Automatic Scanner

    In the modern papermaking industry, the use of advanced technologies and equipment has greatly improved the efficiency and quality of paper production. One such crucial device is the scanning system, used for various measurements and control in the paper machine. In this blog, we will explore the software, functionality, and performance of the scanning system in papermaking machines.

    Software and Functionality
    The scanning system in papermaking machines is based on the Microsoft Windows 10 operating system and developed using Siemens PCS7 software, including CFC (Continuous Function Chart) and WinCC for configuration. It utilizes ProfiNET Ethernet communication, allowing for high-speed data transfer of up to 100Mbps. The system is designed to be compatible with standard interface systems, enabling seamless communication with DCS (Distributed Control Systems), drives, and other equipment using popular communication protocols like OPC. Additionally, it supports TCP/IP communication with enterprise networks and provides user-friendly interfaces for system customization. The software can be easily installed on a PC operator station for convenient operation and monitoring.

    1.1 Basic System Display
    The system offers a comprehensive graphical interface that displays key process parameters, including the overall process overview, banner grammage curve, moisture curve, longitudinal grammage curve, moisture curve, average values, maximum/minimum values, standard deviation, and manual/automatic operation status. It also features real-time measurement of paper width and provides historical data query capabilities. The personalized interface design allows for vertical historical trend display, supporting automatic/manual trend printing. Moreover, it includes settings for scanning frame configuration, event, and alarm display, as well as sensor status monitoring.

    1.2 System Charts and Reports
    The scanning system generates various reports that can be automatically generated or manually printed. These reports include production reports, quality reports, roll reports, shift reports, daily reports, weekly reports, monthly reports, yearly reports, and quarterly reports.

    1.3 Longitudinal Control Software
    1.3.1 Basis Weight Measurement and Control
    The controller compares basis weight measurement data with set values to determine the sizing amount in the paper machine. It adjusts the sizing valve (or the speed of the sizing pump) through the sizing flow control loop to achieve precise basis weight control. Changes in sizing consistency and flow rate are compensated by adjusting the sizing valve (or the speed of the sizing pump) in a feedback control manner, reducing the impact on basis weight control. The system feeds QCS (Quality Control System) with signals such as sizing flow rate, sizing consistency, and on-line instrument data via local instruments or communication with DCS.

    1.3.2 Moisture Measurement and Control
    The controller controls the steamer pressure based on the deviation between moisture measurement values and set values to achieve moisture control by regulating the surface temperature of the steamers. The system directly controls the steam supply to the glazing steam box while maintaining pressure differences among other steam boxes through a heat pump system. In case of web break, the system reduces the steam pressure supplied to the steamers. After web reconnection, the steam pressure is gradually increased until the paper moisture stabilizes, achieving the optimal production state. Steam pressure signals and pressure valve instruments are provided to the QCS via local instruments or communication with DCS.

    1.4 Paper Width Measurement
    The scanning system incorporates paper edge sensors to accurately measure the position of the paper edge. A high-precision rotary encoder and calculation software ensure accurate measurement of paper width, with an accuracy of less than 1mm.

    2. System Performance:
The scanning system guarantees performance through the following sensor and control specifications. Control performance is determined by the reduction in long-term variation (2σ) of paper roll to paper roll during a blind run of three days and a controlled run of three days.

    2.1 Scanning Frame:

•     Measurement speed: >1000 measurements/s
•     Resolution: Positioning ±0.25mm
•     Upper and lower sensor head spacing error: ±0.10mm
•     Horizontal error: ±0.15mm
•     Paper machine direction error: ±0.2mm
•     Scanning speed: 50-500mm/s (adjustable frequency, optimized based on paper machine speed)
•     Scanning frame positioning accuracy: ≤1mm
•     Sealed positive pressure to prevent dust
•     Relative humidity: ≤95%, no condensation
•     Maximum operating temperature: ≤85℃

    2.2 Sensor Performance:

•     Measurement gap: 8-20mm
•     Light guide detection aperture: 5mm
•     Paper basis weight range: 5-250g/m2
•     Measurement range: Moisture: 0-20%, basis weight: 5-250g/m2
•     Repeatability: Moisture: 0.15%, basis weight: 0.25% or 0.25g/m2
•     Moisture dynamic accuracy: 2σ ≤±0.15 (% moisture content, scan head movement, fixed paper sample)
•     Basis weight dynamic accuracy: 2σ ≤±0.25g/m² or ±0.25% of the measured value (scan head movement, fixed paper sample)
•     Dustproof and condensation-proof structure
•     Output: 4-20mA, RS485
•     Maximum operating temperature: 70℃

    2.3 Equipment Performance Assurance:
    The equipment provided in this proposal complies with standards such as IEC1131, IEC1158-2, EN50170, and possesses CE, TUV certification, and the European CE manufacturing mark. A complete spare parts list is provided to minimize downtime in case of equipment failure, ensuring a quick recovery within 20 minutes. The control system (continuous or intermittent) has a fault-free operation time (excluding field equipment) of more than 40,000 hours.

    2.4 Control Performance:
    The control performance associated with the average longitudinal variation of paper rolls is determined based on the moisture control system's generated paper roll reports. The percentage reduction in variation is calculated based on the difference between the average values during controlled operation and blind run operation. The control system aims to achieve the following performance values:

•     Basis weight control accuracy: Improvement rate ≥60%
•     Moisture control accuracy: Improvement rate ≥60%

    Conclusion:
    The scanning system plays a vital role in the papermaking process, providing accurate measurement and control of basis weight and moisture parameters. With its advanced software, superior functionality, and high-performance sensors, it contributes to improved productivity and quality in paper production. The system's ability to generate comprehensive reports and interface with other control systems ensures efficient operation and optimization of the paper machine.