Shaft/shaft-seal interaction of a multiple disk centrifugal blood pump: A study of thermal and wear characteristics

A multiple disk centrifugal pump (MDCP) is under investigation as a potential left ventricular assist device. As is the case with most shaft driven pumps, leakage problems around the shaft/shaft-seal interface are of major interest. If leakage were to occur during or after implantation, potential events such as blood loss, clotting, blood damage, and/or infections might result in adverse effects for the patient. Because these effects could be quite disastrous, potential shaft and shaft-seal materials have been investigated to determine the most appropriate course to limit these effects. Teflon and Nylon were analyzed as potential shaft-seal candidates with both a stainless steel shaft and a Melonite® coated shaft, the latter provided by Houston Unlimited Inc. Metal Processing in Chappell Hill, Texas. The materials and shafts were evaluated under time, motor, and outer diameters. Motor speed and geometrical configurations were typical for the MDCP under normal physiologic conditions. The three parameters analyzed were the inner diameter (ID), the inner temperature, and the outer temperature. Statistical comparisons were computed for the shaft seal materials, the shafts, and the outer diameters along with the inner and outer temperatures.