I. Introduction
The effectiveness of the functioning of engineering or transport networks, allowing transferring from one node to another some product largely depends on the timely maintenance of the elements of these networks. In other words, reliable and trouble-free exploitation of engineering networks is achieved through regular maintenance and repair work, or the replacement of individual nodes and lines of these networks. Therefore, it is very important to monitor its condition and timely spend repair work on the maintenance of elements of these systems. For this purpose, maintenance of networks is carried out, the purpose of which is to carry out a set of measures and works in respect of utility networks, allowing ensuring their reliable and trouble-free exploitation during the entire standard service life.