Assessment of Operational Degradation of Pipeline Steels

This paper summarizes a series of the authors’ research in the field of assessing the operational degradation of oil and gas transit pipeline steels. Both mechanical and electrochemical properties of steels are deteriorated after operation, as is their resistance to environmentally-assisted cracking. The characteristics of resistance to brittle fracture and stress corrosion cracking decrease most intensively, which is associated with a development of in-bulk dissipated microdamages of the material. The most sensitive indicators of changes in the material’s state caused by degradation are impact toughness and fracture toughness by the J-integral method. The degradation degree of pipeline steels can also be evaluated nondestructively based on in-service changes in their polarization resistance and potential of the fracture surface. Attention is drawn to hydrogenation of a pipe wall from inside as a result of the electrochemical interaction of pipe metal with condensed moisture, which facilitates operational degradation of steel due to the combined action of operating stresses and hydrogen. The development of microdamages along steel texture was evidenced metallographically as a trend to the selective etching of boundaries between adjacent bands of ferrite and pearlite and fractographically by revealing brittle fracture elements on the fracture surfaces, namely delamination and cleavage, indicating the sites of cohesion weakening between ferrite and pearlite bands. The state of the X52 steel in its initial state and after use for 30 years was assessed based on the numerical simulation method.

Effect of the Regimes of Machining Butting Edges on the Quality of Permanent Joints Made by Fusion Welding when Assembling Aircraft Titanium Structures

The article presents the results of the study of the effect of machining on the quality of permanent joints made by fusion welding. The effects of various types of machining (high-speed milling, cutting with guillotine shears, grinding) on the level of defectiveness of permanent joints made by automatic argon-arc and electron-beam welding have been determined. It was found that it is incorrect to assess the quality of machining butting edges for welding by the roughness parameter. The most acceptable parameter is the saturation by capillary-condensed moisture. It is shown that the thermal processes occurring during high-speed milling in the near-surface and surface layers, regardless of the roughness, lead not only to the minimum saturation parameter of capillary-condensed moisture (from 1.12 to 2.18), but also to dehydrogenization in the surface layer of the butting edges of future permanent joints. The obtained results of the research can be applied in technological processes of production of aircraft large load-bearing elements performed by welding.

Aggressive environmental factors causing corrosion at gas production facilities in the presence of carbon dioxide

The current stage in the development of promising gas and gas condensate fields in the Russian Federation is associated with facilities whose production includes carbon dioxide. Such objects include the Urengoyskoye oil and gas condensate field (Achimov deposits), the Bovanenkovskoye oil and gas condensate field, and the Kirinskoye gas and condensate field. The presence of CO2 in the produced gas, in combination with moisture condensation and a number of other factors, stimulates the intensive development of local corrosion processes. The main factors that influence the development of corrosion at infrastructure facilities and its localization in the presence of CO2 are considered. It is noted that when assessing the degree of aggressiveness of the environment, it is necessary to consider not only the CO2 content, but also other basic operating parameters that can affect corrosion. During the exploitation of gas fields, the conditions of moisture condensation that contribute to corrosion arise, which occurs when a temperature gradient arises and the produced gas is rapidly cooled. Higher temperatures increase both the amount of precipitated moisture and, accordingly, the rate of local corrosion. Simulation tests have shown that the development of local forms of corrosion (pitting, ulcers) are possible even at low CO2 partial pressures (from 0,025 MPa and above) in the presence of condensed moisture.

Water stable isotopes (δ²H and δ¹⁸O) in the Peninsula of Yucatan, Mexico

The hydrogen and oxygen isotopic composition of water is a very important tool to estimate water balance, groundwater recharge, and evaporation. Water isotopes have been used to increase our understanding of the distribution and amounts of renewable and non-renewable groundwater. Isotopic data from precipitation and groundwater is available in much of Mexico but there is little information from the Peninsula of Yucatan, an area heavily relying in groundwater in which current estimates of groundwater availability are uncertain. In this paper, we compiled published and unpublished δ2H and δ18O data in meteoric (waters derived from precipitation), ground- and pore-waters, to obtain a regional meteoric water line (RMWL) expressed by the equation δ2H = 8.1846 δ18O + 10.289. The data suggest that precipitation originates in convective systems, low-pressure events, moisture from frontal events, and from re-condensed moisture. The evaporation lines from groundwater suggest mixing of water with different isotopic composition, but also provide clues to recent meteoric water rapid recharge, likely from rain events of great intensity. We present a groundwater isoscape of the Peninsula of Yucatan and finally address the lack of conciliation between hydrogeology and groundwater management.

