The Kadant Blog

Seals: A Kadant Johnson Expertise that Assures Great Results

PT2X Rotary Joint s Dryer Section Front SMKadant Johnson uses advanced sealing technologies in its rotary joints. Seals are critical because they ensure the different fluids within the application do not mix or leak into the environment. They are also the primary wear component in a rotary joint and determine its longevity.

Since Kadant Johnson’s invention of the rotary joint in 1930, Kadant Johnson has gained an understanding of sealing properties and technologies. Today, Kadant Johnson uses two different types of seal ring designs in rotary joints to achieve the best performance.

Pressure Seal Designs

The first seal ring design is a pressure type. This kind of seal has a flat seal face and either a convex or concave seal face. A spring force keeps the seals ring in contact with the sealing surfaces when the roll is starting up or when the pressure is low. However, as pressure is increased, a larger force from the fluid pressure is applied to the seal. This action increases its sealing capability with pressure and it is the seal technology used in SX®, SNX™, and ELSX™ rotary joints. As the pressure increases, the torque generated by the seal ring increases and these rotary joints require anti-torque rods. Pressure joints can be mounted directly to a roll and don’t require a mounting bracket or lugs. The wear of a pressure seal ring increases with pressure and speed. Pressure seal designs are used when high-load sealing is needed and are easy to install, requiring no special measurements or mounting on the machine.

Balanced Seal Designs

The second seal ring design is a balanced seal type. This kind of seal also has a flat seal face and either a convex or concave seal face. A spring force keeps the seals ring in contact with the sealing surfaces and is the primary sealing force. As the application increases in pressure, the force on the seal ring is balanced and the increased loading on the seal ring is minimized. This reduces torsional forces on the rotary joint and its mounting. The balanced seal design is used in piston type (PT) type rotary joints. Balanced seal designs require bracket or lug mounting and are therefore more robust to radial loading such as flexible metal hose. The wear of balanced seal ring increases with pressure and speed, but last much longer than pressure seal designs. They are used where rotary joints can be mounted with brackets or lugs and extended wear life is desired.

Additional Considerations

It is also important to mention that the operating life of a seal ring is application specific. Extending the seal wear life of a rotary joint can reduce maintenance costs and increase uptime. For that you must rely on multiple factors when making a selection; OEM genuine seal rings, proper alignment of the rotary joint, avoiding and limiting the amount of superheated steam, and reducing the operation speed or pressure. Kadant Johnson’s team of experts is ready to help you finding the right seal technology for your application.

  • Written by:
    Karen Beker

    Karen Beker

    EMEAI Marketing Manager, Kadant Johnson Europe

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