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May 2 - May 8, 2011
A specification requires Manufacturer X’s system “or equivalent.” What does “or equivalent” mean, and who decides what’s “equivalent?”
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Quality Control
Selected Answers
From
Frank Rea of GPI-Southeast on
May 3, 2011:
Coatings or coatings systems can be evaluated for equivalence to a specified product by any or a combination of the following criteria: generic type of resin, chemical and phyical properties, service environment, required surface preparation, compatibility with existing coatings (if applicable), formula, or performance. The specifier should be the individual to determine whether a proposed alternative is "equivalent".
From
Joseph Schinner of Akzo Nobel Coatings Inc. on
May 2, 2011:
I've dealt with federal, state, architectural, engineering, and general manufacturer's specifications for different types of coatings. It can be a mushball or it can be relatively simple. The detail of the spec itself determines how to approach the equivalent.
The most common "equivalent" is a performance equivalent that may or may not spell out a generic binder type. If a binder is not identified, then you are free to use what you want to match the preformance, but it is always advisable to know what the competitor is using and why it seems to fulfill the requirements before deviating from his lead.
If a spec asks for a 2K epoxy or a single package acrylic, then it doesn't want a performance equivalent in another generic binder system unless you can specifically sell them on value-added qualities that they will accept for their end use. It is best to find someone at the customer's facility who can answer questions about what application/field problems have been encountered and solved that are not directly addressed in the spec tests themselves. Often, this is where "equivalents" can be a struggle until the "hidden specs" are solved. As examples, the specs may not address certain part-handling mar problems, or the finished structure may have temporary ponded water areas with no mention of immersion testing needed. Spec "equivalent" ranges all the way from a DOD spec that may specify coating formulas with specific binder/pigment/solvent types/ratios including exact hydrogen-amine ratios all the way to simple gross (e.g., anything that won't fall off the wall for 5 yrs. and still look white).
Note: the more specific the formulation spec is, the more likely it was written around the competitor's or his predecessor's actual formula or submission, making it seem easier to match, but these are sometimes the hardest to overcome the "tricks" built in to prevent an easy match.
From
Brian Chapman of Cadillac Fabrication on
May 2, 2011:
We generally take this to mean a coating that CLOSELY matches the spec in performance. The equivalent should be decided by the manufacturer's rep for the coating you want to use, based soley on performance characteristics.
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Tagged categories:
Specification writing
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