This publication intends to familiarize those interested in the history of national atomic industry with the R&D landmarks contributed by a Russia’s leading engineering centre — I. I. Polzunov Central Boiler-Turbine Institute. This may also be of interest, since works performed by us have not lost their signifi cance to present, as they comprise a solid knowledgebase for both current and future generations of nuclear power equipment.

The publication covers the period from 1945 (when NPO CKTI was fi rst involved in the USSR Nuclear Project) and to present. We have contributed to a widest range of power equipment — steam generators for plants equipped with pressurizedwater reactors or fast breeders; steam generators for marine nuclear energy installations (NEI); separator-superheaters for nuclear plant (NP) turbines; NP and NEI heat exchanges for space applications; reactor process channels; transportation and storage containers for spent fuel of water-cooled or gas-cooled NPs; and many more.

At our unique facilities (with the capacity of up to 10 MWt), we have researched a very wide range of physical processes — heat transfer, hydraulics, hydrodynamics, steam separation, and endurance.

Continually, we work to intensify such processes, increase their reliability, improve forecasting, and extend the equipment lives.

For this article, we used NPO CKTI publications, reports and projects, some of them being now mentioned for the fi rst time, as the secrecy regime prevented such publications in the time when the related works were in progress. If you would like to learn more details, please use the list of sources attached hereto. 

GTE-110 is the only powerful energy-generating GTU currently manufactured in Russia. With its advanced technical and economic parameters, the unit is well above its foreign analogs in terms of its weight and dimensions. The attractiveness of mass-scale production of unit GTE-110 is significantly hampered due to its insufficiently high operational reliability. A significant part of abnormal operational situations is associated with destruction of rotor blades of the turbine first stage. Analysis of the design of the unit developed by GENPKG «Zorya-Mashproekt» (Ukraine) before the year 2000 performed by JSC «NPO CKTI», has shown that the project has serious deviations from the standards of stationary gas turbine construction. The joint eff orts of JSC «ODK-Saturn», OJSC «NPO CKTI» and LLC «IC «Gas Turbine Technology» have made it possible to optimize the design of the blade system of the turbine fi rst stage. In particular, introduction of a sub-platform damper has improved vibration characteristics of rotor blades. Trimming output edges of the nozzle blades of stage 1 and increasing the axial clearance between the nozzle blades and the rotor blades serves to reducing the value of variable aerodynamic forces exciting the blades. Besides, the trailing edges of rotor blades have been trimmed, and the gaps in their locking connection with the first stage disk, optimized. The cooling system of rotor blades in the first channel area in the root zone trailing edges of the deflector, which enabled to reduce the temperature of the trailing edge of the airfoil. Modernization of cooling systems made it possible to improve thermal stress condition of blade systems of the turbine first stage.

Domestic hydraulic power engineering developed during the Soviet years according to a diff erent concept than at the present time. The task was set to make cheaper and faster hydraulic power construction, while today the hydraulic power industry is focused on obtaining maximum energy production from the passing volume of water. The article investigates the dependence of energy, cavitation and reliability parameters of hydraulic turbines on the concept of hydraulic power development. The work is based on the generalization of experience in the design and operation of turbines with an extremely long service life.

Unlike the existing point of view of many experts, the article shows that the equipment of operating hydroelectric power plants created 50 – 60 years ago preserve high reliability up to the present time. This conclusion is the result of analysis of availability factors of hydraulic units on 20 hydroelectric power plants and the study of the condition of resource-determining units of turbines. Such situation is connected with two reasons. Design installed capacity of hydroelectric power plant was selected by the Hydroproject based on the condition that it exceeded fi rm capacity 80 – 90 % of the time per year. Appeared power reserve allows turbines to operate under generating condition only 50 – 70 % of the calendar time. The second factor is increased specifi c quantity of metal of the Soviet equipment by 1.5 and more times in comparison with modern units.

