One of the biggest challenges for manufacturing businesses is reducing wastes. So what is waste? Waste is defined as any activity that does not add value from the customer?? perspective. This wastage is not just inefficiency in terms of cost and return on investments (ROI), it also has a direct impact on the sustainability of a business. The waste of resources, directly or indirectly, impacts every factor in the manufacturing process and its efficiency. The War on Waste (WOW) must, therefore, be waged at multiple fronts to make a noticeable and measurable impact. The key will lie in leveraging technology to plan, implement, improve, and monitor process optimisation. Industry 4.0 will be dictated by the need to eliminate waste and the removal of non-value added (NVA) activities from the manufacturing process.
What is War on Waste?
The fight for reducing wastage is almost as old as the history of manufacturing. Some amount of wastage is inevitable and often written off as part of the production costs. However, the struggle to contain waste kicked in as soon as manufacturers realised that reducing waste was a more efficient way of increasing their profits as opposed to raising prices. Today the aim for reducing waste is not just about the profit margins. Modern producers also see it as a sustainable practice that must be followed as part of responsible manufacturing. The concept of WOW is a multifaceted approach that focuses on eliminating waste, optimise processes, cut costs, boost innovation, and reduce time in the ever-changing global and local marketplace.
The ultimate goal of practicing WOW isn?? simply to eliminate waste ??it is to sustainably deliver value to the customer. To achieve this goal, WOW defines waste as anything that doesn?? add value to the customer. This can be a process, activity, product, or service; anything that requires an investment of time, money, and talent that does not create value for the customer.. Idle time, underutilised talent, excess inventory, and inefficient processes are all considered waste under WOW concept. It provides a systematic method for minimising waste within a manufacturing system while staying within certain margins of control such as productivity and quality.
Where the traditional definition of waste included ??nything consumed in excess of what is needed for our survival and comfort?? this modern approach sees waste as a ??on-value-added activity that is not beneficial to the consumer, either directly or indirectly?? The distinction here must be made between NVA that is beneficial to the consumer (e.g. quality check processes) and activities that are not beneficial to the consumer (e.g. delayed raw material supply). WOW does not focus exclusively on waste reduction, but waste is minimised or eliminated more as an inevitable byproduct of better production flow. There are numerous areas of waste that go overlooked. WOW typically focuses on seven key wastes:
Wastes in Transportation
Wastes in Inventory
Wastes in Motion
Wastes in Waiting
Wastes in Over-production
Wastes in Over-processing
Wastes in Defect
Once the waste in these areas is identified, a centralised and well-planned approach must be adopted to address these systematic deficits. While some solutions may need tweaking or re-hauling of processes, others may need additional equipment. The cost of process disruption or new equipment is usually offset by the cost-efficiency brought in by the reduction in wastage.
Wastes in Transportation
The wastage of time and resources during the transportation of products/items and information results in a direct loss. Waste in transportation is most likely to occur while the product is in process and needs to be transported over a great distance for its finishing process or in between different warehouses. In the case of information, the wastage is usually during dissemination.
Solution: Waste in transportation at our plant is addressed through the reduction of transit losses at multiple points. This includes clinker, cement, and all other required raw materials, controlling transit damage of cement bags during road and rail dispatch, bringing down raw material and semi-finished goods carpet loss during storage and handling, reduction in demurrage hours & multiple handling inside the factory.
Wastes in Inventory
Any excessive product, service, or information comes under this category for example raw material, semi-finished goods, and final products. It may result in depreciation of material quality or parts and would require additional storage and transportation costs. There are other associated costs, such as wastage of rented godown and working capital. Wastage in inventory is often indicative of internal deficiencies like unbalanced production, delay in material delivery, inadequate supply planning, and unused machine capability.
Solution: To reduce waste in inventory, start with identifying ways to use slow-moving and non-moving spares and scraps. This is followed by an evaluation of the process of disposal of scraps. Once the gaps are identified, the process of optimisation starts with liquidating idle assets and reducing rented godown area.
Aim to manage the operation with lean inventory in terms of raw material, finished goods and semi-finished goods.
