Reciprocating Compressor Rod Seal with Uncut Ring Standstill Sealing
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Solution Overview
Problem
Existing reciprocating compressor sealing devices with segmented packing rings fail to provide a sufficient seal at standstill due to thermal expansion mismatch between the rings and the piston rod, leading to gas leakage, which is problematic for flammable or toxic gases, posing safety and environmental risks.
Innovation Solution
A sealing device with an uncut packing ring and a vent passage that allows gas leakage to be safely vented away, combined with a thermally activated sealing mechanism using a polymer with high thermal expansion coefficient to ensure a tight seal at standstill and during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If segmented packing rings are used, then the sealing device can be activated during operation by differential pressure, but at standstill the segmented rings create gaps due to thermal expansion mismatch leading to gas leakage
Solution Approach 1:
The patent employs a polymer material for the uncut packing ring with a thermal expansion coefficient at least two times higher than that of iron. This parameter change in thermal expansion behavior allows the ring to maintain contact with the piston rod at standstill (cold state) while automatically detaching during operation (hot state) due to differential thermal expansion, eliminating gas leakage at standstill without compromising operational sealing
Solution Approach 2:
The patent transitions from segmented packing rings to a single uncut ring configuration. This eliminates the gaps between segments that cause leakage at standstill, while the ring's material properties enable it to function as a complete seal during both operation and standstill conditions
2Reliability
If an uncut packing ring with high thermal expansion polymer is used, then a tight seal is formed at standstill, but the device complexity increases due to material selection requirements
Solution Approach 1:
The patent specifies a polymer material with a thermal expansion coefficient at least two times higher than iron, which enables automatic thermal activation and deactivation of the sealing function. This material parameter change simplifies the control mechanism by using inherent thermal properties rather than external actuation systems
Solution Approach 2:
The uncut packing ring with high thermal expansion coefficient serves itself by automatically sealing at standstill and self-deactivating during operation through thermal expansion. This eliminates the need for external control mechanisms, valves, or additional components to manage the sealing state transitions
3Object-generated harmful factors
If a valve-controlled support passage is used to vent gas, then gas can be directed away from the crankcase, but the device complexity increases due to the valve mechanism
Solution Approach 1:
The patent introduces a support passage with a valve as an intermediary element to safely redirect gas that leaks past the uncut packing ring. The valve is controllable based on compressor state (open during operation, closed at standstill), providing a controlled path for gas venting without allowing it to enter the crankcase or environment
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
Prevents gas leakage into the crankcase by ensuring a continuous seal at standstill, enhancing safety and reducing environmental impact, even in the event of ring malfunction or wear, and operating effectively across various suction pressures.
Implementation Method 1
the second packing ring is configured to seal the piston rod at standstill of the compressor... when the piston rod cools down after shutdown... the segmented rings and the piston rod having different thermal expansions
Data Source
AI summary
In order to provide a sealing device (15) for sealing a piston rod (8) of a reciprocating compressor (1) at compressor standstill, which enhances the safety of operation, 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 (15a) 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), the second packing ring (21) being configured to seal the piston rod (8) at standstill of the compressor (1), wherein the sealing device (15) further comprises a support passage (28) having a first support passage end (28a), a second support passage end (28b) and a valve (29) for opening and closing the support passage (28), the support passage (28) being configured to vent at least a gas, leaking from the first axial device end (15a) in the direction of the second axial device end (15b) past at least one of the number of first packing rings (19), from the first support passage end (28a) to the second support passage end (28b), wherein the sealing device (15) further comprises an unobstructed vent passage (31) having a first vent passage end (31a) and a second vent passage end (31b), the vent passage (31) being configured to vent a gas, leaking from the first axial device end (15a) in the direction of the second axial device end (15b) past the second packing ring (21), from the first vent passage end (31a) to the second vent passage end (31b).