Kelly Valve Stem Sealing and Bearing Design for Lower Friction
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Solution Overview
Problem
Existing kelly valves face issues such as high friction, corrosion, and operational inefficiencies, particularly in hydraulically actuated systems, leading to valve stem scarring and compression set in wave springs.
Innovation Solution
Incorporation of PEEK thrust bearings, T-shaped valve stem seals, and a modified lower valve ball seat with a seal bypass structure, along with wave springs protected by a circumferential notch, to reduce friction and prevent deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional valve stem seals (O-rings/backup rings) are used, then the structure is simple, but sealing effectiveness is insufficient and valve stem scarring occurs
Solution Approach 1:
The seal cross-sectional geometry is changed from traditional circular (O-ring) to T-shaped configuration. This parameter change in the seal's geometric form provides improved sealing effectiveness and resistance to valve stem scarring while maintaining reasonable structural complexity
Solution Approach 2:
The seal combines multiple functional elements in a T-shaped composite structure that integrates sealing, support, and protective functions into a single component, improving reliability without proportionally increasing complexity
2Extent of automation
If hydraulic actuation is used, then automation is improved, but valve stem hole scarring increases
Solution Approach 1:
The T-shaped seal acts as an intermediary element between the hydraulic actuation system and the valve stem. It mediates the interaction by providing a protective interface that prevents direct contact and scarring caused by hydraulic actuation while maintaining the automation benefit
Solution Approach 2:
The seal structure provides beforehand protection by positioning the T-shaped sealing element in advance to prevent scarring before it occurs during hydraulic actuation operations
3Ease of operation
If wave springs are positioned between lower valve ball seat and canister cage, then valve operation is improved, but compression set occurs
Solution Approach 1:
The circumferential notch is introduced at the specific location where wave springs are positioned. This local structural modification provides targeted support to the wave springs, maintaining their functional quality for smooth operation while preventing deformation in the critical area
4Ease of operation
If PEEK thrust bearings are used, then friction is reduced, but manufacturing cost increases
Solution Approach 1:
The bearing material is changed from traditional metallic materials to PEEK polymer, representing a parameter change in material composition. This change reduces friction and improves ease of operation, while the cost increase is offset by reduced maintenance and extended service life
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 enhances operational efficiency by reducing torque requirements, minimizing valve stem scarring, and preserving wave spring functionality, while maintaining corrosion resistance.
Implementation Method 1
one or more, typically two, circular rings of a non-metallic material, preferably polyether ether ketone (commonly referred to by the acronym PEEK), positioned between the valve stem and the valve stem sleeve, forming a thrust bearing for the valve stem
Implementation Method 2
improved lip seal bypass structure, allowing for pressure bypass around the lower valve ball seat and into the interior of the valve ball
Implementation Method 3
valve stem seals of a generally T-shaped cross section (to seal against the valve stem sleeve)
Implementation Method 4
modified lower valve ball seat geometry to reduce or eliminate compression set on wave springs positioned between the lower valve ball seat and the canister cage
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A kelly valve for placement in a tubular drillstring has an inner cage, which holds a valve ball, lower valve ball seat and other valve components. A valve stem connected to the valve ball extends through a valve stem sleeve, positioned in an opening in the wall of the main body of the kelly valve. A thrust bearing of a low friction material, preferably of polyether ether ketone (PEEK), is positioned between the valve stem and the valve stem sleeve. A port in the valve ball seat permits pressure below the kelly valve to bypass a seal and act on the inside of the valve ball. A circumferential notch in the valve ball seat accommodates a circular spring, and prevents complete compression of the spring when the valve ball seat contacts an interior shoulder in the inner cage.