Why Are Chips Bypassing My Cyclone?

[Mike Chalmers]

Mike, Sorry for the short response above. As you know a cyclone operates on an efficiency curve, it captures a higher percentage of larger particles and a lower percentage of smaller particles. We have had cyclones that caught the fines but allowed larger chips to bypass. The first thing you check is that the cyclone is sealed at the dust discharge.

After that, if the problem still persists, you look at the inlet arrangement to see if the ducting could be an issue (causing turbulence as the air enters the cyclone). Sometimes, this is not easily improved. The main thing is that you do not have elbows causing the air to turn counter-current to the cyclone (as viewed from above). Ideally, you want about 6 straight duct diameters at the cyclone inlet.

If the problem still persists, the next thing to check is the interior of the cyclone. If the curved surfaces are not smooth (large weld gaps, not enough breaks on the curved parts, mis-alignment between body and cone creating a ledge, build up, dents from users trying to free plugs, etc), the large particles will hit these places as they spin around and get thrown back into clean gas vortex and go out the top.

Since you have changed cyclones and getting both fines and chips over to the filters, I suspect it may be related to the cyclone efficiency itself. If this is the shorter Laguna model compared to the Oneida unit, the Oneida unit may be more efficient. Cyclone efficiency is not just about pressure drop, but about proportions and size as well (the last two has a much larger effect on fines).

Hope this helps,
Mike

Thanks for this comprehensive answer. You sure sound like you know what you are talking about.

Not sure I understand what you mean by the "dust discharge".

[Michael W. Clark]

Not sure I understand what you mean by the "dust discharge".

Bottom where the dust comes out. It is the bottom of the cone on most hobby units.

[Michael W. Clark]

Just curious. How can an 1 1/4" pipe extending into the cyclone not cause the same disruption as a bumpy weld or ledge, I know why the hose inlet is there for the collection bag but still this inlet is much larger than the worst weld.

I agree with you. It shouldn't protrude inside, it should flush.

[Chris Parks]

The length of the pipe between the bottom of the cone and the drum will also have an effect if it is too long. Does the manufacturer give a length for this? if not you may need to experiment or Michael C might have a suggestion.

[Mike Chalmers]

The length of the pipe between the bottom of the cone and the drum will also have an effect if it is too long. Does the manufacturer give a length for this? if not you may need to experiment or Michael C might have a suggestion.

What in the world are you talking about? This offshoot of my original subject relates to a hose that runs externally from the cyclone chamber and into the bottom of the barrel to create negative pressure that retains the bag. Was this comment meant to relate to some other aspect?

[Chris Parks]

What I am talking about is the length of the connection to from the cyclone to the collection drum. Micheal C was mean to be Michael Clark not yourself. The external hose is not necessary if the connection to the drum is airtight and the drum has no leaks. Fixing the problem is better than putting a band aid on it.

[Phil Thien]

Whenever I'm dealing with a possibly leaky container, I just silicone all the joints. I run a small bead and push it in with my finger everywhere there is a seam.

I'm not convinced that the fiber drums themselves aren't somewhat leaky. The substrate itself. I guess a large cyclone wouldn't pull enough vacuum but you can pull a vacuum right through MDF. So personally I'd prefer a plastic or steel drum. And plastic is nice because it is fairly translucent, you can illuminate the inside with a single LED and see the level of debris quite easily.

[Michael W. Clark]

The length of the pipe between the bottom of the cone and the drum will also have an effect if it is too long. Does the manufacturer give a length for this? if not you may need to experiment or Michael C might have a suggestion.

I would prefer a longer pipe here than one that is too short. The longer the pipe, the higher you can fill the drum without re-entrainment. If the drum sits directly below the cone, and you fill it, you will pick up material out of the drum and carry it over. If there is a divot (sunken in spot) in the center of the material in the top of the drum when you empty it, you could be pulling material out of the drum.

I am not aware of any ill effects from too long of a pipe on the bottom of the cone from an efficiency perspective. It is done quite often on some industrial applications.

Mike

[Mike Chalmers]

Well, today I replaced the T fitting with a wye. This made a noticeable difference in the amount of air I feel moving in the system. Did not improve my problem. however.

To be clear, my system is not filling the filter bag as fast as it used to. I would rate the amount of chips getting past the cyclone at about 15%. Not bad, and maybe the best I will get with a unit like this.

[mike mcilroy]

I agree with you. It shouldn't protrude inside, it should flush.

On the Grizzly cyclone the inlet goes inside the cyclone about 3". I don't get the chips bypassing but I do notice that if a bigger chunk gets in the cyclone I can hear it spinning forever which probably means that some chips are bypassing but its not a very big amount. I just resealed the barrel lid and its good. I think my next step is to caulk the joint between motor/ impeller housing, impeller housing/inlet ramp and inlet ramp/ cyclone body.
I'm thinking that the rubber seals are not doing the job.

[mike mcilroy]

While adding my replacement canister filter I noticed the attachment ports for the bag vacuum hose on both the cyclone and the barrel had some gaps so hit them with the caulking. Hopefully this ends the endless spinning of debris in the cyclone.

[roger wiegand]

I had a similar problem for a long time with the used Pistorius collector I scrounged. Then one day in a fit of inspiration I reversed the direction of the motor. Flow went up about 2x immediately and, presto, no more dust or chips in the bag. Made me wonder how long it had been running the "wrong" way in its previous life. There is no indication on the machine of what the correct rotation direction is. It's surprising how well it worked going the wrong way. Worth checking...

[Mike Chalmers]

Established contact with King Canada today. Explained what is happening. The questions that were asked of me indicate that the rep is at least familiar with Dust Collectors.

No immediate answer, they are going to look into it and get back to me. Here is where the rubber hits the road. Hopefully, they get back to me with some useful suggestions. I'm getting ready to demand they take this unit back and refund me my money. I will then go back to my 2hp unit with the SDD, and cry every time I look at all the 6" ducting, hose and fittings I bought.

[Michael W. Clark]

Established contact with King Canada today. Explained what is happening. The questions that were asked of me indicate that the rep is at least familiar with Dust Collectors.

No immediate answer, they are going to look into it and get back to me. Here is where the rubber hits the road. Hopefully, they get back to me with some useful suggestions. I'm getting ready to demand they take this unit back and refund me my money. I will then go back to my 2hp unit with the SDD, and cry every time I look at all the 6" ducting, hose and fittings I bought.

Mike, do you have this problem all the time, even when starting with an empty drum? I am assuming your unit is like the shorter Laguna cyclone units with cartridge filter? If so, I would expect the carryover to get worse as the dust level in the drum gets higher. I think it would be worse on this one given the short cone and larger opening at the bottom of the cone as compared to other hobby cyclone that tend to standardize on a 6" cone discharge.

Mike

[Mike Chalmers]

Yes, the carry over gets worse as the barrel fills. This units is the same as the Laguna manual cleaning unit. Videos exist that show a full barrel of dust and chips being sucked up with next to nothing going in the bag. In addition, there are several videos done by owners of the 2 hp Laguna version that are very complimentary. While the short cone may not be as efficeint for the fines and dust, there should ne little in the line of chips going into the filter bag.
I did my research before purchase. I believe there is something wrong with this particular machine.