DESIGN AND DEVELOPMENT OF GAS CUTTING TORCH NOZZLE FOR ENHANCED GAS CUTTING PERFORMANCE

Abstract

Many metal-manufacturing industries include oxyfuel cutting process among their manufacturing processes because cutting and welding are often required in metal processing, specifically in the fabrication of pressure vessels and storage tanks. The oxyfuel cutting process uses controlled chemical reactions to remove preheated metal by rapid oxidation in a stream of pure oxygen. Earlier studies on gas cutting of metals demonstrated that preheat time varied depending on the gas used for the combustion during the process. In this work, initially preheating time was studied using acetylene gas and Bharat Metal Cutting Gas (BMCG) during cutting of 10, 50, 100, 200 and 300 mm thickness structural steel plates under different process parameters (heating oxygen pressure and nozzle clearance). The preheat time study was done with the Quicky (PUG) and optical profile cutting machines. From the study, it is observed that preheating time for BMCG is more than that for acetylene gas. Increase in oxygen pressure in general reduced the preheating time irrespective of gases and machine:' used for study while the effect of nozzle clearance was found to be determined by pressure of oxygen and fuel gases besides the initial nozzle clearance. At high pressures of oxygen and fuel gas, an increase in nozzle clearance showed first decrease then increase in preheat time thus an optimum value of nozzle clearance was found for minimum preheat time. Efforts were also made to improve the efficiency of BMCG by designing and developing new heating nozzles. Three different types of nozzles (model-I, model-II and model-III) were designed and developed using concept of fluid flow and forced convection of heat transfer. The preheating times of these three nozzles have been obtained and compared with the commercially available conventional nozzles. Results showed that the newly developed nozzles take lesser preheating time than conventional nozzles specially at low pressure conditions. Among three newly developed models of nozzle, model-I showed better performance than remaining two nozzles. Further, experiments were also done by complete cutting plate of different thicknesses - using model-I nozzle and cut surface morphology was studied. Cost analysis of different gases for preheating showed that cost of preheating of mild steel work piece with acetylene gas is more expensive than BMCG irrespective of plate thickness.