Safety Valve Positioner Tripping via Loop Current Control

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Solution Overview

Problem

Existing safety systems in process control environments require costly and time-intensive safety assessments for each model of safety valve controller/positioner combination to ensure compliance with safety standards, particularly when tripping functions are involved, which can be complex and labor-intensive.

Innovation Solution

A control panel is used to manipulate the loop current on a safety loop to trigger the trip function of a valve positioner, allowing the positioner to initiate its own trip without the need for digital messaging protocols, thereby avoiding additional safety assessments and ratings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If digital messaging protocols are used to trip the valve positioner, then the tripping function can be implemented, but costly and time-intensive safety assessments are required for each model combination

Engineering Contradiction:

Improvetripping operationVSAvoidsafety assessment complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent replaces digital messaging protocols with an analog electrical signal (loop current manipulation) to trigger the trip function. By using a simple current manipulation approach instead of complex digital communication, the system avoids the need for extensive safety assessments and ratings while maintaining reliable tripping capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a control panel as an intermediary device that manipulates the loop current to trigger the trip function. This intermediary approach allows the tripping operation to be performed through a standardized electrical signal interface, eliminating the need for model-specific safety assessments and simplifying the overall system complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If model-specific safety assessments are performed for each valve positioner combination, then safety compliance is ensured, but time and resources are significantly consumed

Engineering Contradiction:

Improvesafety complianceVSAvoidsafety assessment time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent creates a universal tripping method that works across different valve positioner models by manipulating the loop current in a standardized manner. This universal approach eliminates the need to perform separate safety assessments for each model combination, significantly reducing the time and resources required while maintaining safety compliance through the inherent safety rating of the valve positioner's internal trip function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If digital messaging protocols are implemented for tripping, then precise control is achieved, but the system requires additional safety ratings and certifications

Engineering Contradiction:

Improvetripping control precisionVSAvoidsafety rating requirements

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent substitutes digital messaging protocols with a straightforward loop current manipulation method. This substitution maintains sufficient control precision for tripping operations while eliminating the complex safety rating and certification requirements that would otherwise be necessary for digital communication interfaces.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11732820B2Activating trip functions of a safety valve positioner by way of a control panel to achieve a safe state

Publication Date: 2023.08.22 FISHER CONTROLS INT LLC

AI summary

The described methods and systems enable a control panel for a safety valve in a safety system of a process control environment to couple to a safety loop that couples a logic solver to a valve positioner for the safety valve. The control panel may drive a loop current on the safety loop to a desired range, thereby causing the valve positioner to respond by initiating a desired function triggered by the loop current entering the desired range. The desired function may be a trip function, a reset function, or a stroke test function.