MG-SERVIS - turbogeneratoriMG-SERVIS - turbogeneratoriMG-SERVIS - turbogeneratori

OVERHAUL OF TURBOGENERATORS

One of the basic tasks of turbogenerator maintenance is to ensure high availability of the machine.
Timely assessment of physical condition of individual parts of the machine, as well as their replacement when required is the main task of maintenance - servicing.

Thermal power plants ( gas, coal fired or nuclear) are of recent date and in technological and design terms are more up-to-date than hydro-electric power plants.
As to the cooling media, the generators can be divided in

  • air-cooled generators
  • hydrogen-cooled generators
  • water-cooled generators


The extent of maintenance corresponds to the size of generator and its mode of cooling.

Apart from emergency calls, routine survey and overhauls, taking thorough inside into the condition of the generator and finding out the best solution that would guarantee its service security or longer life, is MG SERVIS basic philosophy. MG SERVIS activities in the field of turbogenerators fall in groups as detailed below:

A >ROUTINE SURVEY

Depending on the degree of technical and technological development reached in the year of their production, turbogenerators are equipped with special protection and measuring devices recording all changes during operation.
Routine survey consists in rolling up of all basic findings, changes during operation and measurements on basic equipment. This survey can be divided into:

  • survey of events in the course of operation
  • survey of end windings
  • survey of water chambers of the state winding
  • survey of coolers
  • survey of bearings and sleeves
  • survey of hydrogen sealings
  • survey of slip rings and brush holders
  • survey of fans
  • electrical tests
  • NDT tests
  • survey of auxiliary equipment for generator cooling and sealing

To carry out such survey, bearing covers, endshields and winding brackets should be dismantled.

B >OVERHAUL SURVEY

When to do overhaul survey? The results of the routine survey along with the hours and conditions of generator operation may give a clear picture as to the need of overhaul. Should the results of a routine survey prove satisfactory, then the equivalent number of operating hours may determine the need for overhaul.

tek = top + 20Ns (h)

where
tek = equivalent time of operation
tpo = effective time of operation
Ns = number of starting

The experience has shown that the first overhaul is made after about 20 000 equivalent hours of operation, and the following one after 60 000 equivalent hours. The condition of components is based on visual check-up, survey of dimensions, alignment and centre line survey, run-out checking, as well as electrical and mechanical tests. Basic overhaul operations assess the condition of:

  • stator frame
  • stator core
  • stator winding
  • water chambers of the stat. winding
  • winding supports
  • rotor covers
  • rotor slot wedges
  • eads to rotor
  • shaft, flange and sleeves
  • hydrogen sealing
  • other sealings
  • bearings
  • fans
  • cooling system
  • slip rings

The condition of the generator and actions required are determined according to above data and the data obtained by routine survey. The overhaul entails dismantling of generator including uncoupling and drawing out of the rotor.

C >REFUBISHEMENT

Long operating life of turbogenerator and differences in technologies of the built in material have made us aware that with the most of old generators (of 25 years age and more) it is more economical to replace the main parts thus obtaining higher output and availability factor. In cooperation with world known companies we can do the refurbishment of the unit, including:

  • project (electrical and mechanical)
  • elaboration of documentation
  • fabrication of parts
  • replacement of parts
  • mechanical and electrical testing

D >MONITORING

The standard equipment required for generator operation consists of measuring and protection devices. The listed equipment ensures operation of generator as physical unit within electricity generation. Equipment required to detect the condition of generator and its wear and tear used not to be a part of standard equipment. Recently special equipment has been installed in the unit to monitor the generator wear and tear. Generators with fenol and epoxy based insulation have been monitored through specific annual electric tests.
In cooperation with world known companies we can provide fixed installment of measuring devices monitoring the condition of a generator, such as:

  • vibration monitoring
  • temperature monitoring
  • air gap monitoring
  • ozone measurement in generator
  • stator winding condition

MG-SERVIS - turbogeneratori