Usually the ball bearings are positioned on the compressor or  turbine shaft so that they can absorb any axial (thrust) loads  or radial loads. Because the roller bearings present a larger  working surface, they are better equipped to support radial  loads than thrust loads. Therefore, they are used primarily  for this purpose. A typical ball or roller bearing assembly  includes a bearing support housing, which must be strongly  constructed and supported in order to carry the radial and  axial loads of the rapidly rotating rotor. The bearing housing  usually contains oil seals to prevent the oil leaking from its  normal path of flow. It also delivers the oil to the bearing for  its lubrication, usually through spray nozzles. The oil seals  may be the labyrinth or thread (helical) type. These seals  also may be pressurized to minimize oil leaking along the  compressor shaft. The labyrinth seal is usually pressurized,  but the helical seal depends solely on reverse threading to  The main disadvantages are their vulnerability to foreign  matter and tendency to fail without appreciable warning.  In general, antifriction bearings are preferred largely because  they: Figure 1-75. Insulation blanket with the temperatures obtained at the various locations shown.  1-54 •  Offer little rotational resistance, •  Facilitate precision alignment of rotating elements, •  Are relatively inexpensive, •  Are easily replaced, •  Withstand high momentary overloads, •  Are simple to cool, lubricate, and maintain, •  Accommodate both radial and axial loads, and •  Are relatively resistant to elevated temperatures. Stainless steel shroud – 350° F Fiberglass Fiberglass Silver foil Aluminum foil Jet tailpipe 900 ° F Exhaust gas Cooling air 120 ° F 1000 ° F