Thermal Imaging Process Monitoring and Installations
Commonly Inspected Components
- Refractory insulation
- Tanks and vessels
- Steam systems/traps
- Pipes and valves
- Heaters/Furnaces
- Manufacturing equipment
- Plastics Industry (Molding)
- Pulp & Paper (Rollers, handling equipment, etc)
- Metal Foundry
- Boilers and Reactors
- Research & Development
Typical Reasons for Temperature Hotspots or Deviations
- Damaged structures caused by worn pipes etc
- Abnormal heat flow/heat gradients
- Gas or steam leakage
Petrochemical - Paper Manufacturing - Plastic Injection Molding - Food Processing - Glass Manufacturing
PetrochemicalThe petrochemical refining process is extremely energy intensive and requires careful thermal monitoring to ascertain the safety and thermal efficiencies of each process. Examining such thermal processes with infrared equipment capable of doing high temperature measurement can provide a quick and accurate diagnosis of problems and save refineries high damage-related costs. Refineries can attain a higher level of productivity and increase profitability by using infrared cameras to carry out tank level verification, condenser fin diagnosis, furnace maintenance, refractory loss management and electrical and mechanical maintenance.
Process monitoring
Furnace Inspection - Infrared cameras facilitate the inspection of heater tubes in furnaces for carbon scale buildup. This phenomenon also known as "coking" can easily be detected with suitable high-temperature infrared equipment because areas with coke buildup show up as warmer than other areas of the tube surface. This shows that the coke is precluding the product from uniformly absorbing the tube's heat. Additional disadvantages of coking include higher furnace firing rates and decreased tube life. This provides more incentive to maintenance personnel to perform regular infrared scans to protect against coking.
Condenser Tube Inspection - Occasionally the condenser tubes in a refinery can get plugged which can significantly deteriorate output and have an adverse effect on the efficient operation of the refinery. Infrared images of such tubes can reveal sections of the tube that are plugged, thereby, alerting maintenance personnel to the problem before it can result in more severe consequences.
Preventative Maintenance
High Temperature Pressure Pipelines - High temperature pressure pipelines are used extensively in petrochemical plants. Leakage and accidents due to it can occasionally take place after a certain period of time due to media corrosion, cracking due to welding defects or stress, and material deterioration. In order to ensure the safe operation of the pipes it is necessary to get an idea of the integrity of the pipe-walls and then replace only the critically damaged pipes. Since infrared thermography is non-contact, fast, harmless and easily deployable, it is a great tool for observing discontinuities in the heat-flow patterns resulting from wall defects for high temperature pressure pipes.
Thermocouple Validation - Infrared equipment can also provide a great non-contact mechanism for validating thermocouple temperature measurement. Thermocouples are installed at several points in a furnace in order to provide very accurate tube temperatures, but when coking occurs around the thermocouple, it is liable to either detach or provide inaccurate data. An infrared scan can prevent this by quickly validating the accuracy of a furnace tube temperature reading provided by a thermocouple. This assures a good product yield.
Paper ManufacturingPaper manufacturing is a competitive industry in which reducing operational costs and increasing profits is a constant challenge. The papermaking process which is based on water removal through drainage, mechanical pressing and the application of heat has several different stages that can provide a thermal imprint. Using infrared equipment to monitor each of these stages as well as preventing electrical and mechanical failure by carrying out traditional predictive maintenance with such equipment can result in a higher quality product and minimize costs by averting failures.
Process monitoring
Drying Stage - Infrared imaging provides an excellent method for monitoring one of the most difficult parts of the paper manufacturing process, the drying stage. The cold streak towards the far end of the roll of paper is caused by evaporating cooling. This corresponds to variations in moisture resulting from uneven drying. Changes made in the drying process to correct this problem can be immediately monitored at all steps of production.
Moist Streaks on Paper - High-pressure showers are used to keep press section fabrics clean. Occasionally, the shower flow-pattern is transferred to the paper web and these patterns can be identified using infrared imaging. This condition can cause problems in the dryer section, such as rusting of return rolls which then leads to premature wear of the dryer fabric. In addition, paper containing wet streaks can have a detrimental effect on the quality and performance of the paper in a subsequent converting and printing process. Hence, infrared cameras can play a crucial role in identifying and eliminating the cause of such patterns before significant damage is sustained.
