With few exceptions, fan vendors do not normally provide a written guarantee for the aerodynamic performance of a fan or even identify tolerances for the rated performance. When requested, the vendor often refers to acceptance criteria established in accordance with fan industry recognized standards and publications issued by the Air Movement and Control Association, Inc. (AMCA). AMCA acceptance criteria are very subjective, allow for very wide tolerances and can result in a very low probability that the purchaser’s performance requirements are met. There are three options available to the purchaser. • Assume the risk that the fan may not meet the performance requirement. • Purchase an oversized fan such that the performance can be met even if the fan performs at the low end of its performance tolerance. • Insure that the purchased equipment will perform as specified and mitigate the risks of deficiency by requiring the vendor comply with a performance guarantee. Test procedures suitable for conducting fan performance guarantee tests are available in many published AMCA, ANSI, ISO and ASME performance test standards. These performance test standards typically provide a procedure to estimate the accuracy of the measurement in the form of an uncertainty analysis. However, the accuracy of the measurement does not necessarily address whether the measurement meets the requirement within an acceptable tolerance. Except for AMCA, these test standards generally do not stipulate acceptable performance tolerances. A tolerance stipulates how much the measured value is allowed to fall short or exceed the required specified value and still be deemed to be acceptable. The system designer should specify suitable acceptance tolerances with consideration of the design margins that have been applied to the flow, pressure and power requirements of the system. This technical paper outlines a guideline of how to assess the accuracy and validity of a vendor’s quoted performance and the implications on system design margins. A case is made for laboratory verification testing in situations where a performance guarantee is required. • Allows proactive verification before final design, manufacture or shipment takes place. • Verification and corrective actions do not interfere with plant startup and production. • Allows for proactive modifications to be made at a fixed cost to the buyer.

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