Since a majority of powder coating systems today include a spray washer system, it seems appropriate to provide a certain
amount of in-depth information on the maintenance of the pretreatment system.Pretreatment
failures are the single largest cause for rejects in the finishing
industry today. Unbalanced chemical concentrations, bad rinse
water, clogged or misdirected nozzles, and other factors left unattended
will certainly cause rejects regardless of the top coat quality.
Rejects related to the pretreatment system can be reduced drastically
with a properly implemented maintenance program.
Pretreatment systems require maintenance for two main reasons,
(1) extended equipment life, and (2) proper operation. Aside
from the daily, and in some cases hourly, titrations that are performed
to determine the chemical concentration levels in each stage, the
pumps, nozzles, and burners, will also need proper attention.
The objective is to deliver parts with clean surfaces and with proper
phosphate coating weights, to the powder coating booth as quickly
as possible.
For this objective to
be met a few guidelines should be followed:
- A maintenance schedule and log book should be kept to track the regularity of the additions of make up water, chemicals, and replacement parts that are used in the pretreatment system. This will help the
systems manager to determine when the next chemical change or tank cleaning is needed.
- Checks should me made on a regular basis for spray nozzle adjustment, clogged orifices, missing nozzles, or damage to the nozzles by parts that have not been properly racked and have fallen off in the
system. A misdirected nozzle from a rinse station can overflow a chemical containing station and dilute the concentration in a matter of minutes.
- Pumps should be inspected and greased on a regular basis to insure proper liquid pressure to the nozzles. Clogged nozzles will increase the pressure delivery of the remaining unclogged nozzles, too much
pressure is undesirable; in some cases the the excessive pressure will result in spotting, uneven coating weights, or parts removed from the racking system.
- Pump screens should be cleaned daily to prevent lint from gloves, rags, and other materials from entering and clogging the pump, header pipes, and nozzles.
- Drains should be free of scale and foreign matter to prevent overflowing of the waste water onto the work area or worse, into the bake oven.
- Interior grids should be in place to prevent parts that fall from the racking system from entering the holding tanks. This will allow the systems operator to retrieve the parts with ease.
- Burners will need air filters replaced on a regular basis to insure clean efficient fuel consumption and maximum control of the liquid temperatures within the holding tanks.
The pretreatment system is essential to any finishing operation. Without clean parts even the most sophisticated coating operation will produce nothing but rejects. Keep it organized, keep it clean,
and keep it running. |
