Letter 33629

Plans on building Powder Coating Oven

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I would like to build a powder coat convection oven. I need the instructions or blueprints for same. The size of oven I want to build is approx. 4 Ft x 4 Ft x 6 Ft deep.

Earl Evans
metal work - Hope, B.C., Canada

You can probably buy a used one for less than building a new one. If you shop carefully, you should find one that includes the original drawings. It would probably be theft of intellectual property to copy it except for replacement, but if it was just for your own use you might be okay.

Many powder coating books explain some of the important design issues though. I strongly recommend "Powder Coating" by Roger Talbert -- a 141-page softcover published by Chemical Coaters Association International, Cincinnati (ccaiweb.com). It has a 10-page chapter about curing ovens, with sketches, as well as info about dry-off ovens, and it clearly explains the features that should be included in each type of oven and why. Good luck.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

I am also planning on building an oven. My past experience is that you are better off to buy off the shelf rather than build especially if a employee is involved and parts are bought new. I have experience with large industrial ovens used in bakeries. I have learned a little lately as I have started to plan my oven.

First if you aren't experienced with gas fired equipment and safety requirements you probably ought to concentrate on safety first. In the bakery environment my experience had taught me that there are 2 types of ovens 1. direct fired and 2.indirect fired. I have learned the indirect fire is the way to go. My experience has been with direct fired ovens so I am learning about how to duct the hot air around the oven for even heating.

I am very honest in what I do and plan to ask one of the powder coaters we use if I can inspect their oven to learn more about the ducting of the hot air and also exhaust. I plan on buying almost everything for this oven from the junk yard and plan on it being around 25' long by 8 or 9 foot tall by maybe 5 foot wide.I am hoping that I can start the ball rolling on developing a plan instead instead of waiting for some manufacturer to chip in and give away their knowledge they have developed (which wont happen).I am thinking I will use a burner similar to what they use in building a forge which is a orifice with propane shot out it and a blower pushing air around it.There would be safeties on it to shut the system down if a flame detector isn't sensing a flame as well as sensors which would shut it down in case of a high temp as well as a number of other sensors for the flame detection safety. It has been a few years since I worked on ovens and I could be all wrong on this but I believe the way to get started is to start. I hope others will chip in their 2 cents that may help put together a plan for a oven. One concern I have is if a 20 ga sheet metal would work for a sheeting inside and out on the oven and if it wont work, WHY? Our scrap yard in town gets loads of square tubing which I plan on using for the frame work. Is there any other input?

Rick Nelson
- spokane Washington

I see several people seeking help/direction in building small powdercoat ovens. I have a website at www.powdercoatoven.4t.com/ that details how I built an oven such as this.

Gary Brady
- Austin, Texas

Ed. note: thanks, Gary! Readers, block pop-ups first!

I am using a modified kitchen oven with thermocouple sensors, and a very sucessful 5' x 7' x 4' oven that I built 10 years ago. It is heated with the core & fan from a home electric furnace. The fan motor is outside and a jackshaft extends inside. After years of trial & error it is now VERY accurately controlled by a new $75.00 PID controller from ebay and SSR "contactors". I can run various programs to powder coat or lower to a specific temp +- 1 degree to mold plexiglass.
I am now building a propane oven 8'x 8'x 24'.
One thing that scares me is an attitude out there that gas is dangerous don't do it, electric is safe.
This is a misleading idea. Some think that a flame could ignite powder and electric won't. I have seen fuel vapours ignited by red hot steel cause an explosion, (like a glowing element), no flame. Don't spray powder in your oven and you should not have a problem with suspended powder in the air in the oven. Direct flame heat is common in comercial ovens, ie: no heat exchanger to isolate the flame from the oven interior atmosphere. But they are behind baffels otherwise radiation heating would create local hot spots on the parts. A very good fan forced circulation system is needed.
I am not an expert and my opinions are suspect, BE CAREFUL and think it through.

Morgan Williams
- Midland, Ontario, Canada

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