Abstract: During the monitoring of the bed test life of mud pump pistons the quantitative technique of ferrography is used to trace, photograph and analyse the formation and changes of wear debris by means of SEM and EDAX. In the meantime, the coverage of wear particles on the ferrography section is measured in due time,anda lot of data are obtained. From a serics of the information, some wear curves related to the ferrography monitoring are drawn. Combining with the occurance of charateristic metallic wear debris and the analysis of rubber debris produced,this technique provides the reliable diagnosis criteria for the failure of the test pistons.

Key words: Quantitative technique of ferrography, Ferrography moni toring, Criterion for the failure, Piston