Author Topic: Spiral "ramp" in Old Jet Dust Collector - but Now a question -  (Read 149 times)

DustySanders

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Hi, everyone, it has been a pleasure reading all of the great information on this board, over the last few weeks. Honestly, I still have plenty to read. But not only is the information good, the tone of the board is nice also.

On to the question - I have an old Jet dust collector, rated at 2-1/2 hp, 1200 cfm. It has a 12" impeller with a 6" input fitting. I had it set up for a while years ago, and it worked well despite what I now know were some pretty inefficient home-made junctions and fittings. But of course, it was spewing fine dust throughout the shop.

Due to space and other considerations in my current shop, which is in the basement of a 110 year old house, now is not the time for me to do a full-on, perfect system. I am leaning strongly toward the kind of modifications shown in this thread - http://www.jpthien.com/smf/index.php?topic=145.0
(maybe without the cool paint job, though.) So, a Thien baffle in the bottom of existing "cyclone," cartridge filter above. One of the features of this particular DC is that it has a spiral ramp inside the "cyclone" part, and I am wondering how that might effect the working of the baffle, and if there are any design changes I should make. See picture, below, if it posts.

A specific question I'd have is, would it be worth me making an output tube with a bellmouth on it to feed up into the filter? I'm going to have to make the "donut" to support the filter,so I'd be halfway there, already. And if so, would it make sense to have a bellmouth on both ends of that tube? I don't think that air straighteners in the tube would be worth the time, since I wouldn't be feeding the impeller directly, but you could talk me into them. The "hole" through the inside circumference of the "ramp" is 9", so I could use a 6" pipe in there and have 1-1/2" of clearance on all sides of the tube.
So, thanks, I look forward to any and all replies - Dusty

« Last Edit: April 28, 2017, 11:31:29 AM by DustySanders »

retired2

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Re: Spiral "ramp" in Old Jet Dust Collector
« Reply #1 on: April 21, 2017, 05:49:58 AM »
I see no benefit to adding a bellmouth or air straighteners to that configuration.  The bigger question is whether that body in combination with a Thien baffle works as well as one without a ramp.  I have no experience wih these modifications, but I know there are numerous threads on the subject.  I wish I could easily point you to them, but you just have to keep searching.  Try using "wok" as a search term, that might produce some hits.

DustySanders

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Re: Spiral "ramp" in Old Jet Dust Collector
« Reply #2 on: April 21, 2017, 01:58:42 PM »
Thanks, Retired 2, and thanks for all of the great information you have provided the forum in general.

In my proposed system, the air will still need to find it's way up into the filter, and of course, I'll want it to do that with the least turbulence and greatest flow, which is why I thought of the bellmouth.

Maybe Vaugn, who posted the project I linked to, will see this thread and weigh in.

Thanks, and of course, I'd appreciate any other comments, from Retired 2 or anyone else who can spare the time. It will be months before I'm ready to start this project.

retired2

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Re: Spiral "ramp" in Old Jet Dust Collector
« Reply #3 on: April 21, 2017, 06:03:06 PM »
Vaughn hasn't logged in since 9/2015.  You might want to try reaching him with a PM.

Schreck

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Re: Spiral "ramp" in Old Jet Dust Collector
« Reply #4 on: April 22, 2017, 08:41:04 AM »
Dusty,
The spiral ramp is not helpful because it forces both air and sawdust down onto the baffle, through the slot and into the collection bag, where you don't want much airflow.  I found that it also caused the baffle to vibrate. 

This was discussed previously here:
http://www.jpthien.com/smf/index.php?topic=1118.0

My Penn State 1.5 HP collector had a spiral ramp and I removed it.  The system is much quieter without the ramp.  I have a large coffee can set in the upper plywood lid as a chimney.  It's definitely not optimal but it works for now.
-Dan

DustySanders

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Re: Spiral "ramp" in Old Jet Dust Collector
« Reply #5 on: April 22, 2017, 03:54:24 PM »
Thanks, Shreck - it's great to be able to to get advice from someone who has direct experience with this kind of ring. Looks like it is " back to the drawing board" for me!

retired2

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Re: Spiral "ramp" in Old Jet Dust Collector
« Reply #6 on: April 22, 2017, 06:23:39 PM »
Dusty, 

Schreck's advice was kinda what I remembered, but I wasn't certain enough to tell you to rip out the ramp.  Thinking more about your plans, I want to clarify and change some of what I advised in my previous message.

If I'm clear about your configuration, you are "pushing" your waste stream into the separator rather than pulling it as I do.  Nothing wrong with that, but it reaffirms my advice that air straighteners would be of no value, that is unless you meant to place them before the blower inlet, then they could add to the efficiency of your fan.

