Today, temperature-profiling systems can be found monitoring virtually every heating and freezing application from -250 to 2,500oF (-157 to 1,370oC) and for an extraordinary range of processes such as:
- Frying and freezing meat and poultry.
- Circuit board assembly.
- Metal slab reheating.
- Paint and powder coating.
- Rotational molding.
- Textile production.
Turkey Processing. Beginning in 1997, food processors were required to develop and implement a hazard analysis critical control point (HACCP) plan from “farm to fork.” One of the critical control points, as established by the USDA, was meeting the appropriate cooking temperature to ensure bacteria were eliminated and food was safe for public consumption.
Willow Brook Foods of Springfield, Mo., is a fully integrated turkey processor producing both ready-to-cook and ready-to-eat meat and poultry products. Its temperature-profiling system helps the company document HACCP compliance, ensure proper oven/freezer maintenance and reduce labor costs. Willow Brook Foods' director of technical services Robert Brooks explains, “Before we purchased a complete
temperature-profiling system, we were using individual temperature recorders. Each recorder needed to be set individually, making it very difficult to compare temperatures collected from different locations within the same process. Now, we define the parameters we want to measure once, hit start and the system travels through the cooking, chilling and product pasteurization processes, and data points from various locations within these processes can be overlaid into a single report. This allows us to reduce the number of personnel required to collect and evaluate our validation data, and has improved our preventive maintenance program.”
Textiles. One of the largest uniform manufacturers in the United States -- more than five million people wear their garments each day -- is also a full service supplier. They not only provide uniforms, they also offer laundry services to ensure their customers' employees present a favorable image to the public. The laundry's process engineer uses his temperature-profiling system to maximize process speed, improve product quality and reduce energy costs. “We use our system for a process that's a bit unusual. Both air and product temperatures are extremely critical during the laundering process. Cotton and polyester fibers react differently to heat, as do various dyes. We use temperature profiling to set up each laundering process by establishing the optimum high and low temperatures, then varying process parameters to achieve the highest throughput and the best quality using the least fuel.”
Circuit Board Processing. Accuspec Electronic Services of McKean, Pa., produces complex circuit boards for all parts of the electronic industry, including medical products such as magnetic resonance imaging (MRI) machines. This application requires a copper finish (because copper does not interfere with the MRI's magnetic properties) coated with organic surface protection to avoid copper tarnish and ensure the solder adheres to both sides of the board. The production challenge is the application's tight heat tolerance -- anything over 424oF (218oC) is unacceptable.
Chad Santos, a process design engineer at Accuspec, uses temperature profiling to set up new production runs and solve problems. He says, “With temperature profiling, I get what I want right away at exactly the right temperature. Profiling not only helps me reduce waste -- I can also prove to our customers that application specifications have been met.”
Paint and Coatings. Intertec Systems in Bardstown, Ky., uses its temperature-profiling system for a variety of purposes. Intertec manufactures instrument panels for the automotive industry. Because they use waterborne paints and an oven with both infrared and convection sections, Intertec must profile while accounting for differing parameters within the same production run. The combination heating profile cannot change because while the infrared heating zone is more efficient in curing and incurs less capital expense, the waterborne paints require convection air movement to cure properly. Given these parameters, the only way Intertec could prove the paint cure was achieved was to measure the surface paint temperature using patch probe thermocouples.
Jim Clark, “When our interior oven thermocouples indicate that oven performance is off, we send through a temperature-profiling system to pinpoint the exact problem. For example, our system immediately identified a cold spot due to a burned out infrared bulb, which we easily replaced, maintaining our production schedule.”
Custom Coatings. Establishing procedures to verify production processes before obtaining a new customer has made temperature profiling a key production element for Matlab Inc., Asheboro, N.C. As a custom coating plant serving the automotive, agricultural and heavy equipment markets, Matlab establishes a pre-production approval process (PPAP) for many of its customers. The “control plan” portion of the PPAP outlines the steps Matlab will take to ensure and prove the proper bake cycle has been achieved. The company runs its temperature-profiling system daily, using the standard report as documentation of product quality.
Press Brower, Matlab's director of engineering, identified an additional benefit of profiling. “Here, we profile all of our ovens, both conveyorized and batch. This allows us to see if we're wasting energy by looking for irregularities in the profiles. If there are air balance or airflow problems the profile shows the cool spots,” Brower says. “Not only can we schedule maintenance more cost-effectively, but if there is a sudden change in performance, we can contain the product prior to shipping. Routine profiling has helped us achieve and maintain a reputation for quality and process documentation. Profiling provides a comfort to prospective customers.”
Temperature profiling data allows process engineers to quickly and easily set up new processes, document and repeat product quality, increase throughput, identify production problems when they occur and reduce rejects. As companies focus on lean manufacturing, temperature-profiling systems are a tool process engineers cannot be without. PH
SIDEBARTemperature-profiling systems consist of a datalogger that is protected by a thermal barrier. Thermocouples are attached to the product and plugged into the datalogger, which travels with the product through the manufacturing process in the thermal barrier. Telemetry profiling options are readily available, which means the temperature data can be broadcast to a receiver and plot a graph on a computer. The data also can be downloaded from the datalogger after the run is complete. A customizable yet easy-to-use software package analyzes the data, comparing actual time at temperatures to the ideal process curve.
Profiling: A Primer
Systems are available for low-clearance, short-duration processes such as surface mount technology to the days-long processes required by sanitaryware manufacturers. Special conditions that cause rapid changes in temperature also are effectively measured. Examples include food processors whose runs go from frying to flash freezing, or aluminum wheel manufacturers whose process goes from 1,000oF (538oC) to a sudden water quench. Various thermocouple types, including Types K, S, R, T and N, can be accommodated, and thermocouples are available in a range of styles such as needle, patch, heavy-duty patch, magnetic, clamp, and exposed junction for example.