Three levels of fan structural analysis are included in this practice:
a. Initial Structural Integrity
b. In-vehicle Testing
c. Durability (Laboratory) Test Methods
The Initial Structural Integrity section describes analytical and test methods used to predict potential resonance and, therefore, possible fatigue accumulation.
The In-vehicle (or machine) section enumerates the general procedure used to conduct a fan strain gage test. Various considerations that may affect the outcome of strain gage data have been described for the user of this procedure to adapt/discard depending on the particular application.
The Durability Test Methods section describes the detailed test procedures for a laboratory environment that may be used depending on type of fan, equipment availability, and end objective.
The second and third levels build upon information derived from the previous level. Engineering judgment is required as to the applicability of each level to a different vehicle environment or a new fan design.
This SAE Recommended Practice is applicable to any engine cooling fan application including medium and heavy-duty trucks, buses, construction equipment, industrial, and agricultural equipment. Some sections are more applicable to engine-driven fans than to hydraulic-driven or electric-motor-driven fans, especially with respect to speed control. Fan failure modes, however, are generally the same regardless of driving modes.
The usage of non-metallic construction necessitates areas of evaluation not required by metallic designs. Chief among these are temperature extremes, moisture content, impact resistance, chemical attack, material purity/homogeneity, and aging/weathering. Areas of evaluation affecting both metallic and non-metallic fans, but requiring somewhat different approaches with non-metallic parts, include natural frequency determination and durability testing.