Wastes in Motion
Excessive movement of material and personnel during manufacturing indicates that there is an unproductive process that can be shortened, thereby reducing the time taken and any deterioration of quality. This also results in inefficient manufacturing.
Solution: Typically a time and motion study is conducted to identify and measure the different steps required in a process. Once the wasteful procedures are identified, a standard time and motion can be fixed for every process, leading to more efficient inter-warehouse movement and the reduction in sub-optimal cement movement. It can also help in addressing shortages in transit. Internal raw material handling is a key challenge in the cement industry, reduction in internal handling by optimum movement helps to minimise cost and wastage.
Wastes in Waiting
This includes the time wasted while waiting for a product, equipment, or information. It means an immediate loss of time and may impact the overall quality standards of raw material, semi-finished and finished goods. Wastage in waiting is indicative of unbalanced processes where one process takes longer than others so that a worker has to wait until they can fulfill their task. Wastage occurs only if the worker is not engaged in pre-planned and productive work while waiting.
Solution: Proper planning of raw material and finished goods helps to reduce bunching of rakes leading to less demurrage cost. Effective scheduling of shutdown, reduced waiting time between activities helps to reduce shutdown time and improve production.
Wastes in Over-production & Processes
Inaccurate estimation of demand or starting the production too soon can cause over-production. This is perhaps seen as the worst type of waste. It also leads to excessive inventory, resulting in wastage and deterioration of quality of semi-finished and finished products. Since the end product is in excess, the production process also becomes unnecessary, involving wastage of energy, raw material, resources, manpower, and time. It also indicates multiple process gaps.
Solution: Managing a proper production schedule will avoid over production. Inaccurate forecasting and demand information leads to higher production. So, projecting proper forecasting & planning gives better accuracy of production plans. For example- A warehouse filled with product that does not sell or has not sold.
The process starts with identifying over-processed products or services. The focus must be on minimising any excessive use of energy, fuel, water, and generation of fugitive dust while processing.
Wastes in Defect
Finally, there are mistakes and defects in the production process that must be eliminated or re-hauled completely. All repairs and inspections that do not add value to the final product must be treated as waste.
Solution: Multiple avenues must be explored in identifying defects and damages. There are various indicators of defective processes, such as customer complaints and product non conformity. It?? always advisable to avoid defects to reduce waste and increase efficiency.
WoW implementation process
To be successful, a process must be codified with well-defined Standard Operating Procedures (SOPs). WOW typically follows the following steps:
Observation of the various processes/products/services.
Identification of the wasteful practices or defective processes/products/services.
Analysis of the processes/products/services to determine the ideal outcome.
Exploring internal and external solutions. It can include a new technique, equipment, or tech support. Alternatively, it may require a readjustment of procedures.
Carrying out cost studies to determine the effectiveness of the alternative processes to identify the most suitable solution.
Carrying out a test run of the new process to understand its challenges and effectiveness.
Establishing the new process across the plant or the chosen area in a well-planned manner.
Educating employees and staff on the new procedures. This will include a clear enunciation of the SOPs. For the successful implementation of any change in tasks, it is also critical to explain the reason for the change and how it can benefit everyone.
The war on waste must be a continuous, multifaceted, and planned battle. Manufacturers can create highly desirable byproducts by following these principles of WOW, adopting these tools, and reducing these key wastes. WOW results in certain agility in meeting the competitive demands of a swiftly evolving marketplace. The focus on total expense and value rather than on single component costs not only eliminates waste and inefficiency, it also promotes quality and customer-driven solutions.
WOW?? seven key focus areas:
Wastes in transportation
Wastes in inventory
Wastes in motion
Wastes in waiting
Wastes in over-production
Wastes in over-processing
Wastes in defect
WOW Implementation process in eight steps:
Observation of the various processes/products/services.
Identification of the wasteful practices or defective processes/products/services
Analysis of the processes/products/services to determine the ideal outcome
Exploring internal and external solutions
Carrying out cost studies to determine the effectiveness of the alternative processes
Carrying out a test run of the new process
Establishing the new process across the plant or the chosen area
Educating employees and staff on the new procedures
Philosophy of High Strength Cement/Concrete
Dr S B Hegde, Professor, Pennsylvania State University, USA, delves into the aspects of durability and sustainability of high strength concrete.
