Calibrating thermal profiling equipment for baked goods.

Brought to you by ECD.

Thermal profiling equipment is a key tool to know how heat transfer equipment, such as ovens, dryers, proofers or freezers, operate. It doesn’t really matter what type of product you make, or if you have a small or large operation. What really matters is that you are sure that your heat transfer equipment provides the intended effect on the materials being processed.

Engineering and maintenance departments often document and implement schedules and procedures for replacing, repairing and inspecting processing machinery, and calibrating ancillary equipment. This is in most cases a very normal practice and is definitely essential for a smooth operation.

Thermal profiling equipment calibration

Calibration is simply the comparison of an instrument under test to a known standard.

One measurement device – the control – is known to have the ‘correct’ measurement accuracy, while the second device’s accuracy is unverified.  Calibrating against a control device proves that an instrument is performing accurately and its measurements are valid. The main reasons for calibration are to ensure the reliability of the instrument, to determine the accuracy of the instrument and to verify that readings are consistent with other measurements.  If equipment isn’t calibrated regularly, accuracy and reliability are in question.

When it comes to calibrating instruments that measure temperature, fluid flow, pressure, humidity or any other process variable, several considerations arise. Defining what, when and how to calibrate, mainly depends on:

  • Processing requirements
  • Critical steps in the process to ensure food safety or product quality
  • FSMA rules and HACCP regulation
  • ISO 17025 compliance (traceability and competency)
  • TPM and six-sigma model implementation
  • Internal policies
  • Equipment supplier reliability

Of course, the OEM is uniquely qualified to test and evaluate the products they manufacture. Also, lab and industry standards, like ISO 17025, ensure the quality of the calibration and may offer value-added services like calibration reminders.

Calibration and plant issues

Let’s suppose that your 6-zone DGF tunnel oven has been consistently producing high-quality products for months but now, it appears to be malfunctioning. You start asking what went wrong… You have noticed a reduction in crust color and crumb firmness but thought this situation would be soon solved with a change of flour lot.

Now, the situation has worsened. You recently received several customer complaints about moldy bread and the Sales Team has reported collapsed sidewalls in products that have been in their DC for only 1 day.

You quickly discuss this situation with maintenance and together address possible issues related to the oven operation. You check the actual temperature vs set point for each zone, band speed, blower for combustion air, coloraiders and exhaust system. Everything looks normal but you still see under-baked products.

Troubleshooting

You now ask when was the last time that oven thermocouples were calibrated. You are pretty aware that if thermocouples are not measuring air temperature accurately, then the whole temperature control loop for heat delivery would be compromised. One of the mechanics takes a thermocouple to the metrology lab and checks the instrument for accuracy. He soon discovers that the device is providing wrong readings. He then goes back to the oven and takes more thermocouples and realizes that some are working well and some others require urgent calibration.

Maintenance team has been very busy dealing with urgent equipment interventions and forgot to execute the calibration program properly. Following this situation, you carry out a thermal profile on the oven. You use a piece of equipment that looks old and not in a very good shape.

When you take a look at the s-curve and air temperature, you realize that the thermal profiling equipment is not working well either. You now have two big problems: you cannot trust readings from thermocouples nor profiler’s.

The metrology technician who checked thermocouples for accuracy reports back to management. The action taken is to replace all thermocouples with new ones that come with a calibration certificate. The technician also takes the thermal profiling device to the lab for calibration.

In the end, not all thermocouples in the oven were working wrong, so the bakery spent a lot of money buying new ones to replace all existing sensors. If the profiling device was working properly, you could have run a normal thermal profile of the baking recipe and seen specific zones (or sensors) that were responsible for under-baking the product.

Proper calibration matters

This situation could have been avoided if equipment instrumentation was properly calibrated. Going beyond, the issue linked to under-baking could have been solved much faster (and even with money savings) if the thermal profiling equipment had been calibrated according to the equipment calibration program.

Contacting the manufacturer of your thermal profiler for at least annual Calibration Recertification service provides the solution to validating production equipment accuracy. The results in a smoothly operating bakery with high yield profitability.