Troubleshooting Major Causes of Rotary Joint and Rotary Union Problems

As mechanical devices with wear components, rotary joints and unions are suspect to premature wear when not properly installed. Below are the leading major causes of premature wear and how to limit the potential for early replacement of components due to improper installation.

Improper Piping

Improper piping that leads to piping strains. Piping strains lead to excessive force exertion on the body of the rotary joint or excessive guide wear with self-supported rotary joints. For rod-supported rotary joints, the support rods deflect under the excessive piping strain and that causes poor seal alignment.

Prevent piping strains by using proper flexible metal hoses, piping support, expansion joints or loops, and accurate rotary joint or rotary union installation.

Rotary Joint or Union Misalignment

Rotary joint or rotary union misalignment occurs when the centerline of the rotary joint components are not accurately aligned with the centerline of the journal.  Misalignment can cause interference with the rotary joint’s internal parts and significantly increases the wear rate of the sealing components. Symptoms of rotary joint and rotary union misalignment include:

  • Broken spring
  • Excessive key and key-way wear
  • Broken horizontal syphon pipes
  • Broken journal flange bolts
  • Broken nipple flange studs
  • Flexible metal hose failures
  • Broken carbon guides

Prevent misalignment by accurately installing the rotary joint and supporting equipment.  Evenly torque journal flange and nipple flange fasteners.  Bent support rods or poorly aligned mounting brackets are common causes for misalignment as well.

Lack of/Improper Torque Restraint

Lack of a torque restraint or an improper torque restraint increases the radial forces that are applied to self-supporting rotary joints. Using flexible hoses as a torque restraint causes high radial loads to be applied to the rotary joint.  An overly restrictive torque restraint can cause excessively high forces as well.  A properly designed torque restraint allows the rotary joint or rotary union to move axially and radially while preventing rotation.

Looking for more insights into maximizing the life and performance of your Kadant Johnson rotary joint? Installation and repair instructions for Kadant Johnson rotary joints and unions are available online at www.kadant.com/literature. You may also request the installation and repair instructions be sent to you by calling 1-800-657-5940 or emailing jan.walter@kadant.com.