The world is passing through difficult and troubled times, and we live in a rapidly changing world. The construction industry is facing many challenges – global warming, climate change forces and the capability to achieve sustainable development and economic progress without damaging our environment. The concrete industry in particular faces further challenges. There is extensive evidence to show that concrete materials and concrete structures all over the world are deteriorating at a rapid rate, and that we are unable to ensure their long-term durable service life performance.
To confound this situation, we are also faced with an urgent need to regenerate our infrastructure systems if we are to eradicate poverty and provide a decent ‘quality of life’ for all the peoples of the world.
Durability vs strength
This paper shows that the current emphasis on high strength and very high strength, and the design philosophy of durability through strength for concrete materials and concrete structures is fundamentally flawed. It is this misleading concept and vision that is primarily responsible for the lack of durable performance of concrete in real life environments.
Making it last longer
This intuitive association of strength with durability is again partly due to the current Ultimate Strength Design approach which creates an implicit belief and illusion that if concrete is proportioned to give high compressive strength, and then, if prescriptive code specifications in terms of cement content, water/cementitious materials (w/cm) ratios, types of cement, steel cover thickness and types and amounts of mineral and chemical admixtures are adhered to, then somehow the durable service life of the concrete structure will be automatically and adequately assured.
About the author: Dr S B Hegde, Professor, Pennsylvania State University, United States of America.
Fuel for Thought
As the world moves towards novel exchange denominators like cryptocurrency, the cement industry is busy battling one of the oldest currencies in the world – fuel.
With the war between Russia and Ukraine continuing to rage, fuel prices have hit the roof, as can be seen from the rising cost of pet coke, diesel, freight and energy, which are important factors for cement manufacturing and mobilisation. The most likely scenario would have been a resulting increase in cement price, however the price correction did not follow through and the cement sector witnessed flat rates in May and a dip in prices in June across India. This has adversely affected the profitability of cement. Amid elevated costs of raw materials and decrease in demand, Emkay Global Financial Services has cut its earnings before interest tax depreciation and amortisation (EBITDA) estimates for the sector by 5-6 per cent for FY 23/24/25.
Apart from this, currently sustainability is also detrimental to cost efficiency for cement companies. Green energy initiatives, such as alternative fuel and raw materials (AFR) and waste heat recovery system (WHRS), are adding to the production costs. These costs are not getting translated into price hike, leaving the cement makers to bear the brunt. However, sustainable production and net zero targets are not to be toyed with, and each player has to put in their best effort. With regards to input costs, experts are hopeful of price corrections through rise in demand for cement in the months to come.
All eyes are right now on Russia, thanks to the compelling need to sourcing fuel from low-cost destinations. Giants from the steel and power industries are already dealing with Russia for its pulverised coal. India has also shown an interest in increasing its import of thermal and coking coal from Russia, and is estimated to import 40 million tonnes tonnes by 2035.
Corrections in pricing and innovations in raw materials and alternative energy might be at different ends of the spectrum but they are bound to have a long lasting impact on cement companies, as each player puts in their best effort to win this fuel fight.
Blended Cement Grinding: Energy Intake and Fineness
ICR delves into the nuances of the grinding processes to understand its impact on energy consumption, quality of output and technology as well as the methodology of producing green cement.
The early adopters of the cement grinding process involved extracted clinker from the clinker tank and transported it to the cement mill hopper by belt conveyors, where a measured quantity of clinker and gypsum was fed into a closed-circuit ball mill and OPC was produced through inter-grinding and blending of 95 per cent clinker with 5 per cent gypsum.
The initial problem was coarseness, as 20 per cent over 100-micron diameter was part of the ground cement. Today with advancement of technology the fineness has been improved (3200 gm/square cm) by adopting specialised steel in the grinding equipment, together with use of grinding media, steel balls where material fed through the mill is crushed by impact and ground by attrition between the balls. The grinding media are usually made of high-chromium steel. Fineness is a controlled parameter for cement to ensure better hydration and strength development. Ground cement is then stored in a water-proof concrete silo for packing.
