Dust Collection

You are not logged in. [ Login ] Why log in
(NOTE: Login is not required to post)

Too much dust collection?

6/26/15       
Karl E Brogger  Member

Website: http://www.sogncabinets.com

My shop is a small, 2500as/ft, two man shop. I'm currently running two 1900 cfm, two bag units. I couldn't guys how much pipe on each. I'm looking at getting a pair of three bag, 10hp, 4000 cfm collectors.

Most tools are fine, but I've got far too much dust stuck to items going through the widebelt. Each head has it's own collector, but it's not nearly enough. I'm hard on abrasives as is, but I think the dc is the biggest culprit. I'm getting about 5 hours of life out of purple 3M belts.

I guess my question is, other than the electrical bill, is there any harm in having way more cfm than needed? I'm thinking I should buy more than I need, and grow into it.

6/29/15       #2: Too much dust collection? ...
JR Rutter Member

Website: http://harmonicdesignworks.com

You can always throttle it down with a damper or VFD. Hard to see where you would have too much suction though.

6/29/15       #3: Too much dust collection? ...
rich c.

You need a minimum area of opening for proper air flow. Get too big of a fan, and you have to start leaving more and more blast gates open. It sounds like the only issue you have is the wide belt, so why two new bigger units? Why two units at all? Just get one properly sized unit for the whole shop. It's my opinion that buying from a company that has an engineering staff is money well spent. Just guessing at requirements, air flow, and duct size can be throwing away more money than what you think you will save by buying a cheap import dust collector. AND, you may still not get good collection despite buying bigger units. Don't forget to talk to your insurance agent. OSHA is getting very strict about nuisance dust and blow out panels to prevent explosion.

7/3/15       #4: Too much dust collection? ...
Ken Member

Before you start adding dust collection you need to determine what the requirements for the wide belt are. This is something the mfg. should be able to tell you. Unfortunately some machine mfgs just stick ducts on a machine and call it good. Should the ports be larger, should there be more of them? I've seen 4" ports on 18" planers, not happening. You should post the WB width and port sizes, might help.

7/3/15       #5: Too much dust collection? ...
Karl E Brogger  Member

Website: http://www.sogncabinets.com

43" dual head with two 7"ports. The manufacturer spec'd 4000cfm I think. Currently I've got one 1900cfm unit on each head, but realistically I'm probably only pulling 2400 total. I've got 8"pipe from the collector right up to the machine.

I've been looking at buying a pair of 10hp, 4000cfm Dustek collectors and splitting the shop like it is, just with more capacity. I'd have to pull basically everything down and start over, which will be expensive and a pain, but I'm also looking at moving into a new building soon, so that isn't a big deal.

Why split it? Mostly because spinning 20hp when you're running just a tablesaw or chop box didn't make sense to me

7/4/15       #6: Too much dust collection? ...
Ken Member

So let's look at some numbers... 7" ports at 4000FPM (velocity needed at the machine port) moves 1100cfm, X2=2200cfm. You're not going to get 4000cfm through those 2 ports. That said think about the WB width, 43" and think how are you going to cover that width with just 2 7" ports? I'd focus on the hood and how to make it more efficient, more ports, ducting etc. then calculate from there for DC requirements. Say you end up with 4 7" ports, you need a DC that can move 4400 cfm at the calculated static pressure between the DC and the ports. This is all from the Air Handling Systems catalog or web site.

7/4/15       #7: Too much dust collection? ...
Karl E Brogger  Member

Website: http://www.sogncabinets.com

How would the ports be made larger? That seems strange to me too that a company that builds a machine, wouldn't have big enough holes in it to move the specified amount of air.

Also, where does the four thousand feet per minute velocity come from? Is that a minimum speed to keep particles suspended in air?

