OTS (February 2009) -- An Auto Dewar Drain upgrade now available for ANTARES® Cryokinetic Cleaning Systems automatically drains liquid nitrogen from the dewar as required during scheduled maintenance or to clear blockages caused by material freezing in the coil or nozzle during routine operations. Automation simplifies the procedure by eliminating the need to manually change hardware, saves time otherwise required to verify draining, and improves reliability by providing positive confirmation that the dewar and coil have reached a temperature high enough to melt and clear any blocking material.
In the ANTARES® system, process gases flow from the gas panel through a coil, immersed in liquid nitrogen (LN2) within an insulated reservoir (dewar), where the gases are cooled to a temperature near their dew points. The dewar must be drained any time the process chamber is opened for maintenance to prevent moisture in the air from freezing on the coil and nozzle. This occurs at least once a quarter during preventive maintenance when the gas lines are checked for leaks. The dewar must also be drained any time the gas lines must be warmed to clear blockages formed from material condensed and frozen out of the process gases - a condition usually indicated by a rise in upstream gas pressure.
In the manual procedure, nitrogen gas inlet and liquid nitrogen outlet lines are connected to the dewar so it may be drained. Then the dewar must be allowed to warm for a sufficient period of time for the coil to reach room temperature so that any blockage will melt and evaporate. If the coil has not been allowed to warm for a long enough time, until it reaches room temperature, the entire procedure would need to be repeated after the dewar has been re-filled. The automated procedure eliminates the need for adding/removing the inlet and drain lines. In addition, a thermocouple monitors the temperature of the coil itself to provide positive confirmation that the coil has reached room temperature, indicating both that the LN2 has drained completely and any blockages have melted.
The Auto Dewar Drain upgrade simplifies maintenance and repair procedures by eliminating most of the associated hardware manipulation. Its ability to monitor coil temperature directly allows the length of the required warming period to be precisely determined, eliminating time that might otherwise be wasted in waiting through an extended warming cycle after the blockage has melted and evaporated. Equally important, it reduces the risk that the blockage is not completely melted or that residual liquid may freeze again when the dewar is refilled, requiring yet another draining and warming cycle. Finally, the automated procedure reduces personal safety risks associated with handling LN2.
For more information contact your local FSI service office toll free at 1(877)723-8324 or call 1(952)361-8188 or click here.