Powder coat oven air flow question

[Mr Fixit]

Hi Gang,

I'm in the process of building a powder coat oven from a food warmer cabinet like in the restaurants. 2'x2'x5' tall. The question is, the air flow is going down the sides as there are existing air ducts down each side and I'm wanting to flow the air around the new element as in the pic [IMG][/IMG]
What i'm thinking of is a round hat with louvers all the way around to get good air flow to the element, but I'm not sure how big the openings should be to get the best flow possible.
Now I know this is a far fetched question but maybe a couple of you could give me food for thought.
PS. I am machining and welding for this so it kind of fits as a topic of discussion.

TX
Mr fixit for the family
Chris

[duckman]

Remember that it's a powder and to much air flow and the powder gets blown off , you just need heat with out air flow.

[Mr Fixit]

Thanks Duckman,

I just don't want to have hot spots around the element and cause it to burn out. It is a conventional oven element so as I think about it, not any air movement in lots of ovens that get used in the house all the time.

I'm going with low air flow and see what happens.

TX
Mr fixit for the family
Chris

[bobw53]

Turn the blower off.. The last thing you need in a powder coat oven is a lot of airflow.. I don't think a little bit
would kill ya,(probably help) but convection oven style, I'd be worried.

Add some heat sinks (piles of scrap aluminum) to maintain temp and let it go..

If you do burn out the element, new elements are cheap. It was something like smallappliancerepair.com or some non-sense that had TONS of different
oven elements, and most of the stuff was dirt cheap.

[CCWKen]

Put a perforated plate or grill over the element(s). This helps disperse heat flow (convection) and blocks much of the IR that will be radiating from the heater coils. IR radiation is what causes hot spots. Most off the shelf fan bearings won't handle the heat anyway.

[RichR]

Put a perforated plate or grill over the element(s). This helps disperse heat flow (convection) and blocks much of the IR that will be radiating from the heater coils. IR radiation is what causes hot spots. Most off the shelf fan bearings won't handle the heat anyway.

The OPs diagram appears to show the heating element at the top of the the oven. I don't think convection is going to be helpful here.

[bobw53]

The OPs diagram appears to show the heating element at the top of the the oven. I don't think convection is going to be helpful here.

Apparently...

I'd flip the thing upside down, or move the heating element to the bottom.

Another thought.. If its a food warmer cabinet (140-160F I'd guess) the heating element might not be
enough to get up to the 350ish you need for powder coating. Might be easiest to spend a few dollars
and slap a new heating element in down at the bottom.

[blckbx]

Used to run a powder coating operation dipping lobster pot frames. The main oven was gas heated. A big internal carousel (12 compartments maybe) would rotate within the oven so by the time a pot had completed one revolution it was up to temp. Open the door, take out the hot frame and then put in a new one. The hot frame was then dipped into an aerated basin containing the powder coating. Rinse and repeat. Hard hot dusty toxic work, thanks for getting me that job dad My point is the oven and the dipping pool were different operations. I would suspect an electrical element may struggle to get the required temperature.

Al

[CCWKen]

The OPs diagram appears to show the heating element at the top of the the oven. I don't think convection is going to be helpful here.

You may be right but I couldn't tell from the drawing. If that's the case, the OP sure doesn't want to draw "cold" air in through that fan either unless that's part of the cool-down cycle. If I were building a new PC oven, I'd build it capable of reaching at least 450 or more. Some of the powders are at or near 400 and you may want include a higher burn-off cycle for contaminates. That also helps heavy items that require preheating.

[Yondering]

Agreed. All the powders I use specify 400F for 10 minutes, I doubt a food warmer can do that.

Definitely ixnay on the air flow, even a soft breath is enough to disturb the dry powder that is only adhered by static.

Honestly, a kitchen oven may be a more appropriate choice if a guy wants to repurpose something like that.

[bobw53]

Used to run a powder coating operation dipping lobster pot frames. The main oven was gas heated. A big internal carousel (12 compartments maybe) would rotate within the oven so by the time a pot had completed one revolution it was up to temp. Open the door, take out the hot frame and then put in a new one. The hot frame was then dipped into an aerated basin containing the powder coating. Rinse and repeat. Hard hot dusty toxic work, thanks for getting me that job dad My point is the oven and the dipping pool were different operations. I would suspect an electrical element may struggle to get the required temperature.

Al

That's a "different" way of powder coating.. 99.9% chance that that method is only used in large quantity production, and also produces a much thicker finish..

I'm pretty sure what we are talking about is shooting the powder on (with some type of electrical charge) and then cooking it. Not getting the metal hot and then
putting it in the powder.

[Mr Fixit]

Hi Gang,

The element is from a domestic oven not the original food warmer. I got the cabinet free and it used to run @ 250*F + so I'm thinking 400*-450*F it will handle it but may get hot on the out side more than when warming food. The type of work is for small bike and car parts or other knickknacks to put a good finish on. It is the static electricity type of powder coat system.
I was thinking since the old unit did have a fan and the element at the top it would be important to get air flow around the element and air down into the cabinet. I hear what you guys are saying air flow could be a real problem, and to stay away from it. The blower is from a draft fan on a large commercial hot water heater and the motor and bearings are external to the heat.
I have the domestic oven idea now, but not quite big enough for a couple of things that the taller cabinet would work for. SO, the moral of this story is, think twice cut once and come up with a different design. I might be building something completely different, well see.

TX
Mr fixit for the family
Chris

[CCWKen]

There's a HUGE difference between 250 and 450. At 450, many materials will self ignite and the insulation may be insufficient to protect even the exterior walls and floor. You could create a shop fire or cause a cement explosion. Watch your electricals too. NONE of the wiring should be plastic coated, except perhaps, the box protected line-in.