Management of air flows inside steel silo during grain storage

A study was conducted concerning effects of temperature and relative air humidity during long-term storage of wheat grain in a steel silo. The study was aimed at identifying the possibility of condensed moisture appearing under the silo roof. The probable periods of condensate in the space under the silo roof depending on the temperature difference inside and outside the silo have been determined. Some ways to prevent the condensate formation are proposed in the paper.

A COMPARISON BETWEEN EXPERIENTIAL AND ECMWF REANALYZED CONDENSED MOISTURE PROFILE OVER THE NORTHEASTERN SPHERE

Base on January and July 4-times daily ECMWF Interim data from 2009 to 2018 over the Northeast Sphere (0–180E,0–90N), the condensed moisture profile of experiential methods and that of ECMWF analysis are compared. The result shows that, the meridional-height distribution of mean cloud condensed moisture has a maximum slab spreading near ground in the Arctic region in July, and the maximum takes a circular shape at 700 hPa above 30N latitude in January. The distribution feature unlike the universal profile, it distributes in a single or double peak function manner, instead of a constant value. The quick decreasing level height and thickness varies with latitude, especially in January. The second experiential profile concerning warm cloud assumes air parcel lifting adiabatically, the liquid water path (LWP) is compared for general information. The result shows that the experiential LWP is much larger than that of the reanalysis by 1 to 2 order, decreasing with latitudes. The possible reason of LWP difference is from the critic water content value of cloud boundary identification. If the value is small, the thickness of warm cloud will be large, temperature and pressure at the cloud base are both large too, results in a larger LWP. These results will enrich the knowledge of the condensed moisture characteristics of ECMWF reanalysis and the experiential moisture profile methods.

РОЗРОБКА ВИСОКОЕФЕКТИВНОЇ СУДНОВОЇ СИСТЕМИ ОЧИЩЕННЯ ПОВІТРЯ ВІД КРАПЛИННОЇ ВОЛОГИ

It is investigated one of the directions of increasing the technical, economic and environmental characteristics of engines and power plants by air cleaning as a working fluid of condensed moisture. Prospective methods of aerosol medium separation with the help of gradient intensification of transfer processes in boundary layers of multifunctional surfaces are also investigated. Multifunctional surfaces include surfaces with a coefficient of compactness more than 2000 m2/m3, characterized by improved heat exchange and separating properties. A characteristic feature of the developed separating profiles is the combination of a waveform part with flat input and output elements. In the assembly, the separating profiles form the curved channels with a number of successive confuser and diffuser elements. In diffusor elements, there are separating zones with the gas reverse flow. The liquid film resulting from the droplets deposition, falling into these zones, is influenced by the vortices effect that counteracts the film motion in the direction of the main flow and facilitates its flow under the action of gravity. The investigations of gas dynamics and deposition coefficients of the separation profile were performed. The coefficient of droplets deposition for flow rates of 5, 10, 15, 20 m/s in separating profiles with a radius of 5, 10, 15, 20, 25 mm was calculated. It was determined that vortex zones provide full removal of captured water from the smooth surface profile up to the airspeed of 5 m/s. Excess of this speed leads to the removal of part of the water from the vortex zones. Drainage elements are provided for preventing secondary flooding of the flow in flat sections of the separation profile. Design solutions and a generalized scheme of the ship system of air cleaning of condensed moisture for the air flow from 20 to 2000 m3/h were developed. The introduction of filters based on gradient technologies will increase the reliability, the life of the marine power equipment and its elements. This will contribute to the creation of high-efficiency energy-saving technologies and efficient design solutions for a wide range of gradient marine power plant separators.

The Influence of Rainfall Humidity on the Moisture Regime of Envelope Structures with Internal Insulation

While the matters of the moisture of external walls of historical buildings it turned out that apart from classical sources of moisture (such as capillary attraction, condensation etc.) there is another source which is often left behind – rainfall humidity which leaks to perimeter walls from the exterior. Whilst the Czech approach of standard assessment works with condensed moisture only, some foreign authors (especially those from Germany) point out a notable influence of rainfall humidity on the moisture regime of the mentioned constructions. Its amount exceeds the amount of rainfall that leaks into the construction due to diffusion by several times. The issue deserves to be examined in more detail, but the use of nanotechnology could help to solve or improve the problem. In some cases it would be possible to apply the suspension with added nanoparticles into the insulated masonry and improve the properties of masonry, which is facing to rainwater