real indicator of motor "loading" is the current.  Loading because even if the motor load is within the nameplate load (say 1 hp, for talking sake), but the voltage is very low due to (for example) very long wiring and/or a long/small extension cord, the motor will draw more current to maintain speed and can exceed the nameplate rating.  The heating from the current is what ages them, so a shorter life can be expected.  So no matter what else is going on with that motor, the current through it is the best single indicator that it's operating within design parameters.  

I love to learn and find clarity on subjects, whatever and whenever I can. So 'Thank You' very much for all the work you put into answering this thread. I've read it several times to absorb it 110%. 

I hooked up the DC to the F.Exhaust arm last night and it performed beautifully! Just as good as any Portable Kemper Ume Ext. Unit that I've used. Unfortunately my amp meter has died since its last use. I turned it off quickly and left there until the next round. I'll be buying another meter today and going from there.

Thankfully you did hit a subject I failed to mention, that I forgot about. The start & stopping of the blower. I'd hoped to have the fume exhaust on a foot switch or something, using it when needed. With longer or short repeating welds, I would leave it running continuously. If I had an idea of the cost to leave it running, I might stick with leaving it on. But, I keep imagining the meter spinning. 

Well, if it wasn't for the stop and start issue, it sounds like I would have this thing licked. I was so happy with how it worked. I do think this is worth worrying about though. Maybe that's why just the fan/blowers for the fume exhaust arms are so expensive? Built to withstand the abuse? ($1,000-$3,000) Or just taking advantage of it's function and demand. 

I had considered the HF blower also. I didn't go that route because I wasn't sure about going from a 6" arm duct to a 4" inlet on the blower? Maybe with the structure inside the arm hose, that could be a good thing? in preservation of my DC motor, I may swing by HF and pick one up. And see how it handles it while everything's ready and set in place for testing anyway. There's a couple on Craig's List,at a decent price. I'll let you know how it goes. Thanks again!

[SpiderDave]

One other comment on current: low line voltage will cause an increase in current draw through the motor, as will an increase in motor torque load, so the real indicator of motor "loading" is the current.  Loading because even if the motor load is within the nameplate load (say 1 hp, for talking sake), but the voltage is very low due to (for example) very long wiring and/or a long/small extension cord, the motor will draw more current to maintain speed and can exceed the nameplate rating.  The heating from the current is what ages them, so a shorter life can be expected.  So no matter what else is going on with that motor, the current through it is the best single indicator that it's operating within design parameters.  

Will I have start/stop issues with any blower that I buy? Should I buy something specific to that need or is the Harbor Freight DC going to hold up, reasonably enough? Or is the pwr bill too small to really worry about?

[TDKPE]

Will I have start/stop issues with any blower that I buy? Potentially. Should I buy something specific to that need or is the Harbor Freight DC going to hold up, reasonably enough? I'd guess the HF unit will do OK, but I don't know that. Or is the pwr bill too small to really worry about?  Almost certainly be too small to worry about.  The welding machines will spin your meter like a top when actually welding, by contrast.  I used to cut with my 230A buzz box when I was a kid (still have it, and still use it), and my Dad used to comment that the meter would spin like a flying saucer when I was cutting.  Didn't occurr to me at the time, but he probably wanted me to kick in some cash to pay for my hobby.  

 Worst-case scenario, take the nameplate current or measured current and multiply by 0.8, and then by the voltage.  That's the approximate full-load watts it's drawing through your electric utility meter.  Divide by 1000 for kilowatts.  If you know your electric rate (energy plus delivery charges, which are usually enumerated separately on the bill), multiply by this rate.  For me, it's almost exactly $0.10/kW-hr including energy, delivery, and taxes, so every hour running a 1. 00W motor (about 1 hp with an 80% efficiency running at full load) adds about ten cents to the bill.  

Choke the air down, and the wattage goes down, so if you don't want to start/stop constantly, just plug the end or put in a blast gate you can close.  Watch your ammeter and you'll see the current drop when it's closed.  Starting doesn't cost as much as you might think, as it's relatively quick even though the current draw is rather huge.  A 1-second start-up event, which is rather long for a small motor, might cost 5-8 seconds worth of full-load energy, which is rather tiny on the grand scheme of things.  But heating is substantial, and can add up if you're cycling it repeatedly without run time after start-up to dissipate the heat (internal fan and rotor swirl the air around the windings, even in a TEFC motor).

