Glossary R


  • 90 degrees to the centerline of the shaft.

Radial bearing

  • In an end suction centrifugal pump it is the bearing located closest to the stuffing box. This bearing handles most of the radial loads put on the impeller.

Reaction bonded

  • A method of manufacturing silicone carbide mechanical seal faces. These materials are sensitive to caustic and some other high pH liquids.

Renkin scale

  • Used to measure low temperatures in the Fahrenheit scale. Similar to Kelvin which is used to measure low temperatures in the Centigrade system.


  • A second impeller used to lower the stuffing box pressure.

Reverse balance

  • A common type of hydraulic balance used on outside mounted mechanical seals.

Rigid shaft

  • A shaft with a rotating speed lower than its first critical speed.


  • Root mean square. A measure of surface finish or smoothness. Metric uses C.L.A. or centerline average for the same purpose.

Rockwell “C”

  • The scale most often used to measure hardness of the hard seal face.

Rotating seal

  • When the spring loaded or moveable portion of the seal rotates with the shaft.

Run out

  • Twice the distance that the center of the shaft is displaced from the axis of rotation.


  • On February 09, 2018