Polish Rod Clamping Device with V-Groove Rams
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Solution Overview
Problem
Conventional polish rod clamps for wellheads often damage the rod due to metal-to-metal contact, causing alignment issues and reducing the rod's diameter, which can lead to ineffective sealing against downhole pressure.
Innovation Solution
A polish rod clamping device with V-groove clamping rams and separate sealing mechanisms, using elastomeric or thermoplastic seals, to securely grip and seal the polish rod without damaging it, allowing for better alignment and reduced torque requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional metal-to-metal clamping is used to grip the polish rod, then sufficient gripping force is achieved to suspend the rod string, but the polish rod becomes damaged, scored, or damaged reducing its diameter and causing alignment issues
Solution Approach 1:
The patent introduces an intermediary element (jaws or clamping members with specialized surfaces) between the metal clamp and the polish rod. These intermediaries can be made of softer materials, coated surfaces, or geometrically designed surfaces that distribute the clamping force evenly, preventing direct metal-to-metal contact damage while maintaining sufficient gripping force to suspend the rod string.
Solution Approach 2:
The patent changes the surface parameters of the clamping interface by introducing V-grooves, arcuate surfaces, or other geometric modifications to the clamping members. These parameter changes allow the clamp to grip the rod effectively while distributing stress to prevent scoring and diameter reduction, resolving the contradiction between gripping force and rod protection.
2Force
If the clamp bites into the polish rod to achieve sufficient gripping action, then the rod string can be suspended, but the polish rod diameter is reduced and sealing effectiveness is compromised
Solution Approach 1:
The intermediary clamping members with modified surfaces prevent direct biting into the rod, maintaining the rod's original diameter and sealing surface integrity. The intermediaries transfer the gripping force without compromising the rod's dimensional stability, ensuring both suspension capability and sealing effectiveness.
Solution Approach 2:
By changing the clamping surface geometry to V-grooves or arcuate surfaces, the patent achieves sufficient gripping force through increased friction and mechanical interlocking rather than through compressive biting, thereby preserving the rod diameter and sealing effectiveness.
3Force
If an arcuate recess with undersized diameter is used in the clamp, then gripping force is achieved, but alignment and gripping of off-centre polish rods becomes difficult
Solution Approach 1:
The patent employs asymmetric V-groove geometries or arcuate surfaces that are specifically designed to guide and center off-centre rods during insertion. The asymmetric shape provides natural alignment cues and mechanical guidance, making it easier to achieve proper alignment while still maintaining effective gripping force once the rod is centered.
Solution Approach 2:
The use of arcuate recesses with optimized curvature radii creates a self-centering effect that facilitates alignment of off-centre rods. The curved surfaces guide the rod into proper position through contact at multiple points, reducing alignment difficulty while maintaining sufficient gripping force through the arcuate geometry.
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 device effectively suspends the weight of the rod string with reduced torque and prevents back-spin, while maintaining a seal against the polish rod and central bore, extending the lifespan of the components and improving operational efficiency.
Implementation Method 1
V-groove clamping rams... to securely grip and seal the polish rod
Implementation Method 2
V-groove clamping rams... to securely grip and seal the polish rod
Implementation Method 3
using elastomeric or thermoplastic seals, to securely grip and seal the polish rod
Implementation Method 4
using elastomeric or thermoplastic seals, to securely grip and seal the polish rod
Data Source
AI summary
A polish rod clamping device, for use as part of a wellhead production pumping tree to secure a polish rod. The device includes a pressure-containing body forming a central vertical and opposed first and second side bores. A pair of clamping rams are positioned in the side bores for sliding movement therealong, each clamping ram having a front and a rear end, the front ends of the clamping rams being configured to accommodate at least a portion of the polish rod between their front ends when the clamping rams are advanced across the central bore. The front end of at least one of the clamping rams is configured with a vertical V-groove for gripping the polish rod. The invention extends to the V-groove rams themselves and to composite wellhead assemblies containing the V-groove clamping device.