Requirements and process control for quantity of product in prepackages

Abstract

Verification of the actual quantity of product in prepackages is an important part of compliance testing to facilitate fair trade, maintain a competitive marketplace and protect consumers against under-filled prepackages. Two of the most widely used legal metrological requirements are (i) the average net quantity of product in prepackages of an inspection lot shall be at least equal to the labelled quantity and (ii) the number of prepackages, in a randomly selected sample, that are under-filled by more than a permitted quantity is less than or equal to a permitted number. Industrial and government metrology officials are required to check whether prepackages in an inspection lot comply with these requirements by sampling prepackages at the point-of-pack, wholesale outlets and retail stores. This paper discusses some drawbacks of the acceptance sampling plans and metrological requirements recommended in the international recommendation OIML R87 developed by the International Organization of Legal Metrology. To counter these drawbacks, alternative sampling plans and average prepackage requirements are proposed. Statistical control of filling processes under the OIML R87 requirements is also discussed.