Is temperature critical to the quality of your product? Can you document your process temperatures? Increasingly, process engineers are turning to the latest infrared (IR) sensors to help them document temperatures in support of their quality control programs. Scott R. Williams reports.

Contact sensors, otherwise known as thermocouples and RTDs, are accurate and cost-effective, but are not practical in applications in which contact would damage the object being measured, when the temperature is very high, or where the object is moving or undergoing rapid changes in temperature. In these cases, a non-contact infrared (IR) thermometer can provide the speed, durability, non-contamination and ease of use you may require.
These non-contact temperature inspection tools have built-in microprocessors, two-way digital communications, and analysis and trending software. With this added muscle, these devices support "forensic tracking" of problems that arise in the manufacturing process and enable product identification and traceability. Through the use of continuously recorded digital output from IR temperature sensors, engineers can now pinpoint the time and/or machine in which the process was out of spec and identify the products affected. Companies can document and archive temperature readings on a computer or transfer the information to another software program for further analysis. Attached to a shipment or maintenance report, printouts of temperature graphs, colour thermograms, or photos of temperature inspections - essential documentation provided by today's IR sensors - verify temperature conformance.
There is a variety of non-contact IR temperature inspection devices available for process applications. For example Raytek, a leading supplier in the infrared measurement industry, provides handheld IR thermometers used as diagnostic tools for process inspection, maintenance and quality control, as well as fixed online temperature sensors and thermal imaging line scanners, which are easily integrated into process equipment for continuous temperature monitoring and trend analysis. Raytek will demonstrate these solutions at ACHEMA 2003 (Hall 10.2, Stand E19). Highlights include:

Real-time thermal imaging

The Raytek MP50 (Fig. 1), a non-contact, infrared thermal imaging line scanner provides edge-to-edge surface temperature imaging with a temperature range of 20° to 3000°C for a variety of industrial processes, with special system solutions for the cement, glass, plastics, food, textile and paper industries. The imager measures a line of 50 points from edge-to-edge along a sheet surface, using a rotating mirror that scans a 90¼ field-of-view up to 48 times per second. The fast scan rate of 48 Hz (without analogue outputs) and 36 Hz (with analogue outputs) allows users to see a real-time thermal image of their product or process on their computer screen. From the thermal images, operators can immediately detect hot and cold spots, which can indicate equipment problems or material defects.
Windows-based software allows operators to remotely configure and control multiple imagers, collect temperature data, and produce two-dimensional thermal images for instant analysis as a surface passes under the field of view. The software also enables users to overlay zones, corresponding to heating/cooling elements in their process. The software automatically triggers an alarm when the temperature falls outside of the desired range and produces a report showing the exact location and time of occurrence.

Tight spaces

With its extremely small temperature sensing head, the low-cost Raytek MID (Miniature Digital) sensor has a temperature range of -40û to 1200ûC and is designed for any process equipment monitoring application, especially in tight spaces where large sensors are impractical, or when multiple, low-cost sensors are required to enable temperature monitoring of several points at once. Built-in digital communication allows remote configuration of multiple MID sensors and data collected to a central PC - performance available otherwise only in larger, more expensive temperature monitoring devices.

For temperature monitoring in high-temperature environments, such as in glass and metal production, Raytek recently introduced two new infrared temperature sensors (Fig. 2) with an industry-tested fibre optic assembly, ensuring their ability to withstand temperatures up to 315°C without the need for water cooling and to resist strong electromagnetic fields, which can interfere with measurement accuracy. The sensors' fibre-optic cable, one of the highest rated temperature cables available on the market, enables the heat-resistant sensor to be snaked around obstacles, and keeps the sensor's electronics, housed separately, away from sources of heat. Ideal for the continuous, fixed temperature monitoring of stationary and moving targets - Raytek's Marathon FA one-colour fibre optic sensor has a temperature range of 475° to 3000°C. The Raytek Marathon FR two-colour, or ratio sensor measures process temperatures from 500° to 2500°C of objects partially obscured by smoke, dust and steam, or which are smaller than the field of view. Software is available for the networked control of multiple sensors and easy acquisition, display and organisation of temperature data. The stainless steel sensor housing can be equipped with optional air purge to keep the lens free of dust or condensation. Laser sighting for marking measurement targets is also available optionally.

Inspections

The first handheld temperature inspection tool of its kind, the Raytek PhotoTemp MX6 (left) combines a precision non-contact infrared thermometer (Range: minus 50° to 900°C) and a digital camera in one lightweight unit. PhotoTemp accurately marks the measurement area with its bright, three-point laser sighting and records it in a photograph superimposed with temperature, location, date/time and other useful data. Up to 100 temperature measurements and images can be stored in the unit and later downloaded to a PC for trend analysis or incorporation into emails and reports. By using such a tool, maintenance and quality professionals can use the detailed images to clearly communicate with management, equipment manufacturers, and service personnel about process, maintenance and quality-related issues.

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Scott R Williams is with Raytek GmbH in Berlin, Germany. www.raytek.com