Friday, January 31, 2014

Water Cooled Oxygen Blowing Lance (a vital utensil for LD-Converter Steelmaking).

 (Steelmaking Department Pakistan Steel )

The optimal design of oxygen blowing lance and lance head with effective passage of cooling water and certain axes of orifice /nozzles as per explicit internal dimensions of LD-Converter is acquired to manage the desired quality of steel production, faster and smooth process and to prevent the excessive wearing of refractory lining of LD-Converter from attack of vigorous slag forming reactions.

The water cooled oxygen blowing lance for LD-Converter (steel making) is comprised of a rear body from which the lance hangs and an orifice tip connected by three concentric seamless pipes or tube sections joined by welding to form a straight continuous member of ample length. In a typical design the oxygen flows through the center pipe which is surrounded by inlet water moving down through the adjacent annular passage to the orifice tip, the water returns through the the outer annular passage to the rear body and discharge connection. The intermediate pipe serves as a baffle separating the inlet and discharge water as it flows through the lance with suitable clearance at either end to minimize the amount of bypassing water.

The lance life is defined as the total number of heats blown by it between replacements of the orifice tip or front end sub-assembly. Lance repairs and frequency of lance changes are a matter of concern due to the labour involved and hence related effect on cost per ton of steel produced.

Lance repairs include skull removal, as well as replacement of the orifice tip or other sections that may be leaking or otherwise defective, restoring the three concentric pipes to full design length, attaching rear body, filling with water and lastly pressure testing to specified limits.

Most lance failures are due to water leaks which develop in or adjacent to the orifice tip, mostly as a result of erosion by molten metal and slag moving down and across the exposed lance surface during process of steelmaking. Survival of the lance under the furnace vigorous high temperature conditions depends completely on the effectiveness of the cooling water in removing the heat absorbed on the exposed surface and proper lance height during course of oxygen blowing.

Appearance of Oxygen Lance Head.

The water cooled Oxygen blowing lance copper head has a set of tapered nozzles with precise dimensions designed according to specific volume of LD-Converter and blowing practice. Slight alteration in dimensions directly affects the quality, production performance and refractory lining campaign of LD-Converter.

Pakistan steel handles lance repairs at “ in house” available facilities in steelmaking department, uses lance heads with five orifice /nozzles for 130 ton LD-Converter steelmaking and is self-sufficient in provision of these important spares.

The copper lance heads are cast and fabricated in foundry shop and are machined from cast blanks of high purity copper ( having high thermal conductivity, weldability, and soundness under repeated thermal cycling ) at  fabrication facilities of Repair Shop Complex (C.M.D) Pakistan Steel and are supplied to Steel Making Department where they  are welded with the body of oxygen blowing lance assembly in order to replace and repair the damaged Oxygen lance heads.