Paper Machine Dryer Journal Fatigue Failure Risk Reduction, 2008 Engineering, Pulping and Environmental Conference

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Several failures of separately cast and press fit journals in a 1950’s vintage paper machine were determined to be fatigue failures due to low strength cast iron. A stress analysis determined the operating stresses at failure and the tensile strength required to avoid fatigue. The journal stresses in a dryer full of condensate were found to be 79% higher than in a normally operating dryer. Weekly dryer temperature surveys were conducted to identify dryers with condensate removal problems for maintenance. A program to measure the Brinell hardness (BHN) of all the journals in the machine was developed to determine the tensile strength based on a correlation between BHN and tensile strength of journals removed from the machine. Journals were prioritized for replacement based on predicted tensile strength, operating stress levels, and risk of a dryer falling out of the machine. Journal replacements were conducted during several normally scheduled annual shutdowns. This program avoided an extended machine shutdown that would have been necessary to replace 123 journals if the low strength journals could not be identified and removed to eliminate the risk of their continued operation. Each removed journal was tested to determine its tensile strength to validate the replacement selection criteria.