Is this CFM rate possible to deliver?

[Alan Lightstone]

Grizzly in my new wide belt sander recommends 1200cfm from the dust collection. The sander has two 4” dust collection ports on top.

Is it even remotely possible to provide 1200cfm from two 4” ports? The surface area of that is only 25.1 sq inches, which is less than a single 6” duct. Basically, two fours does not equal an 8, and I would think I would need 8” ducting to be able to deliver that air flow.

This will be through an Oneida 5HP dust Gorilla Pro, which is rated at 1625 CFM at 3”WC.

I’m basically thinking of putting in a wye connecting those two 4” ducts to a 6” supply duct, and calling it a day.

[Jim Becker]

You hit on the crux of the problem...inlet area is relatively small. Adding a wye is a reasonable compromise for simplicity, but more air flow from larger or more numerous ports would likely kick things up a notch or three. I don't know this particular machine, but wide belt sanders ( and big drum sanders ) present the combination of prodigious fine dust production and difficult collection due to the amount of open area within the machine itself.

[Alan Lightstone]

I’ve enlarged 4” to 6” on a few machines in the past with great improvement in dust collection, but I’m having trouble with the concept of sawing into a brand new $10K machine.

Strangely, Grizzly’s picture in the manual show three 4” ports, but the machine only has two.

[Allan Speers]

Would it help to add a "dummy" port, just to get the air speed up?

[Ole Anderson]

If you provide 5" or 6" ducts up to the 4" port, yes. The ports become an orifice which can easily pass 600 cfm each at fairly low pressure loss.

[Larry Frank]

I think you will be very close or over the 1200 cfm. I have a 5 hp Oneida Super Dust Gorilla and have measured 1345 cfm (4.8" SP) with a 6" gate open. I measured using a hot wire anemometer with multiple measurements across the diameter.
Before doing any modifications, I would try it with the two 4" ports. Based upon my measurements and experience I think you will be fine.

[Ted Reischl]

Sounds like a classic case of "It looks wrong to me, I don't really know if it is or not, but now I am going to over think it until I throw up."

I am with Mr Fink on this, give it a try. If it works you can take some antacids and be all happy. If not, THEN you can start figuring out a solution. Right now you actually do not know if it will work or not.

BTW, the guys who write those requirements probably lean on the heavy side to be safe.

Now, I do not have a big honking wide belt sander, just a piddly 16 inch drum sander. But, I probably have the worst plumbing known to wood workers in several states, a 4 inch duct connects to about 3 ft of 2.5 duct. Amazing, no dust escapes that machine.

[David Kumm]

Put a boot leg wye on the 6", without flex if you can do it. The key will be keeping the filter cartridge clean. You should get adequate DC with clean filters. How much fine dust gets to the cartridge is unknown, but it will eventually plug the filter and reduce cfm. Put a gauge on the system so you can monitor the pressure drop and know when to clean filters. Wood cyclones let fines pass through and cartridges are not the best choice for wide belts but I've found that hobby use and watching the filters does get you by. Dave

[Malcolm McLeod]

... two 4” dust collection ports on top. ...Is it even remotely possible to provide 1200cfm from two 4” ports?... Oneida 5HP dust Gorilla Pro, which is rated at 1625 CFM at 3”WC....

If you provide 5" or 6" ducts up to the 4" port, yes. The ports become an orifice which can easily pass 600 cfm each at fairly low pressure loss.

Ole is correct IMHO. Quick and dirty pass thru an air flow calculator with 4" orifice at 3" WC (::75mmHg) pressure drop at 72degF yields 1447 SCFM. The calculation's math assumes a lot of ideal conditions, so take it with a grain of salt .... I'd figure the real-world flow to be half the math, so ~700 SCFM thru each port, or 1400 SCFM total.

Bottom line, you'll meet the manufacturer's spec.

[John Kee]

According to testing I've done you should be OK for flow with clean filters and low SP to the sander. The main problem you will have is keeping your filters clean especially if the unit is used continuously for extended periods of time. Cyclones are good at fine dust separation not great. The greater the filter surface area the more it will keep cleaning down but will not remove the need. I believe your unit only has a single filter. In my own situation I run a Felder RL160 and its garbage in comparison for this fine dust collection.

[Alan Lightstone]

OK. Finally all the ducts and hoses came in, and I've got the Oneida DC hooked up to the wide belt sander.

It literally took connecting a round duct to two rectangular holes, but my home made adapter seems to be working well.

I sanded a quick board, and my Dylos meter didn't budge. In fact, with only one of the two Jet air cleaners on, the particle count dropped significantly while sanding.

So I'm not sure if I ever got the preferred 1200cfm, but it certainly seems like I have enough.

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BTW, does anyone know how to prevent the attachments from rotating like the second picture?

[Albert Lee]

My sander's user manual says the dust extraction needs be at least 3720CFM (SCM 1100mm wide, dual head)

the ducting connected to the sander is only sufficient to provide 2037CFM
my extractor is a 5.5hp baghouse.

has there been issue with dust? not at all.
there are fine dust buildup within the machine but I give it a regular clean so its all good.

[Joe Jensen]

If you provide 5" or 6" ducts up to the 4" port, yes. The ports become an orifice which can easily pass 600 cfm each at fairly low pressure loss.

Ole, this advice is not true from a practical standpoint.. I just ran some numbers using the fan curve for the Oneida 5HP Smart Super Dust Gorilla Pro. It does have the most pressure for a 5HP system of any I've found and it's what I own. I modeled two ways. Assumed 20ft of hard duct, 3 elbows, and 2 ft of flex. First a 6" duct connected to a wye and two 4" ports. Second two 4" ports connected to dedicated 6" ducts, the same 20 ft run with elbows. With the first single duct, you can pull 660 CFM. With the second model you can pull 670 CFM. Only 10 CFM more. Why is this? Because the smallest restriction in the run drives most of the resistance to flow. I modeled a third way for giggles, 4" duct and 4" ports. Super restrictive. With one 4" duct split to two 4" ports you get only 431 CFM. As you can see one 6" duct or two makes almost no difference. But one 4" duct is super restrictive.

[Jim Andrew]

Venting outside helps.

[Alan Lightstone]

Venting outside helps.

In Florida in the summer, that would suck out all the cooled air in about a minute. Not really desirable in this climate.