On the other hand the level of efficiency of the turbines with long service life is much lower than today’s. This is due not only to moral and physical ageing of the equipment but because of Soviet concept of hydraulic power engineering: installation of runners into «squeezed» in size hydraulic units; forcing of water flow; manufacturing of turbine flow path from materials with low cavitation resistance. Other factors of low efficiency of water course use at operating hydroelectric power plants include discrepancy between design parameters of hydraulic turbines and the actual operating conditions of the equipment. Bringing the parameters of new hydraulic turbines in optimum correspondence with the actual operating conditions at modernized hydroelectric power plants is the main factor ensuring the increase in the efficiency of use water course at hydroelectric power plant.

The materials of the article are of practical importance both for the justification of equipment modernization at operating hydroelectric power plants with service life longer than the standard one and selection of parameters for new turbines. 

The article is dedicated to the actual problem of electroerosion damages of critical joints and parts of turbine sets. The enumeration of typical causes of such damages is presented. It is shown that electromagnetic processes may also defl ect the indications of instruments in control and diagnostic systems of turbine.

The sources of electric current are determined which may cause electroerosion destructions of equipment, such as static electricity, induced voltage impulses on shaft-line elements in relation to static parts, parasite currents of generator rotor, unipolar electromotive forces. The developing mechanisms of such damages are considered which are individuated for every particular source.

It is note that due to improper functioning of grounding brush the cause of damage becomes static electricity, accumulated on the turbine shaft-line. In case of diminishing of isolated bearings isolation resistance down to unallowable values the destruction of joints and parts are caused by the action of parasite generator currents. The high level of residual turbine sets magnetization may bring about the appearance of unipolar electromotive forces and connected to them avalanche increasing of current value, flowing through working surfaces bearings leading to their destruction.

On the basis of carried out analysis of destruction reasons the main requirements are formed assuring the elimination of sources of appearance and development of electroerosion processes, that is: security of adequate functioning of grounding brush as well as satisfactory condition of isolation of isolated bearings, strict demand for fulfillment of measuring of residual magnetization of turbines during their capital repair and in case of necessity carrying out demagnetization alongside with development and implementation of automatic systems for on-line control of electromagnetic control of turbines together the systems for suppression of induced voltage impulses on shaft-lines.

It is stated that the fulfillment of these requirements will allow to minimize the risks of electroerosion destruction in turbine and to avoid the eventual outing of equipment. 

About 600 GTK-10-4 gas-turbine units are currently in operation on trunk gas pipelines in Russia. Data analysis and results of over 200 surveys of the technical state of assemblies and parts of GTK-10-4 gas-turbine units with different running time leads to the conclusion that the elements limiting the service life of GTK-10-4 are disks of high pressure turbines (HPT), which are subject to operational cracking.

The HPT disks are made of heat-resistant steel of martensite class EP428. The rated flue gas temperature before the HPT turbine is 780°С.

Calculation of stresses at the rated rotation speed was performed under a program to solve the problem with taking into account the creep of the materials of the disk and rotor blades in the plane stress axisymmetric condition by the finite element method. A stationary temperature field was used alternating in the radial direction and alternating in the radial direction, and averaged over the wall thickness. The elastic stress state at the initial moment of time without regard to plastic deformation at stresses above the yield limit as well as a technique taking into account small deformations and small displacements were considered. Plastic crumpling of contact surfaces is followed by intense plastic flow due to creep of the material. This crumpling is accompanied by redistribution of loads from the blades between all the pairs of teeth of the shank till the onset of the steady state.

The calculations of stress-strain state enable to estimate the possibility of occurrence of cracks in fir-tree grooves of disks and the lifetime of disks to cracking at operating temperatures above the rated one.

It is shown that overheating of the metal of the drive crown by 35 – 70°C above the rated value causes a multifold decrease of service life and may lead to formation of cracks on contact surfaces of teeth and necks of the inter-groove crown by the running time significantly shorter than that assigned by the manufacturer.

At operation, even short-term deviations of the gas temperature before the turbine above the rated value should be avoided. It is recommended to monitor the serviceability of the system for cooling the disk surface with cooling air and an anti-surge device. 

