Operation, Safety and Quality Management
Principal Elements of the Operation Management
The following are the principal elements of the operation management in a rolling shop:
- 1. Keeping a steady eye on the stability of the rolling process parameters : optimum metal heating cycle, rolling temperature range, rolling rhythm and speed, standard conditions of deformation (reductions and tensions in rolling), working surface condition of the rolls and roll fittings, roll cooling (or lubrication) conditions and conditions of descaling on the metal surface.
- 2. The stability of the rolling process is controlled by means of pyrometers, ammeters (load indicators), dynamometers and tachometers. Hourly rolling schedules and continuous short time testing of final intermediate samples are used to regulate the rolling process including pass and roll changes.
- 3. Preparatory operations for the production, viz., preparing billets for rolling in accordance with monthly, weekly, daily and hourly schedules and getting the mill ready for the operation (preparing sets of rolls for roll changes, as well as roll fittings, straightening rolls, blades and special equipment).
- 4. Repairs of furnace installations and of processing and auxiliary equipment of rolling mills (regular schedule, duration, characteristics of repairs and methods of their organization). Long interval repairs called general overhauls or capital repairs. The periodicity of overhauls may be varied. Lengthy shut downs of rolling mills once a year, adopted habitual generally by most of the rolling mills, cannot be considered as a good practice. A method of fractional overhauls with large scale restoration including modernization of the equipment earned out during running repairs and preventive maintenance should be considered more expedient. Running repairs are made one to five tunes every month, depending on the characteristic features of rolling mills and conditions of the repair sendee management at the works. A method of repairs involving the replacement of whole units or assemblies is a progressive one. Preventive maintenance between shifts and during roll changes includes, in addition to minor repairs, tightening of screwed joints, lubrication and checking of the equipment.
It is expedient that the rolling mill repair crews be integrated so as to form the so-called specialized and centralized repair groups, especially at large works.
- 5. Introduction of the system of efficiency engineering in rolling mill shops, to provides for proper allocation of jobs, multi-specialization of workers, no duplication of functions, gradual elimination of labour-consuming operations, introduction of industrial closed-circuit television systems, automation of production processes, automation of the production management and control including job rating, wage accounting etc.
- 6. Planning and recording of expenditures on basic and auxiliary materials, recording of fuel, power and water consumption, of replacement equipment, rolls, repair services, of semi-finished products, work pieces in production, waste and finished products, alongwith the day-to-day calculation of the actual rolling and final costs.
In a well-managed rolling mill shops the routine production conditions are determined not only by the technological instructions, but also by flow charts drawn upon the basis of optimum process parameters for each type of rolled product. With the improvement of the production techniques these charts are subject to revision. The preparatory stage for the actual production, as well as primary records of the process parameters are regulated by the programmed sequence of rolling operations, hourly rolling schedules and time tables for roll changes, production changeovers and replacements of roll fittings, bearings and shearing blades.
Technological Instruction on Preparation of Rolls and Rolling in Light Structural Mill
(a) Planning & Preparation during planned roll changing
- 1. Preparation of rolls.
- 2. Preparation of roll tackles, filter inserts ,guards for each stand and for each profile, entry and exit boxes, guides for the boxes, inserts for finishing stand, other tools and devices.
- 3. Preparation of rollers of straightening machines, rollers and tools for the same.
- 4. Preparation of cold shears, shear blades for different profiles.
- 5. Roll changing is to done as per the rolling programme. Preparation of rolls and roll tackles and rolling programmes. Preparation of rolls and roll tackles and roll changing programme is prepared by I/c (Operation).
In charge (operation) should have following Information:
- 1. The stock of rolls for different profiles, placement of orders for new set of rolls. In charge (operations) should have the list of womout rolls to be sent to roll turning shop for redressing and schedule for getting them back for further use.
- 2. The stock of roll tackles, develop new roll tackles for new profiles, get the womout roll tackles replaced/modify the existing roll tackles, if necessary.
- 3. The preparation of roll changing programme, as per profile, which should see that the combination of passes in different sets of rolls so that the roll changing of different stands can be reduced and rolls can be economically used.
- 4. In charge (operation) should see that the rolling scheme of the profile to be rolled should reach to Mill Foreman (operations) in time. Any change in the rolling scheme or any modification of passes for better result should be intimated to Mill Foreman.
- 5. In charge (operation) should select sets of rolls for rolling. And give these rolls to bearing shop for the assembly of bearings. Spare rolls are also to be given to meet the emergency.
- 6. In charge (operation) should see the condition of passes of different rolls before bearings are fitted.
- 7. In charge (Mech.) should see that these rolls are ready with bearings fitted at the time of requirement.
- 8. In charge (operation) should see that the furnaces are to be filled with the required quality and size of billets before the start of Mill for profile changing. This job will be done by Shift Managers as per the instruction of In charge (operation).
In charge (Finishing & Shipping), should have following information
for the preparation of straightening machine rollers and shear blades:
- 1. The stock of rollers for each profile. He should order for new rollers when old rollers became under-sized, it become soft. He should send worn out rollers to the roll turning shop for redressing and get them back in tune for further use.
- 2. He should know the stock of Shear Blades for different profiles. He should arrange the replacement of old, broken chipped off blades by new ones.
- 3. He should earmarked rollers and shear blades, which will replace the changing rollers in straightening machine and changing of blades of shears.
- 4. In charge (Mech. - F&S) should see that condition of chain transfers, rope transfers and other equipments which will be in use for the profile should be in good condition.
- 5. hi charge (Elect. - F&S) should see that the condition of Electrical equipments which will be in use for the profile should be upto the mark.
- (b) 1. Planning and Preparation during breakdown
- 1. In case of roll breakage or urgent roll changing, the command for roll assembling can be undertaken by the Shift Manager of that particular shift, with the consent of the In charge (operation). Before the start of roll changing, passes of the assembled rolls should checked carefully to see the condition of pass and whether the correct pass is marked, especially in case of finishing stands rolls for beams and channels. If the pass is found defective. Foreman (operation) should see that these passes are not used. He should inform to the in charge (operation).
- 2. Shift Manager should co-ordinate the roll changing and other jobs in such a way, so that all help and co-operation is available from all sides (Mech. Elec, opm.) to finish the work satisfactorily in time.
- 3. Furnace staff should be intimated, about the probable time the job of roll changing will be taken for change over. Foreman (operation) should be made responsible for carrying out this job with the consultation to Shift Manager.