Safety Management of Rolling Mill
Fig. 12.1 Cobbles in a Structural Mill.
Accident Prevention Regulations in the Rolled Metal Production
Potential hazards from rolling come from heat radiation, high travel speeds of the worked metal, concentration of moving and rotating mechanisms in the operating area. It is also due to scattering of scales and shavings during shearing, sawing and conditioning the metal.
Safety regulations for the operation of crane, railway transport, for repairs, servicing of gas, electrical and oxygen facilities are the same as for the entire iron and steel industry. Great importance is attached to protective garments for workers of different trades, including means of individual protection (protective goggles, deflectors, nets, helmets, asbestos cover plates, special gloves, shoes and so on). Heat radiation is controlled with the help of water net screens, curtains, safety glasses. Much attention is paid to different ventilating, blowing-off and ah conditioning systems.
Moving and rotating mechanisms are guarded with special shrouds.
Finishing and high speed working stands are reliably protected on the sides and at the top by means of removable wire guards.
In rolling mill shops the access to standing mechanisms, rolling trains and working stands should be made absolutely safe. To this end the so-called tag system is mainly used, i.e., handing to the electricians of a division a tag taken off a corresponding starting device and serving as a pass, this confirming that the electrical circuit of the given mechanism or of the entire division has been disconnected. Special interlocks, signaling devices and mechanical shutters serve as duplicating safety arrangements. Various safety devices (guard posts, ledges, deflectors) are used to protect the tandem rolling mill operators.
In rolling mill shops safe, clearly definable passages are made in the form of overhead bridges with railings or of tunnels.
Care should be taken to ensure good lighting, proper metal stacking and timely removal of rejects.
Varying operating conditions of rolling mills require working out of particular additional safety regulations in the form of production instructions which should be strictly adhered to.
Quality Management in Rolling Mills
Quality concept of Products
Quality existed in every walk of life, many decades ago; but the concept upon which this discipline exists has assumed enormous importance in the recent years. What is this ‘Quality’ of Products and What does it mean? The simple answer is of all the concepts in Quality or Quality function; none is so far- reaching or important as “Fitness for use”. All industries are managed by human beings with one objective of providing quality products or quality sendees to human being. This becomes positive and constructive only if the goods and sendees respond to the overall needs of the user in price, delivery time and fitness for use. If the goods and services do respond to these overall needs, the products are said to possess “Marketability or Salability”. But against the overall needs, the extent to which the product services the purposes of the user during usage is known as “Fitness for use”. The concept of fitness for use is properly called by such name as “Quality” is a universal concept applicable to all goods and sendees. “Fitness for use” of the product is mainly determined by the features of the product which the user can recognize as beneficial to him. The ‘Fitness for use’ is the resultant of some well-known parameters.
A customer is one who buys a product from another. But the customer is also the user. User is one who receives the intended benefit of the product. The buyer of services is often called a client. Consumers are individuals or groups who consume goods for personal purposes. To the economist these are products and services and the user is interested only in servrees. To the Technologist, the responsibility is to produce products ‘Fit for use’ economically with the maximum.
Reliability, Availability and Maintainability of Products
In true sense, the product should never fail and its availability should be 100%. But in actual practice products do fail, so that an essential sub parameter of availability, i.e., freedom from failure is formed as Reliability. In other words reliability is the probability of performing without failure, a specified function under given conditions for a specific period of time. Let us take hot rolled products like rails for railways, structures for bridges, rods for buildings etc. the quality involves, use for long time or in other words their products should have maximum reliability, which means they should have the quality properties of materials. Another term ‘Operation Reliability’ is used often to mean the attained reliability. Reliability is not to be confused with conformance to product specifications but it is also the actual use of the product over a period of time plus collection and interpretation of data on performance and failures during that period.
Hence, the important factors which are to be considered, are the (a) Availability and (b) Maintainability. A product is said to be available, when it is in service or in an operative state. The total time in operative state called as “up time” is the sum of time spent in active use, similarly the total time in the non-operative state called as “down time” is the sum of the tune spent under active Repair (diagnosis and Repair) and waiting for Spare parts etc.
Maintainability is the need for continuity of sendee which is the effort to improve the maintenance of long life products.
Inspection: Work of check the product for size, height, quality and any other specifications.
Accuracy of inspection = % of defect correctly identified,
cl is the number of defects reported by Inspection, k is number of good units rejected by inspectors, as determined by check inspection, cl - к true defects found by Inspector; b is the defects missed by the inspector, as determined by check inspection. d-к + Ь will be true defects originally in the product.
Suppose, the number of defects reported by inspection d is 45, and out of this 5 were found to be good by check inspector i.e., к = 5. Hence, d-k = 40, which is the true defects found by Inspector i.e.,d-k + b = 50 (i.e. the 40 found by the Inspector + 10 he missed).
Standards Specifications: All products produced, manufactured and sold to customers for whole end use, requirements are well understood, studied and basic quality requirements are published in codes known as ‘Standards, or Specifications either by Government agencies or various trade agencies.