Třinec, April 27, 2020

Replacement of BOF converter tilting drives at Tŕinecké Železárny

Overhaul during regular shutdowns

After 15 years of operation, SMS group Technical Service replaced the converter tilting drives of Tŕinecké Železárny in two steps during the regular annual shutdowns. In this interview, René Dzivý, Head of Maintenance Steel Plant of Tŕinecké Železárny summarizes the project in his own words.

In 2003 Tŕinecké Železárny (TZ) ordered at SMS group GmbH two new vessels with suspension systems, trunnion rings and two new tilting drives for their BOF shop. This modernization enlarged the capacity and reliability of the steel plant significant. After 15 years of operation, the bull gears of the main gearbox showed smaller wear indications and TZ decided to check and replace both tilting drives for keeping the availability and reliability at highest level. In 2018 and 2019 both tilting drives were replaced during regular shutdowns.

Třinecké Železárny has been a successor of the long tradition of metallurgical production in Těšín Silesia (Czech Republic) for more than 180 years. Třinecké Železárny together with its sole shareholder Moravia Steel and almost thirty subsidiaries rank among the most significant industrial groups in Central Europe. In the last ten years, Třinecké Železárny has been the largest producer of crude steel in the Czech Republic. Annual production reaches around 2.5 million tonnes of steel and the main product portfolio consists of long rolled products.

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Třinecké Železárny at Třinec (Czech Republic).
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René Dzivý, Head of Maintenance Steel Plant of Tŕinecké Železárny.
Mr. Dzivý, what were the reasons to order the new tilting drives from SMS group?

René Dzivý: We had a very good experience with the existing drives. However, at regular inspections, which were carried out twice a year, we found damage to the gearing of the main gearbox and this damage increased further. Therefore, we have decided to replace both drives at appropriate times to avoid unplanned downtime.

What role did the division of the replacement into two steps play in the decision?

René Dzivý: The main reason was the time needed to replace one drive, which exceeded the length of regular converter shutdown. Beside the regular converter repairs, we make a major repair on one of the converters every year. We cannot stop the steel plant completely, because the hot metal from blast furnaces has to be processed. Therefore, the second converter must compensate the lack of production caused by the shutdown of the first converter. Of course, the operation of blast furnaces as well as sinter plants and coke oven plants have to be adapted to such situation.

How did you feel about the assistance during the order handling period? Did you monitor the manufacturing of the parts? What are your impressions about the SMS group workshop?

René Dzivý: The converter steel plant is the heart of our company. Any unplanned production break has an impact on other plant facilities. That is why we visited the workshops in Hilchenbach several times during the production of the gearboxes to check the state of production and, in particular, to be present during the so-called factory acceptance tests.

SMS group delivered the tilting drives two weeks in advance of the shutdown to Trinec and ready for final lifting in the steel bay. What were the main difficulties during the installation phase?

René Dzivý: Probably the most difficult situation occurred when replacing the gearbox on the K1 BOF-converter in 2018, when we were not able to pull the primary gearboxes out of the pinion shafts in a planned way. Finally, we found an alternative method of dismantling the primary gearbox and we finished the job in time. After analyzing the causes together with SMS, we found better method of disassembly of primary gearboxes from pinion shafts, which we successfully used on the K2 BOF-converter in 2019.

How is your remark using the hydraulic device for unshrinking and shrinking the big gear unit onto the trunnion ring?

René Dzivý: This device is used to remove and install the main gearbox on the pin of converter trunnion ring. On both converters, this device worked as expected. It is only a pity that SMS did not develop a similar system for primary gearboxes.

How would you describe your experience with the original tilting drive equipment in terms of reliability, availability or maintenance?

René Dzivý: The original SMS drive from 2004 was absolutely reliable and easy to maintain. Of course, over time, the frequency of replacing consumables such as the rubber parts of coupling between the motor and primary gearboxes has increased. However, all of these exchanges were preventive. There has never been a downtime due to a failure of the tilting drive.

The new gearboxes correspond to the original gearboxes, but they are improved in detail. Have your expectations for the new tilting gears been met?

René Dzivý: Frankly, it is probably too early to evaluate. The original gearboxes were highly reliable, so now we do not expect any significant increase in reliability. As for the minor problems with the rubber elements of couplings we had at the end of the life of old gearboxes, we replaced after about one year of operation the rubber parts for the first time. The most rubber elements were in good condition, almost as new.

What are your next steps in BOF plant or subsequent areas? Do you have any requests or recommendations to SMS group?

René Dzivý: We plan to further improve the existing steel plant step by step, especially in the area of increasing the degree of automation and improving the plant impact on the environment. Of course we count to get in contact with SMS group for these improvements.

Mr. Dzivý, thank you very much for your open and honest feedback and we wish you full order books and we hope you enjoy your new tilting gears.

René Dzivý: I would like to thank SMS group and especially the individual SMS employees who participated in this project for their work commitment. I wish SMS to keep the level of services provided at least at the same level as we experienced in the implementation of this project. If the SMS succeeds, then I am not worried that SMS would lose its leadership at the market.