Part Drying 3

[simoncad]

I am currently working on a project where I have to dry parts in a certain amount of time. Currently there are a continuous line of stainless steel fine mesh buckets filled with stainless steel parts being conveyed through a bath of water. The parts and bucket will be around 175 degrees F when coming out of the bath and there will be a bucket with parts following every 20 seconds. At this point I have 19 feet of conveyor, traveling at 6.5 feet per minute, to completely dry the bucket and parts. The first 5 feet will be open to the atmosphere in the shop. The next 12 feet will be in an enclosed shell. The shell will have 14.4 kw worth of heating elements (can add more) and insulation around the whole shell. The elements can go up to 950 degrees F, but we do not want to have the temperature high enough to heat treat the parts because they will already have gone through the heat treating process. The enclosed shell is the only control area, and I need help figuring out what to do to evaporate all the water off of the bucket and parts. The next 2 feet will be open to the atmosphere in the shop. The buckets will be coming out of the bath every 20 seconds.

Thank you,

simoncad

 

[IRstuff]

Are you sure you want to evaporate the water? Unless the water is softened, you'll leave deposits.

I would have thought you'd want a curtain wall of air first to blow off most of the water

TTFN

 

[simoncad]

it's funny that you should say that. i spent two weeks designing and implementing a piping assembly to do just that. i used 4 super air nozzles and 1 super air amplifier that produced 116 cfm at 80 psi to blow off some of the water but it turned out that the bucket is too hard to get through to dry the parts inside. i found that there will be 3 lbs. of water in the bucket after it comes out of the bath and 1.5 lbs. of water will drain out of the bucket in the first 5 feet.

 

[MintJulep]

IR is right, it would be best to mechanically remove as much water as possible first. Much less energy required.

Then, you need to figure out how much water is left. Is it just a surface film, or do the parts have cavities that could contain significant amounts of water?

 

[MintJulep]

Quick reasonablness calc:

12 feet of drier length, 6.5 ft/min. Each bucket is in the tunnel for 1.8 minutes. Lets call it 2 minutes.

Bucket every 20 seconds, means 5.5 buckets in the tunnel at any given time.

5.5 buckets * 1.5 pounds of water in each = 8.3 pounds.

37 degree sensible rise at 1 BTU/degree. 970 BTU/pound latent. You'll need to put 8,400 BTU into every 5.5 buckets to evaporate the water.

2 minute dwell is 1/30 of an hour.

8,400 / 1/30 = 250,750 BTU/hr, or 73 kW.

This is for the water only, you also have to heat up the parts and the buckets.

Your 14.1 kW isn't going to cut it.

 

[MedicineEng]

Also, why do you need to use buckets? Can't the parts be hanged in a conveyor?
Can't you use buckets with holes?
If the bucket is just to serve as storage to put parts you might want to make it as open as possible exactly to have the water drained. This will be much more economical than evaporate all the water.

 

[vpl]

How about using a mesh bucket ... so it doesn't hold water.

Patricia Lougheed

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[simoncad]

we cannot change the bucket. the bucket is part of the entire process and we have to work around it. i have already tried to convince everyone to change the bucket. it's a loosing battle.

 

[EdStainless]

Come out of the cleaner, dump the parts on a mesh belt conveyor, blow them off, warm them and blow some more, then dump them back into buckets.

Mint, I was trying the same thing before I read your post. Counting the parts and buckets you may need 120-150kW.

The real key is air ciculation. Unless you have a lot of air at low relitive humidity you will not get anything dry.

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[simoncad]

unfortunatly we do not have the option to dump the springs. i have already brought it up. good idea though.

i just received updated information about the process

it turns out that when the buckets are in the bath they are moving at a speed of 4 fpm. 16 inches or 20 seconds apart. when we get them on our conveyor we can slow down to 3 fpm and have the buckets 12 inches apart. this will allow for 4 minutes through the shell. our shell will have fans blowing through the heating elements. this will supply hot dry air to the buckets. we just need some to devise a way to get the humid air out. i also need to figure out exactly how much kw is sufficient.