Classification of Materials and Types of Classifiers...

Classification of Materials and Types of Classifiers Size control of particles finer than 1 mm, are out of the practical range of conventional screens. Separation of such particles is carried out by classification. Classification implies the sorting of particulate material into different size ranges. It is a method of separation of fines from coarse particles and also lighter particles from heavier particles. The two product streams resulting from any classifiers are (i) a partially drained fraction containing the coarse particles, and (ii) a fine fraction of particles. Usually the principle of the classification is based upon the various densities, specific gravity, terminal falling velocities of particles in liquid and in air. Classification is defined as a method of separating mixtures of mineral particles into two or more products according to their settling velocities in water, in air or in other fluids. Classification is performed on the basis of the velocity with which the material particles fall through a fluid medium generally water or air. In view of the fact, that the velocity of particles in a fluid medium is dependent not only on the size, but also on the specific gravity and shape of the particles. In classifiers, use is made of the different rates of movement of particles of different sizes and densities suspended in a fluid and differentially affected by imposed forces such as gravity and centrifugal fields, by making suitable arrangements to collect the different fractions as they move to different regions. Based on their separation principles, classifiers are classified into two major types. They are (i) wet classifiers, and (ii) dry classifiers. Wet classification with hydro-cyclones using separation by centrifugal force typically covers the size range of 10 micrometers to 100 micrometers while wet classification with spiral classifiers using separation...

Management of Security in a Steel Plant...

Management of Security in a Steel Plant The operation of a steel plant requires careful attention to safety, security and safeguards. Security is aimed at preventing intentional acts that might harm the steel plant or result in the theft of materials. Security personnel play a very important role in the steel plant and they are an integral part of the management team. The levels of control required to be provided for security of the steel plant are to be suitable and to meet the threat environment, give proper protection to information, people and physical assets, and to provide assurance to management, employees and various agencies working in the steel plant about safe and secure environment. Fundamental to security is the concept of risk. The risk is ‘a threat or hazard assessed for likelihood and impact’. A threat is ‘an event with negative consequences, brought about through malicious human intent’. A hazard is ‘an event with negative consequences, brought about through natural, environmental or non-malicious human intent’. Steel plant security system is to be based on the physical security mitigation measures to protect people and physical assets on their identified risks. The measures are to reduce the security risks to acceptable levels in the plant by providing minimum controls determined by the impact level of the security risks. Controls needed for the secure operation of the steel plant are to take into account threats which are there both from outside as well as from inside. There are four types of security (Fig 1) that are provided in the steel plant. These are namely (i) preventive security, (ii) protective security, (iii) detective security and (iv) punitive security. The security measures in the steel plant are distinguished from the ‘safety’ functions which aim at protection from damages...

Basics of Tribology Oct31

Basics of Tribology

Basics of Tribology Expenditure on machine condition monitoring and maintenance constitutes a significant cost in a steel plant. Tribology helps in reducing this expenditure. Tribology is a new word coined by Dr. H. Peter Jost in England in 1966. ‘The Jost Report’, provided to the British Parliament – Ministry for Education and Science, indicated ‘Potential savings of over £ 515 million per year for industry by better application of tribological principles and practices’. But tribology is not a new field. Tribology comes from the Greek word, ‘tribos’, meaning rubbing or to rub. And from the suffix, “ology” means the study of. Therefore, tribology is the study of ‘rubbing’, or ‘the study of things that rub’. Tribology is the science and technology of interacting surfaces in relative motion. It is the study (Fig 1) of (i) friction, (ii) wear, and (iii) lubrication. Fig 1 Study of tribology Tribology is the science and technology of interacting surfaces in relative motion and is commonly known as the study of friction, wear and lubrication. It is the science and technology of friction lubrication and wear and is of considerable importance in material and energy conservation. It is an old knowledge of great importance when it comes to everything in movement but as a scientific discipline tribology is rather new. Tribology, although one of the oldest engineering discipline, it is one of the least developed classical sciences to date. The reason is that tribology is neither truly a single discipline nor well represented by steady state processes. It involves all the complexities of materials. Tribology is multidisciplinary in nature, and includes mechanical engineering (especially machine elements as journal and roller bearings and gears), materials science, with research into wear resistance, surface technology with surface topography analysis and coatings, and...

Screening of Materials and Types of Screens...

Screening of Materials and Types of Screens Size control is done (i) to prevent undersize in the feed from blocking the next size reduction stage (scalping), (ii) to prevent oversize from moving into the next size reduction or operation stage (circuit sizing), and (iii) to prepare a sized product (product sizing). There are two methods dominating size control processes. They are (i) screening using a geometrical pattern for size control, and (ii) classification using particle motion for size control. Screening using geometrical patterns for size control (Fig 1) makes use of screening media made of bars, wires, and panels with holes usually rounds, squares, rectangle aligned to length and rectangle aligned to width. Fig 1 Geometrical patterns for the size control Screening is the process of separating solids into two or more products on basis of their size. The objective of screening is size control. The purpose of screening is to separate from a granular substance particles that are smaller than the screen opening from those that are larger. This is not as simple as it sounds, and the difficulties compound as the opening becomes smaller. This can be done dry or wet. Action of screening is aided when screen is subjected to some kind of motion, reciprocating or gyratory in the horizontal plane, or shaken with a reciprocating motion having both vertical and horizontal components. The minus particles pass through the screen at a diminishing rate until all but the particles closest to the opening size have been separated out. The time duration of the shaking to reach this stage is roughly proportional to the amount of the material on the screen. The performance of screens falls back on three main parameters namely (i) motion, (ii) inclination, and (iii) screening media. It is...

Management of Occupational Health in Steel Plant Environment...

Management of Occupational Health in Steel Plant Environment Occupational health is an activity which deals with the protection and promotion of the health of the employees by preventing and controlling occupational diseases and by eliminating occupational factors and conditions hazardous to the health of the employees at work. It deals with the development and promotion of healthy and safe work, work environments and work organizations. The objectives of occupational health are to enhance the physical, mental and social well-being of the employees and support for the development and maintenance of their working capacities. Management of occupational health aims at the following. To prevent, eliminate, control and treat the diseases/ disorders arising out of occupation To participate in the prevention of the physical, chemical, biological, mechanical, and psychological hazards at workplaces, closely working with the shop floor team To plan with evidence based data to place the employees on safe jobs, so as to achieve the benefits which are mutually beneficial both to the employees and the steel plant To promote positive health among employees through continuing health education Management of occupational health of the employees in steel plant is ‘the science and art devoted to the anticipation, recognition, evaluation, and control of those environmental factors or stresses arising in or from the workplace, which may cause sickness, impaired health and well-being, or significant discomfort among the employees. It is essential in steel plant that an occupational health centre is established in or near a place of employment for (i) protecting the employees against any health hazard arising from work or conditions in which work is carried on, (ii) contributing towards the employees’ physical and mental adjustment, and (iii) contributing to establishment and maintenance of the highest possible degree of physical and mental well-being of...