1. Field of the Invention
The present invention is directed to the field of devices for retaining a filtering element containing active reagents for cleansing the gas passing through a gas line for feeding a processing system, and the means for replacing the filter without contaminating the system.
2. Description of the Prior Art
Many processes require a supply of various gases that must be kept scrupulously clean in order to achieve accurate results within the process. It is important to keep contaminants apart from the reacting agents and the delicate instrumentation used in the process since such contamination would affect the results. Gas chromatography is one such process where moisture, oxygen, carbon dioxide and airborne particulate matter must be prevented from entering the system. Aside from yielding fallacious results, these unwanted materials can also damage precision metering devices installed in such a system.
Many filtering elements are available that adsorb gases and trap solids and they are very effective as long as the adsorbent is active and the gas lines are continuous and not exposed to the atmosphere. However, from time to time is necessary to open the system in order to replace the filtering element. Doing so requires breaking the gas line by opening the filter housing thereby creating the problem of exposing the internal components of the system to the atmosphere. Prior art devices provide cut-off valves in the lines surrounding the break to exclude contaminants, but no means is provided to prevent contaminating material from entering through the space between the valves while the replacement filter is being installed. None of the prior art devices known effectively eliminates the entry of outside air into the system when it is opened for replacement of the filtering element.