Can I use two vacuum cyclones in series?

[dwasifar]

I have a dust collection system in my workshop consisting of PVC pipe to various locations, feeding into a home brew cyclone dust separator made out of 5 gallon buckets, and from there to a large shop vac. The system generally works well, except the table saw branch. The table saw drops chunks of scrap and cutoff out the vacuum port, and some of them have been large enough to create clogs and blockages behind them as they try to move down the pipe.

I'm tempted to put another cyclone right at the dust port of the table saw to filter out the chunks so they don't go downstream. But I don't know if I can put a cyclone upstream of another cyclone. Will it work?

 

[couch67]

I think in general this is not a good idea as there will be too much pressure loss going through two cyclones. Maybe the simpler path is to eliminate the scrap chunks from getting sucked up. Do you have a zero clearance insert? Or is your vacuum port above the blade?

 

[firebirdparts]

Relatively good idea. Cyclones have an ideal velocity, so in real design you would only put them in parallel if you specify them to each be too small.

Small cyclones have high centrifugal force so they outperform big cyclones.

 

[cgrutt]

Not sure about cyclone but seem to recall two being used before not sure how that worked out. Just curious if you're getting any static buildup off the pvc may want to run a copper wire through (or around) pipes and ground it to allow a path for discharge. Don't really want any sparks in a mix of combustible materials and high volumes of air...

 

[marinusdees]

I have a dust collection system in my workshop consisting of PVC pipe to various locations, feeding into a home brew cyclone dust separator made out of 5 gallon buckets, and from there to a large shop vac. The system generally works well, except the table saw branch. The table saw drops chunks of scrap and cutoff out the vacuum port, and some of them have been large enough to create clogs and blockages behind them as they try to move down the pipe.

I'm tempted to put another cyclone right at the dust port of the table saw to filter out the chunks so they don't go downstream. But I don't know if I can put a cyclone upstream of another cyclone. Will it work?

 

[dfiler2]

oops

 

[dfiler2]

Not sure about cyclone but seem to recall two being used before not sure how that worked out. Just curious if you're getting any static buildup off the pvc may want to run a copper wire through (or around) pipes and ground it to allow a path for discharge. Don't really want any sparks in a mix of combustible materials and high volumes of air...

This is an old wives tale. Urban legend. No documented case exists where wood dust collected via PVC (or any other plastic tubing) has resulted in a fire or explosion ignited by static discharge.

 

[cgrutt]

This is an old wives tale. Urban legend. No documented case exists where wood dust collected via PVC (or any other plastic tubing) has resulted in a fire or explosion ignited by static discharge.

Don't know whether any explosions and/or fires have been started but what I can tell you from personal experience is you can get one hell of a shock pulling fine dust through pvc and a shop vacuum. It can be minimized with a copper wire running to ground. I was doing a large concrete grinding job and was pulling dust through a piece of pvc pipe connected to floor machine and a standard shop vacuum and nearly got knocked on my *** a couple of times through static discharge. It sounded like a crack of lightening. I ran a wire through the tube and grounded it to vacuum and my floor polisher and wasn't shocked by it again.

 

[PCustoms]

Should work, but you may not have enough suction.

Can you replace the shop vac?

 

[RivennHewn]

Time to upgrade. Shop vacs are kinda silly for dust collection.

 

[dutchgray]

This is an old wives tale. Urban legend. No documented case exists where wood dust collected via PVC (or any other plastic tubing) has resulted in a fire or explosion ignited by static discharge.

What does happen is something goes in the system hot, sets everything else on fire and the plastic ducting melts/ burns. Metal ducting is better.

 

[PCustoms]

What does happen is something goes in the system hot, sets everything else on fire and the plastic ducting melts/ burns. Metal ducting is better.

If you're wood dust and cutoffs are hot enough to melt PVC I think you have another issue.

 

[dutchgray]

If you're wood dust and cutoffs are hot enough to melt PVC I think you have another issue.

