Valve Positioner Pressure Limiting for Actuator Overpressure

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Solution Overview

Problem

Existing process control systems face challenges in providing reliable overpressure protection for electro-pneumatic controllers, as failures in pressure regulators can lead to over-pressurization of actuators, potentially causing damage and safety hazards, and conventional relief valves are expensive and inconvenient to install.

Innovation Solution

A method and device that include a valve positioner with a pneumatic stage and an overpressure protection module, which uses a pressure sensor to detect abnormal pressures and adjusts the drive signal to limit the output pressure, preventing over-pressurization by setting the drive signal to a safe value, such as near zero milliamps or millivolts, thereby ensuring safe operation of the actuator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a relief valve is coupled between the control pressure output and control pressure input to provide redundant overpressure protection, then device safety is improved, but device complexity and installation difficulty increase

Engineering Contradiction:

Improveoverpressure protectionVSAvoidvalve assembly complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The overpressure protection function is merged into the valve positioner by integrating a pressure sensor and drive signal adjustment mechanism into the existing valve positioner architecture. This eliminates the need for separate relief valves while maintaining protection functionality, thereby reducing device complexity and installation difficulty.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The mechanical relief valve system is replaced with an electronic control system comprising a pressure sensor and drive signal adjustment mechanism. This substitution transitions from passive mechanical pressure relief to active electronic pressure management, simplifying the overall system architecture while improving response capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If a relief valve is installed to protect against pressure regulator failure, then overpressure damage is prevented, but installation convenience deteriorates

Engineering Contradiction:

Improveoverpressure protectionVSAvoidinstallation convenience

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The overpressure protection functionality is combined with the existing valve positioner unit through integration of pressure sensing and drive signal control mechanisms. This merger eliminates the need for separate relief valve installation, thereby improving installation convenience while maintaining protection reliability.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If conventional relief valves are used for overpressure protection, then actuator safety is improved, but cost increases

Engineering Contradiction:

Improveactuator protectionVSAvoidsystem cost

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The mechanical relief valve system is replaced with an electronic control system comprising pressure sensors and drive signal adjustment mechanisms. This substitution eliminates the need for expensive specialized relief valves while achieving the same protection objective through existing electronic control components, thereby reducing overall system cost.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The valve positioner system provides its own overpressure protection functionality through integrated pressure sensing and drive signal control. This self-service capability eliminates the need for additional protective components, thereby reducing system cost while maintaining actuator protection.

Inventive Principle:

Principle #25Self-service

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

This solution effectively limits control pressure to prevent actuator damage and ensures safe operation by detecting abnormal pressures and adjusting the drive signal, providing redundant overpressure protection without the need for expensive relief valves, thus enhancing safety and reducing installation complexity.

Implementation Method 1

obtain a pressure measurement from a pressure sensor communicatively coupled to the valve positioner

Methodology Applied

Scientific EffectPressure sensing:

Implementation Method 2

The pneumatic stage typically receives a pressurized supply fluid, such as air, and modulates the pressurized supply fluid in accordance with a control signal

Methodology Applied

Scientific EffectPneumatic modulation:

Data Source

PatentEP3092538B1Valve positioner with overpressure protection capabilities

Publication Date: 2022.12.21 FISHER CONTROLS INT LLC

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AI summary

A method of limiting control pressure provided to an actuator of a valve coupled to a valve positioner, a drive signal is provided to a pneumatic stage of the valve positioner. The pneumatic stage is arranged to control output pressure of the valve positioner in accordance with the drive signal. A pressure measurement from a pressure sensor communicatively coupled to the valve positioner is obtained, and an abnormal pressure is detected based on the pressure measurement. In response to detecting the abnormal pressure, the drive signal is controlled so as to limit the output pressure of the valve positioner, wherein the output pressure provides control pressure to the actuator.