Condensation

Good Afternoon Everybody.
During this period we had several problems due to condensation inside the enameling oven in an magnet wire plant. Regarding this issue I think, there is a huge discussion.
What I'm asking is:

- Why is there condensation generated inside the oven?
- How do I tell if there is condensation inside an oven?
- Some varnishes create more condensation than others. Why?

If I am forgetting something I would appreciate everyone who reminds me!

My Best Regards to everybody

Nicola

Hello Nicola

I have asked a magnet wire specialist to respond to this question but in the meantime the following seems appropriate,

Please take a look at the thread titled "Magnet Wire Failing Pinhole Test" at www.wirenet.org/forum/5-electrical/249-m...ling-in-pinhole-test

Condensation inside the enamel oven is due to the humidity of the air feeding the oven, the recycling of the air inside the oven and the amount of water absorbed by certain enamels before use. (Hygroscopic)

Thus, rather than being a universal problem, it is more of an issue for specific ovens. It also reflect on the way you are storing your enamels between runs. It is important to keep the hygroscopic enamels away from the moisture in the air.

Thanks Peter as Always for your fast answer.
I'd like also to contact Spectre to ask him something in relation with condensation and specific varnishes.

My best Regards and I wish you an happy new year.

Nicola

Hello again,

I did talk with Spectre by E-mail last night but he could not get on the website. Perhaps it was down for a while for maintenance.

Condensate in wire enameling ovens.

Without going into great detail about oven design, air flow, etc.,  thr condensate that Nicola is concerned about is enamel or varnish condensate.

When wire is coated and pulled into the oven it is wet with enamel and as it passes through the oven the solvent in the enamel evaporates.  The type and design of the oven determines what happens to these solvent vapors.   As the wire continues to pass through the oven the heated path changes from the evaporation zone to the curing zone.  In the cure zone all of the solvents are supposedly removed and the enamel coating is curing and is becoming a hard coating.   When the wire leaves the oven the enamel should be fully cured.

Sometimes that is not true.  With most ovens fresh air enters or is sucked into the wire chamber at both the wire entrance and the wire exit.  When the oven is properly adjusted the amount of air being sucked in is the minimum amount to draw the wet enamel solvent vapor into the oven.  At the other end of the oven it is supposed to strip off any fumes still be released from the wire, prevent any smoke from leaving the oven, and help cool the wire before it exits the oven. By cooling he wire it makes the surface do the enameled wire harder and less "plastic".  Most ovens also have a wire cooler between the oven exit and the turn around sheaves or rollers.  

Enamel can build up anywhere the wire touches while the coating is wet or still in a plastic state.  This is not condensate and eventually looks like an enamel drip.  

Whenever as you see smoke in a heated air stream what you are seeing is the accumulation of vapor, droplets of moisture (solvents), or some of the materials that are in the enamel.  In certain ovens these vapors are drawn through a catalyst or burner and burn, with the released energy recovered and used to help heat the oven.  When the evaporation process is incomplete then there will be excess vapors in the curing zone. (a wide variety of reasons can cause this) which the slows down the further evaporation of solvents and also affects the curing process.  These vapors have to go somewhere and since they are more than normal they will condense when the cooler air enters the oven.  When they condense they have to go somewhere and in most cases they adhere to any surface that they can find - in the oven near the exit, in the wire cooler, on the ceiling, literally anywhere.  I allowed to continue to happen it can accumulate to the point that it touches the wire or obstructs the wire line.   Once sit contacts the wire the problem gets worse fast.  

Additionally if you have a catalytic oven, the solvent vapors containing enamel components will contact the heated catalyst and then coat it rendering it useless.  The catalyst is designed to burn the solvents it is not designed to filter the air stream but that is what happens.  Resins, fillers like titanium oxide, and other materials contact and contaminate the catalysts.  Since the catalysts are now performing at a lower effect level, the vapors in the recirculated air, the exhausted air, etc will condense where ever it can.  This usually means somewhere near the wire exit of the oven. When it builds up in this area it usually looks dry and crusty and if it gets too thick the wire might come in contact with it with it causing wire quality problems.  Gravity and vibrations may cause some of it to break off an fall into the wire chamber on vertical ovens again causing problems.

Bottom line is that this is a process set up problem or an equipment problem.  I will be glad to discus further here or via email. R
Specte