7/4/15       #8: Too much dust collection? ...
Ken Member

Yes, 4000fps to capture the dust at it's source, 3500fps in the main duct. These are industry standards for the woodworking industry. I would start with the mfg. and talk about what the requirements really are. If they say 4000cfm ask them how you're going to get that through 2-7" ports. The key to dust collect is moving the right amount of air through the point of where the dust is being created. Assuming 2-7" ports are correct, 1100 cfm each, they would Y together, the branch connecting those 2 would have to be able handle 2200 cfm at 3500fps. A 10" duct moves 1900cfm @ 3500fps and a 12" moves 2800cfm @ 3500fps so you would really need a 12" main. At this point you would calculate all your lose and come up with a static pressure, let's say all the pipe and 90s add up to 6" of static pressure. You then need to look at the fan curve of the DC and see, at 6" of SP does it move at least 2200 cfm? I think the 4000cfm of the 10hp unit you're looking at is with no restriction on the inlet.

7/8/15       #9: Too much dust collection? ...
Curt Corum

Guys, great input. As far as the branch and main velocity being different, a higher branch velocity does create a better capture velocity as well as lift to the main pipe. Almost like driving up a thruway entrance ramp. By having the velocity a little slower in main but not below transport velocity, it does reduce some static pressure (friction / resistance) verses having 4,000 fpm in the branch and main. In addition, a cyclone or bag house will perform better by having that velocity a little lower. Also, yes, some machinery manufacturers do provide undersized hood outlets, especially planers. Crazy, but true. I feel machine hooding is as important as what you need the machine to do for you. I've attached some air flow charts for reference.

Curt

Click the link below to download the file included with this post.

Air_Flow_Charts.pdf

7/8/15       #11: Too much dust collection? ...
Karl E Brogger  Member

Website: http://www.sogncabinets.com

Thanks for that curt.

So, obviously at some point the fan can only produce so much vacuum and move so many cfm. Is there a wall that it hits on velocity where you're only moving so many cfm? According to that chart, a seven inch pipe is moving 1200 cfm at 4500 fpm. Well a fan not move air any faster than 4500?

7/10/15       #12: Too much dust collection? ...
Curt Corum

Karl,

You want to use velocities and coinciding CFM for particulate being collected. If you move the air faster than necessary, will require more horse power to overcome the additional static pressure (friction/resistance).

If you use a dedicated dust collector for sander, I would target 1,100 CFM for each 7” port. Since 2,200 CFM in a 11” diameter pipe has a velocity of 3,400 FPM, I will select 10” diameter as we don't want to drop below 3,500 FPM. 2,200 in 10” diameter is moving at 4,000 FPM.

Once CFM is arrived at, now we have to calculate the resistance of piping etc. It is the collectors job to overcome the resistance/static pressure and deliver CFM needed.

Here is an example. Lets say the dust collector is 40' away from sander and will have 3, 90 degree elbows in the 10” diameter run. Also, 5' drop pipe with a wye to 2, 7” diameter and 3' of 7” flex off each leg of y-branch. Now we will calculate resistance. 2,200 CFM in 10” diameter has a static pressure of 2.4” WG per 100' pipe. 1,100 CFM in 7” diameter has a static pressure of 3.8” WG per 100'.

Static pressure/resistance factors

Entry loss – 1”

Seasoned filters – 2”

Note – Have to convert all elbows to straight feet of pipe.

7” diameter – 6' flex = 18' straight pipe.

2, 7” 45 degree elbows = 13' straight pipe.

Total 31' 7” diameter straight pipe.

1, 100 CFM in 7” diameter has a static pressure of 3.8” WG per 100' or 1.18” WG in 31'.

10” diameter – 3, 90 degree elbows = 20' each + 45' straight pipe. Total 105' 10” diameter straight pipe.

2,200 CFM in 10” diameter has a static pressure of 2.4” WG per 100' or 2.52” in 105'.

Collector requirement is 2,200 CFM at 6.7” SPWG.

