WIKA (Germany) - An operator of steam methane reformers was able to minimize burner fuel consumption and increase productivity after installing XTRACTO-PAD® assemblies on furnace tube walls.

WIKA USA has developed a comprehensive portfolio of tubeskin thermocouples for refineries, chemical plants, and superheated steam applications. Knowing our reputation for innovative temperature sensors, an SMR operator reached out to us several years ago for advice on continuous tube wall temperature (TWT) monitoring. Their goal was to operate more efficiently by minimizing fuel consumption and increasing productivity.

Challenge: Continuous Tubeskin Measurement Without Repeated Welding:

The furnace had a two-chamber design with a side-burner configuration. Other specifications:

• Number of tubes: 96
• Tube material: 24/35 Cr/Ni and Nb/Ti
• Tube dimensions: 6 inches (154.6 mm) outer diameter, 43.6 feet (13.3 m) length
• Tube wall temperature: 1,382 to 1,508°F (750 to 820°C)

In addition to tubeskin temperature monitoring, the SMR operator wanted to avoid repeated welding for thermocouple replacements.

Solution: Custom-Engineered Tubeskin Thermocouple Assemblies:

Our temperature and welding experts examined the furnace and came up with a solution for optimizing this operator’s reformer. We proposed the XTRACTO-PAD®, a thermocouple assembly where a padded guide channel and heat shield are welded to the tube, with the removable thermocouple sliding in and out through the end of the guide channel.

This special design makes it easy to replace thermocouples between turnarounds without compromising tube integrity. The patented heat shield over the thermocouple protects it from the surrounding hotter furnace environment, thus providing the most accurate temperature measurement currently available and increasing the sensor’s lifespan.

A piston-style exit to the bottom of the furnace was used to install the thermocouple transition lead wires to the terminal block and complete the installation. Standardized methods were used to ensure proper routing distances and also that the thermocouple transition did not exceed its maximum allowable temperature.

As each SMR is different, we engineered the contoured thermocouple sensor, the guide channel, and the patented heat shield for each tube and sensor size.

Results: Better Performance and Cost Savings:

The customer was very happy with the performance of the XTRACTO-PAD®. Thanks to continuous TWT monitoring, they were able to:

• Obtain highly accurate temperature measurements during startup, thereby preventing catastrophic damage to the tubes or the catalyst.
• Maximize tubes lifespan by preventing overheating.
• Decrease fuel consumption through proper burner management.
• Monitor catalyst performance and accurately estimate catalyst age.
• Maximize production through proper balance of burners and feed rates with minimum risk of overheating and tube creep failure.

Four years later, during the plant’s first turnaround after installing the tubeskin thermocouple assembly, they were happy to find that all temperature elements were fully functional and operating as expected. During the next turnaround, which is scheduled for 2023, the customer plans to proactively replace the thermocouples – a process that will not require additional hot work, thanks to the XTRACTO-PAD’s unique design.

The furnace tubes are now approaching the end of their natural lifespan. When they are replaced, this SMR operator is considering having the thermocouple assembly’s weldable parts – guide channel, heat shield, tube clips – installed at the tube manufacturer’s facility in order to save time and to minimize any issues related to heat treating. When the new furnace tubes arrive, this customer will simply slide in the thermocouple sensor inside its mineral-insulated sheath, thread it through the clips, and complete the installation.

This long-time customer was so pleased with WIKA’s tubeskin temperature monitoring system that they are actively planning to implement it in two other plants.