Unique process technology for weld overlay cladding of tubesheets by automatic submerged welding with a wire and tape electrode, shielded gas automatic welding with a consumable electrode, manual arc welding with a coated electrode by corrosion-resistant materials with special properties has been developed at the company. The method of cladding the tubesheets with non-ferrous metals (brass, bronze etc.) by explosion welding has been incorporated.
Produced by the company tubesheets for heat exchangers and tube bundles are drilled on a unique CNC machine for deep-hole drilling of HTB-III “KOLB” model (Germany).Tubesheets with diameter up to 4 m and thickness up to 600 mm can be drilled on this machine. The required dimensions of the holes with diameters up to 38 mm and stringent tolerance band as well as the surface roughness are provided without additional countersinking and reaming. One more thing that makes the machine unique is that the deviation of the drilled holes direction from the nominal position at length 600 mm does not exceed 0,02 mm. None of universal drilling machines can provide such accuracy which is a very important factor ultimately influencing the tube bundle quality.
New process technology of steel 15X5M tube-to-tubesheet welding with subsequent local heat treatment and a process technology of an austenitic version of welding tubes to tubesheets made of steel 15X5M with clad austenitic material without following heat treatment have been implemented for manufacture of tube bundles made of steel 15X5M.
For manufacture of tube bundles consisting of austenitic class tubes (type 08X18H10T) the version of tubesheets made from pearlitic steel with clad corrosion resistant austenitic material with following welding of tubes by austenitic materials is applied.
The process of U-tubes manufacture for heat- exchange equipment from steel 15X5M with u-bends welding by argon arc process with non-fusible electrode and pearlitic consumables with subsequent heat treatment of welds of has been introduced at Volgogradneftemash JSC.
Seal welding of tubes in tubesheets is conducted only by argon arc welding with non-fusible electrode which assures high quality of weld seams.
Tube expansion with limited torque moment is performed by an expansion tool (adjustable and non-adjustable) on machines of the firm “Kotthaus+Busch” (Germany).
The quality of the tube-to-tubesheet joints is checked by pneumatic and hydraulic methods with luminescent indicating coating.