Subsurface Safety Valve Piston Deflection Reduction

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Solution Overview

Problem

Pressure-controlled pistons in subsurface safety valves experience deflection due to circumferential unsupported lengths and radial offsets between the piston axis and the flow tube, leading to bending moments, which affect the operation of closure mechanisms like flapper valves.

Innovation Solution

An actuation assembly with a piston and sleeve member, where the piston exerts an actuation force on a radially outwardly extending projection or stabilizer, ensuring alignment of actuation and reaction forces with the piston axis to minimize bending moments, using non-planar contact surfaces and stabilizers to maintain alignment and reduce deflection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a piston with circumferential unsupported length is used to actuate the flow tube, then the device complexity is reduced, but piston deflection increases due to bending moments

Engineering Contradiction:

Improvepiston structure complexityVSAvoidpiston deflection

Core Design Contradiction:

Device complexityVSStability of the object's composition

Solution Approach 1:

A stabilizer is introduced as an intermediary component between the piston and the flow tube. The stabilizer has a first end coupled to the piston and a second end coupled to the flow tube, providing additional support to the circumferentially unsupported portion of the piston. This mediator reduces piston deflection without requiring a complete redesign of the piston structure, thus maintaining relative simplicity while improving stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If a radial offset exists between the piston axis and the flow tube coupling surface, then ease of operation is improved, but bending moments increase causing excessive deflection

Engineering Contradiction:

Improveflow tube actuationVSAvoidbending moment

Core Design Contradiction:

Ease of operationVSForce

Solution Approach 1:

The stabilizer acts as a mediator that connects the piston to the flow tube at optimized locations. By coupling the stabilizer's first end to the piston and its second end to the flow tube, the system can maintain operational ease while the stabilizer geometry is designed to minimize bending moments caused by radial offsets.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The stabilizer provides localized support at specific positions along the circumferentially unsupported length of the piston. This local reinforcement allows the piston to maintain its simple structure overall while having enhanced stability at the critical unsupported region where deflection occurs.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS9151139B2Method of reducing deflection through a rod piston in a subsurface safety valve

Publication Date: 2015.10.06 BAKER HUGHES CO

AI summary

An actuation assembly including a sleeve member having a radially outwardly extending projection and a piston having an axis, the piston operatively coupled to the projection of the sleeve member and arranged to exert an actuation force on the projection of the sleeve member for actuating the sleeve member, the actuation force positioned about radially aligned with the axis or radially outwardly from the axis.