One of the main NPP operation condition is maximum electricity production under constant reactor core thermal power with safety requirement implementation. It is necessary to carry out thermal tests of steam turbines. The objectives are to find out thermal efficiency reduction of equipment and reserves of electricity production. The important stage of thermal test data processing algorithm is to adjust mass and thermal balances over cycle arrangement of power unit. This is achieved by thermohydraulic model development of steam turbine cycle arrangement. The results of thermal tests show that electricity production reserves of NPPs under operation are from 6 – 8 MW(e) to 20 – 30 MW(e). The analysis shows that electricity production reserves are hidden in improvement of steam turbine condenser operation. The rejection of steam turbine condenser performance parameters defi nes main component of power production increasing. The course of thermal efficiency control level improvement of NPP power units is developing power unit mathematical models. These models must adjust characteristics of real equipment. The performance of these models is associated with comparison NPP performance parameters and models ones. When rejection is increasing over set margins the monitoring system is put into operation and show possible reasons of available rejection.

During long-term operation heat-resistant ferrite and martensitic steel welds have type IV cracking in a so-called ‘soft layer’, which contains part of fine grain region and inter-critical region of heat-aff ected zone (HAZ). The rupture of dissimilar welds occurs in the carbonless soft layer near fusion line. Therefore the strength reduction factor of welds decreases significantly with increasing lifetime and operating temperature.

Based on experimental investigations the design model is constructed to predict the welds strength reduction coefficient at the design stage, taking into account different structural and technological factors, also changes creep and fracture mechanisms. Creep strength tests of martensitic steel P91 welds and dissimilar welds P91 + Cr-Mo-V steel were performed at temperature of 620°С. The HAZ metal investigation was performed after the thermal welding cycle simulation at the «IMETCKTI» and «Gleeble-3800» units. In addition, numerical modeling was carried out, using the Kachanov-Rabotnov constitutive equations, taking into account the three stages of creep, the influence of complex stress state, changes creep and fracture mechanisms.

Based on the calculation results, the life time of P91 welds depends from the soft layer relative width and the creep rate ratio the base metal vs. the soft layer metal. A quantitative evaluation of the dissimilar welds creep strength is obtained using a sample model with two soft layers. Both have the same properties corresponding to the weakened region HAZ metal of the similar weld. According to the calculation results, the dissimilar welded samples rupture location moves to carbonless zone at lower stress level. Calculation results have good agreement with the experimental data. The obtained dependences are in good agreement with the theoretical and experimental studies of L. M. Kachanov, D. R. Hayhurst, V. N. Zemzin, R. Z. Schron et al. 

As the operating experience shows, a large number of cases of damage of natural gas pipes with natural and forced circulation are observed at domestic and foreign CCGTs. Basically, the damage is caused by the thinning of the wall of metal tubing bends.

In a number of studies, the thinning of the metal of the bends of the low-pressure evaporator (LPE) pipes is explained by high-speed corrosion (FAC) and droplet-erosion. The intensity of FAC depends on the flow velocity, water temperature, wall material, water-chemical regime (WCR), and the LPE design. Unfortunately, published papers provide no specific recommendations on selection of optimal flow parameters, pipe material, or the optimal boiler water-chemical mode.

On the basis of the experience obtained, the causes of erosion wear of metal tubing bends of evaporation heating surfaces are determined.

Analysis of damage to bends shows the presence of dependency of erosive thinning of the pipe wall on the speed of the steam-water mixture.

The damage to the evaporative tubes of the LPE is caused by destruction of the oxide protective film on the inner surface of the pipes, due to intense turbulence of the wall layer of water flowing in the bend having a saturation temperature, which causes cavitation due to formation of vapor bubbles and their condensation. The aforesaid mechanism of damage is confirmed by the absence of erosion wear of metal on concave and straight sections of pipes, as well as the absence of similar phenomena in the circuits of the medium pressure evaporator and high pressure evaporator of waste heat boilers.

The protective oxide film formed during the hydrate water-chemical mode is characterized by the highest sustainability. 

