Rotating Machine Element Sensor for Tissue Moisture Profiling
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Solution Overview
Problem
Current methods for measuring moisture in fibre webs, especially in tissue machines, face challenges such as inaccurate real-time moisture profiling, sensitivity to air humidity and conductivity issues, and the need for direct physical contact, which complicates impedance measurements and limits comprehensive profile measurement capabilities.
Innovation Solution
Measuring the temperature of the fibre web, as there is a correlation between temperature and moisture, allowing for indirect moisture profiling without physical contact, using sensors integrated into machine components like rotating machine elements or coatings, which reduces external errors and fouling issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impedance measurement is used to measure moisture directly from the web, then moisture information can be obtained, but measurement accuracy deteriorates due to air humidity and conductivity issues
Solution Approach 1:
The patent replaces the electrical impedance measurement system with a thermal measurement system. Instead of using electrical sensors that measure impedance through the web, the invention uses temperature sensors to measure the thermal state of the web, which correlates with moisture content. This substitution eliminates the harmful effects of air humidity and conductivity on measurement accuracy.
Solution Approach 2:
The patent introduces temperature as an intermediary parameter to indirectly measure moisture. Rather than directly measuring electrical impedance through the web, the system measures temperature which serves as a mediator that correlates with moisture content, thereby avoiding direct exposure to the harmful electrical measurement environment.
2Loss of information
If direct physical contact is made for impedance measurement, then moisture data can be collected, but sensor fouling and breakage increase
Solution Approach 1:
The patent replaces direct contact electrical sensors with non-contact or minimal-contact thermal sensors. The temperature measurement system can be implemented without the sensors directly touching the web, or with significantly reduced contact requirements, thereby preventing fouling and breakage while still acquiring moisture information through thermal correlation.
3Ease of operation
If boundary-layer air separates the web from the roll surface, then web transport is facilitated, but impedance measurement becomes difficult
Solution Approach 1:
The patent substitutes the impedance measurement method with thermal measurement. Since thermal conduction can occur through the boundary-layer air and does not require direct web-to-roll contact, the temperature-based moisture measurement works effectively even when the boundary layer separates the web from the roll surface, unlike electrical impedance measurement.
4Measurement precision
If scanner measurement is used after the dryer section, then moisture profile can be measured, but real-time control capability is lost
Solution Approach 1:
The patent implements temperature-based moisture measurement at multiple points throughout the drying process, including before the dryer section and during drying. This preliminary and continuous measurement approach provides real-time feedback that enables proactive control adjustments, rather than waiting for post-dryer scanner measurements.
Solution Approach 2:
The patent establishes continuous temperature monitoring throughout the drying process using multiple sensors positioned at different locations and stages. This continuous measurement provides uninterrupted real-time moisture information, enabling ongoing process control adjustments rather than discrete post-process measurements.
5Measurement precision
If comprehensive profile measurement is implemented, then accurate moisture data is obtained, but system complexity and cost increase
Solution Approach 1:
The patent makes existing rotating machine elements in the tissue machine perform the additional function of moisture measurement through temperature sensing. By integrating temperature sensors into components that already rotate with the web, the system achieves comprehensive profile measurement without adding separate complex measurement devices, thereby reducing overall system complexity.
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 approach provides accurate, real-time, and robust moisture profiling, enabling online adjustments and automatic feedback, while being insensitive to air humidity and conductivity-related inaccuracies, and allows for better control of drying and profiling processes.
Implementation Method 1
heat is for example conducted, and more generally, heat conduction takes place, and it is possible to measure temperature through a material
Implementation Method 2
There is a mutual correlation between the temperature and moisture of the fibre web. In this case, for example, any moist places in the fibre web are seen as cooler in a temperature measurement, and any dry places are correspondingly seen as warmer.
Data Source
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AI summary
The invention relates to a method for measuring the moisture of a fiber web (W) in a tissue machine (10), which includes, as sub-entities, a forming section (11), a press section (12), a Yankee drier (13) and a reel (15), each of which performs one or more process stages (39.2) included in the sub-entity and where the fibre web is taken through the sub-entity via one or more rotating machine elements (41), of which one or more are equipped with a sensor assembly (24). In the method, the temperature of the fibre web is measured directly and/or indirectly in one or more sub-entities of a tissue machine by means of a sensor assembly arranged in the coating (43) disposed on the shell (31) and/or over the shell of a rotating machine element for establishing the temperature profile (21) in the cross direction (CD) of the machine, and the moisture profile (21') in the cross direction of the machine is generated on the basis of the temperature profile. The invention also relates to a corresponding system, a rotating machine element and a computer program product.