A recent back to basics project undertaken by ArcelorMittal Dofasco to ensure the accurate measurement of coal bulk density is proof that operational improvements in this case a 35% reduction in oil requirements are possible without a large capital investment.
Coal bulk density is a key process parameter for oven charging that, when kept to a constant target level by constant screw feeder counts, allows for the same amount of coal to be charged into each oven. The two factors affecting coal bulk density are coal moisture and coal grind.
Previously, to control the amount of oil added to its coal to reduce the impacts of coal moisture variation, ArcelorMittal Dofasco used a measurement cone size of 4.5in, but that was proven to be insufficient when coal moisture content was greater than 7%. Because of that, the company recently redesigned the measurement apparatus to have an 8in cone, which was found to be more reliable to measure moisture contents of up to 13%.
Also, as part of its latest project, ArcelorMittal Dofasco changed the size of its collection box from 12in by 12in, which, when full, could weigh up to 50 pounds and therefore could present health and safety challenges for workers manually lifting that box to one that is 8in by 8in in size and weighs only 35 pounds when full.
ArcelorMittal Dofasco also implemented a new oil addition system with redesigned spray headers, and an updated flowmeter and controller using spray headers as opposed to an unpressurized oil application system, resulting in a significant improvement in the safety and accuracy of coal bulk density measurements.
In addition to achieving more consistent test results and reducing the potential for worker injury, test sensitivity was greatly improved at high coal moisture levels, the variability in the measurement of coal bulk density was reduced by 40%, the oil rate was controlled within 0.21 litre per minute for 75% of the run time, the oil required for bulk density control was reduced by 35% and the volume of coal charged in the ovens was more consistent.
Gerdau Long Steel North America
To keep its employees safe while they load kegs of wax into a tank as part of the finishing process, Gerdau Long Steel North America developed a new design for a keg grabber at the steelmakers Memphis, Tennessee, metals finishing plant. This was done to prevent kegs from breaking, which could result in hot liquid splashing out, possibly injuring workers not wearing proper personal protective equipment.
First, Gerdau constructed a lumber and acrylic glass barrier between operators and the hoist, keg and tank, mounting the hoist controls inside the booth for maximum shelter throughout the operation. But, although that worked well as a shield, it did not stop kegs from falling and breaking. That was because the hooks grabbing near the top of the keg did not dig into the keg evenly. Instead they sliced into the kegs too deeply, therefore weakening the keg and increasing the potential for breakage. Also, the hooks did not release the keg once it was lowered into the tank and it took several hours for the keg to melt off the hooks.
Gerdau consequently decided to create a new, hands-off design that grabbed the keg near the bottom without digging in too deeply, and that released the keg immediately once it was in the tank. This design used steel tubing for the main frame, curved pads with teeth to dig into the wax, and pneumatic cylinders with an inner diameter of 4in to open and close the device. All the controls to operate the hoist and grabber are in the booth, therefore greatly reducing the chance of employees being injured from splashing hot wax.
This entire investment both for the booth and the grabber was achieved at a cost below the budget of $3,000.
GrafTech International Ltd
As part of its strategy to be the lowest-cost, highest-quality producer of graphite electrodes without compromising its service to its customers, GrafTech International Ltd, Brooklyn Heights, Ohio, recently took several steps to improve its business. It has maximized
its asset base, divested non-core assets, increased its focus on best-in-class product quality, and focused upon continuous improvement and cost reduction moves to maximize profitability across the company. It has strategically repositioned the company to provide its customers with reliable, long-term supply of graphite electrodes, despite the current tightness of petroleum needle coke supply, through the use of three- to five-year take-or-pay contracts.
This comes on the back of GrafTechs recent move, from 2012 to 2016, to concentrate its electrode production at its largest-scale, lowest-cost plants. This has included debottlenecking production at its three electrode facilities in Calais, France, Pamplona, Spain and Monterrey, Mexico.
