The "JJF (Petrochemical) 053-2021 Gap Film Applicator calibrating specification" clarifies the calibrating requirements of Gap Film Applicators and provides a unified technical basis for their performance testing. The specification applies to the calibrating of Gap Film Applicators in the Petrochemicals field, including calibrating conditions, technical specifications, calibrating steps, data processing and uncertainty assessment. The specification aims to ensure the accuracy and conformity of the Moulding Film thickness of Film Applicators, providing reliable support for material performance testing and mass evaluation. Through scientific calibrating, the application effect of Film Applicator can be improved, and the standardization and efficiency of experimental and production processes in the petrochemical industry can be helped.