# Analysis of the Static Strength of the Emergency-Cooldown Heat Exchanger with the Use of the Design Tightness Value of Flange-Joint Pins

 DOI https://doi.org/10.15407/pmach2020.03.037 Journal Journal of Mechanical Engineering – Problemy Mashynobuduvannia Publisher A. Podgorny Institute for Mechanical Engineering Problems National Academy of Science of Ukraine ISSN 0131-2928 (Print), 2411-0779 (Online) Issue Vol. 23, no. 3, 2020 (September) Pages 37-45 Cited by J. of Mech. Eng., 2020, vol. 23, no. 3, pp. 37-45

Author

Tymofii V. Pyrohov, SE «State Science and Engineering Center for Control Systems and Emergency Response» (64/56, Heroiv Stalinhradu Ave., Kyiv, 04213, Ukraine), e-mail: t.v.pirogov@gmail.com, ORCID: 0000-0002-0877-1251

Abstract

Analysis of the design calculation of the 08.8111.335 СБ emergency-cooldown heat exchanger (ECHE) strength revealed a number of deviations from the requirements of current regulations of Ukraine in nuclear energy, which, in particular, include the lack of information on the calculation of the static strength of heat-exchanger flange elements and the excess of allowable stresses in their pins. This article describes a mathematical model for calculating the ECHE thermal stress state, which is used to simulate the ECHE operation under conditions of normal use. A number of computer calculations of ECHE deformation processes were performed using the described equations of the three-dimensional theory of elasticity. Such calculations were performed, using the finite element (FE) method, to analyze the strength of the ECHE and, in particular, elements of its flange joints. Results of ECHE static strength calculations are given. The calculations were performed using the general FE model of the ECHE, the model including all its basic elements. In addition, individual FE models of ECHE flange joint elements DN2130 and DN2080 were developed, on whose basis their static strength calculations were performed. As a result of calculations of the strength of the main ECHE elements, it is concluded that the operating stresses for the considered groups of categories of design stresses in the design zones of the ECHE design do not exceed the allowable values, and, accordingly, the static strength conditions are met. Given the symmetry of ECHE flange joints, FE models of the half-period of one bolted joint were used to calculate their static joint strength. The main boundary conditions for all calculations were: the tightening force of pins, as well as the pressure and temperature of the operating environment. The calculation of the static strength of the flange joint elements  DN2130 and DN2080, using the design value of the pre-tightening force of the pins, showed that the conditions of static strength are not met for the considered groups of categories of design stresses.

Keywords: emergency cooldown heat exchanger, extension of service life, design substantiation of safe operation, assessment of technical condition, thermal stress state of the ECHE, FE method.

References

1. (2004). NP 306.2.099-2004 Zahalni vymohy do prodovzhennia ekspluatatsii enerhoblokiv AES u ponadproektnyi strok za rezultatamy zdiisnennia periodychnoi pereotsinky bezpeky [General requirements for continuation of operation of NPP power units beyond the design period based on the results of periodic safety reassessment]. Kyiv: State Committee for Nuclear Regulation of Ukraine, 16 p. (in Ukrainian).
2. (2010). PL-D.0.03.126-10. Polozheniye o poryadke prodleniya sroka ekspluatatsii oborudovaniya sistem, vazhnykh dlya bezopasnosti [Regulation on the procedure for extending the life of equipment of systems important to safety]. Kyiv: State Committee for Nuclear Regulation of Ukraine, 34 p. (in Russian).
3. Pyrohov, T. V., Iniushev, V. V., Kurov, V. O., & Koliadiuk, A. S. (2020). Analiz proektnykh rozrakhunkiv na mitsnist teploobminnyka avariinoho rozkholodzhuvannia na vidpovidnist vymoham diiuchykh normatyvnykh dokumentiv v atomnii enerhetytsi [Analysis of design calculations for the strength of the emergency cooldown heat exchanger for compliance with the requirements of current regulations in nuclear energy]. Yaderna enerhetyka ta dovkillia – Nuclear power and the environment, no. 2 (17), pp. 30–38 (in Ukrainian). https://doi.org/10.31717/2311-8253.20.2.4.
4. Malygina, Yu. V., Kovalev, A. V., & Semykina, T. D. (2016). Teoriya uprugosti [Theory of elasticity]. Voronezh: Voronezh State University Publishing House, 25 p. (in Russian).
5. Zienkiewicz, O. C. (1971). The finite element method in engineering science. London: McGraw –Hill.
6. (1987). PNAE G-7-002-86. Normy rascheta na prochnost oborudovaniya i truboprovodov atomnykh energeticheskikh ustanovok [Rules and regulations in the nuclear power industry PNAE G-7-002-86. Standards for strength calculation of equipment and pipelines of nuclear power plants]. USSR State Committee for Supervision of the Safety of Work in Industry and Atomic Energy. Moscow: Energoatomizdat, 525 p. (in Russian).
7. (1982). 61409 RRI. Teploobmennik avariynogo raskholazhivaniya. Raschet na prochnost [Emergency cooling down heat exchanger. Strength calculation]. Moscow: All-Union Research and Design Institute of Nuclear Power Engineering, 70 p. (in Russian).
8. (1982). 08.8111.335 IE. Teploobmennik avariynogo raskholazhivaniya [Emergency cooldown heat exchanger]: User’s manual. Moscow: All-Union Research and Design Institute of Nuclear Power Engineering, 19 p. (in Russian).