Cryogenic Piston Rod Seal Using Tubular Labyrinth Segments
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Solution Overview
Problem
Piston rod seals in cryogenic pumps have a short service life due to wear from non-translational forces, leading to frequent maintenance and reduced operational efficiency, especially in continuous applications where longer service lives are needed.
Innovation Solution
A piston rod seal using tubular labyrinth seals with targeted radial play and annular seals at both ends, made from Teflon with glass fibers for enhanced strength, to accommodate unequal force applications and reduce wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tubular Teflon seals are used to seal the piston rod, then sealing performance is improved, but service life is reduced due to wear from non-translational forces
Solution Approach 1:
The seal is divided into multiple Teflon segments that can move independently relative to each other. This segmentation allows the seal to accommodate misalignment and non-translational forces without causing wear, as each segment can adjust its position to maintain sealing contact with the piston rod while the cylinder bore guides the overall motion.
Solution Approach 2:
The invention changes the physical state and mechanical properties of the sealing material by using Teflon (PTFE), which has low friction coefficients and high compliance. This material parameter change enables the seal to deform and adapt to non-ideal motion paths, reducing wear while maintaining sealing effectiveness under cryogenic conditions.
2Reliability
If a precise fit is used between the piston rod and seal, then sealing performance is improved, but wear increases due to non-translational forces
Solution Approach 1:
The seal design transitions from a static, fixed-fit configuration to a dynamic system where Teflon segments can move and deform relative to each other. This dynamic capability allows the seal to absorb and accommodate non-translational forces and misalignments, maintaining sealing performance without generating excessive wear on the piston rod or seal surfaces.
Data Source
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AI summary
Disclosed is a piston rod seal for pumps that are used for cryogenic media and encompass a piston rod (2). The sealing effect in relation to the cylinder (18) is obtained by means of at least one tubular labyrinth seal (23, 24) which is arranged in the cylinder (18) and in which the piston rod (2) translationally travels back and forth. The two tubular labyrinth seals (23, 24) in the cylinder (18) shown in the example are disposed so as to lean on each other like a tandem while being specifically provided with clearance on all sides in a radial direction. Each face of the tubular labyrinth seals (23, 24) is sealed towards the cylinder (18) with the aid of an annular seal (27, 28). The tubular labyrinth seals (23, 24) are made of a material from the Teflon family, with an optional glass fiber percentage.