The reliability analysis of the high-pressure regeneration system of the K-1000-60/1500 turbine.

Students Name: Shmatko Ivan Dmytrovych
Qualification Level: magister
Speciality: Heat and Power Engineering
Institute: Institute of Power Engineering and Control Systems
Mode of Study: part
Academic Year: 2022-2023 н.р.
Language of Defence: ukrainian
Abstract: Shmatko I. D., Kuzyk M. P. (supervisor). The reliability analysis of the high-pressure regeneration system of the K-1000-60/1500 turbine. Master’s thesis. – Lviv Polytechnic National University, Lviv, 2022. Extended abstract Performance indicators of high-pressure heaters (HPH) at nuclear power plants with K-1000-60/1500 turbo-installations are unsatisfactory. Analysis of the reliability of the high-pressure regeneration system at NPPs with VVER-1000 equipped with low-speed turbines indicates a significant number of HPH failures. Almost 30% of the time, the power units work without HPH at all, and 17% of the time – with one thread disconnected [1]. Damage statistics show that 10-12% of all damages are due to HPH [2]. At the same time, about 70-75% of the damages belong to the bending damages of the coils of the heat exchange surface. Damage to coils leads to the forced shutdown of power units [3, 4], dissection of the HPH housing, replacement of damaged coils. The dense arrangement of the coils and the inaccessibility to replace the internal coils require the installation of plugs. A large number of installed plugs leads to a change in parameters of the working environment, such as steam movement speed, local temperature. It is also worth noting the complexity and large volume of repair work, underproduction of electricity during the repair. Operation with disconnected HPH s is associated with a loss of 12 MW of power [1], which, taking into account the duration of downtime, leads to significant economic losses. In this case, the repair of the HPH, which lasts according to the network schedule of 9 days, is very time-consuming and requires significant labor costs and the availability of spare parts. All this suggests that measures should be developed aimed at increasing the reliability of HPH. Study object – the high-pressure regeneration system of the NPP power unit with K-1000-60/1500 turbine. Scope of research – methodical approaches to solving the problems of calculation substantiation of increasing the reliability of the high-pressure regeneration system of the K-1000-60/1500 turbine due to the implementation of measures that eliminate erosion and corrosion wear. Goal of research: ensuring the efficient operation of the high-pressure regeneration system of the NPP power unit with the K-1000-60/1500 turbo installation, improving the design of the HPH from a two-pass to a single-pass heater in the condensate cooling zone. The master’s thesis considers the option of changing the design of the high-pressure heater from a two-pass to a single-pass heater in the condensate cooling zone in order to reduce erosion and corrosion wear of the elements of the heat exchange device. For this purpose, the following measures are proposed: remove the throttle washer; remove the auxiliary collector; replace part of the collection collector with a perforated pipe; install coils similar to the steam condensation zone in the condensate cooling zone. In this case, the heat exchange conditions should deteriorate, and accordingly, the temperature of the feed water at the exit from the HPH system will decrease. The paper analyzes the high pressure regeneration system of the K-1000-60/1500 turbine. The optimal values of underheating and minimum temperature pressure were determined according to technical and economic calculations. A number of requirements for surface-type regenerative heaters and the composition of a high-pressure regenerative installation were analyzed. To calculate the thermal circuit of the turbo installation, the parameters (pressure, temperature, and enthalpy) of the heating steam of the selections directly at the entrance to the regenerative heaters, drains of the condensate of the heating steam, and the heated media were found. In the fourth chapter of the master’s thesis, the design thermal calculation of regenerative high-pressure heaters is performed. The initial data are determined from the calculation of the thermal circuit. When performing thermal calculations, the amount of transferred heat in individual heater elements is estimated based on the temperatures of the heating media being heated. In the work, the analysis of changes in the damage of HPH with the improvement of their design was carried out. The reason for the deterioration of operational reliability is a change in the design of the heaters. With the increase in the capacity of the heaters, measures aimed at intensifying heat exchange, organization of parallel flows in the condensate cooling zone, installation of throttle washers and a bypass pipe were introduced into the structure. All this leads to significant turbulence of the flow and, along with the intensification of heat exchange, is the main cause of intensive erosive and corrosive wear. Underproduction of electricity due to a decrease in the temperature of the feed water is compensated by increasing the reliability of the HPH operation and the duration of its operation. Thus, in the case of impossibility of replacing collector-type HPH with chamber or screen HPH made of stainless steel, it is economically expedient to perform their reconstruction. Keywords: high pressure regeneration system, work space, steam cooling zone, steam condensation zone, life-giving water. References 1. Vakulenko B. F. (1991). On the regenerative heaters of the turbine plant. K-1000-6/25 for NPPs with VVER-1000. – Teploenerhetyka, № 11. РР. 27 – 34. 2. Semerak M.M., Rymar T.I., Hlova T.Ya. (2022). Mathematical modeling of a thermally stressed mill at a nodal joint of a serpentine shank with a high vise collector. Fizyko-khimichna mekhanika materialiv– Т. 58, № 4. – PP. 45 – 49. 3. Эrhashev M., Sadullaev Z., Rakhmatullaeva Sh. (2020). Investigation of the causes of damage to coils of high-pressure heaters // Universum. – № 3 (72). 4. Ozhyhov L., Mytrofanov А., Krainiuk Ye., Bazhukov A., Melnyk P. (2013). Operational wear and tear of pipelines of the second circuit of VVER-1000 power units. Visnyk Ternopilskoho Natsionalnjhj Tekhnichnoho Universytety. – № 1. – PP. 55 – 62.