Interpreting a Conflict Between Specification and Product Data Sheet
A project specification for a wastewater clarifier interior states: 'Surface preparation shall be SSPC-SP 6/NACE No. 3 commercial blast. Primer: zinc-rich, 3-5 mils DFT. Intermediate: epoxy, 6-8 mils. Finish: polyurethane, 2-3 mils. Total DFT 12-16 mils. Holiday test at 100 V/mil.' The selected coating system's product data sheets state: immersion service requires SSPC-SP 10/NACE No. 2 near-white; the zinc-rich primer is not recommended for immersion or for pH above 9; the epoxy intermediate is the immersion-grade product at 10-15 mils; and the polyurethane topcoat is for atmospheric exposure only, not immersion. The owner's engineer says 'the spec is the spec, build to it.' The contractor has already blasted to SP 6 in one tank and wants to prime.
1. Identify the conflicts between the specification and the product data sheets, and explain why each matters for a wastewater clarifier interior.
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There are at least four material conflicts, each with real failure consequences in immersion service:
- Surface prep: SP 6 (commercial) vs. SP 10 (near-white) required by the product for immersion. SP 6 leaves up to 33% staining and mill scale; in immersion, residual scale and staining are initiation sites for undercutting and blistering. The product's warranty/performance basis assumes SP 10.
- Zinc-rich primer in immersion: zinc-rich primers are designed for atmospheric exposure; in immersion, especially at pH above 9 (wastewater can be alkaline), zinc can react, passivate poorly, and the primer is not formulated for continuous wet service. The data sheet explicitly excludes it.
- Epoxy DFT: spec says 6-8 mils; the immersion-grade epoxy requires 10-15 mils. At 6-8 mils the barrier is below the product's immersion minimum, so the coating will not perform as tested.
- Polyurethane topcoat in immersion: the data sheet says atmospheric only. Polyurethane topcoats are not formulated for continuous immersion and will hydrolyze/blister. Using it as the immersion contact layer is a direct misapplication.
Additionally, the 100 V/mil holiday test voltage assumes a total DFT of 12-16 mils; if the epoxy is corrected to 10-15 mils plus other layers, the voltage must be recalculated.
2. What is the correct professional action when the owner's engineer insists on building to the conflicting specification? Describe the process and the documentation.
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The inspector/contractor should not silently build to a specification that conflicts with the manufacturer's written limitations, nor unilaterally substitute. The correct process is a formal request for information (RFI) / clarification, in writing, that:
- States each conflict specifically, citing the spec clause and the product data sheet clause side by side.
- Explains the technical consequence of each (as above) in terms the owner can evaluate - i.e., reduced service life, likely blistering/under-cutting, potential warranty voidance.
- Requests a written direction: either (a) revise the specification to match the product's immersion requirements (SP 10, epoxy-only immersion system at 10-15 mils, no zinc or polyurethane in immersion), or (b) confirm in writing that the owner accepts the deviation and that the coating manufacturer's warranty is not applicable.
- Notes schedule and cost impacts of either path.
The inspector should document the RFI, the response, and the date/time of each communication, and should not release the hold point (priming the blasted tank) until direction is received. If the owner insists on the non-conforming system, the inspector records the objection in the daily report and obtains the owner's written acknowledgment. 'The spec is the spec' is not a defense against a known misapplication; the professional duty is to surface the conflict and document the decision.