GrafTechs workers now concentrate exclusively upon graphite electrodes and petroleum needle coke, including concentrating upon what they can do to improve the consistent overall quality of the companys core products and services. This includes the performance characteristics of the products, uniformity of the products from plant to plant, and the ability to expand the range of products that the company offers.
Overall, GrafTech has achieved annual fixed manufacturing cost improvements and capital expenditure reductions of approximately $190 million since 2012, while also improving the productivity of its plant network. It has also successfully implemented a new commercial strategy to sell 60-65% of its production capacity through three- to five-year fixed-volume, fixed-price take-or-pay contracts. GrafTech believes its customers will benefit from the fact that these long-term contracts give them a reliable supply of a high-quality product. GrafTech itself expects to benefit from lowering the risks associated with pricing volatility.
Outokumpu Americas continues to combine additional operational improvements with its company-wide culture of self-help to attempt to become the best value creator in the stainless steel industry by 2020 a goal that it announced in April 2016.
This has included implementation of the SafeStart® human-error prevention ideology, which drives employee engagement and safety awareness not only in the workplace, but across all areas of employees lives. Outokumpu says the implementation of this program throughout its American operations has resulted in a 14% improvement in total recordable incident rates and a 45% reduction in injuries by comparison with 2016.
Outokumpu has also made several operational improvements in its Calvert, Alabama, melt shop. This included adding an aggressive predictive maintenance schedule to limit unplanned delays due to unforeseen issues. The company used tools such as thermography, unmanned aerial vehicle inspections, ultrasonic analysis and vibrational analysis to identify problems prior to failure.
In addition, the steelmaker has implemented single minute exchange die principles to routinely evaluate such meltshop activities as caster turnarounds, electrode changes, pit pushes and drop-out box cleans, evaluated by utilizing time-lapse cameras and statistics and enabling Outokumpu to continuously reduce the time to perform these activities safely.
Outokumpu also made four argon oxygen refractory lining design changes at Calvert in 2017, resulting in a performance gain of 15%. The steelmaker has also installed tiltable virtual lance burners to address cold spots in the melt shops furnace caused by the fact that Calverts original EAF was not installed with a side-wall burner system.
The company has also made moves to improve the performance of and debottleneck Calverts cold annealing and pickling line (CAPL). Since 2016 the CAPLs strip breaks were reduced by 50%, its maintenance delays were reduced by 33%, its process speeds were increased by 10% and its annual capacity was improved by 7%, while process speeds on its hot annealing and pickling line increased by 19%. Calverts overall equipment effectiveness was improved by 22% in its melt shop and 8% at its cold rolling works area.
After deferring its commissioning for more than a year, now that market demand for heat-treated bar and tubes has been increasing daily, TimkenSteel Corp began commercial operation of its advanced quench and temper facility (AQTF) at its Gambrinus Steel Plant in Canton, Ohio, in October 2017, supporting the steelmakers ability to grow sophisticated, value-added product lines to serve the energy, automotive and industrial markets.
This $40 million line, which was first announced in October 2014, has the capacity to process 500,000 short tons of 4in to 13in bars and tubes per year. Unlike TimkenSteels other thermal treatment facilities, the AQTF, which was made by SMS group with custom modifications by the companys team of in-house engineers, has a unique shell-shaped spray nozzle that enables it to provide a more thorough quench in a faster time.
As the line is still ramping up, TimkenSteel is just beginning to realize the benefit of the AQTF, which was built to complement the steelmakers other thermal treatment facilities. It is expected to give the steelmaker many advantages, including tighter temperature tolerances; uniform product heating, quenching and cooling; strong quench capabilities to produce high-martensitic structures; efficient throughput and high productivity rates; and high-level piece tracking throughout the production process. The fact that it is highly automated enables it to operate faster than other heat-treating lines.
Because the AQTF offers more capacity for the company to produce a larger range of bars and tubes, TimkenSteel believes that it should generate significant profit for quench-and-temper product. Also, as this gives the steelmaker greater overall production capacity volumes, TimkenSteel says it will enable the company to offer shorter lead times to its customers than many of its competitors.