April 3, 2007
Humidifier Allows Sterile Transfer of Water Vapor into Process Gases

RASIRC introduces the RainMaker Humidifier, a device that controls the transfer and purification of water vapor directly into a gas stream. With the RainMaker, controlled and purified water vapor can be delivered into most carrier gases, including inert, corrosive, and flammable gases such as hydrogen, at a wide range of flow rates. The membrane assembly has no epoxies or adhesives so is the first humidifier that can be steam sterilized for sanitary applications. This is especially beneficial for medical and pharmaceutical applications, where sterilization of components is often a critical requirement. In addition, the Rainmaker can tightly regulate relative humidity (rH) by controlling water supply temperature. Constructed of 316L stainless steel and Teflon, the RainMaker is designed for high-purity applications.

The RainMaker Humidifier consists of a non-porous, hydrophilic Teflon membrane that excludes particles, micro-droplets, volatile gases, and other contaminants in the liquid source from permeating the membrane while rapidly transferring water vapor across it. Many controlled processes require precise amounts of water vapor to be added to ensure that the correct humidity level is maintained. Processes using nitrogen, CDA, or synthetic air are dry and must be re-hydrated for the process to proceed. Examples include cell growth, combustion temperature control, fuel cell stability, and plasma etching of surfaces for adhesives and paint processes.

Bubblers are lowcost, but have inaccuracies due to the temperature of the gas and liquid, the operating pressure, liquid level, and thermal droop. They cannot prevent entrainment of dissolved gas, volatile molecular contaminants, and micro-droplets which can carry particulate and ionic molecular contaminants. Membrane contactors use porous hollow fibers to allow transfer between a liquid and gas, but allow transfer in both directions. They cannot be used above 50 degrees C. Membrane contactors and bubblers have high pressure drops and very limited gas flow rates.