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October 1, 2011
By Pulp & Paper Canada

Infrared sensor boasts improved machine and process diagnostics

Infrared sensor boasts improved machine and process diagnostics

Some tissue mills are now replacing nuclear basis weight sensors with Metso IQFiber infrared sensors which measure both weight and moisture. The new combined sensors are easy to service with extensive diagnostics. Furthermore, certain costs are eliminated if a tissue mill is nuclear-free.

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Until now, nuclear basis weight sensors have been the standard for scanning the tissue web. Today, infrared technology has been developed by Metso and refined to the point where it can take over the task of measuring oven dry basis weight (fibre weight) with the same precision as a nuclear sensor and, furthermore, measure moisture simultaneously at the same spot.

IQFiber uses a four-channel infrared detection system in which there are no rotating filters. The IQFiber is a new application of previous Metso multi-channel infrared sensors for moisture. A single semiconductor detector in IQFiber senses the absorption of infrared energy by the tissue sheet at wavelengths specifically sensitive to water and fibre content of the sheet. Two reference measurement points ensure the readings are absolute.

Unlike nuclear sensors whose source strength decays and measurement sensitivity is diminished over time, the infrared measurement sensitivity is constant.

Side-by-side sensor comparison trials in a tissue mill have confirmed that the infrared measurement of fibre and the oven dry weight measurement derived from the nuclear sensor minus the moisture measurement were essentially the same. The fibre measurement and the on-control stock flow changes tracked closely during normal production periods and grade changes, and the profiles were equivalent. Data shows the online fibre reading was slightly closer to the laboratory result than the nuclear reading.

Customers report more precise control and improved machine operations with the sensors installed with new PaperIQ Select QCS systems.

The speed of response and signal to noise ratio of the dry fibre weight measurement is significantly better than traditional nuclear sensors, making it most appropriate for online web variability analysis and more precise control. The MD and CD variability in a sheet are measured at exactly the same spot with a small 5 mm streak resolution and very fast response, with sampling rates of 1 KHz. The frequency components of these fast-responding online measurements are determined by the spectral analysis capability built into PaperIQ Select. This adds a significant diagnostic and machine troubleshooting capability to the system.

Metso, www.metso.com

Solenoid valve cost-effective for pulp and paper uses

Parker Fluid Control Division introduces the High Flow direct mount NAMUR solenoid valve, part of its expanding line of valve actuation products.

The High Flow product line provides new, cost-effective solutions for general-purpose valve actuator applications including water and sewage, and pulp and paper.

Compact in its design, the High Flow NAMUR valve is built with an anodized aluminum body and a stainless steel spool, as well as internal parts made of brass. It operates in a pressure range of 30 – 150 psi.

A spring return allows fail-safe operation in the event of a power loss, and a screened exhaust nut protects valve function during outdoor use. Additionally, the O-ring seal design increases sealing force at higher pressures and offers less breakaway resistance at lower pressures.

Parker Fluid Control Division 800-Valve05, www.parkerfluidcontrol.com

ORP sensors offer better control for making bleach

Commonly, bleach making consists of mixing sodium hydroxide (caustic) with chlorine to produce sodium hypochlorite of various strengths. The initial strength of the caustic determines the overall concentration of bleach and its stability. The amount of chlorine will determine the pH value and the bleaching effectiveness of the solution. Measurement and control of the solution’s oxidation-reduction potential (ORP) serves as an effective way to achieve specific ratios of the two bleach components.

ORP and pH sensors are similar. The difference is that the ORP sensor measures the electrochemical effect of all ions in solution, while the pH sensor looks only at hydrogen ion concentration. For bleach making, ORP sensors offer more resolution and tighter control. They also last longer because pH sensors lose efficiency more quickly in the strong caustic solutions.

Excess caustic produces low, negative ORP readings (in millivolts). Chlorine, on the other hand, raises the ORP readings. An ORP measurement and control loop can effectively achieve whatever bleach strength is desirable. The graph shows ORP values of various concentrations of sodium hypochlorite solutions. The steep step change in an ORP reading indicates the completion of the desired reaction.

The Endura TBX587 is the latest addition to ABB’s successful line of industrial pH/ORP sensors. The sensors are renowned for their ability to outperform conventional gel filled sensors in the toughest process applications.

The TBX587 electrode design eliminates failures due to thermal stress caused by rapid temperature excursions. Unlike other sensors that use a large inner air bubble for expansion absorption, the TBX587 electrodes use a unique inner plunger that provides more effective protection against temperature fluctuations.

ABB, www.abb.com

IR sensor reduces defects in coated products by up to 15%

Honeywell has introduced new infrared-sensing technology designed to help packaging makers significantly reduce defects in their coated products, as well as reduce the amount of raw materials used to produce them.

The Reflectance Infrared Spectrometer (RIS) uses proprietary array detector technology to provide the industry’s highest resolution and the broadest IR spectrum range, which allows mills to achieve unsurpassed quality by measuring multiple components of coatings, even on reflective or printed substrates.

RIS can be used in quality control systems like Honeywell’s MXProLineTM, which uses an array of scanners and sensors to monitor the quality of coated products such as liquid and aseptic packaging. The total solution helps producers more accurately measure and control multi-layer or barrier coatings and adhesive layers, discriminate components with very similar spectral characteristics, measure on printed and reflective backings, and quantify variations in additives and fillers such as Ti02 and CaC03.

This approach can reduce defects by up to 15% and raw material usage by up to 8%. Additionally, the calibration tools can save time by cutting the calibration effort by up to 40%.

Honeywell, www.honeywell.com/ps


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