DC question

[LarryG]

That IS an odd design ... looks like someone didn't think the whole problem through.

I bought these self-cleaning blast gates from Lee Valley, to replace my troublesome black-plastic cheapies. Note how the sliding piece seals both sides of the gate, regardless of position. I had only installed one of them by the time I had to pack up my shop, but it worked great, didn't clog, and didn't leak. Being able to operate the slider from either side of the gate was handy, too.

[Uncle Cracker]

I use the above-type metal gates (not the LV) that I got from WC. The slot is indeed to keep build-up from preventing the gates from closing. Yes, there is some minor suction pulled in when the gate is open, but the cross-sectional area is still minuscule compared to that of the 4" duct, so there is not much performance lost (I've never had a problem with it). And since the "leak" only exists when the gate is open, and I only have one open at a time, it's still much better than seven gates that leak closed from build-up. I did try one gate with the LV design solution, but the exposed portion of the gate when closed was so weak that the slightest bump bent it, and I'd have to straighten it out to open it, which usually came at an inconvenient moment, so I moved it to a more protected spot to avoid the aggravation...

[jussi]

Thanks for explanation guys. I was seriously thinking about returning them.

And the questions keep coming...

Is there an easy to check for leaks between the connections? I was thinking those puffer gizmos HVAC guys use to test for drafts within a house. The ones that puff out a cloud of smoke. But I have no idea where to get them or even what they're called.

And this one isn't crucial but I'm curious what cfm the DC is pulling from different locations. Do they make a machine that would test for that?

[master53yoda]

one thing to remeber is that leaks have a different affect on the dc depending on if they are on the positive side of the fan or the negative pressure side.
1.If on the positive side between the fan and the dust separation system it puts contaminants into the air but does not reduce the ability of the fan to move the dust.
2. If on the negative side the leaks reduce the available static pressure on the system which reduces the ability of the system to pull at the machine port. DCs usually can generate 8" to 10" Water column of static, if the leaks close to the fan reduce the static by 2" it reduces the air flow at the machine port by about 40% or more. Leaks on the low pressure side of the system do the same thing to the ability of the DC to remove dust as to small a piping system. Inlet leaks are imperative to seal if you want to move the dust effectively. The only way around this is more HP on the DC. to find low pressure leaks hook the discharge of the dc to the inlet piping and pressurize the system. Spray a 50% dish soap and water solution on the joints if you get bubbles seal the joints better. I use commercial HVAC duct sealer that can be bought at Lowes and I think ad HD it is painted on with a coarse brush and allowed to dry. it will seal against up to 20" static. It isn't pretty but it stops the leaks.

good luck