Assam Carbon Products Limited Delhi

DC traction systems have inherent differences to their industrial counterparts having to cope with increased levels of vibration and thermal shock as a result of rapidly changing load currents. The advent of fast switching thyristor control and regenerative braking have added to the harsh conditions already experienced by the carbon brush which is a vital part of the current carrying chain, so it is imperative that the correct grade of brush is chosen to optimize the performance and reliability of the equipment. Traction applications may be divided into three categories: 1. On pure electric systems: ventilator motors, lighting alternators or generators, motor alternatorgenerator sets. 2. On diesel electric systems: main and auxiliary generators. (Often replaced by brushless alternators with diode rectifiers). 3. Traction motors: traction motors are generally quite different from industrial motors. In order to obtain the required torquespeed characteristic, they are almost always series wound motors. This gives a fairly constant powder output over the speed range, with torque declining as speed rises. Thus, on starting, the high armature current gives a high field current, which provides the torque needed to accelerate the locomotive from rest. As the speed increases so does the back emf; thus the current falls, the field weakens and the speed rises further.

Silver Impregnated Graphite (SIG) contacts are used in high safety applications of railway signaling, traffic signaling, and numerous other applications due to high silver content that eliminates the risk of welding in the presence of graphite. High contact resistance (>200mΩ) was observed in the SIG contacts in a railway signaling operation after a few thousand operations of the relay. The high contact resistance was discovered to be a result of loose dustforeign particles residing between the two contacts. Silver had been preferentially removed from the contacting surfaces during switching operations by an abrading effect of the dustforeign particles, leaving only graphite on the contact area. Wear was accentuated by the presence of porosity and low hardness of the contacts, leading to improper interaction between the mating surfaces.

Steam heated rolls are used in the production process of many industries like Paper making, Petrochemical, Plastics, Rubber and Textile etc. One of the most common application is in paper making where the wet paper supported on felt passes over a steam-heated drying roll. The most efficient way to connect the steam supply to the rotating unit is a by means of a steam nozzle using Carbon sealing rings, which have a high degree of reliability and maintainability. Carbon is self-lubricating and has excellent resistance to wear; it beds in rapidly and does not wear or score the counter faces. Carbon has high mechanical strength under compression and maintains its properties at high temperatures. Although, theoretically it is possible to use sealing rings of rectangular cross section but, in practice it would be extremely difficult to obtain proper alignment. That is why a self-aligning spherical construction is adopted. It is, of course, essential that all sealing surfaces are highly finished; and also, sufficient clearance must be provided at the bores to allow the rings to float freely. Assam Carbon Products Ltd. have been manufacturing Steam nozzle joint rings and bearings for many years in collaboration with Ms. Morganite Special Carbons Ltd., U.K. These are manufactured in grades for operating temperature up to 3500°C. Specially for high pressure steam joints our metal impregnated Antimony class grade is recommended.

Steam heated rolls are used in the production process of many industries like Paper making, Petrochemical, Plastics, Rubber and Textile etc. One of the most common application is in paper making where the wet paper supported on felt passes over a steam-heated drying roll.

Steam heated rolls are used in the production process of many industries like Paper making, Petrochemical, Plastics, Rubber and Textile etc. One of the most common application is in paper making where the wet paper supported on felt passes over a steam-heated drying roll.

Linear current collection is similar to carbon brush collection except that in linear collection the collector is moving rather than the conductor. Current collectors have relative motion along a line instead of around a rotating cylinder; point or line contact is present, as opposed to the area contact of a brush. There is more frequent and more complete rupture of contact with the consequence of sparking and arcing. In addition, linear current collectors are more likely to operate outdoors, subject to the variations of environment and weather. In order to cope with these disadvantages, collector materials have to be much harder, denser and more abrasive than brush materials.