Large Shop Dust Collector - Advice Please

[William Dameron]

If it comes to it Phil, I'll try that. But I think that this guy could fail my inspection, citing bugs bunny, if he wanted to. I could try to ask him for details, like you said, and see if it changes his mind at all, but if it doesn't... I could probablly fight it, but the resulting hold-up might really hurt me. For now I'll play along and see what I can achieve to make things go as smoothly as possible, and most importantly as quickly as possible. We'll see...

[Michael W. Clark]

Hi William,
I'm with Phil, Jerry, and the others on the bag/filter switch. We are an OEM of industrial dust collection equipment that includes baghouses and high efficiency cyclones. Personally, I have never heard of the switch your inspector is requiring. The broken bag detectors are very common though and are adjustable to alarm at different dust loadings. This is something you would use on a centralized collector or cyclone and you record events as part of your continuous emission monitoring plan. Its not something you would typically see on an 8,000 CFM system, more like on a 50,000 CFM system or larger.

One thing I would like to ask is in regards to your air flow. If you think you need 8000 CFM, I am 100% certain you will not pull that much flow through cyclones and filters with only 12HP (four of the 3HP units).

If you are in the used market for a central collector, you may find an Aget or Torit system. They do a lot of work in the wood industry on systems this size and may have a system with all the vents configured (I don't work for either, so I'm nuetral there). You will need a backdraft or isolation device as well. If you are returning the air from a central collector, then there are other requirements. People typically do not return air directly from a baghouse, you have additional filtration to polish off any fines and act as a second stage in case you have that bag leak.

If your inspector or landlord is going to be a stickler for NFPA, it will take some time/money to put together a central system that satisfies them. Many shops like yours use multiple single stage bagger units. Get a free login on the NFPA site. You can access NFPA 664 (standard for wood processing facilities) and look through the chapter on collectors.

Mike

[William Dameron]

Awesome, thanks for the info Mike. I'll start looking into the NFPA stuff.

Also, I have always figured that my cyclone units, which are rated according to the manufacturer at 2125 cfm each, on only 3hp each, meaning 8500 cfm between them off of 12 hp, is stretching it. I do think that these 4 units should be sufficient for my machines though, although we'll see. I may eventually incorporate some automatic blast gates to help even more, but we'll see.

Having weighed all my options, I feel like putting the collectors inside is definitely easiest, if I can get around this stupid auto-shut off rule.

If I do locate them outside, I will end up with some duct runs which are pretty long - maybe 50 feet-ish, with a few elbows in there. If that's the case, will I lose too much vacuum?

I definitely want to keep this on the cheap, but effective side, and hopefully not jump into full on NFPA details...

[Michael W. Clark]

I definitely want to keep this on the cheap, but effective side, and hopefully not jump into full on NFPA details...

Take a look at that NFPA reference I mentioned. You want to stay under 5000 CFM/system and go with the open style bagger units. You will get more CFM/HP because you do not have the cyclone loss. If you add 50 feet of duct to those units, you will take a major hit on airflow. Check out industrial auction sites and you may find some of these collectors for low $$, then plan on replacing the filters with good bags, easire to clean.

[David Kumm]

The operating range of a 3 hp 14" impeller cyclone with filters will be in the 700-1000 cfm range. Dave

[William Dameron]

Thanks for the info guys.

I have always guessed that the manufacterers stated CFM's are false, but I hoped they would be higher than 700 to 1000cfm. Oh well, this is what I have for now.

I definitely would like to upgrade at a later date, to an external unit, of sufficient CFMs. But for now, I have already purchased these, and will attempt to make them work, however I can. I believe they will be sufficient. Perhaps if I have many people using the same set of tools on one collector at once, I could run into issues - we'll see. If and when that happens, I'll look into upgrades.

I stayed away from the bag style units, despite the higher CFMs, because of the level of filtration I can get through cyclones. I could be wrong, but my research led me to believe that because the cyclone spins so much material out of the air before it reaches the filter, that the filter could be very fine, without clogging. Since I'm the one who is going to be in this shop more than anyone else, I really want clean air. I'm hoping that these filter the air out well enough that it is healthy for me to be in long term.

Ugh, dust collection is quite a complicated subject, and is expensive. I talked to dust collection engineering firms, and their prices were quite prohibitive. I'm hoping that one way or another I can make this work...

Will

[Michael W. Clark]

Good luck Will and let us know what you find out on the filter switch.

As far as the cyclone goes, it's function in life is to reduce loading on the filter inyour application. This translates to less filter cleaning and less wear and tear on the filter. The dust level in your shop will depend on the filter media efficiency and how well you do at getting the dust at the source. The latterwill depend largely on air flow for agiven hood. You have to keep the filterclean to keep the airflow up.

