Informatics Publishing Limited

M. S. Bagavathiammal ¹, P. Sivaraman ¹

Affiliations
1 Department of Computer Science and Engineering, Karpaga Vinayaga College of Engineering and Technology, IN

Abstract

Now a day’s Vehicular Ad hoc Network (VANET) plays a key role in wireless communication. It uses some special techniques like PBSM (Parameter less Broadcast in Static to highly Mobile), which does not depend on any parameter or threshold value. So the performance of VANET degrades during the packet transmission. To improve the network performance we propose a new technique ABSM (Acknowledged Broadcast from Static to highly Mobile), which is developed upon PBSM for better performance. ABSM needs local information to perform the broadcasting task which is obtained from beacon messages, and it does not increase message overhead because of safety applications. And it creates a broadcast delivery backbone based on a CDS (Connected Dominating Set) heuristic. Vehicles in the CDS choose a shorter time-out, to give them a higher priority to retransmit. This makes ABSM a better technique when compared to PBSM in Vehicular Ad hoc Network.

Keywords

Broadcasting, Connected Dominating Set, ABSM Protocol, Multicast.

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M. Divya ¹, C. R. Das ¹, S. K. Albert ¹, V. Ramasubbu ¹, A. K. Bhaduri ¹, P. Sivaraman ¹

Affiliations
1 Materials Joining Section, Materials Technology Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu, IN

Abstract

Cracked shrouds of the 3^rd stage of a Low Pressure turbine was in-situ repaired by removing the cracked pieces of the shroud and welding new shroud pieces to the existing shroud. The shroud material was made of AISI414 martensitic stainless steel (SS), and the repair welding was carried out using ER 410NiMo filler wire. The tenon heads of the blades, which were removed for carrying out the in-situ repair, were also built-up by weld deposition. The repair welds were subjected to in-situ two-stage post weld heat treatment (PWHT) as required for the 414 SS material and the 410NiMo weld metal. For prior to simulation of the constraints of actual in-situ repair, a mock-up piece was made using the same blade material, welding consumable, welding procedure and PWHT as were to be used for the actual repair. After successful completion of the repair, the mock-up piece as well as separate weld pads prepared using the shroud material and ER 410NiMo consumable were subjected to detailed microstructural characterization and mechanical properties testing to generate data on the properties of the repair weld now in service. The paper discusses the details of the in-situ repair and results of the characterization of the weld joints. Results confirm the repair weld has adequate strength and ductility. The turbine with repair welded shrouds has been performing satisfactorily since 2008.  

Keywords

Repair welding, Turbine Shroud, PWHT, Supermartensitic Stainless Steels.

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R. Veluswamy ¹, A. Md. Muneer ¹, M. Krishnamoorthy ¹, P. Sivaraman ¹, A. S. L. K. Rao ¹, M. Vasudevan ², A. K. Bhaduri ²

Affiliations
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

Abstract

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.

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R. Veluswamy ¹, P. Sivaraman ¹, N. Easwaran ¹, M. Krishnamurthy ¹, A. S. L. K. Rao ¹

Affiliations
1 Indira Gandhi Centre for Atomic Research, Central Workshop Division, Kalpakkam, IN

Abstract

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.

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K. S. Krishnamurthy ¹, P. Sivaraman ¹, R. N. Palani ¹, R. Deivasigamani ¹

Affiliations
1 Central Workshop, Indira Gandhi Centre for Atomic Research, Kalpakkam - 603 102, IN

Abstract

Primary Heat Transport (PHT) System Pumps are used for circulating Heavy Water at high temperature in the PHW Reactors. A pair of statioi^ry and rotary S.S. mechanical seals are used in these pumps. To provide sufficient weatf resistance, corrosion resistance and a variety of additional properties, the hard cobalt based alloys are faced on the mating surfaces of the pair of mechanical seals. Initially, Stellite-6 was hard faced on the seals. Since the seals were wearing out fast, the need for a much harder facing material, to extend the life of the mechanical seals, was felt. Hence, Stellite-1 was an obvious choice. Nevertheless it was not an easy task to replace Stellite- 6 with Stellite-1.

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