The design and construction of underwater pipeline crossings is a complex multifactorial task. Unfortunately, the existing recommendations on the design of these facilities, aimed at ensuring the reliability of structures, are not confirmed in operational practice. For example, with the trench method of building a single-pipe double-stranded structure, the distance recommended in the regulatory and technical documentation between the main and backup pipelines is often insufficient with intense deformation of the channel, which leads to a loss of bearing capacity of both strands of the underwater passage. Modern trenchless pipeline laying methods can minimize the risks of emergency situations. However, a number of factors, such as the pumping of corrosive products, the construction of oil and gas pipelines in difficult natural conditions (permafrost, increased seismic activity) require additional measures to ensure the reliability of underwater crossings. Our proposed option is to replace the single–pipe structure in trenchless pipeline laying with a two-pipe one. The objective of the study was to influence the fillers of the inter-tube space on the structural reliability of the pipeline and the feasibility of using the pipe-in-pipe construction method.

Keywords: underwater pipeline passage, pipe-in-pipe construction, trenchless technologies, inter-tube space filler

Features of sampling of the piezoceramic transducer for the arrangement of structural monitoring of water supply systems are in-process observed and calculations of basic performances of the sensing transducer (material PZT-5A) are led

Keywords: piezoceramic transducer, ultrasound, monitoring, structure, extending, water supply systems

In the article a double-gap cavity with anti-phase excitation that has wide application in designs of floating-drift klystrons is considered. One of the ways of reduction of time during machine design of klystron’s cavity is using of the simple analytical expression, allowing to determine the main klystron electrodynamic parameters with a sufficient accuracy for practice. In the article we presented the results of physical and mathematical modeling of the double-gap cavity, the corrected mathematical models were introduced that can be utilized in programs of a prompt optimization of klystron's type devices. The technique of creation of approximate mathematical model in this case was reduced to definition of basic analytical function, and the subsequent approximation between experimental and calculated data by means of a method of planned experiment. In presented work the analysis of adequacy was carry out. Analysis revealed inaccuracy of a resonance frequency of an anti-phase type in chosen ranges of change of influencing factors doesn’t exceed 1%, characteristic impedance- 5%. The received analytical ratios allow carrying out quickly calculation of parameters of the cavity, without labor-consuming and expensive experiments and calculations.

Keywords: double-gap cavity, electrodynamic parameters, mathematical simulation, resonance frequency, characteristic impedance, method of planned experiment