51314-3928-Reducing Casting Leaks in Pumps and Valves using Solidification Simulation

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Product Number: 51314-3928-SG

ISBN: 3928 2014 CP

Author: Raymond Monroe

Publication Date: 2014

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Castings used for the production of valves can leak even when they pass a full gamut of stringent quality requirements. Unanticipated leakage from valves and pumps is costly and disruptive.To prevent leakage from the cast bodies equipment manufacturers and users specify NDE examinations. Radiography is the most common method but discrimination between different quality levels is unreliable. Not only is it unreliable the sensitivity of the radiographic technique does not resolve any indications below 2% of the wall thickness. This means that castings with no radiographic indications can leak.Work has shown that the use of solidification simulation can verify casting quality. Solidification simulation predicts areas within castings where shrinkage porosity may occur. The Niyama criterion based upon the thermal gradient and the cooling rate of a casting during solidification can predict shrinkage. Solidification simulation can provide a way to assess casting quality prior to production at sensitivity levels unavailable from radiography or ultrasonic methods usede after production.The application of solidification simulation to predict shrinkage is common but requires good thermo-physical data for the alloy. Extensive work has been funded by MTI carried out by the University of Iowa and supported by SFSA members; that has resulted in new thermo-physical data for selected stainless steels and nickel-based materials.A procedure has been developed that will allow producers to qualify their solidification simulation to reduce shrinkage defects in critical sections of pump and valve castings.