Estimating Utility consumption during HALT

Thursday, March 26 2020

Thermal Step Testing Graph
Thermal Step Stress Graph

Estimating Utility consumption during HALT

When a company is considering implementing HALT at their facility, a common question is “What can I expect for utility costs when running a HALT?” Unfortunately, this isn’t an easy question to answer. There are many variables that can have a huge effect on total utility usage. Of course, the size of the system is the biggest factor. The bulk of the utilities are used heating and cooling the vibration table and the stainless steel walls of the system, so a larger system will have higher utility usage. The actual mass of the product isn’t that significant, simply because the thermal mass of a typical product is much less than the thermal mass of the interior of the system. A bigger factor is the thermal range of the steps and ramps. Doing HALT on a product that can operate over a wider range of temperatures, and especially to lower temperature extremes, will use more utilities than would a product with a narrower operating range of temperatures.

That said, it is possible to do some utility consumption estimates, with the proper assumptions in place. ESPEC has developed tools to calculate the actual LN2 and power consumption during a test based on log file information from the chamber while the test was run. Recently I used these tools to calculate the utility usage during a ‘typical’ HALT in the Typhoon 3.0 system in the lab in Denver, Colorado. This HALT included thermal step testing to -70°C and +200°C, then rapid thermal and combined testing that cycled from -30°C to +170°C. The thermal mass of the product was negligible, it was a PCA for a down hole tool. During this test the total LN2 consumption was 192 gallons, and power used was 76 kW.

That number will at least give you a data point to base some intelligent estimates on for your own utility usage. If you have a log file from a Qualmark system and want to know the usage during the logged test, contact ESPEC support, we should be able to help you out.

And remember – if it isn’t broken, you’re not done yet!

Neill Doertenbach

Customer Solutions Engineer