Confused

[Carpenter96]

Hi Retired2. My DC is portable and I just hook it up to which ever machine requires it. It has never been over whelmed by shavings. I could not justify the cost of solid piping and a larger more powerful DC. Regards Bob

[retired2]

Hi Retired2. My DC is portable and I just hook it up to which ever machine requires it. It has never been over whelmed by shavings. I could not justify the cost of solid piping and a larger more powerful DC. Regards Bob

Bob,

I asked that question even though I was pretty sure of the answer.  I just didn't want anyone to get the idea from your original post that they can build a stationary dust collection system around a 1HP 750CFM unit.  With a Thien separator, it simply will not work.  In fact, even without the separator, it is doubtfult the performance would be acceptable.

Moving a DC from tool to tool will work with a smaller unit because the line losses are minimal, but anyone planning to build a stationary DC system should purchase nothing less that a 1-1/2 HP 1200CFM unit.

Regards

[Dougp28704]

Hi Retired2. My DC is portable and I just hook it up to which ever machine requires it. It has never been over whelmed by shavings. I could not justify the cost of solid piping and a larger more powerful DC. Regards Bob

Bob,

Did you make a cart so the DC, can and top hat all roll around? Or, do you use a flex hose to hook up to the various machines? Do you have your blower mounted sideways above the top hat?

[Peter]

Okay...First run on my Worst Duct calcs. It ain't pretty.

25 feet of straight pipe
3 90 Ls (2.5 R/D) = 15 feet
1 45 L = 2.5 feet
1 Wye = 2.5 feet
Total effective length = 45 feet  :o
Figuring the required CFM at the tool = 440 CFM, 4" duct allows 5000 FPM, 5" duct allows about 3200 FPM. (I'm gonna abandon 6" duct).  Loss per foot for 4" = .070, for 5" = .042. (about)
SP loss in duct, then is 3.15 @ 4", 1.89 @ 5". Allow 1" loss at tool, 1" at duct end, and 2 for the Thien.
Total SP Loss for 4" = 7.15; for 5" = 5.89.
According to the Wood Mag test, the HF unit (<6 " SP at 400 CFM) can't move enough air.

I'll need to relocate my machines. Damn.
I think I'm okay at my table saw, because it's only 29 feet (effective length) from the DC and loses 1" SP less. (6.4@4" and 5.4@5").

Y'know, if I didn't feel the need to walk around in my shop, I could just have the pipe at impeller level and avoid all these verticals and bends.  ;)

Am I assuming correctly, that if the SP losses in the ductwork add up to less than the overall SP at the desired CFM for the blower, the system will work?

[retired2]

Okay...First run on my Worst Duct calcs. It ain't pretty.

25 feet of straight pipe
3 90 Ls (2.5 R/D) = 15 feet
1 45 L = 2.5 feet
1 Wye = 2.5 feet
Total effective length = 45 feet  :o
Figuring the required CFM at the tool = 440 CFM, 4" duct allows 5000 FPM, 5" duct allows about 3200 FPM. (I'm gonna abandon 6" duct).  Loss per foot for 4" = .070, for 5" = .042. (about)
SP loss in duct, then is 3.15 @ 4", 1.89 @ 5". Allow 1" loss at tool, 1" at duct end, and 2 for the Thien.
Total SP Loss for 4" = 7.15; for 5" = 5.89.
According to the Wood Mag test, the HF unit (<6 " SP at 400 CFM) can't move enough air.

I'll need to relocate my machines. Damn.
I think I'm okay at my table saw, because it's only 29 feet (effective length) from the DC and loses 1" SP less. (6.4@4" and 5.4@5").

Y'know, if I didn't feel the need to walk around in my shop, I could just have the pipe at impeller level and avoid all these verticals and bends.  ;)

Am I assuming correctly, that if the SP losses in the ductwork add up to less than the overall SP at the desired CFM for the blower, the system will work?

Peter,

In a matter of hours I will be leaving on a three week trip to India and Nepal, and I won't be able to help once I leave.  So, when it goes quiet on my end it is not because I am ignoring you. 

I have not checked your calculations, but your worst case SP loss is slightly less than 6", and I think you might be O.K.  Draw a horizonatal line on the fan curve at the at 5.89".  That shows you will still be moving about 500 CFM of air.

Remember there are a number of less than precise assumptions in this process.  Entry and exit port losses at 1" are probably conservative and they may not be quite that bad.  And the separator, could be more or less than 2".  But you have to start with something and if the fan curve for your unit is reasonably accurate, the 500 CFM might mean the FPM's are a tad low, but not so low it won't work.  You can readily calculate FPM from CFM.  You should have no problem finding the formula, it is simple math.

Another reason I think you will be O.K. is my system works with a longer equivalent straight length of 5" pipe than you have, but I do have the Delta 50-760 which has a better performance curve.

In any case, I think you are within the accuracy of the assumptions, calculations, and fan curve for you unit.  But you can see the value in this exercise.  4" or 6" pipe clearly would not have been a good choice for you.