Now we look for a dust collector. Please see attached performance chart for a 7 ½ HP (Model 750) dust collector. We can see that we are right in the middle of 2,000 CFM at 7.1” SPWG and 2,500 CFM at 6.6” SPWG. Bingo, that's our unit. In addition, 1 micron filter material is good for a sander.

Click the link below to download the file included with this post.

Performance_Chart.pdf

7/10/15       #13: Too much dust collection? ...
Curt Corum

Please also see attached.

Click the link below to download the file included with this post.

What_is_Static_Pressure_5.pdf

9/15/15       #14: Too much dust collection? ...
Larry

Using HP to size a dust collector isn't very valid. There are lots of differences in the design of fans that affect performance. Also the CFM #'s given by cheap collectors are usually wishful thinking and based on no resistance. The fan manufacturer should provide the charts that show CFM, power, static pressure. If they won't or their chart is a lot different than the quality manufacturers you've got a con job going. A fan motor takes the most power when the inlet is wide open. The least power when partially blocked, fewer gates open.
Do your duct design based on how many gates are/will be, open at one time. Having a trunk line that will support all gates open in a one man shop where only one is likely to be open at a time results in to little velocity in the over sized trunk. BTW, trunk line velocity needed depends on what is being transported. Sanding dust takes less velocity to stay moving than do chunks from a big planer.


Post a Response
  • Notify me of responses to this thread
  • Subscribe to email updates on this Forum
  • To receive email notification of additions to this forum thread,
    enter your name and email address, and then click the
    "Keep Me Posted" button below.

    Please Note: If you have posted a message or response,
    do not submit this request ... you are already signed up
    to receive notification!

    Your Name:
    E-Mail Address:
    Enter the correct numbers into the field below:
     

    Date of your Birth:



    Return to top of page

    Buy & Sell Exchanges | Forums | Galleries | Site Map

    FORUM GUIDELINES: Please review the guidelines below before posting at WOODWEB's Interactive Message Boards (return to top)

  • WOODWEB is a professional industrial woodworking site. Hobbyist and homeowner woodworking questions are inappropriate.
  • Messages should be kept reasonably short and on topic, relating to the focus of the forum. Responses should relate to the original question.
  • A valid email return address must be included with each message.
  • Advertising is inappropriate. The only exceptions are the Classified Ads Exchange, Machinery Exchange, Lumber Exchange, and Job Opportunities and Services Exchange. When posting listings in these areas, review the posting instructions carefully.
  • Subject lines may be edited for length and clarity.
  • "Cross posting" is not permitted. Choose the best forum for your question, and post your question at one forum only.
  • Messages requesting private responses will be removed - Forums are designed to provide information and assistance for all of our visitors. Private response requests are appropriate at WOODWEB's Exchanges and Job Opportunities and Services.
  • Messages that accuse businesses or individuals of alleged negative actions or behavior are inappropriate since WOODWEB is unable to verify or substantiate the claims.
  • Posts with the intent of soliciting answers to surveys are not appropriate. Contact WOODWEB for more information on initiating a survey.
  • Excessive forum participation by an individual upsets the balance of a healthy forum atmosphere. Individuals who excessively post responses containing marginal content will be considered repeat forum abusers.
  • Responses that initiate or support inappropriate and off-topic discussion of general politics detract from the professional woodworking focus of WOODWEB, and will be removed.
  • Participants are encouraged to use their real name when posting. Intentionally using another persons name is prohibited, and posts of this nature will be removed at WOODWEB's discretion.
  • Comments, questions, or criticisms regarding Forum policies should be directed to WOODWEB's Systems Administrator
    (return to top).

    Carefully review your message before clicking on the "Send Message" button - you will not be able to revise the message once it has been sent.

    You will be notified of responses to the message(s) you posted via email. Be sure to enter your email address correctly.

    WOODWEB's forums are a highly regarded resource for professional woodworkers. Messages and responses that are crafted in a professional and civil manner strengthen this resource. Messages that do not reflect a professional tone reduce the value of our forums.

