How power engineers prepare HPPs for winter

How power engineers prepare HPPs for winter

In winter, every citizen feels the result of work of power engineers: warm batteries in our homes and hot water in the tap. And what happens at combined heat and power plants with the onset of summer heat? Maybe all employees go on vacation? Let's figure it out.

In fact, summer is almost the most intense season at CHPPs. In a couple of months it is necessary to make a huge amount of work, check everything, carry out repairs, and replace the equipment. This is the only way to guarantee that during cold weather the complex system will work without failures and ensure a decent quality of life of the metropolis.

Turbine

Turbine is the real heart of the power plant. Although it is a very reliable machine, it also requires repair from time to time. And all is done strictly according to the rules, every n-hours of work.

General view of the CHPP's steam turbine

Depending on the scope of work, repairs can be current, medium and major. The current repair is performed annually, provides for the elimination of small faults and is usually not accompanied by a complete disassembly of the unit.

Once in five years the turn of the major repair comes. After this, the turbine is as new and ready to efficient and reliable work with maximum performance.

First, the machine is carefully disassembled: Protective enclosures are dismantled, insulation is removed, pipelines are disconnected, the case is opened. Internal elements are disconnected from each other — now each of them will be checked by specialists.

With the help of a powerful crane and special accessories, a huge rotor with blades on it is removed from the turbine body.

Transportation of the turbine rotor to the repair site

Steam affects the working blades during the operation and forces them to rotate and rotate the rotor of the power generator. There are many such blades which form several rotor steps.

Low pressure turbine rotor

Despite the fact that each rotor weighs from 10 to 16 tonnes, the huge internal steam energy rotates them at exactly 3,000 rpm. Such accuracy is required to comply with the frequency of 50 Hz in the unified power system of the Russian Federation and is achieved through the operation of the turbine unit control system controlled by a specialist on the control board.

Medium pressure turbine rotor

When the rotors are installed on the trestles of the repair site, it is time to examine the impellers and the blades installed on them. If necessary, repair is carried out with restoration of the geometry of the blades or replacement of some of them.

Visual inspection of low pressure rotor impeller

Each blade is a piece of engineering art, with its own aerodynamic profile, designed to work in harsh environments of high temperatures, pressures and speeds.

The impeller blades are installed strictly to the definite position
The flow part of the steam turbine is also not left unattended, the work is humming in all areas
Works on the running part of the turbine
Diagnostics of all nodes

At the same time, other parts of the turbine unit are checked, including the largest unit — the generator. It's repaired, too.

The generator rotor in the repair area is carefully covered, and workers examine each element
Vortex canals are carefully cleaned from dirt by hand
The painstaking work goes on the generator stator windings

It is all right here, but it is very important to check everything — the integrity of insulation of the windings, the quality of joints, and the workability of all parts. Then the machine will properly and reliably generate electric current.

Generator stator windings

Heating system water

A CHPP is not only electricity, but also a considerable amount of heat, which is used for heating water in the city's transit pipelines. This heat comes to us in the winter in batteries and all year round in the form of hot water.

After working in a turbine, steam still maintains a higher temperature and it enters the horizontal water heater through an intermediate selection. It is a cylinder which is filled with metal pipes and has a diameter of 2.5 and a length of about 6 meters.

The task of the network heater is to heat the water at the expense of residual steam energy. After working its cycle on the turbine stages, steam enters the plate heat exchanger. There is a constant pumping of water in the pipes which is heated by steam.

Heating system water

No matter how the heating system water is prepared, the pipes eventually appear to scale, and they cloak up. Then they can be washed with high pressure during a major repair, and sometimes it is necessary to change the bank of pipes completely.

Bank of heat exchange pipes

This is a very great work. Thousands of five-meter pipes are needed not only to be installed and expanded, but also carefully boiled from the ends to ensure the tightness of the cameras. This hard work can be done by a welder for several weeks!