Just out of curiosity, what tool is at the end of this worse case scenario? 
 

[Peter]

Retired,

Wow, have a WONDERFUL trip! Take a pic of Everest for me, will ya? (Or K2, I probably wouldn't know the difference ;) )

Anyway, I do appreciate your help. At the end of The Worst Duct is either: a group of sanders (disk, belt, spindle) or a thickness planer. There's a sketchup drawing of my shop layout in Post #4, where I hijacked this thread (Sorry, Doug!). It shows the planer at the end of Worst Duct, but I could move the sanders to just across the wall from the DC closet and put the drill press at the end of Worst Duct and the planer where I show the sanders.

One thing my calcs do NOT account for is the 3'-4' long sections of hose that connects the machines to the blast gate. If it weren't for the need to slide the machines away from the wall for accommodating longer stock, I could hard pipe them.

I don't mind sweeping up chips, such as might be generated by drilling huge holes in pine with a forstner, or by hand planing at the workbench. And, I am hoping that by investing in an air cleaner, I can trap some of the fines that the DC system misses.

Thanks again, sir.
Be safe in Asia.
Peter

[retired2]

Retired,

Wow, have a WONDERFUL trip! Take a pic of Everest for me, will ya? (Or K2, I probably wouldn't know the difference ;) )

Anyway, I do appreciate your help. At the end of The Worst Duct is either: a group of sanders (disk, belt, spindle) or a thickness planer. There's a sketchup drawing of my shop layout in Post #4, where I hijacked this thread (Sorry, Doug!). It shows the planer at the end of Worst Duct, but I could move the sanders to just across the wall from the DC closet and put the drill press at the end of Worst Duct and the planer where I show the sanders.

One thing my calcs do NOT account for is the 3'-4' long sections of hose that connects the machines to the blast gate. If it weren't for the need to slide the machines away from the wall for accommodating longer stock, I could hard pipe them.

I don't mind sweeping up chips, such as might be generated by drilling huge holes in pine with a forstner, or by hand planing at the workbench. And, I am hoping that by investing in an air cleaner, I can trap some of the fines that the DC system misses.

Thanks again, sir.
Be safe in Asia.
Peter

Figure flex pipe as 3X the length of rigid pipe.  The fines from sanders require more air than the thickness planer, so if you are going to start moving things keep that in mind.

If I had not been so far along I would have incorporated one of Phils suggestions, i.e. move the separator away from the DC in a branch so it only separates the waste from the heavy chip producers.  Allow the tools that produce fines to be piped directly to the DC..  That gives maximum CFM to the machines that need it, i.e. sanders, etc.  It keeps the shop cleanest, and dedicates the separator to the task it handles best.  The down side of course is a lot of fines are going to end up in the filter.

Good luck.

[phil (admin)]

If I had not been so far along I would have incorporated one of Phils suggestions, i.e. move the separator away from the DC in a branch so it only separates the waste from the heavy chip producers.  Allow the tools that produce fines to be piped directly to the DC..  That gives maximum CFM to the machines that need it, i.e. sanders, etc.  It keeps the shop cleanest, and dedicates the separator to the task it handles best.  The down side of course is a lot of fines are going to end up in the filter.

Good luck.

I usually tell people to put the separator in front of the heavy chip producers, and add a baffle to their DC.  That way they get the best of both worlds (sort of).  But adding a baffle to some of the Delta units is problematic.

[retired2]

If I had not been so far along I would have incorporated one of Phils suggestions, i.e. move the separator away from the DC in a branch so it only separates the waste from the heavy chip producers.  Allow the tools that produce fines to be piped directly to the DC..  That gives maximum CFM to the machines that need it, i.e. sanders, etc.  It keeps the shop cleanest, and dedicates the separator to the task it handles best.  The down side of course is a lot of fines are going to end up in the filter.

Good luck.

I usually tell people to put the separator in front of the heavy chip producers, and add a baffle to their DC.  That way they get the best of both worlds (sort of).  But adding a baffle to some of the Delta units is problematic.

Thanks for the clarification Phil.  I've got one of those problematic Delta's, so I'm limited as to what I can do. 

[Peter]

I usually tell people to put the separator in front of the heavy chip producers, and add a baffle to their DC.  That way they get the best of both worlds (sort of).  But adding a baffle to some of the Delta units is problematic.

Something like this?

Planer (jointer, table saw) ? very short duct ? Separator ? ? ? ? duct as required ? ? ? ? Impeller ? Filter ring with baffle.

As opposed to:

Any machine(s) ? ? ? ? duct as required ? ? ? ? Top Hat Separator / Impeller ? Filter ring with baffle.

[Carpenter96]

Hi Retired2 I agree that a larger system would be neccessary for a stationary DC but I don't really spend much time to connect my DC to each machine as I need it. Like I said it has never been overwhelmed by shavings or dust even when I planed a couple of hunred board feet. Yes I had to empty several times but very little was left around the palner. Regards Bob