Capacitive Liquid Level Sensor for Fire Suppression Tanks

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Solution Overview

Problem

Existing liquid fire suppression systems face challenges in accurately measuring the fluid level within tanks without venting, as current methods are often costly, inaccurate, prone to human error, and require frequent maintenance.

Innovation Solution

A capacitive liquid level sensing system is integrated into the discharge conduit of the fire suppressant storage device, utilizing a capacitive gauge with insulative layers and conductive traces to measure the level of the fire suppressant, allowing for non-invasive and automated level detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If float-based level sensing systems are used, then liquid level measurement capability is provided, but device complexity and maintenance requirements increase

Engineering Contradiction:

Improveliquid level measurementVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical float-based level sensing system with a capacitive sensing system. The capacitive gauge measures liquid level by detecting changes in capacitance caused by the dielectric properties of the liquid versus vapor, eliminating moving mechanical parts while maintaining measurement capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts the level sensing function from a separate float-based system and integrates it directly into the discharge conduit wall. The capacitive gauge is formed as an integral part of the conduit structure, removing the need for separate float mechanisms and reducing overall system complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

2Ease of manufacture

If manual measurement methods are used, then equipment cost is reduced, but measurement accuracy and reliability deteriorate

Engineering Contradiction:

Improvesystem costVSAvoidlevel measurement accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The capacitive gauge provides automated level measurement without requiring manual intervention. The system self-measures the liquid level by detecting capacitance changes, eliminating the need for human operators to physically measure levels while providing continuous, accurate data.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces manual mechanical measurement methods with an electrical capacitive sensing system that automatically detects liquid level through dielectric property changes, providing both accuracy and cost-effectiveness.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If frequent maintenance is performed, then system reliability is maintained, but productivity and operational time are reduced

Engineering Contradiction:

Improvesystem reliabilityVSAvoidoperational time

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent replaces mechanical float components that require maintenance with a solid-state capacitive sensing system. The capacitive gauge has no moving parts, eliminating wear and maintenance requirements while maintaining measurement reliability throughout the system's operational life.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Measurement precision

If venting the tank is done to measure liquid level, then measurement access is obtained, but suppressant loss and safety risks increase

Engineering Contradiction:

Improvelevel measurement capabilityVSAvoidsuppressant loss

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent uses the discharge conduit as an intermediary structure that contains the capacitive gauge. The gauge measures liquid level through the conduit wall without requiring direct access to the tank interior or venting operations, allowing non-invasive measurement while maintaining system integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces physical access methods that require venting with electrical capacitive sensing that measures level through the conduit wall, eliminating the need to open or vent the tank for measurement purposes.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 capacitive system provides accurate and reliable liquid level measurement, reducing human error and maintenance costs, while eliminating the need for float-based systems and offering ease of servicing by replacing the discharge conduit.

Implementation Method 1

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

The capacitive system provides accurate and reliable liquid level measurement

Methodology Applied

Scientific EffectDielectric: Dielectric

Data Source

PatentEP4148398B1Printed capacitive liquid level sensor for fire suppression

Publication Date: 2025.01.01 KIDDE FENWAL LLC

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Figure 2A~2B
Figure 3~4

AI summary

A method for manufacturing a fire suppressant discharge assembly is described. The discharge assembly may be for a fire suppressant storage device (20) comprising: a tank (22) having a first port and an interior for storing fire suppressant; with the discharge assembly being mounted to the first port. The discharge assembly has a discharge valve (48) and a discharge conduit (50) at least partially within the interior. The discharge conduit has an interior surface (60) and an exterior surface (58). The discharge assembly further comprises a gauge (80) on the discharge conduit.