Oil and Gas

Rebuildable pH Sensors Reduce Costs and Improve Performance

Archer Daniels Midland Company is one of the largest agricultural processors in the world producing food ingredients, animal feed ingredients, renewable fuels and naturally derived alternatives to industrial chemicals. Founded in 1902, ADM operates more than 250 processing and manufacturing facilities across the United States and worldwide. In 1971 ADM acquired Corn Sweeteners, Inc., Cedar Rapids, Iowa, and in 1981 the Cedar Rapids facility was expanded to produce ethanol.

Slipstream measurement not enough

Managing pH in high-temperature chemical applications is critical for consistent product quality, efficient process reaction, and compliance in environmental regulations. But because accurate measurement requires immersing pH sensors in hot, strongly acidic substances for extended time periods, companies have traditionally had to replace them every few days. ADM Cedar Rapids, needed a pH sensor that they can use for months without replacing, thus significantly reducing equipment and labor costs, while maintaining high process quality standards.

“We tried taking pH readings directly from the process, but the 235°F temperature ate sensors up,” says Lloyd Feickert, instrumentation supervisor at the ADM Cedar Rapids facility. “To reduce excessive sensor costs we set up a slipstream arrangement, whereby we run a sample of the ethanol offline to cool it down to 140°F, and measure that,” says Feickert.

While the slipstream arrangement significantly extended pH sensor service life, inherent process conditions still caused frequent replacement of components in the rebuildable pH sensors. “At the lower temperatures, pH sensors could last for weeks, but process conditions caused temperature fluctuations within the slipstreams. Since we had standardized on the Foxboro 871 rebuildable pH sensors, we once again turned to them for a solution,” says Feickert.

Finding the right sensors

Since rebuildable sensors are the most cost-effective way to measure pH for their applications, ADM needed sensors that could withstand the high temperatures, be easily replaceable and last months, not days. Finding the right high-quality sensors could help cut costs, time and labor while giving them much more consistent and accurate measuring capabilities.

Increasing sensor service lifespan

“I heard about the DolpHin line of high-temperature pH sensors and asked Foxboro if they could develop a similar product for rebuildable sensors. The folks at Foxboro studied my application and came back with a replaceable electrode that, after a

Archer Daniels Midland Foxboro pH Senors

cooperative testing period, increased our sensor service life from days to months,” says Feickert.

The newly developed measuring electrode features a unique pH glass formulation that provides superior measurement stability, accuracy and longer service in high-temperature applications. This pH glass also increases response speed up to five times. The electrodes are available in domed, spherical, or ruggedized flat glass. The domed glass electrode is for the harshest applications: temperatures up to 250°F and extremes of chemical concentrations. 

The right tools for the job

In addition to the product cost savings, ADM has significantly reduced labor and maintenance costs. “Every time you send a person out to work on a sensor, it’s at least an hour’s worth of labor. I estimate that we have reduced time spent on changing electrodes over the course of a year from 36 hours per electrode to three hours per electrode,” says Feickert.

In addition, they have improved the stability and performance of their pH sensing, heightened worker safety and lowered inventory and supply. “We have standardized on the Foxboro 871 line and now, with the addition of the high-temperature domed electrode, we have all the tools to cost-effectively handle pH sensing throughout our plant,” Feickert added.

To learn more on how Archer Daniels Midland found the right tools to improve performance, access the full case study.


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