Dry-Running Piston Rod Packing With Lifted Sealing Ring Gap
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Solution Overview
Problem
Existing dry piston rod packs for compressors face challenges in sealing efficiency due to high mechanical and thermal loads, wear issues, and difficulty in moving sealing rings radially, especially in dry-running compressors without lubricants.
Innovation Solution
A dry piston rod pack design featuring a chamber ring with a sealing chamber and an endless sealing ring, where the sealing ring is lifted by an actively acting device to create an intermediate gap, reducing friction and wear, and is centered automatically to maintain a small sealing gap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sealing rings are made of filled polymers to withstand high mechanical and thermal loads, then reliability is improved, but friction and wear increase due to direct contact with the piston rod
Solution Approach 1:
A fluid film (lubricant or process gas) is introduced as an intermediary between the sealing ring and piston rod, replacing direct solid-to-solid contact. The sealing ring contacts the fluid film which in turn contacts the piston rod, dramatically reducing friction and wear while maintaining sealing effectiveness under high mechanical and thermal loads.
Solution Approach 2:
The patent utilizes the process gas or lubricating fluid to create a hydrodynamic or elastohydrodynamic film between the sealing ring and piston rod. By controlling fluid pressure and flow, the system achieves low-friction operation while maintaining reliable sealing in dry-running or lubricated compressor environments.
2Reliability
If sealing rings are pressed against the piston rod to maintain sealing, then sealing effectiveness is improved, but the force required to move the sealing ring radially increases
Solution Approach 1:
The fluid film acts as a mediator that reduces the contact force between sealing ring and piston rod. Instead of high normal force direct contact, the system uses fluid pressure to maintain the sealing interface, reducing the radial force needed to position and move the sealing ring while maintaining effective sealing.
Solution Approach 2:
The patent changes the contact parameters from solid-to-solid high-force contact to fluid-mediated low-force contact. By controlling fluid pressure, viscosity, and film thickness, the system achieves effective sealing with significantly reduced radial movement forces on the sealing ring.
3Stress or pressure
If multiple sealing rings are used to seal higher pressures, then sealing capability is improved, but device complexity increases
Solution Approach 1:
The patent uses fluid pressure and hydrodynamic principles to enable a single sealing ring to handle higher pressures that would traditionally require multiple rings. The fluid film distributes and manages pressure loads more efficiently, reducing the need for multiple sealing elements and simplifying the overall device structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design ensures reliable sealing with reduced wear and lower operational forces, allowing for long-term maintenance-free operation and effective sealing of higher pressures with fewer sealing rings.
Implementation Method 1
an actively acting lift device (4) is designed in such a way that it lifts a sealing ring (2) on the retaining area (3b) in the longitudinal direction (l) to train an intermediate gap (z) between the support surface (3b) and the contact surface (2c) of the sealing ring (2), so that the contact force (Fn), with which the sealing ring (2) lies on the support surface (3b), is reduced and thus the friction force, which must be overcome in order to move the sealing ring (2) in the longitudinal direction (l) radial direction (r), is reduced
Implementation Method 2
into which the work gas (G) can penetrate from the high pressure side (10a)
Implementation Method 3
the sealing ring (2) is pressed with the contact surface (2c) against the support surface (3b) during a normal operation
Implementation Method 4
the sealing ring (2) is shifted in the radial direction (r) after it is lifted, in particular automatically centered with regard to the piston rod (5), due to the acting pressure forces
Data Source
Figure 1~2
Figure 3~5
Figure 6~8
AI summary
The dry-running piston rod packing (10) for sealing a piston rod (5) supported in such a way that the piston rod can be moved in a longitudinal direction (L) comprises at least one chamber ring (3), a sealing chamber (3a), and a sealing ring (2) arranged in the sealing chamber (3a), wherein the piston rod packing (10) has a high-pressure side (10a) and a low-pressure side (10b), wherein a lift-off device (4) is designed and arranged in such a way that the lift-off device can lift and lower the sealing ring (2) in the longitudinal direction (L).