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Extending the campaign life of a furnace — that is, the period between required interior and refractory refurbishments — depends upon a consistent temperature and thermal profile. These conditions also help maintain production at high quality levels. Useful temperature measurements can be taken at different locations within the furnace, allowing trending conditions at key positions such as the crown, ports and burner blocks to be tracked.

It is important to be able to visualize cold spots in the refractories to detect air leaks that may be caused by structural issues or the condensation of volatile components. Fortunately, in-furnace thermal imaging technology has improved the understanding of furnace operations. The data obtained can be used to develop controls that meet the needs of Industry 4.0 and help optimize furnace processes.

Using Thermal Imaging to Drive Improvement

To illustrate, consider the example of a thermal imaging system supplied to SGD Pharma, a glass pharmaceutical packaging manufacturer that produces more than eight million vials and bottles per day at its five manufacturing plants in Europe and Asia. The company operates to high quality standards in line with ISO 15378, Good Manufacturing Practices for Primary Packaging) certification. The company has a culture of continuous improvement and performs regular quality reviews using data analysis to define a quality roadmap. In addition, each year, the company sets targets to drive quality improvements. Part of this process involves implementing technologies to increase process robustness.

Following a rebuild, SGD Pharma installed a thermal imaging system on an oxy-gas furnace used exclusively for the production of borosilicate glass for pharmaceutical packaging at its facility in St Quentin Lamotte, France. The thermal imaging system replaced the existing closed-circuit television (CCTV) system.

In the past, the highly aggressive furnace atmosphere made it difficult to obtain clear images from the furnace using the CCTV system. Often, the results were blurry images and inconsistent, inaccurate measurements. Actual temperature measurements typically were performed only at critical locations using thermocouples embedded in the walls or intermittently using a handheld portable infrared (IR) pyrometer.

Part of the purpose behind SGD Pharma’s rebuild was to progress from monitoring visual images to monitoring thermal images. This would help ensure consistent temperatures and thermal profiles in the glass-melt tank. The goal was to improve the overall efficiency of the process, maintain high quality glass production and extend the furnace’s campaign life. Accurate and repeatable temperature measurements are essential for efficient control and optimization of glass manufacture and processing. This is even more important within an oxy-gas furnace because the flame’s temperature is significantly hotter.

A key objective of SGD Pharma was to obtain clear, high resolution images to monitor batch line/flow and improve the setup of the batch line. There also is an inherent risk of damage to burner blocks in oxy-gas furnaces when borate condensate/rundown can deflect the flame and potentially damage the burner block; therefore, monitoring hot spots and burners also was critical.

Thermal imaging was added to help SGD Pharma monitor for consistent temperatures in the glass melt tank. Photo credit: Ametek Land

The lower temperature band with greater resolution shows that the rundown on L4 batch line is skewed and longer on the left-hand side. Photo credit: Ametek Land

The glass is inserted through the furnace wall. Photo credit: Ametek Land

Adding Thermal Imaging

The in-furnace thermal imaging system provides SGD Pharma with a true-temperature radiometric image. This means live continuous temperature values for the glass melt tank can be obtained.

The thermal images provide an equivalent of 320,000 temperature data points that can be used to optimize the furnace and validate computational fluid dynamics (CFD) models. A high quality purge applied on the lens ensures a clear image and gives the operator the same views as their previous CCTV system. In addition, using thermal imaging software, it is possible to measure the temperature of the melt line, the batch coverage and the batch transit time for recording and comparison.

The thermal imaging system was installed above the throat in the furnace’s centerline to provide a good view of the refractories, including the crown, sidewalls, burner blocks and batch line. Dedicated infrared shields protect the imager’s retraction mechanism against the infrared radiation coming from the hole camera block and the glass working zones around the instruments.

Windows-based software system can be used to configure the imager, display properties and advanced temperature analysis options. Photo credit: Ametek Land

Because there are no regenerators with a reversal, the infrared thermography system allows long-term data trending for flames optimization. It also enables thermal optical profiles to be measured uninterruptedly, which is important for oxy-gas borosilicate furnaces with continuous operation.

