dust collection duct sealing
dust collection duct sealing
(OP)
Howdy:
I am looking for some advice as to what I should spec to seal the high-pressure spiral ducting used for dust collection systems.
Max negative operating pressure will be 10"
So far, I believe the best way is to use a slip coupling, riveted 3 or so times or ether side of center, with a silicon sealer. No Duct tape allowed, as it will likely dry rot.
Any thoughts?
Anybody have a good experience with a company’s sealant for this type of application?
I am looking for some advice as to what I should spec to seal the high-pressure spiral ducting used for dust collection systems.
Max negative operating pressure will be 10"
So far, I believe the best way is to use a slip coupling, riveted 3 or so times or ether side of center, with a silicon sealer. No Duct tape allowed, as it will likely dry rot.
Any thoughts?
Anybody have a good experience with a company’s sealant for this type of application?





RE: dust collection duct sealing
RE: dust collection duct sealing
---KenRad
RE: dust collection duct sealing
After checking them out, I dont think they will work for me, as they are rated as seal class c, which SMACNA indicates is not acceptable for any ducting operating at a positive or negative pressure greater than 2".
RE: dust collection duct sealing
My Lindab catalog shows that it meets SMACNA leakage class 3 from -20 in WG to +12 in WG.
---KenRad
RE: dust collection duct sealing
Regarding the specific sealant, they state that the gasket or sealant materials must be selected based on temperature and material being handled, so it sounds like doing a search on sealants and/or contacting reps is a good idea for the sealant portion (as krb stated). That being said, MASTERSpec calls out for flanged joint mastics: One-part, acid-curing, silicone, elastomeric joint sealant complying with ASTM C 920, Type S, Grade NS, Class 25, Use O; and for flanged gaskets: Butyl rubber or EPDM polymer with polyisobutylene plasticizer. This could be a good place to start.
SMACNA also has another typical connections detail for light gauge duct (I'm not sure what qualifies) which shows 4 types of joints in addition to the flanged methods:
1. Large and small end riveted joint ("slipped joint") where they call for rivets 3" center to center in addition to soldering (for steel duct)
2. Butt welded joint
3. Draw band joint where the axial length of the banded part is 4" min.
4. Beaded sleeve joint, also 4" min length; This last one is similar to the “slip joint” but it has an additional “fitting” with male & female ends, conceivably to allow the two same size duct ends to be mated. I suppose this could be riveted and soldered as well, although there would be twice as many required at each connection. It also may be one of those proprietary-gasketed types that KenRad was referring to.
By the way (KenRad or Lorus), is Selkirk Metalbestos one of those pre-fabricated manufacturers for this type of system, or are they just for the flue gas type jobs?
Olaf
RE: dust collection duct sealing
RE: dust collection duct sealing
Is there a reason that you "don't spec those gasketed fittings" that we should know about? I have not only specked them, but have actually installed them myself. And in the ductwork world, they are the best thing since cordless drills and sawzalls. Anyone out there who has installation experience with these types of fittings AND the more traditional ones will agree.
You cut the spiral duct to length (most sizes come in 10 foot sections), push the pipe onto the fitting, install 3 or 4 self-tapping screws, and you're done. No sealants needed. Even an Engineer can handle that.
---KenRad
RE: dust collection duct sealing
Ductmate proseal is good to 15" wg.
RE: dust collection duct sealing
Hardcast or it's equal is a good sealing option.
rogzog
RE: dust collection duct sealing
Gasketed duct is great with Lindab ok for fine particles where likelyhood of cleaning out is low. If plugs are expected and you need to get into the duct use either siliconed spiral with vanstoned bolted angle-ring connections (12" diameter and larger) or even better and more expensive, one of the quick-clamp products which feature rubber o-rings such as Nordfab or the Kirk and Blum equivalent.
I suppose on the cheap, riveted slip coupling would work but watch that the edges are turned the right direction and use plenty of silicone. May want to install some cast-alumninum cleanouts too. Also, if using formed elbows these often need to be siliconed as well and watch the direction of installation, i.e. ensure that the folds are going the right way with the airstream.
Not sure how typical HVAC mastic holds up in material handling applications. Silicone does well.