Chemical Buildup

Would stainless steel chain and hangers prevent the buildup? Or is there some other prevention?


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Q. We have a customer with two powder coating systems that has had an ongoing problem with chemical buildup on their overhead monorail conveyor chain and hangers, see photo below. They apply zinc phosphate coating in their spray washers. They currently want to install stainless steel sheet metal guarding around the chain and hangers to keep contamination off the product. Would stainless steel chain and hangers prevent the buildup? Or is there some other prevention? Seems to me that the sheet metal guarding is just a band-aid fix. 

chemical buildup
The complete washing process is as follows:

 

Stage 1     Alkaline wash at 125°F
Stage 2       Water Rinse at Ambient
Stage 3       Fixodine Prep at Ambient
Stage 4       Zinc Phosphate Coating at 125°F
Stage 5       Water rinse at Ambient
Stage 6       Sealer at 105°F J. B.
 
 

A. Wow!!! That’s some build-up you got there!!! Great picture…thanks for sending it. Now I will use a few of my own pictures to illustrate my answer.

Conveyor splash guarding (shielding) is part of normal spray washer design for conveyorized systems. Almost every system design house uses them as part of their standard washer designs. Therefore, this would not be considered a band-aid fix, but rather an appropriate use of known technology. (See drawing below)

diagram

Ideally the system should have been designed with a top-of-rail-to-top-of-part dimension of at least 36 inches to keep the conveyor well outside the spray zone of the washer (see dimension F on drawing). I have seen and specified for our clients a top-of-rail-to-top-of-part dimension of up to 48 inches to ensure trouble–free service from the system. This is one instance where “more is better”. However, you have to be careful with part stability, equipment height, and equipment costs if you go too far with this.

diagram

Your customer may even want to install a patented Protectaire Systems conveyor shielding system that includes a shroud and a fan that provides positive pressure. These devices are often installed to overcome problems such as yours. They have been around a long time and have a good product.

What I would not do is install a stainless steel chain, trolleys, “H” attachments, and “C” hooks. This is very expensive and still will not prevent the trolley and chain from being degraded by the washer chemicals. Furthermore, the conveyor lubricant will be removed from the chain and trolleys if they are not protected from the spray zone in the washer. You can consider using stainless steel rail over the washer to prolong the life of the rail. This cost is relatively cheap and can greatly improve the life of the conveyor.

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