Making Cement Green
The rise of blended cement, starting from use of fly ash (30 per cent to 35 per cent) in PCC and blast furnace slag (65 per cent to 70 per cent) in slag-based cement, as an additive with clinker, together with 5 per cent gypsum, made the introduction of green cement as a better environment friendly product. The use of fly ash or blast furnace slag with clinker created avenues for commercial consumption of coal-fed pPower plant waste (fly ash) and steel blast furnace waste (slag) leading to the green cement that used 60 per cent of clinker in PCC and 35 per cent clinker in slag based cement.
This development has seen progressive increase of both fly ash and slag in the ground cement as well as in concrete, where fly ash or ground slag is added to OPC at the concreting stage. Such processes had enormous logistics challenges and in India the adoption of such a process during concreting is less prevalent.
Grinding a mixture of clinker with the fly ash or slag, together with gypsum has implications of cost stemming from use of electricity for grinding and landed cost of all inputs for the grinding process. Cement grinding is the single biggest consumer of electricity in the entire manufacturing process of cement, the rest is in the grinding of limestone in the crushers and in the fuel mills for grinding fuel used in the clinkerisation process. Finished grinding may consume 25-50 kWh/t cement, depending on the feed material grindability, additives used, plant design and especially the required cement fineness.
The grinding process absorbs more energy due to the losses attributable to heat generated during grinding, friction wear, sound noise and vibration. Less than 20 per cent of energy absorbed is reckoned to be converted to useful grinding: the bulk is lost as heat, noise, equipment wear and vibration. For ball mills, only 3 to 6 per cent of absorbed energy is utilised in surface production, the heat generated can increase mill temperature to more than 120⁰ C and causes excessive gypsum dehydration and media coating, if mill ventilation is poor.
Understanding the Process
There are four types of grinding mills in use today are:
Ball Mill (BM): Predominant despite higher energy consumption partly because of historical reasons but partly also because it still offers considerable advantages over other mills, often operating with roller press for pre-grinding or in combined grinding.
Vertical Roller Mill (VRM): Gained popularity in the last decade due to lower energy consumption and higher capacity, with relatively few plants in service.
Roller Press (RP): A more recent choice especially after the advent of the V-separator and improved roller life, offers the lowest energy consumption but even few plants in service.
Horizontal Mill (HM): A very few in service and found mainly in companies related to the
The chart below shows the relative power consumption for the different types of grinding process:
The implications of higher cost in installation, maintenance, operating cost, availability and quality of ground cement, makes the BM still the most common type of technology used, while VRM scores on electrical consumption.
The role of grinding media cannot be ignored in this entire process of grinding. The BM is a horizontal cylinder partly filled with steel balls (or occasionally other shapes) that rotates on its axis, imparting a tumbling and cascading action to the balls. Material fed through the mill is crushed by impact and ground by attrition between the balls. The grinding media are usually made of high-chromium steel. The smaller grades are occasionally cylindrical (‘pebs’) rather than spherical. There exists a speed of rotation (the ‘critical speed’) at which the contents of the mill would simply ride over the roof of the mill due to centrifugal action. The critical speed (rpm) is given by: nC = 42.29/√d, where d is the internal diameter in metres. A BM is normally operated at around 75 per cent of critical speed, so a mill with diameter 5 metres will turn at around 14 rpm.
The mill is usually divided into at least two chambers (although this depends upon feed input size – mills including a roller press are mostly single-chambered), allowing the use of different sizes of grinding media. Large balls are used at the inlet, to crush clinker nodules (which can be over 25 mm in diameter). Ball diameter here is in the range 60–80 mm. In a two-chamber mill, the media in the second chamber are typically in the range 15–40 mm, although media down to 5 mm are sometimes encountered. As a general rule, the size of media has to match the size of material being ground: large media can’t produce the ultra-fine particles required in the finished cement, but small media can’t break large clinker particles. Mills with as many as four chambers, allowing a tight segregation of media sizes, were once used, but this is now becoming rare.