I am an avid reader of your magazine. In your April 2001 column you were asked about phosphate system pressure. One area that you should take into concern when discussing operating pressure is the spray pattern that the nozzle is designed to produce. I have viewed many washers that use fan sprays in the phosphate section. If the pressure is too low, a pattern will not be created. The hollow cone nozzle is more suited for low pressure. It produces a more efficient spray pattern and more droplets. We have performed numerous nozzle audits on multi-stage washers and found this to be a common concern. Proper nozzle selection is a very important factor in producing a clean part. It is also the most overlooked component in the system. B.T.
I appreciate the feedback and without a doubt, nozzle pattern and system maintenance are probably the most significant factors to the success of any spray wash or pretreatment system. In that column, I was speaking in generalities regarding system pressure with regard to a phosphate stage in a pretreatment system. This stage will frequently use a hollow cone nozzle, which is meant to operate at lower pressures while minimizing the chance of plugging. The lower pressure also minimizes the chance of carryover to other stages of the pretreatment system due to overspray. The other stages, especially the wash stage, will use higher pressures, often near 30 psi, and frequently will use a more "standard" vee-jet type of nozzle. Thanks for the comment!