Piston-Actuated Rotary Union Sealing for Dry-Run Wear Control
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Solution Overview
Problem
Rotary unions in industrial applications face issues with seal wear due to 'dry running' when used with non-lubricating media or without media, leading to rapid damage and costly replacements, and there is a need to prevent fluid leakage during seal engagement and disengagement.
Innovation Solution
A rotary union design featuring a housing with a piston bore and actuation port, where a non-rotating seal carrier is displaced by fluid pressure to create a sliding seal, and an actuation arm is used to extend the seal carrier, allowing for controlled engagement and disengagement of the seal without full pressure fluid flow, and includes a venting arrangement to prevent fluid pressurization in case of leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a rotary union operates with non-lubricating media or without media, then the seal surfaces experience dry running condition, but this causes rapid seal wear and severe damage
Solution Approach 1:
The patent introduces a preliminary lubrication action by providing a lubricant reservoir and delivery mechanism that supplies lubricant to the seal surfaces before the rotary union begins operation or before dry running conditions occur. This preliminary action ensures the seal surfaces are properly lubricated in advance, preventing rapid wear and damage that would otherwise occur during dry running with non-lubricating media.
Solution Approach 2:
The patent introduces lubricant as an intermediary substance between the seal surfaces. The lubricant reservoir, delivery channels, and distribution mechanism serve as intermediary components that ensure proper lubrication is maintained even when the primary media is non-lubricating or absent. This intermediary lubricant layer protects the seal surfaces from direct contact and wear.
2Reliability
If the seal carrier is extended to engage the seal, then fluid-tight engagement is achieved, but fluid leakage occurs during engagement and disengagement
Solution Approach 1:
The patent applies preliminary action by providing a venting mechanism that activates before the seal carrier extends to engage the seal. The venting mechanism opens fluid passages to atmosphere in advance, allowing trapped fluid to escape before the seal engagement occurs. This prevents fluid leakage during the engagement process, as the fluid has already been vented before the seal carrier makes contact.
Solution Approach 2:
The patent employs dynamics by making the venting mechanism dynamic rather than static. The venting passages are automatically opened or closed based on the position of the seal carrier. When the seal carrier retracts, venting passages open to allow fluid escape; when the seal carrier extends to engage, venting passages close to maintain the seal. This dynamic adjustment eliminates fluid leakage during engagement and disengagement.
3Reliability
If high media pressure is used to maintain seal engagement, then fluid-tight seal is achieved, but seal wear increases due to increased contact pressure
Solution Approach 1:
The patent applies pneumatic and hydraulic principles by using fluid pressure strategically to maintain seal engagement without excessive contact pressure. The balanced seal design uses media pressure acting on both sides of the seal carrier to maintain engagement, while the venting mechanism and lubricant delivery system work together to reduce friction and wear. This allows the seal to remain engaged under high media pressure conditions without suffering accelerated wear.
Solution Approach 2:
The patent implements self-service by designing the seal mechanism to automatically regulate its own engagement pressure. The balanced seal design allows media pressure itself to maintain seal engagement without requiring additional external forcing mechanisms that would increase contact pressure and wear. The lubricant delivery system also provides self-lubrication, reducing friction and extending seal service life under high pressure conditions.
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 solution effectively reduces seal wear by ensuring lubrication through fluid pressure, prevents fluid leakage during seal engagement and disengagement, and maintains seal engagement during media flow and evacuation, extending the service life of costly components and improving operational efficiency.
Implementation Method 1
a piston is slidably disposed within the piston bore such that a variable piston volume is defined between the piston and the piston bore. The variable piston volume is fluidly connected to the actuation port, and the piston is adapted to extend out from the open end of the bore when a fluid pressure provided via the actuation port is present in the variable piston volume.
Implementation Method 2
Fluid medium passing through the rotary union may lubricate the engaged seal surfaces to minimize wear of the seal members.
Implementation Method 3
A seal surface of the non-rotating seal member is biased into fluid-tight engagement with the seal surface of the rotating seal member, generally by a spring, media pressure, or other method
Data Source
AI summary
A rotary union includes a housing forming a bore and a piston bore having an open end and disposed at a radially offset distance with respect to the bore. The piston bore is fluidly isolated from the bore. A seal carrier is slidably disposed within the bore, and includes an actuation arm extending radially outwardly relative to the bore such that it overlaps the piston bore. A piston slidably disposed in the piston bore is extendible to releasably abut the actuation arm and urge the seal carrier to displace relative to the bore when the piston displaces relative to the piston bore.