Shaft/shaft-seal interface characteristics of a multiple disk centrifugal blood pump

A multiple disk centrifugal pump (MDCP) is under investigation as a potenti al left ventricular assist device. As is the case with most shaft driven pu mps, leakage problems around the shaft/shaft seal interface are of major in terest. If leakage were to occur during or after implantation, potential ev ents such as blood loss, clotting, blood damage, and/or infections might re sult in adverse effects for the patient. Because these effects could be qui te disastrous, potential shaft and shaft seal materials have been investiga ted to determine the most appropriate course to limit these effects. Teflon and nylon shaft seals were analyzed as potential candidates along with a s tainless steel shaft and a Melonite coated shaft. The materials and shafts were evaluated under various time durations (15, 30, 45, and 60 min), motor speeds (800, 1,000, 1,200, and 1,400 rpm), and outer diameters (1/2 and 3/ 4 inches). The motor speed and geometrical configurations were typical for the MDCP under normal physiologic conditions. An air and water study was co nducted to analyze the inner diameter wear, the inner temperature values, a nd the outer temperature values. Statistical comparisons were computed for the shaft seal materials, the shafts, and the outer diameters along with th e inner and outer temperatures. The conclusions made from the results indic ate that both the tested shaft seal materials and shaft materials are not i deal candidates to be used for the MDCP. Teflon experienced a significant a mount of wear in air and water studies. Ny ion did experience little wear, but heat generation was an evident problem. A water study on nylon was not conducted because of its molecular structure.