Preventative Maintenance
Steam Leaks - Steam leaks on steam coils for the dryer section pocket ventilation system can be identified during an infrared inspection of the paper machine. Such leaks can cause the paper machine to experience frequent paper breaks which can have an adverse effect on production. By virtue of a single infrared scan, not only is future inconvenience prevented, but the paper mill gains thousands of dollars in increased production.
Electrical - Paper mills, like other plants, can experience unexpected downtime due to electrical component failure such as electrical bus bars, line splices, switch disconnects, transformers, circuit breakers and distribution panels. These failures can easily be spotted ahead of time using infrared equipment and fixed before a breakdown stalls production.
Mechanical - Regular infrared inspection on mechanical systems such as motor windings, roll bearings and gearboxes can be carried out and maintenance work can be scheduled if aberrant 'hot spots' are observed.
Plastic Injection MoldingPlastic manufacturing is a wonderful application for infrared cameras, both in monitoring the manufacturing process as well as traditional predictive maintenance. The nature of the manufacturing process is thermal. Obtaining a thermal image of a newly formed plastic part as it exits the mold can be used to diagnose quality problems and reduce scrap while increasing productivity and profitability. The plastics industry, hit hard by international competition, has an extreme focus on finding any conceivable way to increase profitability. Infrared cameras assist the manufacturing process to attain a higher level of productivity.
Process Monitoring
Cores and cavities - Monitoring the thermal profile of cores and cavities can predict problems with the process. An infrared image of a core can be used to determine if it is running too hot. A large temperature difference between cores in excess of 20deg F usually means the system is unstable.*
Cooling lines - The wrong heat transfer in the wrong place at the wrong time can result in short shots, galling, splay, stuck parts, shear, material degradation and brittleness. Changing molds at times results in improper connection of cooling lines. Comparing thermal images of plastic parts as they exit the mold may be used to determine if the cooling lines are connected correctly and transferring the correct amount of heat.
Preventative Maintenance
Heater bands - The feed throat must not exceed a specific temperature or clogging will occur. The temperature of the heater bands near the feed throat can be easily monitored with an infrared camera.
Dryers - Drying systems, used to remove moisture from hoppers, must be monitored for correct temperatures. An infrared thermal analysis is a very quick method to ensure the drying process is functioning correctly.
Electrical - Thermal scans of electric motors and connections can prevent premature failure and costly down time.
Food ProcessingFood processing is a natural application for thermal imaging. Pre-cooked meats are an increasingly popular convenience for busy consumers. Cereals, pastries and snack foods all require precise baking protocols. In these food applications and many others, large volumes of food product must be cooked or baked with precision.
The Competing Boundaries of Safety, Quality and Economy Process engineers constantly face the competing boundaries imposed by safety, product quality, and economy. Safety requires that the all parts of a food product be maintained above a threshold temperature for a specific time period to kill potentially dangerous bacteria. However, if the temperature is raised too high or the time period is excessive, the product becomes dry and overdone -- an unacceptable product quality. Production economy dictates that the line move rapidly to achieve targeted volumes and that the oven operate at a minimum temperature to reduce fuel expenses. The daily economies of production are tempered by the realization that a single safety violation may have disastrous economic and moral consequences for the entire corporation. Likewise, a brief lapse in product quality may undo years of accomplishment in a competitive marketplace.
Factors Impacting Product TemperaturesThermal imaging provides the measurement capability to safely and economically achieve a product of high quality. Thermal imaging provides the ability to constantly monitor the temperatures of the product itself. Sophisticated oven and belt controls are valuable, but it is the product temperatures that are most critical. Product temperatures may vary significantly due to such parameters as:
- Oven temperature
- Belt speed
- Product volume
- Product composition
- Start-up conditions
- Product separation or placement
A Distribution of Product TemperaturesAs they exit an oven, products typically have a range or distribution of temperatures throughout their surface and volume. This distribution of temperatures is influenced by the numerous factors listed above. Those who measure the 'temperature' (singular) of a product with a single thermometer may be surprised to see the temperature variations evident in a thermal image. A thermal image is equivalent to an array of thousands of temperature probes placed over the surface of the product with the resulting data organized in the format of an image. A distribution of temperatures, instead of a single product temperature, is supported by common observations such as cookies with burnt edges and semi-liquid centers. Since safety, quality and economic concerns apply to all parts of the product, it is valuable to measure temperatures throughout the product.
