November 2025 Volume 7

EQUIPMENT & TECHNOLOGY

Installation Overview The solution was deployed on furnace 8001 the week of March 31st, 2025. Six set points across four calendar-days (April 4th – April 7th) were trained and tuned. The training and tuning algorithms run unattended so the estimated labor hours to set up and run the process at all six set points was approximately two hours. Example Training Experience – 800F Training at 800F ran from 7:52am to 10:16am on April 5th, 2025, for a total of 2 hours and 24 minutes. The furnace PID tuner was disabled for this training and each burner’s actuated gas valve was locked in place at its last position. One at a time, each automated burner gas valve was opened by 50% to allow more fuel to flow for three minutes before lowering back to its initial position for 15 minutes. An adjustment amount of 50% was arbitrarily chosen to elicit a strong temperature response. As each burner’s firing rate was adjusted, a unique temperature characteristic was measured across all 12 thermocouples (SIFCO requires three additional thermocouples for its TUS). The difference in each thermocouple’s temperature rate of change and amplitude is the foundation for the training algorithm’s furnace map. Example Tuning Experience – 800F After the 800F training was completed, three tuning iterations spaced eight minutes apart at 10:40am, 10:48am, and 10:56am on April 5th, 2025 were conducted. The result of the tuning iterations was a reduction in the temperature span (hottest minus coldest) from 20.2F to 5.3F, and a reduction from +4.7F, -15.5F to +1.3F, -4.0F with respect to the set point, well within the range of an AMS2750H Class-I furnace.

Figure 3: Linearized Furnace Equation & Response Matrix Creation Once the response matrix is known, the linearized furnace equation can be reversed. By dividing a vector of thermocouple temperatures T by the response matrix K , the equation yields a vector of automated burner gas valve positions B . In a steady state furnace, starting with a vector ΔT representing the required changes in temperature for each thermocouple to reach the survey temperature, this equation can solve for ΔB , the necessary burner gas valve adjustments to achieve temperature uniformity. The process of training entails the CertiFire map out the general valve positions needed to bring the furnace close to uniformity. Metaphorically, it is writing the manual of the furnace’s behavior which takes time to develop (a few hours). The tuning operation, which is the next and final step after the training, is like reading the manual and applying the guidelines set by the training. This process takes only a few minutes to dial in the valve positions for improved uniformity as discussed below in the case study. Case Study: SIFCO Industries, Inc. – Cleveland, Ohio SIFCO furnace 8001 is a single zone box furnace with four high velocity burners firing above the load on the left wall of the furnace and four high velocity burners firing through piers below the load on the right side of the furnace. All burners were configured with a cross connected variable ratio regulator. The combustion air was fixed for fuel only turndown and furnace control was achieved through a single impulse air bleed valve which affected all regulators equally. Adding the linearizing technology to furnace 8001 required the installation of eight (8) actuated gas valves, replacing the existing manually adjusted limiting orifice gas valves, and a PLC subpanel. This added subpanel controls each motorized actuator independently. To drive the actuators, the subpanel was wired with two inputs from the existing panel: the tuner control variable (CV) over a 4-20mA signal, and the controller set point (SP) over ModbusTCP. The existing control panel was left in-place and is still the primary furnace control interface. Pyrometry Furnace 8001 is certified according to the AMS2750H pyrometry standard at the following three temperature SPs: 900F, 1500F, and 2100F. Additionally, the survey process requires first holding the furnace 100F colder than each SP (800F, 1400F, and 2000F) before increasing the temperature to the desired production SP to prevent overshoot. According to the AMS2750H standard, the furnace’s internal volume requires nine type-K thermocouples placed at each vertex of the cubic work zone and one at the geometric center for temperature measurements during certification. Furnace 8001 had historically been certified as a Class-III furnace (±15F). The customer’s goal was to reduce the overall temperature span at each of the six set points to move furnace 8001 to AMS7250 Class-II (±10F).

Figure 4: Thermocouple temperatures during 800F tuning The temperature range, shown in Figure 4, illustrates the initial span on the left half of the chart. A clear reduction in span can be noted at the inception of the first tuning iteration around the 10:40 mark. Note how not only are the coldest and hottest thermocouples brought in towards center, but the overall spread is also closer centered on set point. The same process was done for five additional set points yielding the following data in Figure 5. Note that the training was only needed for three temperatures. Since this initial data was captured, SIFCO has conducted three monthly TUS surveys. Prior to each survey, only tuning by the CertiFire at the required temperatures was performed. The simplicity, efficiency, and accuracy of the linearizing technology ensures the subsequent customer TUS will easily pass and maintain Class II uniformity.

FIA MAGAZINE | NOVEMBER 2025 13