Wednesday, September 03, 2008

Viewing lens / HMI moisture indicator

Moisture indicators on refrigeration equipment are critical early-warning components in the effort to lessen the long-term effects of water damage and reduce repair and maintenance costs. The proper moisture indicator must sense and report just how much water is in the system’s circulating refrigerant. An indicator in a viewing lens changes color as the moisture content reaches potentially damaging levels. Be sure to choose an indicator that is sensitive enough to alert operators early on that moisture levels are rising, allowing corrective action to be taken before serious system damage occurs. The Hermetic Moisture Indicators (HMIs) from Emerson are able to read moisture levels far below industry standards. The HMI actually begins to change color at two percent relative humidity (RH), which is a “very dry” indication. At 3% RH, the purple caution color begins to appear. Many other indicators do not begin changing colors until about seven to eight percent RH; however, early detection is critical with HFC refrigerants and POE lubricants. POE oil can hold up to 20 times more moisture than the mineral oil used by older refrigerants, which can allow corrosive acids to build up and totally destroy a system. The HMI is UL listed with a 680 psig maximum working pressure, making it acceptable for use with higher-pressure HFC refrigerants. It has a larger viewing window for easier visibility and charging. It is resistant to “washout” from water and can withstand brazing temperatures up to 450 degrees Fahrenheit [ 232 degree C]. The fully hermetic design includes a corrosion-resistant, all-brass body with no o-rings or knife seals that are likely to leak. The indicator features solid copper fittings for easy, universal replacement.

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