The commercial woodshops I have been in use bagger units or central systems. Some central systems are cyclones only, some are a cyclone followed by a baghouse. Some baghouses use cartridges, but the dust is on the outside with much more filter area as comparedto the flow. This makes them easier to clean, usually with an automatic system.

I used to work for one of those engineering firms specializing in dust collection. The cost is not related to the flow, so on smaller systems like yours and other commercial shops, the cost can be prohibitive.

[Matt Mattingley]

You might be able to apply over/under amperage shut offs. This would help out with almost everything except for a almost clogged filter that gets a rip in it, and keeps you within the norm high/low amperage . If the filter is removed it would get tripped, if the filter gets to clogged it would get tripped, but a almost clogged, then ripped might keep you in the non-shutdown mode. Maybe a promise for daily inspection and a sign-off sheet would clear this with the fire inspector.

[Steve Rozmiarek]

Is there an allowance for "mobile" units? Put the lagunas on wheels and don't make them a fixture. Might be a whole different regulatory situation that is much more rational.

[William Dameron]

The units are on wheels, but it seems to not matter.

I think I'm going to try to talk my way out of it for now, and if that doesn't work, try to put on a sensor of some sort - most likely a vacuum switch.

But, I have been thinking about using the ivac system, so that appropriate blast gate opens when a tool is turned on, and the dust collector fires up - this also would satisfy the 'interlocked' feature the inspector wants. It will concentrate the suction, which is good, and you can program the run time of the collector if you want, or just turn it on permanently. We'll see, decisions, decisions...

[John Donhowe]

I might be able to convince the inspector to let us use an alarm. Overall this is quite a stupid requirement I feel, because in a relatively small shop like mine, if there's something wrong with the dust collector, you'll know it, because you're right next to it. But, if he sticks to his guns with the auto-shutoff....

Just a random, late to the party thought: why not drop by the UNLV EE Dept, where you can probably find a bright, eager and hungry student who could easily and economically design and build a circuit to feed the alarm signal to relays which would also shut off power.

[Phil Thien]

Just a random, late to the party thought: why not drop by the UNLV EE Dept, where you can probably find a bright, eager and hungry student who could easily and economically design and build a circuit to feed the alarm signal to relays which would also shut off power.

I'd be careful about implementing any sort of one-off solution that isn't listed with any certifying organization.

Doing so is basically saying you agree a solution is required, but demonstrating that you haven't implemented one known to be effective.

True story: A client was moving into a new office. He had my firm pull new network and phone wiring. I specified plenum-grade insulation on my network cabling because the entire dropped ceiling was being used for return air. The telephone cabling was supplied by the phone guys, it was not plenum grade. My guy pulled it anyhow.

The client hired a security firm to install a system with some bells and whistles. Basically an alarm system with card access and fire detection. Everything to be centrally monitored, of course.

So the day comes for the fire inspection and the inspector goes RIGHT to my cables. Teflon jackets. Then he asks for my plan, and I show him the layout I was given by the architect. I had made some notes with a red marker and we talked and then he stamped my copy of the plans and signed them, and said I was good.

The phone guys lucked out because the inspector figured if the network cabling jackets were plenum rated, the phone cabling would be, too. Nope, just PVC. That got missed. (BTW, the ceiling was FULL of PVC jackets from before these restrictions, so in reality the requirement is kinda pointless in older construction).

He then turns to the security company and says "hey, there are fire detectors." The security guy thought he had scored some points, fire detectors were not required in this case. The inspector wanted to see plans, but there were none, nothing had been submitted ahead of time.

So the inspector said all the fire detectors had to be pulled, and then he'd sign-off. If fire detectors were to be used, a plan would need to be submitted. BTW, in a commercial space, that plan would need sections for testing and periodic replacement of detectors (they become MORE sensitive over the years, eventually leading to false alarming).

So the fire detectors were pulled and left out of the system.

THAT is the kind of mentality with which you're dealing, when dealing with fire inspectors. Just because a plan hadn't been submitted and agreed to, they were now requiring all of the fire detectors be yanked.

My recollection was, the detectors were removed for a time (maybe a month or two) and then quietly reinstalled. I don't believe any subsequent inspections noted them as a problem.

[Anthony Whitesell]

I'd be careful about implementing any sort of one-off solution that isn't listed with any certifying organization.

Doing so is basically saying you agree a solution is required, but demonstrating that you haven't implemented one known to be effective.

I disagree and agree. I agree I would be be careful about implementing a system before you have to. If you install a system based on their word, rather than a cited regulation then you are agreeing to and going to be bound by what they said. I said, they said. On the other hand, depending on the regulation and decision, there may not be a "certifying organization" for this (as yet) unspecified interlock system. A simple "refrigerator" door switch on the filter mounts and a low pressure detector in the outlet plenum does not have much to be "certified".