Centrifuge rotor having a fused web

A centrifuge rotor operable to rotate about an axis of rotation at a predetermined operating speed, the rotor having

• a central hub,
• a ring disposed concentrically about the hub, the ring having a plurality of cavities formed therein, the ring having an annular rim with an upper surface thereon, the upper surface having a predetermined reference line thereon, the ring having a center of mass,
• a relatively thin web connecting the hub and the ring, the web defining a localized region which exhibits a stress therein that is greater than the stress present in any other portion of the rotor when the rotor is operating at the predetermined operating speed so that, over operation time, the probability that rotor failure will occur only in the web is enhanced,
• the web being spaced a first axial distance from the surface of the rim and the center of mass of the ring being spaced a second axial distance from the surface of the rim, one of the axial distances being greater than the other axial distance,
• a portion of the upper surface of the rim disposed on at least one predetermined radial side of the reference line being relieved, the portion of the surface that is relieved being determined in accordance with which of the axial distances is the greater, and
• a cover disposed over the rotor,
• at least one of the cover or a portion of the upper surface of the rim having an annular seal groove therein, the groove having a radially inner and a radially outer wall, the radially outer wall of the groove being substantially radially aligned with the reference line on the upper surface of the rim while the rotor is operating at a predetermined rated operational speed.