Rick Busche wrote: I have a projector assembly which is essentially a large metal structure (frame) with a metal projector platform which swivels for purposes of maintenance. The structure is painted steel, with pressed in bronze bushings at all motion points each of which have been measured at significantly less than 0.10 ohms. Arguably, there is no guarantee that these structures will remain bonded at these levels over time and bonding wires (braid, with crimped ring lugs) have been added across the pivot points. These wires are secured to the structure using a toothed washer and screw. The intent of the toothed washer is to bight through the paint to ensure conductivity. My customer's safety officer (in Europe) is now insisting that the paint must be ground off to bare metal and coated with Zinc paint prior to affixing the lug to the structure. I am concerned that this is an excessive requirement. It has been my understanding that the toothed washer (and the screw for that matter) creates a gas tight connection which is acceptable for all bonding requirements. I would be interested in hearing from the group regarding this bonding issue. I can find no standard or specification which disallows this biting washer or requires Zinc paint. Any comments would be appreciated. Rick Busche [email protected]
Reply: You may have already thought of this but... My approach to this kind of requirement is to respectfully ask the customer to cite the language in the standard that requires this construction. If they are unable to provide this reference, I would ask if they have a specific requirement for this construction method other than a standard. If they still cannot supply you with a good reason, I would have to say that you can decline their request. Bear in mind that these folks are your customer and this may be an unspoken expectation on their part. If it is something they are willing to pay for and you can charge them for it, it may be desirable to do. I learned long ago that if I cannot cite the standard that is the basis for my requirement (or finding in the case of auditing), I don't insist on having it my way. Regards Bob Collier Graphics Microsystems [email protected] Nobody pays me for these opinions, perhaps there is a reason...
