A pilot plant scale fiber membrane system was developed for the removal of dissolved oxygen from water via nitrogen vacuum. Feed water was introduced to the shell side; a nitrogen gas was applied to the lumen side, as an inert gas, of the hollow fiber. Outlet concentrations of oxygen in water depend on membrane module, inlet concentrations of oxygen in water, water flow, and nitrogen concentrations in inert gas and nitrogen flow. The effects of nitrogen purity on removal efficiency of dissolved oxygen were investigated. Equations for oxygen concentrations and efficiency due to nitrogen purity have been given.

This paper presents new methodology for determining the actual stress–strain diagram based on analytical equations, in combination with numerical and experimental data. The first step was to use the 3D digital image correlation (DIC) to estimate true stress–strain diagram by replacing common analytical expression for contraction with measured values. Next step was to estimate the stress concentration by using a new methodology, based on recently introduced analytical expressions and numerical verification by the finite element method (FEM), to obtain actual stress–strain diagrams, as named in this paper. The essence of new methodology is to introduce stress concentration factor into the procedure of actual stress evaluation. New methodology is then applied to determine actual stress–strain diagrams for two undermatched welded joints with different rectangular cross-section and groove shapes, made of martensitic steels X10 CrMoVNb 9-1 and Armox 500T. Results indicated that new methodology is a general one, since it is not dependent on welded joint material and geometry.

During service of thermal power plant (TPP) units, different components are exposed to high temperature due to technological cycle of TPP unit. Service lifetimes of these components, especially boiler heating surfaces, may be limited due to creep, fatigue or oxidation, but materials designed for use at high temperatures have been developed primarily for their creep properties and microstructural stability during long term exposures at elevated temperatures. Having in mind that oxidation in steam environment on the inner surface of boiler tubes and in flue gass on the outer surface of boler tubes could lead to a different consequences regarding service life of tubes, either directly through metal wastage or indirectly through raising local temperatures due to the lower thermal conductivity of the oxide scale, the oxidation behaviour of a different heat resistant steels become very important characteristics. In this paper are presented some data about the oxidation behavior of boiler tubes made of 2.25Cr1Mo and 12Cr1Mo0.3V steel after service of approximately 130.000 and 200.000h in two 620MW TPP units. Characterization of oxide scales on the inner side on tubes made of two steels with different chromium content, after two different prolonged periods of service, were compared and also their influence on the service life of tubes and kinetics of oxide scale growth were analyzed

This research focuses on the erosion wear behaviour of two Fe-Cr-C alloys with similar chemical compositions obtained using different production methods. The first alloy belongs to the high chromium cast irons (HCCI). It was made by casting, after which the samples were heat treated by annealing. The second alloy in the form of the coating was applied by the plasma transferred arc (PTA) surface welding process at the substrate material (structural carbon steel). Damage to the components of industrial plants due to erosive and/or abrasive wear is a frequent cause of failure and outages of such systems. For this reason, and to bring the experimental research closer to real service conditions, an erosion test was performed at a gas blast sand facility with a high erodent speed of 90 m/s and a higher feed rate than standard erosion testing parameters recommended in ASTM G76 standard. Microstructural characterisation of all samples was done using a scanning electron microscope (SEM). The X-ray diffraction analysis (XRD) was used to identify the phases present. Similar erosion mechanisms were observed on all tested specimens, but coated samples (PTA alloy) had a lower mass loss during the erosion test compared to cast samples (HCCI alloy), i.e. they showed better erosion resistance.

Parts of industrial machines and structures are often exposed to the action of aggressive environments, which in a short period of time can provoke the loss of their integrity. It is well known that for extending the service life against erosion and corrosion, protection of the exposed structure zone by coating is frequently used. Various application methods of protective coatings are applied, and the most common are welding and thermal spraying processes. The aim of this study was characterization of coatings made of stainless steel 316L, widely used in chemical and petrochemical industries. The coating was applied on a structural steel S235JR by plasma transferred arc using powder as a filler material. Due to a number of advantages, the plasma transferred arc (PTA) surfacing process has found significant usages in the field of surface protection. This paper presents results of hardness measurements in characteristic zones of the coating and the base material, as well as microstructural characterization of coatings using optical and scanning electron microscopy. Results of EDS analysis of the coating and hardness measurements indicated that a relatively high dilution (26.1 %) of the base material (BM) and the filler material (FM) occurred in a very narrow zone above the fusion line, and thus did not significantly affect the chemical composition of the rest of the coating. Also, erosion resistance tests of coatings were performed by changing the basic functional parameters that is the impact angle and the speed of erodent particles. It was observed that the erosion resistance of the coating material decreases approximately linearly with the increase of the particle speed. Also, with the increase of the impact angle of the erodent (up to 45 ?), the mass loss of the coating material is increased.