The subject of the studies is the evaluation of the operation of a production system after modernization. The analysed case concerns the modernization forced by the end of the product lifetime. The proposed methodology is that of a multicriterial evaluation of the system operation after modernization. The evaluation criteria are selected TPM indices: availability of machinery and equipment, production process capacity, product quality and overall equipment effectiveness (OEE). The additional criteria are reliability indices MTBF and MTTR of studied production lines and the MTTR of the most unreliable equipment in each analysed line. A yearly monitoring of production process was proposed for obtaining the statistical credibility of the evaluation results. Additionally, a fuzzy indicator of acceptability of the modernization assessment was proposed. The paper presents the results of studies of the system for production of zinc concentrate from post-production waste. The obtained values of OEE, MTBF and MTTR indicators for the three tested lines make it possible to state that the modernization carried out is acceptable.