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Rao, A. S. L. K.
- Automation of GTAW Process
Authors
1 Central Workshop Division, Indira Gandhi Centre for Atomic Research, Kalpakkam - 603102, IN
2 Materials Technology Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, IN
Source
Indian Welding Journal, Vol 42, No 2 (2009), Pagination: 49-53Abstract
The soundness of welds is primarily determined by the quality of the ischolar_main pass. In order to ensure quality welds with full penetration, the gas tungsten arc welding (GTAW) process is widely used in industry. Usually, the quality of manual GTA welding almost solely depends on the experience of individual welders, but the quality of automatic welding is greatly influenced by proper selection and control of welding parameters to overcome the influences from gravity, arc force, surface tension, heat accumulation, joint preparation and fit up precision, etc. Consequently, an automatic-welding system with penetration enhancing activating flux (PEAF) may easily resulting good welding quality, especially in shop floor welding without the joint preparation and good fit up. Automatic GTAW Process is being used widely in the manufacturing industries to weld the pressure vessels, irrespective of the material and its thermal conductivities. Optimal performance of any welding process is based on choosing the right combination of input parameters by trial and error method. This paper deals with the development of an automatic welding system by converting the existing welding machine in to a full fledged automatic machine by addition of wire feeder, a servo controlled carriage, etc. to obtain the optimal combination of input parameters in order to achieve a good quality of weld as per code requirements. Experiments show that the welding quality on steel plates was very successful by using WEAVER and carriage with activated flux.
Keywords
Automatic-Welding, PEAF-TIG, Wire Feeder, Optimization, Servo Control.
- Salvation of S. S. Surge Tank for HTHP Loop
Authors
1 Indira Gandhi Centre for Atomic Research, Central Workshop Division, Kalpakkam, IN
Source
Indian Welding Journal, Vol 41, No 2 (2008), Pagination: 17-22Abstract
As constituents of nuclear industry, we all know the significance of the stringent specification to the practical level on the manufacture of nuclear components. More so for the primary system of High Temperature High Pressure Loop (HTHP) situated at Water & Steam Chemistry Division (WSCD). The pressurizing of the system is done by heating through immersion heaters provided in the surge tank. The surge tank, at its rated condition, has steam on the top, above the water level. The surge tank has got a l5 0 NB size nozzle at the bottom dished end. A 1500 # flange is welded to this nozzle. The heater unit of the surge tank is connected to this flange. The heater unit consists of a 150 NB, 1500 # blind flange (tube sheet) with eight number of SS U-type immersion heater pins welded to it. Welding of stainless steel heater pin is a demanding task. The task becomes even greater when the job involves welding of 16 pins with a triangular pitch of 25 mm, such as those for the high temperature & pressure loop. Actually, the tank was manufactured by a private firm. During final leak testing, it was found that there were leaks through the heater pins to sleeve welding in three of the heater pins. They could not rectify the leak. Subsequently, the rectification of the weld was referred to CWD. A novel technique was developed and due care was taken to weld the heater pins. The tank was successfully salvaged and tested hydrostatically at 170 bars and pneumatically at 7 bars. The method of fabrication of heater assembly, problems anticipated, problems encountered and measures taken to solve them are dealt with.