Abstract: A process for sterile entry/exit into a closed system permits safe addition of reagent/nutrient/process modules, etc., removal of biological samples or depleted process modules such as filters, etc. all without exposing the operator to possibly dangerous materials such as blood and without endangering the contents of the system such as in cell-culturing. A novel welder and process is disclosed to illustrate the process.

Abstract: Plastic tubes are welded by placing a pair of tubes in a pair of aligned holders with each tube folded toward itself. A wafer is movably mounted in the gap between the tubes and is heated to cause the ends of the tubes to melt without actually cutting through the tubes. The melted ends of opposed tubes can be pressed into contact with each other to form a welded connection. In a variation a pair of cutting blades cut the folded ends of the tubes and the cut ends are then melted by a wafer and subsequently pressed into contact with each other.

Abstract: A process for sterile entry/exit into a closed system permits safe addition of reagent/nutrient/process modules, etc., removal of biological samples or depleted process modules such as filters, etc. all without exposing the operator to possibly dangerous materials such as blood and without endangering the contents of the system such as in cell-culturing. A novel welder and process is disclosed to illustrate the process.

Abstract: A thin wafer for cutting plastic tubes which are to be butt welded together includes a high temperature insulated plate-like core with a resistance circuit on the core for heating the wafer to a temperature sufficiently high to melt through the tubes. A glass layer may be on the outer surface of the water, particularly in the contact area with the tube. The wafer may be used in an arrangement wherein residue is removed from the water by having the residue adhere to unused portions or stubs of the tubes which then would be stripped from the wafer.