PSI - Issue 20

Ivanov V.N. et al. / Procedia Structural Integrity 20 (2019) 222–229

223

Ivanov V.N. et al. / Structural Integrity Procedia 00 (2019) 000–000

2

1. Introduction

The system of maintenance, repair and reconstruction should ensure the normal functioning of buildings and engineering systems during the entire period of their use as intended. The timing of the repair of buildings, engineering systems or their elements should be determined on the basis of an assessment of their technical condition found by Ionin (1989). The reliability of the individual elements of heating systems and heat networks depends on the life of each element. One of the areas of prevention and prevention of failures, improving the efficiency of operational work of the building's heat supply systems is the definition of the service life of each element of heating systems and heat networks.

Nomenclature 

failure rate of the heating system estimated time estimated time



λ i

thermal conductivity of the material of thermal insulation, (W/m·º С )

d str d out

outer diameter of the insulating structure, (m) outer diameter of the isolated object, (m)

the heat transfer coefficient from the outer surface of the insulating structure, (W/m 2 ·º С )

α

d int

internal diameter of the steel pipe, (m)

coolant density, (kg/m 3 )

ρ c c c

specific heat carrier coolant, (kJ/kg·º С )

d ext external diameter of the steel pipe, equal to the internal diameter of the heat-insulating layer, (m) t cr crystallization temperature of the coolant, (º С ) t out outdoor temperature, (º С ) t c coolant temperature, (º С ) t vk acceptable minimum value of t i , (º С ) Standard service life (the minimum duration of the effective operation of the elements) of engineering equipment are given in reference books and they contain the recommended frequency of repair and construction works. See VSN (1990), GOST (2015). The standard service life of each element of the heating system and heating networks is determined for the operating conditions of central Russia. It does not take into account the geographical place of use of the equipment, climatic conditions of operation. The heating system and heating networks in the North are designed the same as in the middle lane, but they work in more difficult conditions due to the extended heating season and low average temperature of the heating period. 2. Materials and methods The analysis was carried out according to the method of calculating the reliability indicators, given by Ivanov (1990) in Chapter 2. The probability of trouble-free operation of the heating system and heat networks is determined: ܲ ൌ ݁ ఒήఛ (1) In the analysis to determine the service life of the element of the heating system and heating networks, only the change in the heating period and the average temperature of the heating period are taken into account. The following assumptions are made in the calculations: the heat supply systems are designed to be the same, the failure rates of the same type of elements are equal and are distributed according to the exponential law.