Reduction Heat Treatment

Reduction heat treatment (RHT) is a set of production processes and operations enabling the extension of the fleet life of power generation equipment, which has exhausted its design service life. The purpose of the reduction heat treatment is to restore the structure and properties of the long-term operated metal in the process of full phase recrystallization to a level that corresponds to the initial condition of the metal.

The range of restored equipment includes turbine high- and intermediate-pressure cylinder housings, steam chambers of steam distribution units, stop and control valve bodies, diaphragm carriers, elements and bends of live steam pipelines.

Technology and appropriate equipment for the reduction heat treatment procedure have been successfully piloted for stop valve boxes of the 200 MW K-200-130 turbine at Unit 1 of Zmiivska TPP. We performed a package of work for inspecting, repairing, renovating, machining and checking the metal of steam chambers after RHT, which enabled us to extend the life of already decommissioned equipment by 80 thousand hours.

The list of major types of work when performing RHT includes:

• Conducting studies, cutting test specimens for nondestructive testing, measuring the geometry, and evaluating the integrity;
• Gouging out all cracks on the inner and outer surfaces;
• Welding up the cracks and leaving a surplus for machining purposes;
• Regenerating the structure of the metal by two-step heat treatment in the furnace; the heat treatment mode is developed for each specific case;
• Machining to a nominal size;
• Checking after repair; issuing a conclusion.

As a repair operation, reduction heat treatment is a full-fledged alternative to a fairly costly replacement of equipment with new equipment, which, with a comprehensive professional approach, allows restoring the properties of the components of power generation equipment close enough to the quality level of new equipment. Furthermore, carrying out the RHT procedure takes a much shorter time than manufacturing new equipment (3 to 4 months) and is much cheaper (up to 40% of the cost of new equipment).

Heat treatment services are provided by HEAT-KHAER, LLC, a separate subdivision of KHARKIVENERGOREMONT-HOLDING.