Aggressive Liquids Research Articles

Flow rate measurement in aggressive conductive fluids

Two non-contact experimental methods of flow rate measurements for aggressive conductive liquids are described. The techniques are based on electromagnetic forces and Faraday’s law: Lorentz force is induced inside moving conductive liquid under influence of variable magnetic field of permanent magnets. They are mounted along a liquid metal channel or (in case of the second method) inserted into rotated metal wheels. The force acts in the opposite of fluids’ velocity direction and hence it is possible to measure reaction force of it that takes place according to Newton’s law on magnetic field source – permanent magnets. And by knowing the force, which linearly depends on velocity, one can calculate mean flow rate of liquid. In addition experimental “dry” calibration and its results are described for one of the measurements’ techniques.

Controlled surface functionalization of multiwall carbon nanotubes by HNO3 hydrothermal oxidation

Controlled surface functionalization is demonstrated by nitric acid hydrothermal oxidation on multiwall carbon nanotubes (MWCNTs). The formation and evolution of oxygen functional groups were systematically investigated as a function of the HNO3 concentration on MWCNTs with different structural and morphological characteristics, employing temperature-programmed desorption coupled with mass spectrometry, thermogravimetry and differential scanning calorimetry, Raman spectroscopy and N2 porosimetry analysis. Hydrothermal treatment provides controlled MWCNT modification by specific oxygen functionalities at amounts determined by the morphology, texture and crystallinity of the pristine materials. Hydrothermal oxidation competes well with the harsh boiling nitric acid treatment regarding the total amount of oxygen functionalities, while requiring much lower amounts of oxidizing agent and, most importantly, reducing amorphous carbon deposits on the MWCNT surface, a major drawback of aggressive liquid phase oxidation methods. Detailed pore structure analysis revealed a progressive increase of the surface area upon hydrothermal functionalization, whereas the mesopore structure varied consistently with the intrinsic MWCNT properties related to the packing of the nanotube bundles and the reduction of amorphous carbon. These advantageous features render nitric acid hydrothermal oxidation an efficient functionalization process to fine tune and optimize the surface chemistry of MWCNTs for target applications, circumventing the need for additional purification post-processing.

Influence of Pozzolana Admixture on Long-Term Chemical Characteristic of Cement Mortars

nfluence of non-flowing model sulphate solution determined for cement mortar with pozzzolana admixture are presented in this paper. In the predetermined time intervals the influence of the aggressive liquid on chemical properties and mineralogical composition was tested. The changes caused by corrosive sulphate environment on the testing specimens were determined in dependence on the different type of cement and used ground clay brick as pozzolana admixture. From the results obtained follows that the additive of ground clay bricks has positively impact on the sulphate resistance.

The Effect of the Polyamide Reinforcement on Mechanical Properties of Fluorocarbon Rubbers Exposed in Aggressive Environment

The aim of presented study was to select a proper material for caterpillar application in mobile robots. The fluorocarbon rubbers were chosen for investigation. The samples hardness of 40 and 50 Sh⁰A either without or with polyamide reinforcement were prepared. The uniaxial tensile tests on mini-samples were carried out. The tests were performed on virgin samples as well as on previously exposed for one hour in aggressive liquids. The changes of the surface before and after the exposition were observed via SEM. The relation between the surface changes and the mechanical properties were described

Modern Vacuum Pumps for the Vacuum Degassing of Steel in Small and Large Vacuum-Degassing Units

This article discusses a new design for Roots pumps and screw pumps which uses hermetically sealed motors. The new pump is easy to maintain, alleviates wear, and increases safety, which makes it more reliable than traditional Roots pumps. The screw vacuum pumps operate within a wide range of pressures. Thanks to the absence of friction in the vacuum chamber and the use of special coatings on the working elements, these units can be used in place of water-ring and rotary vane pumps for the high-vacuum evacuation of gases and vapors of liquids (including aggressive liquids). In this case, the gas being pumped is not contaminated by water vapor or oil. The absence of friction elements in the vacuum chamber means that the unit requires almost no maintenance. The use of standardized pre-equipped modular building blocks reduces fabrication and installation/startup costs, makes the equipment more compact, and saves power, oil, and water compared to other systems. The small size of both types of pumps – which can be used in any configuration – not only shortens delivery times and simplifies spare-parts management but also facilitates equipment assembly or (if necessary) replacement. Attainment of the pumps’ rated productivity is assured by parallel connection of several compact modules. The mechanical pumps can be used for VID, VIM, VD, RH, VIT (vacuum ingot teeming), and VAR (vacuum-arc remelting) units, including units that perform vacuum-oxygen decarburization. The pumps’ design incorporates measures to protect against dust and water-vapor condensation, which can lead to the formation of acidic liquids. The pumps can be used in all types of vacuum processes – including processes that involve the injection of oxygen – while observing existing safety standards. The low inertial mass of the pumps helps them respond rapidly to frequency control, which facilitates the evacuation process. Redundant operation is provided for in all the pumping-unit configurations.

