Many industrial laundry processors use sizeable industrial machines to process laundry on a large scale. In many countries, industrial laundry processors must follow regulations to confirm — via temperature verification — that proper processing has occurred. (Most regulations were enacted following the outbreak of certain illnesses such as E. coli, likely due to the processing of underwear.)
Closer to home, many also states have requirements to ensure that there is proper sanitation before the laundered materials are placed into use again. For instance, Hawaii’s Department of Health regulations state in Section 3.a.7: “…being laundered in an acceptable manner…subjected to a sanitizing process which will hold such laundry for at least 20 minutes at a temperature of at least 180°F.” While not all regulations are so rigorous, many have a similar requirement.
One of the major factors that affects the effectiveness of this process is the wash-water temperature. Having proper wash-water temperature is critical to ensuring that the correct amount of sanitation occurs within the laundry load.
The higher the temperature of the water in the washer, the more microorganisms killed: Most agree that viral and bacterial survival rates increase with reduced wash temperatures. Likewise, soil removal and bacterial reduction are closely linked. As visible soils are removed, the bacteria and viruses that often live in these soils are removed as well.
Within the laundry machine, the cleaning process relies on the physical actions of dilution; the mechanical action of the water and machine; and the temperature of the water. Yet, bacterial spores will survive wash temperatures higher than 160°F (71°C). Rather than trying to kills spores via temperature alone, laundries seek to remove them through the mechanical action and dilution of the laundry cycle.
As a result, some companies are seeking effective ways of monitoring the laundering process using dataloggers. These recording devices can monitor temperature, pressure or other variables in an environment and store that data for later use. They typically have a metal tip measuring 1 to 5” long, called the measurement probe. It is used with a body — typically made of a durable material such as stainless steel — that houses the electronics. Some dataloggers are built to be rugged and self-contained, making them a good choice for high temperature processes that are harmful to typical electronic systems.
Case in Point: Industrial Laundry in China
One industrial laundry processor in China added datalogging capabilities to its operation to validate the process and document data verification. In China, laundry facility regulations require that processors confirm that the washing water reaches a minimum temperature for a sustained 10-minute interval.
The washing operation uses a continuous batch tunnel washer (CBTW) with seven compartments. Continuous batch tunnel washers are capable of washing multiple loads of laundry at one time. In addition, they typically can handle different load types and wash times at the same time. In all, a single CBTW can process up to 3,000 lb of laundry at once.
The wash cycle for the continuous batch tunnel washer at this laundry processor includes a 10-minute ramp period to reach temperature. It is followed by a 10-minute dwell cycle where the wash water is maintained above 140°F (60°C). This ensures that the processor meet regulations to reduce any bacteria or other pathogens to an acceptable level. The 10-minute dwell cycle reduces the bacteria load to an acceptable level and ensures the regulations are met.
After washing, the laundry is pressed to extract excess water. A large membrane press is positioned to compress the clothes and create a “laundry pancake.” The laundry is subjected to more than 500 lb/in2 of crushing force. Following dewatering, the laundry passes to the dryer for a full drying cycle.
The dataloggers first selected for the task were chosen for their durability at process temperatures up to 284°F (140°C). They fit into small spaces, withstand harsh chemicals, have a high degree of accuracy throughout the process, are self-contained and operate wirelessly.
When subjected to the industrial laundry process, the logger chosen performed well initially. After the process was complete, however, it was discovered that the sharp probe tips were shredding the laundry. In addition, when the clothes were placed in the membrane press, the datalogger model chosen was destroyed from the press’s crushing force. It was clear that a new datalogger plan was needed, and these challenges would need to be overcome.
Custom Engineering a Laundry Solution
The goals were to keep the sensing probe from damaging the laundry during the wash cycle, and keep the washer from damaging the datalogger during dewatering. The solution designed accomplished both preventing the tip from reaching the laundry material and by reinforcing the logger housing. The datalogger design engineers did so by creating a Teflon outer shell custom-designed for the logger. The shell was designed with a hole so that the temperature probe could be exposed to the process temperature. At the same time, the shell encompassed the probe, and only the shell would come into direct contact with the laundry material. This prevented the probe itself from shredding the clothing during the agitation cycle. The Teflon shell also would protect the logger in the membrane press.
After running several test cycles, it was clear there were two things wrong with the Teflon shell design. The first issue was that the Teflon shell still was crushed by the membrane press. This meant a more rugged design should be considered.
The second issue related to the temperature probe. With the probe in the shell, a temperature offset and consequent lag in the response time of the logger could be seen. The Teflon shell design meant that the temperature probe was delayed in receiving the full temperature exposure. In some cases, it never received the proper exposure.
After a thorough review, the datalogger engineers determined that the Teflon armor case was designed with the walls of the lid too close to the tip of the logger. This caused an absorption of the water temperature before the probe tip could receive it. The phenomena occurred because the case was made from Teflon: a material known to be a good insulator, able to absorb heat quickly and pull it away from other materials. It was clear that the hole in the cap surrounding the probe tip would need to be widened to reduce the temperature-absorption effect.
After reviewing the design, a black Teflon armored shell was chosen with the same basic properties of the first one. The engineers designed in a wider opening around the probe tip to allow for less heat radiation from the Teflon. In addition, a different, more resilient Teflon material — stronger and more resistive to the effects of the membrane press — was used.
After several trials, this design worked well. As a result, the Chinese laundry processor is able to validate its processes and document its success in satisfying the health regulations.