Ann E. V. Posted July 4 Report Share Posted July 4 I need to use extensions on the kiln vent ductwork to exhaust my kilns. Galvanized metal corrodes very quickly. What material is recommended for duct elbows etc. iffetorbay 1 Quote Link to comment Share on other sites More sharing options...
Bill Kielb Posted July 4 Report Share Posted July 4 (edited) Galvanized metal should not corrode quickly. The majority of the air should be dilution air from the studio with very small amounts of kiln air. Moisture accumulation will speed up degradation. So decent velocity of air usually ensures the moisture is stripped from the metal. Also, really cold areas of ductwork will likely condense because the duct is the dewpoint of the air. So sometimes insulating terminations or for a bath fan using duct in a cold attic completely insulated. So galvanized should give really good life properly designed. Stainless is crazy expensive, plastic products have melting temperature, aluminum not as structural as galvanized steel. Usually more of a design and operating condition than the galvanized steel actually which is generally economical and has medium double digit lifespan without significant maintenance. I would check the mixing manifold on your kiln vent(s) and ensure the proper amount of room air is coming in. Enough to be sure the exhaust duct remains approximately 120 degrees or less (mildly warm to the touch) with the kiln at top temperature. negative vs positive Exhaust fans that have the fan located as close to the outside termination as possible will provide suction through the duct thereby reducing leakage (air leaks into the duct, not out) of contaminated air into the living space. If the fan has to blow through a lot of duct (pressurize), then leakage becomes more of an issue and so will maintenance. Edited July 4 by Bill Kielb HenryBurlingame and Rae Reich 2 Quote Link to comment Share on other sites More sharing options...
Ann E. V. Posted July 7 Author Report Share Posted July 7 Hi Bill, Thanks so much for your input. As I understand what you are telling me, I should take the temperature of the kiln vent when the kiln is at its highest temperature and if it is 120 Degrees F or more, I should open the sliding vent on the exhaust to include more fresh air. This will increase air flow and lower the temperature and the humidity in the ductwork so that moisture does not continue to corrode the galvanized elbows connecting the ductwork to the outside air. Please confirm that I understand this correctly? It would be nice to have such a simple fix! Ann E. V. Quote Link to comment Share on other sites More sharing options...
neilestrick Posted July 7 Report Share Posted July 7 Which brand of vent do you have, and which kiln? Quote Link to comment Share on other sites More sharing options...
Ann E. V. Posted July 7 Author Report Share Posted July 7 It is a vent sure system from L and L kilns. It has the doubler package on it. It is connected to an easy fire L and L kiln and an evenheat kiln. Both approx 7 cubic feet capacity. All the galvanized elbows on the vent ductwork are corroding. Quote Link to comment Share on other sites More sharing options...
Bill Kielb Posted July 7 Report Share Posted July 7 (edited) 1 hour ago, Ann E. V. said: Thanks so much for your input. As I understand what you are telling me, I should take the temperature of the kiln vent when the kiln is at its highest temperature and if it is 120 Degrees F or more, Yes, most likely they are very hot and of course the heat and humidity along with any strong corrosive gasses and a lack of airflow causing early failure. Dilute all that with room air and things last a long time. Post a picture or two, right now we are assuming normal duct, normal environment . How hot the duct is in operation presently at top temps is key here. Don’t forget to check for an obstructed discharge. Same issue - little or airflow. Edited July 7 by Bill Kielb Quote Link to comment Share on other sites More sharing options...
neilestrick Posted July 8 Report Share Posted July 8 On 7/6/2024 at 9:11 PM, Ann E. V. said: It is a vent sure system from L and L kilns. It has the doubler package on it. It is connected to an easy fire L and L kiln and an evenheat kiln. Both approx 7 cubic feet capacity. All the galvanized elbows on the vent ductwork are corroding. The slider on the collection box should be set with the hole half open for starters. From there if you need to make adjustments they should be done in 1/16" increments. In kilns that size you really shouldn't need to close the hole any more than that. Quote Link to comment Share on other sites More sharing options...
Ann E. V. Posted July 24 Author Report Share Posted July 24 Thank you for all of your help! I have replaced the necessary parts and will check the temperature of the ductwork for my next firing. I don't remember seeing anything about this in the kiln or vent manual. I would have never figured how to solve the problem with out all of you! Keep makin'! Hulk 1 Quote Link to comment Share on other sites More sharing options...
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