ABHIJIT DAS, BE(Elec)
CONSULTING ENGINEER ON RUBBER/PLASTIC INDUSTRIES
In today’s cut-throat competition in manufacturing sector, reduction of operational costs has become imperative. Rubber industry too is witnessing significant developments in this aspect globally. We will enumerate and study a few of them here.
- Good in-process testing systems ensure that WIP beyond desired specs do not move forward in the manufacturing chain , thereby saving the cost of waste/scrap and recycling. A good quality management system on the shop-floor which ensure best practices need to be incorporated. TQM, Kaizen or Six Sigma practices have been successfully implemented to achieve minimum defect generation. Common rubber industry testing machines are tensile testers, hardness testers, abrasion testers, rheometer, viscometer and flex testers, aging ovens etc.
- It is imperative to have processes under control so that no material is wasted or over-used in shop floor.
- All fine chemicals to be stored properly in clearly designated areas so that no spillage, wear and tear of packaging materials occur.
- Raw material ingredients, when being handled during batch making should be done on elevated platforms, on large trays, so that residual quantities can be retrieved back after a particular operation and be reused.
- House-keeping and cleanliness should be properly maintained in all mixing areas like kneaders/open mills. Under trays should be properly maintained under open mills, so that all residual crumb compounds can be retrieved back.
- Sweeping compounds in mixing area floor should be retrieved back and mixed in small proportions with virgin batches so as to utilise them as well.
- Spew and flash recycling technology according to the nature of polymer should be well-defined, so that all flash can be recycled into the system through incorporation in virgin batches in small proportions.
- Reclaiming of scrap rubber is the most desirable approach to solve the disposal problem. Reclaim is produced from vulcanized rubber granules by breaking down the vulcanized structure using heat, chemicals and mechanical techniques. Reclaim has the plasticity of a new unvulcanized rubber compound, however, the molecular weight is reduced so reclaim compounds have poorer physical properties when compared to new rubber. The main reasons for their use are price and improved processing of rubber compounds. The main processing advantages claimed can be summarised as: - shorter mixing times - lower energy consumption - lower heat development - faster processing on extruder and calenders - lower die swell of the unvulcanized compound - faster curing of the compounds.
- Recovered rubber can cost half that of natural or synthetic rubber.
- Recovered rubber has some properties that are better than those of virgin rubber. Though it undergoes double vulcanisation, small granule sizes ensure better surface area and hence better bonding with parent material. Ideally, for inert filler loaded compounds, we can use upto 35 % and for reinforced filler loaded compounds, we can use upto 15 % of recycled rubber with virgin material.
- Producing rubber from reclaim requires less energy in the total production process than does virgin material.
- Every rubber industry has to review its electrical energy and fuel energy cost for economic viability :
- Review of Electricity Bills, Contract Demand, Power Factor, Load Factor, No load losses of machineries for the last one year, in which possibility will be explored for further reduction of contract demand and improvement of power factor by installation of capacitor banks, ac line reactors, variable frequency drives. Implementation of TOD meters to take advantage of variable electrical unit cost at different times of the day.
- Study of Motors and Pumps Loading : Study of motors in terms of measurement of voltage (V), Current (I), Power (kW) and power factor and thereby suggesting measures for energy saving like reduction in size of motors or installation of energy saving device in the existing motors. Temp rise and voltage imbalance study, no load study of motors, proper rating choice will lead to energy savings. Study of Pumps and their flow, thereby suggesting measures for energy saving like reduction in size of Motors and Pumps or installation of energy saving device in the existing motors / optimization of pumps. Proper maintenance standards of impellers, bearings, seals, lubrication and alignment; wear monitoring and vibration analysis, reduction of throttling losses, pressure/flow monitoring; reduction of heads, proper pipe sizing etc will lead to considerable savings.
- Energy savings in enclosed chamber and open mill mixers by improvement of power transmission systems and incorporation of variable frequency drives.
- Energy savings in vulcanisers by implementation of correct heat generation and transfer technologies.
- Performance Evaluation of Boilers: This includes detailed study of boiler efficiency, Thermal insulation survey and flue gas analysis. Condensate recovery, scale removal, boiler blowdown heat recovery will ensure energy savings.
- Performance Evaluation of Air Compressor: This includes detailed study of Air compressor system for finding its performance and specific energy consumption. Plugging of leakages, proper maintenance to ensure proper gradient in line, installation of electronic condensate drain traps for removal of condensate, reduction of inlet air temperature, choice of proper dryer, heat recovery unit etc.
- Evaluation of Condenser performance: This includes detailed study of condenser performance and opportunities for waste heat recovery.
- Illumination: Study of the illumination system, LUX level in various areas, area lighting etc. and suggest measures for improvements and energy conservation opportunity wherever feasible.
- Proper blade alignment in fans will give considerable savings.
- DG Set: Study the operations of DG sets to evaluate their average cost of Power Generation, Specific Energy Generation and subsequently identify areas wherein energy savings could be achieved after analysing the operational practices etc. of the DG sets.