Polymer Packing Ring Sealing for Compressor Standstill Leakage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing sealing devices for reciprocating compressors fail to maintain a sufficient sealing barrier at standstill, leading to gas leakage due to thermal expansion differences between segmented packing rings and the piston rod.
Innovation Solution
A sealing device featuring a second packing ring made from a polymer material with a thermal expansion coefficient at least two times higher than iron, allowing for automatic thermal activation and deactivation to form a tight seal or provide a leakage path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If unsegmented sealing ring is used with valve control, then sealing at standstill is achieved, but ring wear increases due to continuous contact
Solution Approach 1:
The patent implements a dynamic sealing mechanism where the packing ring's contact state with the piston rod changes automatically based on thermal conditions. During operation, the ring is thermally expanded and maintains sealing contact; at standstill, the ring remains in an expanded state due to the high thermal expansion coefficient material, preventing gap formation without requiring continuous mechanical contact or valve control
Solution Approach 2:
The patent exploits thermal expansion as the primary activation mechanism. The polymer material with at least twice the thermal expansion coefficient of iron ensures that temperature changes during operation and standstill automatically adjust the ring's dimensions to maintain sealing effectiveness without continuous contact pressure that would cause wear
2Reliability
If soft and elastic material is used for unsegmented ring, then pressure activation is achieved, but wear resistance and pressure withstand capability decrease
Solution Approach 1:
The patent changes the material parameters by selecting polymer material with specific thermal expansion properties (at least twice that of iron) that provides both the necessary elasticity for pressure activation and sufficient strength for wear resistance and pressure withstand capability. This parameter optimization eliminates the need to choose between soft elastic materials and rigid materials
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 ensures a reliable sealing barrier at both operational and standstill conditions, minimizing wear and eliminating the need for external energy sources or residual pressure, thus preventing gas leakage and ensuring safety and environmental compliance.
Implementation Method 1
the second packing ring is made from a material comprising a polymer, the material having a thermal expansion coefficient, which is at least two times higher than the thermal expansion coefficient of iron, wherein at or below a defined activation temperature an inner diameter of the second packing ring is smaller than an outer diameter of the piston rod to be sealed
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
In order to provide a sealing device (15) for sealing a piston rod (8) of a reciprocating compressor (1), which provides good sealing properties at compressor standstill, which has a simple structure, which allows for a simple handling and which requires no external source of energy, the sealing device (15) comprises a number of first packing retainers (18), each retainer including a retaining opening (18a) in which a first packing ring (19) is arranged, a second packing retainer (20), including a retaining opening (20a) in which a second packing ring (21) is arranged, the second retainer (20) being positioned closer to the second axial device end (15b) than the number of first packing retainers (18) in an axial direction of the sealing device (15), wherein the second packing ring (21) is an uncut ring, comprising a continuous inner circumferential sealing surface (21a), wherein the second packing ring (21) is made from a material comprising a polymer, the material having a thermal expansion coefficient (a), which is at least two times higher than the thermal expansion coefficient (aFE) of iron, wherein at or below a defined activation temperature an inner diameter (d_i) of the second packing ring (21) is smaller than an outer diameter (D_a) of the piston rod (8) to be sealed, such that in the mounted state of the sealing device (15) in the compressor (1) the second packing ring (21) is prestressed in a radial direction in order to form a tight seal between the continuous inner circumferential sealing surface (21a) of the second packing ring (21) and the outer circumferential surface (8a) of the piston rod (8), wherein at a given operating temperature, the inner diameter (d_i) of the second packing ring (21) is larger than the outer diameter (D_a) of the piston rod (8), such that in the mounted state of the sealing device (15) in the compressor (1) the continuous inner circumferential sealing surface (21a) of the second sealing ring (21) is detached from the outer circumferential surface (8a) of the piston rod (8) in order to provide a leakage path past the second packing ring (21) in the axial direction.