Floating Back-up Rings For High-Pressure

How the Floating Back-up Rings Addresses High-Pressure Rotary Seal Implementation Challenges

Our floating backup rings help rotary seals achieve the highest possible operating pressures by defining the smallest possible squeeze gap. The support ring assembly is used to seal between the pressure housing and the rotating shaft to retain the high-pressure lubricant. The rotating seal is mounted in a metal support ring. The rotating seal is radially compressed and establishes a seal between the support ring and the shaft. High-pressure lubricant is located between the pressure housing, seals, and shaft.

The hole in the metal support ring fits the shaft very tightly and positions the support ring laterally. This tight fit allows the rotary seal to bridge under high-pressure conditions more easily than a larger gap.

Face seals establish the seal between the support ring and the pressure housing. Rotary seals and face seals together retain high-pressure lubricant within the pressure housing.

The metal back-up ring is positioned axially through the bulkhead. Internally balanced seals and externally balanced seals create a seal between the bulkhead and the metal support ring. End face seals and internal and external balanced seals are specially designed high-pressure seals.

The pressure of the lubricant acts on the sealing area defined by the rotating seal and the face seal. This creates hydraulic pressure acting downward on the back-up ring.

The axial bore conducts the pressure of the lubricant to the sealing area between the inner and outer balanced seals. The inner and outer balanced seals define the sealing area on the underside of the back-up ring. The lubricant pressure acting on this sealing area creates a hydraulic force acting upward on the support ring.

The upward hydraulic force and the downward hydraulic force are essentially equal. As a result, these forces cancel each other out, and the net hydraulic thrust acting on the back-up ring is essentially zero. This axial force balance allows the support ring and rotating seal to move laterally to follow shaft runout.

We offer rotating back-up ring seals designed specifically for high-pressure service. During rotation, the corrugated geometry on the seal's dynamic lip pumps a film of oil between the seal and the shaft and into the gap between the shaft and the back-up rings. This reduces seal friction and heat generated by the seal and lubricates the support ring.

To prevent cross-sectional distortion of the back-up rings, the rotary seal is axially offset relative to the face seal. This slight axial offset provides a slight pressure imbalance acting radially outward. This slight imbalance creates a counteracting torque that counteracts the torque caused by the radial misalignment of axial hydraulic forces. This provides additional dimensional stability to the support ring so that its fit with the shaft can be as small and stable as possible.

The resulting small gap between the backup rings and the shaft is optimal for high-pressure rotary seals because it reduces pressure-related seal extrusion damage. Contact Linde Polymer to discuss implementing this high-pressure seal design into your equipment.

Common application scenarios

1. Hydraulic system: The high-pressure liquid in the hydraulic system requires reliable sealing to ensure the normal operation of the system. Floating backup sealing rings can be used to seal hydraulic cylinders, hydraulic pumps, hydraulic valves, and other components to prevent fluid leakage and maintain system performance.

2. Pneumatic system: In high-pressure pneumatic systems, floating backup sealing rings can be used to seal cylinders, pneumatic valves, and other components to ensure that gas does not leak and maintain system reliability and efficiency.

3. High-pressure pipelines: In high-pressure pipeline systems, such as oil and natural gas transmission pipelines, chemical process pipelines, etc., floating backup sealing rings can be used to seal pipeline connections to prevent medium leakage and reduce pressure loss.

4. Pressure vessels: High-pressure containers (such as pressure tanks, gas bottles, etc.) require reliable sealing to prevent medium leakage and reduce pressure hazards. The floating backup sealing ring can be used at the flange connection or other sealing locations of the container to ensure the safety and sealing performance of the container.

5. High-pressure valves: In high-pressure valves, such as ball valves, gate valves, butterfly valves, etc., floating backup sealing rings can be used for sealing between the valve stem and the valve body to prevent medium leakage and maintain the valve's operating performance.

Backup Ring Size Chart

The chart below gives the metric and inch dimensions for the most common AS568 sizes of backup rings.