Serbia: TPP Nikola TESLA TENT, A3 unit overhaul project report

13. May 2015. / News Serbia Energy

The synchronization of the unit A3 was successfully completed on 4th February at 9:27 PM, and on 6th February the unit achieved the nominal power of 328.4 MW. More than 30 domestic and foreign companies participated in the 78 million euros worth project.

The revitalization and overhaul of the unit A3 in TPP “Nikola Tesla A” in Obrenovac was the most important work and construction achievement of the PE “Electric Power Industry of Serbia” and company TPPNT in 2014. The funds for the 78 million euros worth project were provided by EPS and TPPNT, and over 30 domestic and foreign companies participated in the realization of the project.

The effort of all the participants in this project that was put in during 218 days of work on “triplet” was crowned with the synchronization of this unit on the electric power system of Serbia on 4th February at 9.27 PM. Only two days later, on 6th February, after going on the system, the unit A3 achieved the increased the nominal power of 328.4 MW, for 23 MW more than earlier and remained stable.

Since 1st July 2014, when the works started on this unit, up to the moment of its release to the system, there were many complex procedures. Two-thirds of the equipment was replaced and many modernized devices were installed. The success of the constructors is even greater because they courageously entered this difficult and complex work only a month and a half after the catastrophic floods that hit Obrenovac in May last year. The facilities of TPPNT A were seriously endangered by the disaster. The achievement of the constructors if even greater due to the unfavorable circumstances that accompanied the realization of this project, but also due to the high goals that had to be achieved. Finally, everything was fully completed.

For the first time since the founding of the thermal power plants in Obrenovac, the overhauls of a unit were completed in the winter, thereby “bounding” two calendar years and three seasons. However, the winder was mild to the constructors, who showed the maximal commitment, proficiency and readiness for work, even in the adverse weather conditions.

Chronology

After more than seven months, the unit A3 appeared from the revitalization treatment “younger”, more powerful, more reliable, more energy efficient and less damaging to the environment. The power of the unit, which was synchronized for the first time to the power system of Serbia on 10th November 1976, is now increased from 305 to 328.4 MW. This is the third facility in the Branch TPPNT A which, in addition to the units A5 and A6, was reinforced for additional megawatts.

In a situation where for almost three decades no thermal power capacity was built in Serbia, the revitalization of the existing facilities, such as this one, which increases the power, represents a significant contribution to preserve the stability of the electric power system in Serbia.

Let us remind, the “triplet” was stopped on 6th June 2014 at 7 h and 17 minutes. During the period from the stopping of the unit to the beginning of the revitalization works, all necessary preparations were performed to ensure that the site was operational for the entry of the workers. At the first meeting of the management of TPPNT with the contractors and equipment suppliers, held on 25th June 2014, the basic parameters of the project divided into nine LOTs, objectives, organizational team scheme for its guidance and time schedule of the revitalization. The official work on the revitalization of the unit A3 began with the disassembly-assembly works on the turbine facility on 1st July. The dismantling works were performed in July on the boiler, generator and electric filtering facility, and the first delivery of the arranged equipment to the construction site was initiated.   This project was full of difficult and complex procedures. Only in the boiler facility of this unit, the 800t of the pipe system of the boiler and equipment were replaced and 28.422 joints were welded, after which, on 1st December 2014, the cold test of the boiler’s pipe system was successfully conducted. Even the existing turbine was replaced by the new. Retrofitting was performed on all three cylinders of the turbine with the power increase to 328.4 MW, which is designed to operate in the heating mode, that is, it is equipped for the production of the thermal energy for heating the citizens of Obrenovac in winter. The major overhaul of the generator was conducted with the replacement of the corset and factory overhaul of the generator rotor. In addition to standard overhaul which were conducted at all the facilities of the nit A3, the refractory walling of the channels and metal support structures of the walling were replaced, where the 776.5 t of the refractory materials, 27e tons of the insulating refractory material and 38 tons of steel were installed. Also, 17.381 m2 of the new insulation was installed and 1.112 m2 of the existing was repaired. The management system of the unit was modernized as well, that is the migration of the application software, interface with TGC, was made, as well as the adaptation of the control system DCS unit “Siemens”, (migration from “Siemens THP” to system “Siemens SPPA T3000”).

Environmental segments

Several “premier” procedures were performed, without previous exampled in the operation of these plants, such as delivery and unloading of the new generator corset and its lifting to the elevation of nine meters. This device weighs about 180 tons was delivered by truck, ship and train from France, over Croatia to Obrenovac. The unloading of the corset was one of the most interesting events in the site. The procedure of its unloading lasted 10 hours and was carried out at late September 2014 by two telescopic high-lift trucks with capacity of 130 and 200 tons. Then, after more than a month, the corset of the generator was erected and installed in the machine hall at the elevation of nine meters. This complex procedure was performed using a special set steel construction for load lifting up to 240 tons and special tools and hydraulic cylinders. The load was lifted at a speed of 0.7 millimeters per second. In order to machine hall, the “door” were previously made by the temporary removal of the glass wall measuring 50 m2.

The revitalization project of this unit had two very important environmental segments. With the implementation of the system for the reduction of the emission of nitrogen oxides (LNOx), in which 564 tons of various parts and equipment were integrated, and with the replacement of the NOx coal burner in the boiler facility with the modern design and shape, the conditions were created for the reduction of the emission of nitrogen oxides to 200 milligrams per cubic meters, which was in accordance with the European standards.

The reconstruction of the electrostatic facility enabled the reduction of the dust materials to fewer than 50 milligrams per cubic meter, as it is stipulated by the European standards. For example, the new electrostatic facility is two times heavier than the old one (2.200 tons), with the height of 32m and width 21m. At its base, a large plate was constructed out of concrete with the surface area of 800 m2 and thickness of 95 cm.

According to Mr. Mihailo Nikolić, the project director and director of TPPNT A, thanks to the very good cooperation between the team member for the project management and the contractors, the works are still advancing without deadlock.

– An extensive work like this is necessarily accompanied by certain difficulties, and the biggest uncertainty was in the works on the reconstruction of the electrostatic precipitators and replacement of the LNOx burners – said Mr. Čedomir Ponoćko, the director of TPPNT. –The major effects of the conducted work will be known after the expiry of the guarantee tests.

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