Reciprocating Check Valve Packing Structure for Leak Tightness
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Solution Overview
Problem
Commercially available lift type check valves experience issues with water stopping performance and durability of the packing, particularly in underwater installations and above water surface installations, where dynamic, thermal, and chemical loads are applied.
Innovation Solution
A lift type check valve design featuring a reciprocating body with a valve element, a deflecting surface, and an annular packing made of a softer material than the valve element, where the packing is circularly brought into contact with the valve seat, supported by a flange surface and recessed to enhance contact and reduce stress, allowing for improved water stopping performance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a packing made of elastic material is used to ensure water stopping performance, then the packing can be brought into close contact with the valve seat, but the durability of the packing deteriorates under dynamic load, thermal load, and chemical load
Solution Approach 1:
The packing is designed with different material properties in different regions: the inner peripheral surface has a first coefficient of friction while the outer peripheral surface has a second coefficient of friction that is different from the first. This local differentiation allows the packing to maintain effective sealing at the critical inner region while the outer region provides enhanced durability and resistance to degradation under dynamic, thermal, and chemical loads.
Solution Approach 2:
The invention changes the frictional parameters of the packing by providing different coefficients of friction at different locations. The inner peripheral surface is designed with a specific friction coefficient to ensure water stopping performance, while the outer peripheral surface has a different friction coefficient to improve durability under various loads, thus optimizing both sealing and longevity.
2Reliability
If the packing is made softer to improve water stopping performance, then the packing conforms better to the valve seat, but the packing is more easily dislodged and loses durability
Solution Approach 1:
The packing exhibits local quality through differentiated friction coefficients: the inner peripheral surface (in contact with the valve seat) has a first coefficient of friction optimized for sealing, while the outer peripheral surface has a second coefficient of friction that provides enhanced anchoring and resistance to dislodgement, allowing the soft packing to maintain both sealing effectiveness and structural integrity.
Solution Approach 2:
The invention addresses the dislodgement issue by transitioning from a uniform packing design to a differentiated design where the outer peripheral surface has distinct frictional properties. This adds a dimensional aspect to the packing design, considering not just the sealing interface but also the anchoring interface with the valve body, thereby preventing dislodgement while maintaining softness for sealing.
3Duration of action of stationary object
If a recess is formed on the outer periphery of the extending portion to fit the packing, then the packing is secured and durability increases, but the device complexity increases
Solution Approach 1:
The recess is pre-formed on the outer periphery of the extending portion during manufacturing, allowing the packing to be easily positioned and secured in the correct location. This preliminary structural feature simplifies assembly while ensuring the packing remains firmly in place, enhancing durability without requiring complex assembly procedures or additional components.
4Reliability
If the flange surface is formed larger than the extending portion to support the packing, then the packing is stabilized and water stopping performance improves, but the weight of the valve element increases
Solution Approach 1:
The flange surface is designed with local quality by extending it beyond the outer periphery of the extending portion only where necessary to provide packing support and stabilization. This selective extension provides the required sealing stability and water stopping performance while minimizing the additional weight compared to a uniformly larger flange design.
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 significantly enhances the water stopping performance and durability of the packing by dispersing stress symmetrically and preventing the packing from being dislodged, thus ensuring effective fluid control and longevity.
Implementation Method 1
a valve element (6) including a deflecting surface (10a) which causes a fluid to be deflected from the primary flow passage side to the secondary flow passage side
Implementation Method 2
a packing (8) having an annular shape which is made of a material softer than the valve element (6), and which is circularly brought into close contact with the valve seat (12a)
Data Source
AI summary
A reciprocating body (2) has valve element (6) including deflecting surface (10a), valve shaft (7) guided by guide cylinder (4), and packing (8) having an annular shape circularly brought into close contact with valve seat (12a) in a state where the reciprocating body (2) is in a closed position. The valve element (6) includes large diameter portion (9a), and small diameter portion (9b) and deflecting portion (10). The large diameter portion (9a) has flange surface (9d) supporting the packing (8) in a state where the packing (8) is exposed to the primary flow passage side. The flange surface (9d) is formed such that the flange surface (9d) is allowed to come into contact with the valve seat (12a) via the packing (8). Recess (9c) is formed on the outer periphery of the small diameter portion (9b), and a portion of the packing (8) is fitted in the recess (9c).