With regard to a bellmouth, it would smooth the air exiting your separation chamber and possible add a few CFM to your performance.  Even a coffee can exit can be made more efficient if it siits on a wood collar that is thick enough so that the corner of the exit can be rounded over.  Even a crude round-over formed with a wood rasp is better than a sharp corner.  Hope what I'm describing makes sense.

DustySanders

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Re: Spiral "ramp" in Old Jet Dust Collector
« Reply #7 on: April 23, 2017, 10:16:41 AM »
Thanks, Retired2. I think that making a top hat will likely be easier than taking out the ramp, or at least be more the kind of work I like to do, so I'll probably go in that direction now. Part of the reason I was thinking about keeping the collector as much "as-is" as possible was that the configuration, with the intake close to the ground, worked well for ducting in the location I have chosen for the collector. But last night I had an idea of a good way to make it work with the high input of a top hat on a barrel, so there is one less reason to not do it the right way, with the blower up top, etc.

That being said, I'm about to embark on a major shop improvement project, specifically casting a new, flat and level floor.  The existing floor is untroweled concrete that looks to have been poured over unlevelled dirt, and I've run out of flat places to put tools... Once I get that done, I think I might find that a whole different arrangement of my workspace is possible, so I'm not going to finalize my dust collecting plans until I get that finished, and see what it feels like. It is exciting but frustrating because I have to wait a bit to work on any of it, but at least I can enjoy reading this forum and planning as much as I can in the meantime. I'd post pictures of my shop as is, but I'd have to include warnings for the faint of heart; it is hardly the operating room a lot of you guys are able to maintain!  ;D

retired2

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Re: Spiral "ramp" in Old Jet Dust Collector
« Reply #8 on: April 23, 2017, 02:23:54 PM »
Another benefit of a new floor is it is much easier to keep clean.  I have a pretty nice dust collection system, but there are still times when it is easier to let everything go to the floor and clean it up later.  For that I have a strategically placed floor sweep and a 24" push broom.  Works very nicely and it doesn't require me to do much bending over.

DustySanders

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Re: Spiral "ramp" in Old Jet Dust Collector - but Now a question -
« Reply #9 on: April 28, 2017, 11:54:40 AM »
OK, so I am now in the design phase for my top hat separator. because of height restrictions, I am planning on a single height unit. I plan on following retired2's design pretty closely, but from what I have found from testing my collector, I can use 6" pipe for the main run. I plan to transition that round into a rectangle for the top hat inlet, and I'm wondering about proportions of that rectangle.

The six inch pipe has an area of 28.27 square inches, so I could pretty much match that if I transitioned to a 7 inch tall by 4 inch wide inlet. Obviously, I could make the rectangular end of the inlet in any variety of proportions to equal the cross sectional area of the round duct, and I am wondering what people's thoughts are on what the ideal proportion would be.

It would seem to me that the closer to square the proportions get, the more it is like a round inlet, so I would lose some of the benefits. On the other hand, I know that there are ideal proportions for duct work, and tall and skinny isn't among them. So, do we say, as in life, all things in moderation? What do you all think?

Oh - by the way - in regards to the air straightener question - I have been in contact with the people who make the Vortab flow conditioner mentioned in another thread. http://www.fluidcomponents.com/products/flow-conditioners/vortab-products/vip-flow-conditioner
They think their product will work for our use, when I hear back from them in regard to cost and distance from the impeller, I'll let you all know.

BTW, retired 2, I am jealous of all of your nice old green Powermatic equipment. I bought mine after they switched to the current mustardy gold.
« Last Edit: April 28, 2017, 11:59:08 AM by DustySanders »

retired2

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Re: Spiral "ramp" in Old Jet Dust Collector - but Now a question -
« Reply #10 on: April 28, 2017, 08:12:18 PM »
I always wondered what in the world Powermatic was thinking when they switched to that mustard yellow or gold.  I much prefer the green. 

I would suggest making the area of your rectangular inlet a little larger than the area of the round.  7x4 is very close, so it probably isn't critical, but the HVAC industry says rectangular duct is less efficient than round, and somewhere I found they recomment a 10% size increase for rectangular duct to avoid additional line losses.  Since a separator takes a big bite out of your blower's performance, you don't want to add any more loss than absolutely necessary.

"Tall and skinny" probably isn't the best, but remember you are trying to put the waste stream against the outside wall and over the drop slot.  If the rectangular opening is too wide or oversized it allows waste to enter the separator too close to the exhaust pipe, especially if you use a bellmouth whose wide flange draws in air from a larger diameter.  So, you have a couple competing objectives to consider, and they also have impact on the optimum diameter of your separator.