On the left there are pipes that have yet to be scaled

Boiler

There is a boiler hall through the wall from the turbine hall. There water is heated in boilers, the size of a nine-storey building, from the heat of fuel burned in the furnace and converted into steam. It reaches a temperature of 525 degrees and a pressure of 125 atmospheres and goes to turbines. By the way, all these hundreds of kilometres of pipelines also require scheduled maintenance and replacement.

General view of the steam boiler

During the major repair, you can look even in the boiler. There are scaffolding for repair staff inside, but we are interested in the pipes that make up the walls of this large chamber.

Inside the boiler furnace

Natural gas is burned in the furnace, and water is supplied through the pipes. After years of work they wear out. The pipes are cut off and new ones are put instead. The boiler is good as new!

Gas is fed to the furnace through burners which need to be changed from time to time. It is better if they are replaced for new, more advanced, efficient, and equipped with intelligent automation.

Gas burners of the steam boiler

Automation

When the main equipment is in repair, it is the right moment to improve the power plant control system.

Computer control system for boilers

A new generation of computer systems comes to replace outdated devices which have served us well. Performance servers replace analogue relays.

Cabinets with obsolete equipment control systems
New automation and control systems
The old panel has analogue keys, tumblers, switches and recorders.
The new panel has all information on monitors. You can control everything with just one click. It is not only effective, but also more reliable and safe

Intelligent control systems and telemechanics are introduced in addition to the user-friendly interface. There are more sensors, more fault protection, and fewer manual operations are required. The duty shift has literally everything at the fingertip: any gate valve, if necessary, can be controlled without leaving the place, and the readings of any device can be displayed on the screen.

However, rounds are still needed. Human control remains.

Boiler facility rounds

Heating grids

Once a year the CHPP is shut down for several days to perform the work that cannot be done at other times. First of all it is the work on heating systems and pipelines. In normal times they are filled with hot water or steam and no repair can be made.

Line pump

All pipe fittings are diagnosed. It is impossible to allow any of the valves and cranes to fail during the heating period. There are thousands of all possible fittings at the plant, and it is necessary to carry out audit of each one according to regulations.

Electric valve actuator

Some of them are declared inefficient and should be replaced. Here the new one has just come and is waiting for installation.

The new valve will soon be installed in place

Work on the main areas of the heating grid is carried out during summer stops. For example, it's time to replace pumps that pump water. It is not just repair, but also improvement of the unit and increase of its productivity and reliability. This type of work is already called renovation.

Pump replacement

Territory

The CHPP's building also requires attention. After half a century of service, it is time to replace the glazing of the turbine hall. Thousands of windows are replaced by new ones. This is also renovation which is possible only in summer.

Replacement of facade glazing of the CHPP's turbine hall

Natural gas is the main fuel for our CHPP. It is supplied through a gas pipeline which is important to keep from corrosion. The pipe is covered with a special protective paint by mechanised method. Manual — the last strokes — marking.

Gas pipeline marking

Locomotive

Further challenges arise if the combined heat and power plant does not run on gas. Apatitskaya CHPP is the only coal-fired CHPP of TGC-1. There are four own locomotives in the plant's fuel and transport hall.

Maneurotic locomotive

This year one of them went to St. Petersburg for specialised maintenance. Others were examined on site.

Inspection of locomotive

The locomotive's units are checked for vibration, and defects of hydraulics and electrical wiring are eliminated. Specialists in diesel engines, hydraulic transmissions and wheel fleet work on the plant and serve diesel locomotives by themselves.

Tracks

The condition of tracks is even more important for a coal or fuel oil CHPP. At Apatitskaya CHPP, part of the tracks is converted to accept dangerous cargo (fuel oil used as start fuel, acid and alkali). In the summer, power engineers repaired sleepers here.

Station tracks of Apatitskaya CHPP

Repair works are underway at all TGC-1's facilities. This summer, power engineers plan to carry out 17 major and 9 medium repairs of the main equipment in St. Petersburg, Leningrad and Murmansk Oblasts, and the Republic of Karelia.

Repair and maintenance of machinery is a continuous process accompanying production. This is the only way to guarantee reliable and uninterrupted supply of electricity and heat to consumers.

Next time we'll see how hydroelectric power plants are repaired.