Powder pre-heating
10-20-2010, 10:19 PM, (This post was last modified: 10-21-2010, 02:43 PM by Met.Eng..)
Powder pre-heating
Hi SEF membersSmile,

How many degrees do you think should be pre-heating of the powders.
We usually do pre-heating 100 degrees for 15 minutes to evaporate the physical water in the powders.
10-21-2010, 01:56 AM,
RE: Powder pre-heating
Hi Metallurgy_eng

With an opening question like this, I would suggest addressing to all members of SEF as I am certainly not the only, nor best person to answer your query. You may put people off from making valuable responses by addressing a thread to one person.

I know a lot of people swear by preheating powder prior to spraying and even going to the point of fitting powder hopper heaters. I am not totally convince that temperature alone effects flow properties, but moisture content certainly does.

My view is that powders should not be allowed to absorb moisture in the first place. So, some thought needs to go into the storage area for powders. This needs to be kept warm and dry relative to the surrounding environment. I like the idea of a warming cabinet place next to the work stations, where powders that are being used or planned for a job can be kept at a nice and cosy ~50C continuously.

Quote:We usually do pre-heating 100 degrees for 15 minutes to evaporate the physical water in the powders.
If you find this works for you, I see no problem.

You need to be careful though, preheating a powder that has become damp may not help. I remember a case where some chromium oxide powder (I think a silica loaded composite 136F type) brought in for some spray trials refused to feed. It was pop into an oven spread out on a tray, cooked on a medium heat for a couple of hours and the result was a perfectly bake biscuit Rolleyes Moral of the story - don't let your powder get damp, particularly if it is a composite based powder with organic binders.
10-21-2010, 02:46 AM,
RE: Powder pre-heating
Most powders are in a sealed container with a moisture absorbing pack. Most oems ask for powders to be kept at 140F. I personally dont think it makes a difference in my climate, maybe if you live somewhere where the humidity is very high.

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