Water Heater Cathodic Protection With Anode Depletion Sensing
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Solution Overview
Problem
Existing electric liquid heating apparatuses face challenges in effectively and efficiently providing cathodic corrosion protection, with sacrificial anodes having limited life and requiring periodic inspection, while impressed current cathodic protection systems are complex and costly.
Innovation Solution
The implementation of a specially designed electric resistance type immersion heating element with a dissolvable magnesium anode and a sensing and control system that monitors the anode's depletion, allowing for precise determination of when replacement is necessary, and an alternate system using impressed current cathodic protection to prevent corrosion and dry firing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sacrificial anode is used for cathodic protection, then continuous protection is provided without power requirements, but the anode has limited life and requires periodic inspection
Solution Approach 1:
The patent implements a sensing system that continuously monitors the electrical resistance between the sacrificial anode and the tank. As the anode depletes, its resistance increases, and this change is detected by the sensing system. The control system receives this feedback and can alert users or automatically adjust protection parameters, enabling continuous protection while extending effective monitoring of anode life.
Solution Approach 2:
The patent replaces periodic manual inspection of the sacrificial anode with an automated electrical sensing system. Instead of mechanically examining the anode's physical state, the system uses electrical resistance measurements to monitor anode depletion, eliminating the need for manual intervention and extending the practical service life of the protection system.
2Measurement precision
If an ICCP anode protection system is used, then precisely controllable potential and current outputs are achieved, but the system becomes more complex and costly
Solution Approach 1:
The patent makes the heating element serve multiple functions: it acts as both the primary heating device and as part of the cathodic protection system. The heating element's sheath functions as the ICCP anode, eliminating the need for a separate corrosion protection system. This multi-functionality reduces device complexity while maintaining precise control capabilities through the existing heating element control circuitry.
Solution Approach 2:
The patent combines the heating function and corrosion protection function into a single integrated system. The heating element and ICCP anode are merged into one component, with the heating element's sheath serving as the protective anode. This consolidation reduces the number of separate systems and components, thereby reducing overall system complexity and cost.
3Reliability
If the sacrificial anode dissolves excessively, then cathodic protection capability is lost, but tank corrosion increases
Solution Approach 1:
The sensing system continuously monitors the electrical resistance between the sacrificial anode and the tank. When the anode dissolves excessively and resistance increases beyond a threshold, the control system receives feedback and can alert users to replace the anode before protection capability is lost, preventing tank corrosion.
Solution Approach 2:
The system performs preliminary monitoring of anode condition through electrical resistance measurements. By detecting anode depletion trends before complete dissolution occurs, the system enables proactive maintenance actions, ensuring continuous cathodic protection capability and preventing tank corrosion from occurring in the first place.
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 provides continuous and precise cathodic protection, extending the life of the anode and reducing maintenance costs, while preventing excessive tank corrosion and dry firing, thereby enhancing the operational reliability and efficiency of electric liquid heating apparatuses.
Implementation Method 1
cathodic protection is a commonly used method of combating it. The most common techniques for providing such cathodic protection for the liquid-containing vessels or tanks of electric liquid heating apparatus are (1) utilizing an erodable sacrificial anode in the vessel
Implementation Method 2
the liquid to be heated is disposed in a vessel into which a resistance-type submersible electric heating element projects and may be selectively energized to heat the liquid to a predetermined temperature
Implementation Method 3
The anode depletion sensing system includes an ohmmeter circuit having a first lead connected to the tank and a second lead connected to the heating element
Data Source
AI summary
The metal tank portion of an electric water heater is protected against corrosion utilizing a corrosion protection system that detects a voltage potential between the sheath portion of a tank water-immersed electric heating element and the tank. In one embodiment of the corrosion protection system the sensed sheath/tank potential is utilized to enable a user of the water heater to accurately gauge the necessity of replacing a sacrificial anode extending into the tank. In another corrosion protection system, the sensed sheath/tank potential is utilized to provide impressed current cathodic protection of the tank and also to prevent dry firing of the electric water heater.