Assembly in Action: Humidification Units Solve Static Problems
June 23, 2008
Founded in 1977, Itron Inc. (Liberty Lake, WA) manufacturers metering devices for electric, gas and water utilities. At its plant in Waseca, MN, the company assembles radio frequency devices and automated meter reading equipment used by utilities to monitor high-volume water and power users.
Like many electronics manufacturers, the 110,000-square-foot Waseca plant has long struggled to eliminate defects due to electrostatic discharge, especially in winter. When the outside temperature falls to 10 F, heating the plant to the necessary 70 F results in a relative humidity (RH) of as little as 10 percent. The ideal relative humidity for the plant’s operations is 40 percent to 50 percent. Below 30 percent, production can become seriously impaired.
“Static electricity, and the potential for defects due to electrostatic discharge (ESD), is one of the biggest manufacturing headaches a board manufacturer can face,” says plant facilities operations manager Paul Anderson. “For years, we operated a compressed-air humidification system throughout the plant. It did a good job, but as humidification technology has moved forward, so has the capability to control RH levels.”
Ultimately, Itron elected to go with a number of ML System Princess 2 high-pressure humidification systems from Husson Inc. (Sturtevant, WI). Each Princess 2 has a 10 gph capacity and produces a fine mist that is quickly absorbed into the air. In addition to providing consistent humidification, the units cost about $300 per year to operate and are plumbed via a series of high-pressure hydraulic hoses-as opposed to steel pipe-making it easy to shift the units throughout the plant.
In terms of the specific layout, Itron deployed eight humidification units in two separate zones comprising its warehouse and production areas. The system includes a reverse-osmosis feature to eliminate minerals from the water and a UV filter to kill bacteria. Humidity sensors in each zone monitor RH levels and report to a remote PLC. If RH in a zone drops below Itron’s 40 percent set point, the PLC activates the Princess 2 units in that zone until RH returns to the desired level.
According to Anderson, the company has had very few mechanical problems with the ML system, and it has lived up to all of the company’s expectations.
“[The system] is virtually automatic. We rarely think about dry air and static electricity. They really aren’t issues anymore,” he says.
For more on humidification, visit www.hussoninc.com or call 262-884-4669.