Isotherms provided by the thermal imager are highlighted to show cold and hot locations. Alarms and temperature isotherms also provide SGD Pharma with long-term asset protection against overheating and condensation zones.

On the firing side, burners block cleaning and inspection will be shown as the flame risk of impact on refractories. Utilizing the overtemperature alarm function can monitor hot spots and burners.

Setting minimum or maximum temperatures triggers an alarm; then, a snapshot is taken of the whole image and stored for future analysis. An area function of the software enables multiple areas to be configured. Examples could include the crown, port target wall, tuck stones, breast walls and skew line.

This rainbow palette shows that the right-hand side glass flow is hotter than the left-hand side cold spot in the crown skew corner, with cold spots on the tuck stone joints. Photo credit: Ametek Land

Benefits of Thermal Imaging

For SGD Pharma, the most important benefit of the thermal imaging system is obtaining a furnace thermal profile continuously in the oxy-gas furnace. This allows the company to confirm the hot spot locations are well aligned with the furnace design and batch line. A thermal profile is obtained continuously by drawing profile lines at desired points such as crown or skew. This is in contrast to previous manual measurement methods or through the thermocouples that can be checked and verified with the virtual thermocouples provided by the imager.

Additional benefits of using a thermal imaging system for daily operation in an oxy-gas furnace include:

• Thermocouple verification.
• Air ingress and batch control.
• Combustion optimization for energy efficiency.
• Emission optimization.
• Same views as a conventional CCTV system.

At SGD Pharma, the infrared thermography system is used in several ways.

By utilizing a specific thermal palette and adjusting the temperature bands, SGD Pharma can identify refractory temperature and see which flames and blocks are the most intense (or hottest) and generate the best flame patterns and heat transfer. These images show the right-hand side is hotter due to possible crown overheating above R2. Photo credit: Ametek Land

Batch Line Location. Initially, batch flows are impacted by the charging control and, potentially, the flames; however, the flow patterns are driven by the thermal flows/convection currents. For better batch tracking, SGD Pharma uses software that provides batch coverage data based on a grid with rows and columns. Because the image is based on thermal data, SGD Pharma can add areas and apply alarms if the cold batch reaches a certain point. Whenever an alarm is triggered, the image is recorded for QA and troubleshooting purposes. Utilizing a specific thermal palette and adjusting the temperature bands can identify which flames and which blocks are the most intense (or hottest) as well as those generating the most suitable flame patterns and heat transfer.

Isotherms for Hot and Cold Spot Locations. From an asset-protection perspective, one of the most important analytical tools is the negative image that can be displayed instantly. This function shows SGD Pharma the areas with the greatest cooling. Utilizing the up to 400-times zoom function, the thermal imager can help identify the relative location of a small hole  and assist in determining the absolute location. It also can be used to identify any overcooling of the metal line that leads to increased wear due to the Marangoni effect and cold batch piles scraping along the furnace length.

This image identifies refractory cold spots. Photo credit: Ametek Land

Using the thermal imager’s zoom functionality, SGD Pharma can identify potential refractory damages, especially on burner blocks, and then take action to clean or repair them. These images show the L4 block at 300 percent zoom. Photo credit: Ametek Land

The heatup fill shows early damage on L4. Photo credit: Ametek Land

“We are very pleased with the results we have achieved so far,” said Francois Deblock, the glass melting director of SGD Pharma. “It has allowed us to improve response times, identify and troubleshoot furnace operations to achieve improved yield and higher pull, as well as lower specific energy usage. We expect this will mean cost and efficiency savings over the lifetime of the furnace.”

The use of a thermal imaging system can result in increased asset life for furnaces and potentially achieve future energy optimization and cost reductions. What can be seen is that temperature measurement at critical locations in SGD Pharma’s production process is essential for efficient control and optimization of the glass melt process.

This thermal image shows the furnace heatup at the start of fill. Photo credit: Ametek Land

A thermal survey, using a transportable thermal imager, was used to explore other locations in the furnace. Using available peepholes, snapshots of the refractories and many other details are revealed on flames, batch patterns, electrical boosters and glass temperatures. Photo credit: Ametek Land