The normative documents, which determine requirements to the scope, procedure and methods of assessing the strength and lifetime of equipment of TPP, NPP and HPP developed in the 1970s-1980s relied on the technical capabilities available at the time. The calculations were mainly based on analytical approaches and were consistent with the safety factors taking into account the inaccuracy of calculation, possibilities of technologies of manufacture and diagnostics of resource defining elements, features made inherent at the stage of design of operating conditions.

Currently, numerical approaches based on the finite element method (FEM) are widely used. They enable to perform simulation without adopting various kinds of assumptions, suppositions and simplifications, which is one of the significant advantages of this method. However, the accuracy of the calculation largely depends on the quality of the design model: specified external loads, conditions of matching of the elements, set boundary conditions.

For long and ultra-long useful life of equipment, exceeding the design life two-fold or with a larger factor, application of conventional approaches based on regulatory requirement would lead to failure to meet safety factors, although their technical state is satisfactory. In this case, an improved approach is required, which would take into account specific features of particular equipment and extensive opportunities off ered by modern computational methods.

The paper describes the basic principles of approaches currently used by JSC «NPO CKTI» to assess the strength and lifetime of power equipment [1 – 3]. 

The article presents technical proposals for calculating the maximum grinding capacity of medium-speed mills using an equation based on the practice of operation of medium-speed mills, the eff ect of which is confirmed by comparing the calculated results with experimental data, and the development of technical proposals for static and dynamic separators for medium-speed mills designed to isolate the finished product from the milled cement clinker.

Besides, development is considered of a series of powerful mill fans with a capacity from 60 to 120 t/h, equipped with state-of-art inertial separators, providing finer fuel grinding in comparison with previous models, which in its turn reduces approximately to a half the losses due to incomplete combustion of fuel and, accordingly, leads to an increase in the boiler efficiency. In addition, an inertial separator of a new design with a two-stage scheme of return of partially ground fuel is described and illustrated. A new solution for installation of guide fuel ducts in the inlet branch of the mill fan is also considered. This provides a multilevel supply of fuel to the rotor blades with uniform distribution of the specified fuel along the width of the branch pipe, which has considerably extended the service life of grinding elements of mill fans. The practical record of operating mill fans of TPP «Honsha» (Laos) developed according to technical documentation by Russian specialists is also described.

The article describes a modern design of the developed small-sized separator made for the purpose of improving the quality of finished coal dust and explosion safety of hammer mills. It is based on the technology of classification of separators of mill fans. The practical record of operation of this separator on boilers of «Gusinoozerskaya» GRES is presented, as well. 

Development of advanced high-power steam-turbine plants (STP) involves paying a particular attention to design of reliable and economical high-pressure heater (HPH) capable to maintain the specified thermal hydraulic performance throughout its service life. Comparative analysis has been performed of the known designs of HPH, such as the spiralcollector HPH, the collector-coiled HPH, the collector-platen modular HPH, and the chamber HPH. The advantages and disadvantages of each design are pointed out. For better comparison, the heaters are divided into two groups — horizontal and vertical ones. The weight and dimension characteristics, the materials and features of the basic elements, and operating features of diff erent HPH are presented. At operation of the spiral-collector HPH used in most of regenerative arrangements of high-pressure STP of thermal and nuclear power plants, the disadvantages reducing the economy and reliability of their operation have been revealed. Recommendations are presented aimed at raising the reliability of HPH, reducing underheating of feed water, making the dimensions more compact. Some of these were developed by specialists of OAO «NPO TsKTI» and are successfully implemented at thermal power plants and nuclear power plants. Technical solutions have been proposed to reduce the cost of the regeneration system and the weight of chamber HPH, and to ensure reliability of the steam and condensate coolers built in the HPH housing under all operating conditions. Design solutions are described that have been implemented in HPH of the regeneration system of 1000 and 1200 MW turbines with a water-moderated watercooled power reactor (WMWCPR). The optimal design of HPH for the high-pressure regeneration system of a turbine plant with BN-1200 reactor has been selected.