Questions are considered of the reliability of assembled welded joints of valve fittings. It is proposed to use impact strength as a criterion of welded metal durability for welded joints. The effect of welding heating cycle on the structure and phase composition, and properties of metal around the joint (MAJ) of the heataffected zone (HAZ) of welded joints made from steel of strength categories K42 and K52 is studied. The effect of strain ageing on impact strength characteristics of the MAJ of the HAZ is analyzed for steel 17GS with different structure and phase compositions. It is shown that metal of the MAJ of the HAZ with a predominantly bainitic structure is most resistant to strain ageing. Dependences are plotted for evaluating welded joint material endurance and determination of the duration of the operating period, during which there is no critical fall in impact strength, and rational welding regimes are also established that make it possible to prolong safe operation of valve equipment to 30-35 years.Valve fittings are one of the most important elements of a gas pipeline system, and therefore in assembly of the valve fittings high specifications are laid down both for the material used, and also the production process. In welding, the welded joint metal structure and properties change considerably compared with its original condition, and therefore in order to provide a service life of an assembly with welded joints, comparable with the standard service life of a gas pipeline (40 years), it is necessary to consider both the production factors in performing welding operations, and also the operating parameters.Most critical for the operating capacity of a welded joint is embrittlement of the heat affected zone (HAZ) metal, in particular metal around the joint (MAJ). In view of this impact strength may be adopted as a criterion for metal endurance of welded joints.In order to estimate the effect of welding technology on the loss of ductility properties for MAJ of the HAZ immediately after welding in the standard of Gazprom 2-4.1-212-2008, impact strength of welded metal is regulated with a test temperature of -40°C, that should not be less than 25 J/cm 2 . Alongside this in the standard of Gazprom 2-2.3-137-2007 specifications are regulated for metal hardness of a welded joint HAZ that should be not more than 300 HV 10 . A significant part of an assembled welded joint of valve fittings, used in main gas pipelines, is made in steels of the strength category K42 and K52, that have a ferrite-pearlite structure. The chemical composition of steels of these strength categories is given in Table 1.

This paper discusses the use of materials with shape memory in various industries, including the oil and gas industry. The advantages and disadvantages of metallic and non-metallic materials with shape memory are presented. The possibilities of using composite materials with shape memory in the oil and gas industry are considered. The use of composite materials for the manufacture of diaphragms in diaphragm pumps to increase the energy efficiency of equipment is proposed.

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The article considers questions of changes in pipe steel properties of strength category K50-K56 during operation under conditions of the action of seismic loads. The limiting permissible number of loading cycles is shown for pipelines made from test steels with earthquakes of different intensity.Within the Russian Federation regions with seismicity of seven points and higher embrace about 2.3 million km 2 of area, which comprises more than 13% of the territory. The territories that are most critical in a seismic respect relate to Kamchatka, Kuril Islands (more than nine points); the Transbaikal and Baikal regions, southern regions of the Krasnoyarsk and Altai rims (six-nine points), Dagestan (eight points), the resort regions of the Black Sea coast of the Caucasus, and the Caucasus Mineral Waters (seven-eight points).The seismic resistant planning of structures, including objects of pipeline systems, within Russia is controlled by a number of standard documents [1][2][3]. For systems of pipeline transport, consideration of seismic activity is carried out for building regions with seismicity of seven to nine points [1]. Earthquakes with an intensity lower than seven points are not considered for pipeline objects since it is assumed that as a rule the loads created by them are not definitive in the level of stress-strained state, formed in the wall of a pipeline [1]. In addition, it should be noted that the frequency of occurrence of earthquakes of low intensity is considerably higher than for high-point occurrences. The total number of cyclic loads created by them in the operating time of a pipeline is very significant and may have a marked effect on promoting the occurrence of crack defects in a pipeline wall.It should also be considered that calculation of the limiting stressed state of a pipeline, including additional stresses, which arise in the walls of a pipeline under the action of a seismic wave, are carried out proceeding from the level of strength properties of new pipe material [2]. However, during operation of a pipeline and cyclic loads, which arise with low intensity earthquakes, there may be a marked change in metal strength property indices as a result of the occurrence of strain aging. Embrittlement of metal under the action of these factors leads to an increase in the sensitivity to the action of alternating loads of low intensity and may promote crack generation, which it should be considered in evaluating the level of operational safety for gas pipelines, planned in areas of increased seismicity. In this article, an estimate is provided of the probability of gas pipeline failure made of low-alloy steels of strength categories K50, K56 during their operation in a seismically active area of the Caucasus region (in the region of Grozny).