Once the temperature distributions are measured, the process can be managed and optimized. If the distribution of temperatures is too wide, perhaps the belt speed may be reduced slightly to permit all parts of the product to achieve the desired temperature. Conversely, if the distribution is narrow, the belt speed may be increased while still maintaining product safety and quality.
Figure 1. shows a series of thermal images of chocolate chip cookies after they were removed from a common kitchen oven. The upper left image in Figure 1 shows the cookies on a tray. The color bar to the right indicates the temperature (degrees Fahrenheit) of the image colors. The upper right image shows the product image extracted from the background tray. The lower left image shows a 3D representation of only the cookie temperatures. The lower right graph shows the temperature distributions of only the cookies and not the background. (The analysis and processing were provided by Cardiowave, Inc.)
Figures 2 and 3 shows thermal images of bacon strips at two different times after the strips were removed from a microwave oven. The variations in temperature are evident, as are the cooling effects from Figure 2 to Figure 3. 
Strengths of Thermal Imaging for Food Processing ApplicationsThermal imaging technology, in its basic form, provides accurate measurements of surface temperatures. This is ideally suited for measuring products such as chips or bacon because of their thin profile. The calibrated images from a radiometric, infrared camera work well without further processing.
For products with substantial thickness, the surface temperatures may be used as an input into a mathematical model describing the thermal properties of the product. With such a model, volumetric thermal properties and statistical analyses may be extended to many additional products. With sufficient post-processing power, these measurements may be made in real-time.
Glass ManufacturingMonitoring temperatures at critical junctures during production is imperative for the full understanding and efficient control of the glass manufacturing process. Since the nature of the glass manufacturing process is thermal, the quality of the glass manufactured is dependent on obtaining accurate temperature readings of various elements such as the glass mold, "gob", steel conveyor belt and the furnace. Using easily deployable infrared equipment to monitor these temperatures as well as preventing electrical and mechanical failure by carrying out traditional predictive maintenance with such equipment can result in a higher quality product and minimize costs by averting failures.
Process Monitoring
Gob Temperature - Glass is transported from the furnace to the mold in a runner. At the end of the runner, a plunger forces out the glass in balls called "gobs" into chutes that lead up to the mold machine. It is extremely important to monitor the temperature of the "gobs" because it controls the weight of the glass, its viscosity and the formation of the container in the mold. Therefore, the quality of the final product can be ensured by carrying out convenient non-contact infrared inspection of the gobs as they leave the plunger.
Belt Temperature - Glass containers are transported on a steel conveyor belt from the mold machine to the annealing lehr. In order to prevent the belt from cooling the bottoms of the containers unevenly, thereby causing breakage, the belt is heated with gas flames before reaching the bottling machines. It is critical for manufacturers to measure the belt temperature at regular intervals in order to prevent breakage and guarantee a high enough return to maintain profitability in a competitive industry. An infrared camera is ideal for such an application.
Preventative Maintenance
Glass Mold - It is necessary for manufacturers of glass containers to monitor the temperature of the glass mold closely because it affects the quality of the containers. If the mold is not cooling properly, the container will not retain its shape after exiting the mold or if the mold is too cool, the container will not be molded properly. Hence, it is to the benefit of container manufacturers to use infrared equipment to acquire mold temperatures from time to time in order to ascertain that the cooling is proceeding at an appropriate temperature.
Furnace Monitoring - Economical melting of raw materials into glass requires constant supervision and monitoring. Depending on their size, glass furnaces are capable of producing anywhere from 50 to 600 tons of glass per day. Most furnaces are fired by natural gas through the side ports and the melting temperature is around 1200°C. Molten glass eventually flows out of the furnace through the feeders to the forming machines attached to each furnace. The condition and safety of the refractory structure of the whole furnace and refiner is extremely important. A high-temp infrared camera can very easily be used to do check-ups to minimize the possibility of glass break-out or refractory failure. |