Last December we were contacted by ENERGO-PRO BULGARIA Ltd.

They were looking for an emergency solution for cleaning the rotor and stator of the №2 hydrogenerator (HG-2) at the Petrohan HPP.

As usually happens in our work, a convenient time for the client is during the weekend, and the deadline is “immediately”. After talks with colleagues, a team of BlastVV performed the cleaning with dry ice in the period 20-23.12.2019.

Petrohan HPP

Petrohan HPP has a total installed capacity of 7.56 MW, the turbines are two Pelton type with a capacity of 3.78 MW, and the generators are two with a nominal voltage of 6.3 kV, and with a capacity of 5.5 MVA each.

The generator was overhauled on the hydrogenerator №2:

  • The stator winding has been replaced;
  • Class F insulation is laid;
  • The rotor insulation has been replaced.

As a result of the performed repair works, the power of the generator has been increased by 15%. Based on the operational indicators at present, its service life is expected to be within 16-20 years.

BlastVV work on field

After getting acquainted with the technical documentation of the generator and inspection, we chose the technology of implementation. Cleaning areas: stator and rotor by dry ice blasting.

We determined the size of the granules, as well as the distance from the nozzle to the object. One of the main parameters was the explicit preservation of the “foreheads” of the winding.

To adjust the flow rate of the blasting equipment, we had provided a section of copper with insulation from our previous project, on which to calibrate the equipment.

Our activity was performed in the agreed schedule. We must emphasize the good cooperation of the specialists from HPP “Petrohan”. The main goal – cleaning in order to preserve the insulation characteristics and ensure the performance of HG-2 was achieved.

In recent years, dry ice blasting has proven its effectiveness. Through it we achieve extremely short lead times, without polluting the environment or the need for additional cleaning of the work site. The equipment after the work of the BlastVV teams is ready for use, without the need for drying.

Dry ice blasting is applicable in the energy, electrical, food and printing industries.

In parallel with our work on the hydrogenerator №2 at the Petrohan HPP, we were implementing another interesting project. In Sofia, we accepted the task of sandblasting and corrosion protection for 8 mobile control rooms and mobile substations for South Korea.

We will soon tell a little more about this project, here >>>