But remember that your a hobbiest, and even getting ridden hard and put away wet, the motor may still outlive you.  In an industrial situation, probably not so much.  Motors intended to be started frequently are designed for that, like overhead cranes in production environments (think scrap handling), starting under load and running hard for hours on end.  Small motors in hobby shops certainly can be beaten into the ground, but it's not that common (I don't think).

[SpiderDave]

 Worst-case scenario, take the nameplate current or measured current and multiply by 0.8, and then by the voltage.  That's the approximate full-load watts it's drawing through your electric utility meter.  Divide by 1000 for kilowatts.  If you know your electric rate (energy plus delivery charges, which are usually enumerated separately on the bill), multiply by this rate.  For me, it's almost exactly $0.10/kW-hr including energy, delivery, and taxes, so every hour running a 1. 00W motor (about 1 hp with an 80% efficiency running at full load) adds about ten cents to the bill.  

Choke the air down, and the wattage goes down, so if you don't want to start/stop constantly, just plug the end or put in a blast gate you can close.  Watch your ammeter and you'll see the current drop when it's closed.  Starting doesn't cost as much as you might think, as it's relatively quick even though the current draw is rather huge.  A 1-second start-up event, which is rather long for a small motor, might cost 5-8 seconds worth of full-load energy, which is rather tiny on the grand scheme of things.  But heating is substantial, and can add up if you're cycling it repeatedly without run time after start-up to dissipate the heat (internal fan and rotor swirl the air around the windings, even in a TEFC motor).

But remember that your a hobbiest, and even getting ridden hard and put away wet, the motor may still outlive you.  In an industrial situation, probably not so much.  Motors intended to be started frequently are designed for that, like overhead cranes in production environments (think scrap handling), starting under load and running hard for hours on end.  Small motors in hobby shops certainly can be beaten into the ground, but it's not that common (I don't think).

I'll very likely be out there full time when this is finished - cross your fingers. That's why I'm so worried about it. I was supposed to be done some time ago. Life got in the way with some surprise expenses slowing us down - typical luck. in trying to prevent further discouragement and set backs on this project, maybe it's made me overly cautious. I have jobs piling up and can't afford to have anything going wrong anytime soon. 

With what you've given me here, I can probably sleep at night if I skip the HF blower, save that money and make a damper or a plug like you said to 'choke the air down'. As something to gauge my understanding by, with general use of wood particles or fume extraction; what would you consider for small jobs and short usage to be a safe amount of time to run the machine before shutting it down? To cool it down properly and treat it right when I only need it for one or a few cuts on the bandsaw etc.  

I'm going to put that equation to use tonight. Thank for you patience and knowledge TDKPE. Hopefully someone else in my position will find this post as helpful as I have. You've explained it so well,... even I understood it.

[TDKPE]

I'll very likely be out there full time when this is finished - cross your fingers. That's why I'm so worried about it. I was supposed to be done some time ago. Life got in the way with some surprise expenses slowing us down - typical luck. in trying to prevent further discouragement and set backs on this project, maybe it's made me overly cautious. I have jobs piling up and can't afford to have anything going wrong anytime soon. 

With what you've given me here, I can probably sleep at night if I skip the HF blower, save that money and make a damper or a plug like you said to 'choke the air down'. As something to gauge my understanding by, with general use of wood particles or fume extraction; what would you consider for small jobs and short usage to be a safe amount of time to run the machine before shutting it down? To cool it down properly and treat it right when I only need it for one or a few cuts on the bandsaw etc.  For a few cuts, I wouldn't sweat it.  If it's on a foot pedal switch and you're starting it for every cut (or weld), you'll prematurely age it.  But it's impossible to predict by how much without burying thermocouples in the windings (which is done on many industrial motors as a standard or custom option) to monitor the temperature.  Just use common sense.  Long off times are just as good as short run times for allowing 'recovery' from starting, by the way.  I don't mean to scare you.  Some here use a remote motor control for their DC systems, and they're not burning their motors out regularly.  Just be aware that a DC blower is relatively hard-starting due to it's large inertia (a table saw or band saw, not so much - they basically just snap to attention), yielding relatively long start times, so just be conscious of that and don't be cycling it on/off every 30 seconds - let it run in that case, and choke off the flow between uses if you like.  

I'm going to put that equation to use tonight. Thank for you patience and knowledge TDKPE. Hopefully someone else in my position will find this post as helpful as I have. You've explained it so well,... even I understood it.