Apparatus with a thermoplastic tube to tube-sheet joint and associated friction stir based fabrication method
An apparatus and method of manufacturing a thermoplastic tube-to-tube-sheet joint is disclosed. The method provides at least one tube-sheet having a first aperture and a plurality of holes. Further, the at least one tube-sheet fixes into a welding fixture using a plurality of bolts through the holes. The welding fixture has a second aperture. The method inserts a tubular member within the first aperture and the second aperture and fills an adequate molten workpiece material, using an FSW process, in a clearance gap between the tubular member and the at least one tube-sheet. The apparatus includes at least one tube-sheet having a first aperture, a welding fixture having a second aperture, a tubular member inserted into the at least one tube-sheet, and an adequate molten workpiece material, using the FSW process, is filled in a clearance gap between the tubular member and the at least one tube-sheet.
1 . A method of fabricating a thermoplastic tube-to-tube-sheet joint, the method comprising:
providing at least one thermoplastic tube-sheet having a first aperture extending therethrough and a plurality of mounting holes;
securing the at least one thermoplastic tube-sheet to a welding fixture using a plurality of bolts inserted through the mounting holes, the welding fixture having a second aperture aligned with the first aperture such that the first aperture is positioned above the second aperture;
inserting a thermoplastic tubular member through the first aperture and into the second aperture such that a radial clearance gap of at least 0.5 mm is maintained between an outer surface of the tubular member and an inner surface of the first aperture;
performing a friction stir welding (FSW) process at the interface between the thermoplastic tubular member and the tube-sheet such that:
frictional heat generated during the FSW process produces in situ molten thermoplastic workpiece material from the tube-sheet and/or the tubular member; and
the molten thermoplastic workpiece material flows into and fills the radial clearance gap;
forming a sealed joint between the tubular member and the tube-sheet without the use of any external consumable filler material.
2 . The method of fabricating the thermoplastic tube to tube-sheet joint as claimed in claim 1 , wherein the tube to tube-sheet joint configuration is done for a thermoplastic material, and wherein the tubular member and the at least one tube-sheet are made of a carbon black reinforced high-density polyethylene.
3 . The method of fabricating the thermoplastic tube to tube-sheet joint as claimed in claim 2 , wherein the thermoplastic material configured with the tube to tube-sheet joint is substantially corrosion resistant in acidic or corrosive environments in comparison with metals.
4 . The method of fabricating the thermoplastic tube to tube-sheet joint as claimed in claim 1 , wherein the FSW process used for joining workpieces comprising the at least one thermoplastic tube-sheet and the thermoplastic tubular member, comprises the steps of: plunging a welding tool into the workpieces to a specified plunge depth, wherein rotation and plunging of the welding tool creates frictional heat along with plunging pressure for proper joining of the workpieces; rotating the welding tool at the plunge depth for a specific time period; maintaining the welding tool at the plunge depth for a specific time duration after the rotation is stopped; and retracting the welding tool from the workpieces when the specific time duration is over to obtain an end result, wherein the end result is the tube-to-tube-sheet joint, wherein the FSW process is performed at a rotational speed between 800 to 850 rpm, a plunging depth of 0.5 to 0.8 mm, and a protrusion of 0.5 to 0.7 mm, using a friction stir welding tool fabricated from H13 steel, comprising a tool guide and a tool shoulder designed for centering and plunging into the workpieces.
5 . The method of fabricating the thermoplastic tube to tube-sheet joint as claimed in claim 4 , wherein the FSW process results in formation of tube to tube-sheet joints (TTJs) which are tough with higher extensions value corresponding to maximum pull-out strength compared to adhesive joining cases and achieving an adequate leak path.
6 . The method of fabricating the thermoplastic tube to tube-sheet joint as claimed in claim 5 , wherein TTJs formed comprise welding parameters that lies between 800 to 850 rpm rotational speed, 0.5 to 0.8 mm plunging depth, and 0.5 to 0.7 mm protrusion.
7 . The method of fabricating the thermoplastic tube to tube-sheet joint as claimed in claim 1 , wherein the fabricated thermoplastic tube to tube-sheet joint is used in many apparatuses comprising a thermoplastic shell and tube heat exchanger, a thermoplastic pipe to flange joints, and a thermoplastic boiler.
8 . The method of fabricating the thermoplastic tube to tube-sheet joint as claimed in claim 1 , wherein the second aperture of the welding fixture is less (interference fit) than a tubular member's outer diameter for holding the thermoplastic tubular member stationary during the FSW process.
9 . The method of fabricating the thermoplastic tube to tube-sheet joint as claimed in claim 1 , wherein the thermoplastic tubular member and the at least one thermoplastic tube-sheet are made of a thermoplastic material.