It's not that, it's hitting embedded metal or a tooling failure that causes it.
Local plant to me had it happen once, they were running spindle moulders so hard the cutters were running so hot that one day a cutter came apart, got sucked in the extraction and up it went.
Mind you same place had a concrete block wall on fire one time from decades of fine wood dust embedded in the pores.

 

[kaymccampbell]

I have a dust collection system in my workshop consisting of PVC pipe to various locations, feeding into a home brew cyclone dust separator made out of 5 gallon buckets, and from there to a large shop vac. The system generally works well, except the table saw branch. The table saw drops chunks of scrap and cutoff out the vacuum port, and some of them have been large enough to create clogs and blockages behind them as they try to move down the pipe.

I'm tempted to put another cyclone right at the dust port of the table saw to filter out the chunks so they don't go downstream. But I don't know if I can put a cyclone upstream of another cyclone. Will it work?

To keep it simple, I would try connecting a 5 gallon bucket in the tablesaw line, as close as possible to the saw outlet, to trap larger items. Ideally the bucket would be directly under the saw. Depending on the vacuum, this has been an effective chip collector for me.

 

[Yankeefarmer]

I have a dust collection system in my workshop consisting of PVC pipe to various locations, feeding into a home brew cyclone dust separator made out of 5 gallon buckets, and from there to a large shop vac. The system generally works well, except the table saw branch. The table saw drops chunks of scrap and cutoff out the vacuum port, and some of them have been large enough to create clogs and blockages behind them as they try to move down the pipe.

I'm tempted to put another cyclone right at the dust port of the table saw to filter out the chunks so they don't go downstream. But I don't know if I can put a cyclone upstream of another cyclone. Will it work?

I installed a small piece of 1/2 x 1/2 hardware cloth on my table saw dust collection adapter to prevent small pieces of scrap from entering the ductwork.

 

[PCustoms]

@dwasifar

Post a pick of your setup. I'm having a hard time visualizing a shop vac system effectively sucking dust from saw let alone chunks.

Is your setup over the table? Mine is in the cabinet.

 

[jar944]

If you're wood dust and cutoffs are hot enough to melt PVC I think you have another issue.

Hot wood (chared) + high air flow = smouldering embers and a dc fire. I know a couple people it happened to both on a cnc. Neither was catastrophic as they noticed it and got everything under control before the DC burned up.

I was cutting a bevel on some boards not that long ago and was getting significant burning. It was a combination of a slightly skewed pm66 trunion and a dirty blade. It was bad enough I checked the collector and thr saw base for a fire after the cut, fortunately there wasn't one.

 

[brianh]

A shop vac is not a lot of volume the piping is always going to be a clog issue.

I built a homebuilt system with metal duct piping going to a cyclone and a grizzly 4 bag collector. It is ugly as hell made with what was laying around at the time with the intent of making a nicer one that was 13 years ago. I have a 20 inch planer, table saw 12 inch planer moulder and sanders hooked up to it. Blast gates are homemade with sandblasting mask on the suction side for sealing when closed, they work great.

The cyclone gets almost all of it as long as I do not let the garbage can overfill in the cabinet.

 

[dwasifar]

Okay, to answer some of the questions and comments:

• I am not using a zero insert. Probably should be, that's a good idea, though it won't help me on angled cuts.
• This particular shop vac is quite powerful. If I accidentally shut off all the inputs, it's strong enough to mostly collapse the cyclone buckets. I have a port on the other side of the workshop; there's about 35 feet of PVC between that port and the cyclone, and I can plug a 15' hose into that for cleanup and still get plenty of suction to vacuum the floor.
• Dust collection for the saw is underneath. There's a port on the back of the saw cabinet.
• I actually did try a piece of 1/2" hardware cloth in the line behind the saw for a while, for exactly this reason, but thin pieces would get caught halfway through it and it was a pain to clear it.
• I do get static buildup in the PVC, but I've been hesitant to include any wires inside it because I don't want something else that could cause a clog. Wrapping the pipe with wire is impractical because a lot of it is under the floor. Though I suppose it wouldn't hurt to do that to the exposed sections.