    Messages are inappropriate when their content: is deemed libelous in nature or is based on rumor, fails to meet basic standards of decorum, contains blatant advertising or inappropriate emphasis on self promotion (return to top).

    Libel:   Posts which defame an individual or organization, or employ a tone which can be viewed as malicious in nature. Words, pictures, or cartoons which expose a person or organization to public hatred, shame, disgrace, or ridicule, or induce an ill opinion of a person or organization, are libelous.

    Improper Decorum:   Posts which are profane, inciting, disrespectful or uncivil in tone, or maliciously worded. This also includes the venting of unsubstantiated opinions. Such messages do little to illuminate a given topic, and often have the opposite effect. Constructive criticism is acceptable (return to top).

    Advertising:   The purpose of WOODWEB Forums is to provide answers, not an advertising venue. Companies participating in a Forum discussion should provide specific answers to posted questions. WOODWEB suggests that businesses include an appropriately crafted signature in order to identify their company. A well meaning post that seems to be on-topic but contains a product reference may do your business more harm than good in the Forum environment. Forum users may perceive your references to specific products as unsolicited advertising (spam) and consciously avoid your web site or services. A well-crafted signature is an appropriate way to advertise your services that will not offend potential customers. Signatures should be limited to 4-6 lines, and may contain information that identifies the type of business you're in, your URL and email address (return to top).

    Repeated Forum Abuse: Forum participants who repeatedly fail to follow WOODWEB's Forum Guidelines may encounter difficulty when attempting to post messages.

    There are often situations when the original message asks for opinions: "What is the best widget for my type of shop?". To a certain extent, the person posting the message is responsible for including specific questions within the message. An open ended question (like the one above) invites responses that may read as sales pitches. WOODWEB suggests that companies responding to such a question provide detailed and substantive replies rather than responses that read as a one-sided product promotion. It has been WOODWEB's experience that substantive responses are held in higher regard by our readers (return to top).

    The staff of WOODWEB assume no responsibility for the accuracy, content, or outcome of any posting transmitted at WOODWEB's Message Boards. Participants should undertake the use of machinery, materials and methods discussed at WOODWEB's Message Boards after considerate evaluation, and at their own risk. WOODWEB reserves the right to delete any messages it deems inappropriate. (return to top)


  • Forum Posting Help
    Your Name The name you enter in this field will be the name that appears with your post or response (return to form).
    Your Website Personal or business website links must point to the author's website. Inappropriate links will be removed without notice, and at WOODWEB's sole discretion. WOODWEB reserves the right to delete any messages with links it deems inappropriate. (return to form)
    E-Mail Address Your e-mail address will not be publicly viewable. Forum participants will be able to contact you using a contact link (included with your post) that is substituted for your actual address. You must include a valid email address in this field. (return to form)
    Subject Subject may be edited for length and clarity. Subject lines should provide an indication of the content of your post. (return to form)
    Thread Related Link and Image Guidelines Thread Related Links posted at WOODWEB's Forums and Exchanges should point to locations that provide supporting information for the topic being discussed in the current message thread. The purpose of WOODWEB Forums is to provide answers, not to serve as an advertising venue. A Thread Related Link that directs visitors to an area with inappropriate content will be removed. WOODWEB reserves the right to delete any messages with links or images it deems inappropriate. (return to form)
    Thread Related File Uploads Thread Related Files posted at WOODWEB's Forums and Exchanges should provide supporting information for the topic being discussed in the current message thread. Video Files: acceptable video formats are: .MOV .AVI .WMV .MPEG .MPG .MP4 (Image Upload Tips)   If you encounter any difficulty when uploading video files, E-mail WOODWEB for assistance. The purpose of WOODWEB Forums is to provide answers, not to serve as an advertising venue. A Thread Related File that contains inappropriate content will be removed, and uploaded files that are not directly related to the message thread will be removed. WOODWEB reserves the right to delete any messages with links, files, or images it deems inappropriate. (return to form)