1.the system principle and compositio
Paper quality control system mainly consists of measurement and control. The on-line detection of basis weight, moisture, caliper, ash of the sheet etc is the measurement part, and the key point is high-precision and high stability sensors and scanner.
2.technological process 
Basis weight is the weight per square meter of paper (g), which is controlled by changing the opening of the BW valve to change the sizing dry component. In order to ensure the stability, must ensure the stability of sizing concentration firstly. as a result, it needs a concentration regulating circuit before the sizing box.
Moisture is the water content of the paper (%), which is controlled by changing the steam pressure in the cylinder to change the drying capacity of the cylinder.
Caliper is the vertical distance (um) between the two surfaces of paper measured under special space and pressure, which is controlled by passing it through a rotating roller.
Ash is the remaining substance burned completely at a temperature of 925℃. It is the ratio of ash to paper dry component, usually expressed as a percentage, and controlled by changing the mineral fillers applied in the ratio of the pulp or coating.
Through the controll of the paper basis weight, moisture, caliper and ash can not only improve the product yield and high quality rate, but save raw materials energy and reduce costs.
3.system structure
The control system aDOpts PLC + computer structure with resource co-allocation measurement and control on time. the field display panel + field button is combined with computer operation to make dual control insurance and protect the system operate stable.
Open system structure communicates conveniently with the third-party system. PLC support the user for secondary development. high-precision basis weight valve to ensure control accuracy, user-friendly interface design to make the field personnel easier to master.
4.the scanner
the advanced and robust scanner frame is the foundation platform for accurate on-line measurement and excellent control of QCS system. the high-performance O type scanner is the critical componet of the system. In an advanced structure and high standard platform, BMCS scanner can adapt to different accuracy requirements. It is the only domestic similar product that obtained free support from the national innovation fund.
the scanner column is designed as ┥ , which effectively reduces the girder deformation.
5.sensor introduce
BW sensor
GBW-101 BW sensor uses beta rays from radioactive sources to measure the BW of sheet material through the absorption patterns of the material.
It is widely used for online non-contact continuous measurement of paper, film, plastic sheet, film and other sheets, providing real-time quality detection signals for automatic control of the production process
detection accuracy: 2δ≦ 0.25%
stability: continuous operate 8 hours, with a drift of no more than 0.25%
GMS-201 infrared moisture sensor is based on the principle of infrared absorption, using some wavelengths of infrared radiation energy in the near-infrared spectral area by the water molecules selective absorption, and the central wavelength of radiation energy is almost not absorbed characteristics, by measuring infrared energy absorbed through the page to characterize the moisture content of the page.
detection range: 1~25%
detection accuracy:2σ≤±0.15%
stability: continuous operate 8 hours, with a drift of no more than 0.15%
MWM-20 microwave moisture sensors use water dielectric parameters (about 75) far higher than cellulose (about 2.5), and the proportion of water in the paper will therefore be strongly reflected in the dielectric parameters of the paper. This effect can be measured with high precision by microwave technology. The moisture sensitive part is a microwave resonant cavity, one of its resonant frequencies is sensitive to the amount of material involved in the resonant cavity and its dielectric parameters, and the other is insensitive the material and serves as the reference frequency. The difference between these two frequencies as a basic measure reflects the moisture content of the object under test.
detection range: 0~70%（basis weight 40~2000g/m2）
detection accuracy: 2σ≤±0.25%
stability: ≤2σ/48h ( σ: standard deviation)
contact caliper sensor:
GCL-401 the caliper sensor uses a light-touch airbag design to accurately and reliably measure the thickness of the paper of all grades, using the principle of electromagnetic induction measurement through the paper to directly measure the paper thickness, regardless of the paper composition and density. This measurement technology provides excellent precision in the range of 20-2000 m. It is widely used for on-line contact thickness measurement of paper and format materials, providing real-time thickness detection signals for the automatic control of its production process.
detection range: 20~2000μm
Ash sensor
GAS-102 ash sensor uses x-rays emitted by radioactive sources to measure the amount of ash or inorganic coating of the material through the absorption patterns of the material. It is widely used for on-line non-contact measurements of paper, film, plastic sheet and and other sheets, providing real-time quality detection signals for the automatic control of their production processes.
detection range: 2~40%（basis weight 15 ~ 300g/m2）
detection accuracy: 2σ≤±0.25% or 2σ≤±0.15g/㎡ (take the max)
stability: continuous operate 8 hours, with a drift of no more than 0.25% or 0.15g/㎡ (take the maximum)
The measurement panel adopts the embedded controllable resistance wire heating technology to effectively solve the condensation phenomenon of environmental temperature difference and paper water vapor on the surface of the box and detector, eliminating the influence of external changes on the measurement and the paper disease caused by water droplets.
The overall constant temperature design of the detector chamber creates a constant working environment for the measuring electronic circuit.
The constant temperature of measured gap ensures that the measurement results are not affected by the external air density and humidity.
The measured gap temperature change will affect the air density. A temperature change of 10°C will affect the BW of 1.393 g/m2(the measured gap calculated as 10mm)
The paper pages pass between the upper and lower girders, and the pages have a large heating effect on the upper girder, which leads to the temperature difference between the upper and lower girder of QCS. The temperature difference can easily lead to the vertical deformation of the main girder. Each 50-micron change in the vertical position will affect the 0.35~0.45g/m2
The deformation of the girder affected by temperature is determined by its physical characteristics. The deformation can only be reduced by special structural design. Through the sensor in real-time detection and compensate for the signal by software, it fundamentally addresses the influence of mechanical physical properties on BW moisture measurement.
The built-in Z-direction high-precision ranging sensor measures the detector gap in real-time, and the real-time software compensates the offset of girder deformation.
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