Clarion Partners - Owner's Engineer

Major overhaul works completed on TENT

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This year’s overhaul season in Economic Association “Thermal Power Plants Nikola Tesla” (hereinafter TENT) nears completion.  In September, after completed overhaul works, units TENT A-4, TENT B-2 and TPP “Kolubara” A-3 were connected to the grid. In TPP “Morava” the capital overhaul started on the 12th of September while the unit A-3 on TENT A also entered the overhaul season on the 29th of September.

As a reminder, major overhaul works were skipped this year in accordance with the schedule for capital overhauls by Electric Power Industry of Serbia (EPS), considering that most of them were done during last year.  The most important accomplishment was a complete rehabilitation of unit TENT A-6.

The first 620 MW unit in TENT B entered the overhaul phase in early April. Although these repair works lasted shortly, important works were completed during that time, especially on boiler pressure parts. The same extensive work was also performed on the boiler plant equipment, particularly on the parts which were exposed to high abrasive effect – flue gas, air mixture or atmospheric air. All other standard works typical for this type of overhaul were also completed. 

In the first half of May, the capital overhaul of the Unit TENT B-2 started and lasted 120 days. This unit was connected back to the grid on September 11th, and from that time runs in stable condition, with minor problems, expected after such complex works. Reconstruction of electrostatic precipitator was the work which determined the time of whole TENT B -2 unit overhaul. With reconstruction of electrostatic precipitators, the emission of powdery substances through the flue gas is now reduced to the values less than 50 milligrams per cubic meter, defined by national and European standards. The reconstruction of ESPs alone was very complex and difficult work. It was funded mostly from EU donations, more exactly around 5, 5 million Euros, and that part of work was assigned to the Polish company “Rafako” with subcontractors “Goša-Montaža” and “Izoprogres”. Part of the work founded by TENT was assigned to the same subcontractors, but value of these works was around 4 million Euros. Extensive works were carried out also on the boiler pressure parts. Companies “Termoelektro” and “Feromont” in cooperation with subcontractors replaced Reheater 3 and Superheater 1. On turbine unit, the replacement of all turbo feed pump rotor and stator blades was done, according to the contract placed with German company “Alstom”. At the same time, the replacement of all main turbo set condenser tubes was successful, which will significantly reduce the number of so called “partial outages” of unit B-2. More than 26 thousand tubes were replaced on the condenser by the Public Enterprise PK “Kosovo” – Obilic. During four month long overhaul of the unit B-2, major works were also completed on the system for pneumatic transport of ash and some parts of the installation were changed in order to increase the reliability of the plant.

So-called extended overhaul of unit TENT A-4 is finished. It lasted 60 days and, from the standpoint of scope and importance, falls under the biggest overhaul in TENT A this year. Its duration was determined by works on the mills. Namely, modernization of mills included the replacement of all six mills in order to increase capacity and quality of coal grinding. Identical work was carried out last year on four mills of unit A-3, which significantly improved the operation of the boiler unit. The contractor engaged for these works was “Hitachi” and costs were financed by KfW bank loans. During two month long overhaul of unit A-4, the new turbine controller was set as it was done last year on the unit A2. This complex and extensive work was done by experts from Institute “Mihailo Pupin” – Automation together with TENT’s engineers. Simultaneously, standard works were performed on other parts of the unit A-4. On other TENT A units, mainly standard overhaul works were carried out.

In the oldest production unit, TPP “Kolubara”, Veliki Crljeni there was no significant overhauls, except the overhaul of unit A-3. Unit A-3 is in the overhaul phase since the January last year, due to repair of the turbine after the outage. Planned overhaul works entered the final phase in the beginning of September, so the unit A-3 was stable on the grid on September 26th. On the largest 110 MW unit A-5 and the oldest A-1 unit (32 MW) in TPP “Kolubara”, only standard overhauls were done this year.

The only production unit (125 MW) in TPP “Morava” is in the overhaul phase after a two-year delay. In the whole TENT ltd, that is the only capital overhaul this year. It will last 70 days. Besides main and regular repairs of the vital parts of the plant, the reconstruction ofevaporator to membrane type is also planned during this overhaul. Repairs shall be done also on other parts of the plant. Connection of 125 MW unit to the grid is planned by the end of November 2011. 

Railway transport in the last nine months achieved 100, 29% of the plan for transportation of coal to TENT A and TENT B . Dinamics of the coal transportation in the last period of time followed the trend of company’s power production. Eight hundred milionth ton of coal railway workers transported on holiday Sretenje, on 15th of February this year. At the same time, that was the highest transportation since the year 2002, acomplished with 62 trains , that is, 95.500 t of coal was transported. Overhaul works in Railway transport were already completed in June, although started in the middle of April, at the same time as the overhauls in mining basin „Kolubara“ and production facilities in TENT ltd. Significant overhaul activity worth mentioning was a complete sieving of the tracks and partial replacement of rail gauge on the right line from settlments Stubline to Brgule.  On the part of the railway Tamnava –Brgule new gauge was set, while the sieving of the tracks was done on the critical part of the crossing Stubline-Vorbis. Corrosion protection on one of the bridges on railway Brgule – Vreoci  and also on the bridges of double -track railways was done. Overhauls of engine and wagons were completed so the Railway transport is fully ready for trasportation of coal in the upcoming period. 

Source: TENT Magazine



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