Development of a Novel Experimental Device to Investigate Swelling of Elastomers in Biodiesel Undergoing Multiaxial Large Deformation

The lifetime of an elastomeric product depends on the nature of mechanical loading and the environmental condition during the service. In this context, at least two important aspects contribute to the degradation of the elastomeric parts in service: diffusion of aggressive liquids leading to swelling and fluctuating multiaxial mechanical loading leading to fatigue failure. Moreover, the amount of swelling of elastomers in solvent is affected by the presence of mechanical loading. Hence, it is essential to understand the interactions between the two phenomena for durability analysis of the component. The present study investigates the swelling of elastomers due to diffusion of palm biodiesel in the presence of static multiaxial large deformation. For this purpose, new experimental device and specimen are developed. The device consists of a hollow diabolo elastomeric specimen attached to specially-designed circular metallic grips and plates such that immersion tests can be conducted while the specimens are simultaneously subjected to various mechanical loadings: simple tension, simple torsion and combined tension-torsion. Thus, diffusion of liquids takes place in the material which concurrently undergoes multiaxial large deformation. Two types of elastomers are investigated: Nitrile Rubber (NBR) and Polychloroprene Rubber (CR). The particular features of the device and specimen are discussed and perspectives for further improvement are drawn.

Durability of Lightweight Expanded Clay Aggregate Concrete

The paper describes a development and use of lightweight concrete and lightweight self-compacting concrete using artificial lightweight aggregate based on expanded clay for ready mix concrete and precast elements. The objective of this research was to evaluate the lightweight concrete on durability of concretes placed in chemically aggressive liquid and gaseous environments (high concentrations of sulphate, chloride ions, automotive gas, oil and gaseous CO2 and SO2 environments).

Investigation of Corrosion of Cement-Based Materials by Using of Rotating Disc Method

The paper introduces the rotating disk method, its features and the scope of application. It also describes the application of this technique in the research of corrosion of cement-based materials caused by aggressive liquid solutions and the effect of flow of solutions on the corrosion rate

Formation of plasma technological influence of vacuum arc on the internal surfaces of metal pipes and putting of the protecting coatings

In many cases of industrial applications it is economically profitable or technically necessary to combine bulk features of one material with surface features of another one in a single material. Vacuum-arc treatment of products from inexpensive materials to form new required features of surface layers is more perspective owing to its unlimited feasibility in process efficiency. Pipes are in great demand in oil-gas industries and power engineering. But there are no effective methods for pipe inner surface treatment and pipe coating deposition, which makes it impossible to use inexpensive steel pipes under conditions of aggressive liquids, high temperature, high pressure and other parameters leading to oxidation, erosion and pipe life. Therefore, development of plasma-arc technologies of pipe inner surface treatment and pipe coating deposition is very topical and actual. A specific effect of vacuum-arc discharge on material surface is due to high concentration of energy in a chaotically rapidly moving cathode spot, short-term local heating of surface and its rapid cooling. The technological effect of cathode plasma on surface is based on cathode spot movement. The effect of a plasma flow of cathode spots formed on the outer surface of a pipe cathode and controlled by a system of vacuum-arc cathode spot fixation with magnets placed inside an electrode has been considered. A great number of studies have been devoted to explaining and investigating “anomalous” movement of the cathode spots. It has been shown that the cathode spot moves in the direction of the greatest action of discharge’s own magnetic field and outer magnetic field. The magnets initiate an arc magnetic field that confines the cathode spots and makes it possible to scan (control) them on the electrode-cathode surface and act with a plasma flow and deposit coats on inner surface of a coaxially placed pipe-product. The high efficiency of the plasma vacuum-arc method for pipe inner surface treatment and coat deposition has been found.

Procedure for determination of the speed of sound in liquids

Experimental values of the speed of sound in nitrogen tetroxide and hydrogen peroxide are obtained using a procedure that eliminates direct contact with the aggressive liquids. The relationship between the speed of sound and the concentration of hydrogen peroxide in an aqueous solution is revealed.

Impact of a synthetic leachate on permittivity of GCLs measured by filter press and oedopermeameter tests

Geosynthetic clay liners (GCLs) are used in landfill liner applications due primarily to their low hydraulic conductivity to water. The low hydraulic conductivity of GCLs comes from the structure of the clay in the bentonite. However, the interaction between clay and aggressive liquids may alter the structure of the clay and, thus, result in an increase in the hydraulic conductivity of the GCL. This paper presents the results of a project aimed at evaluating the impact of a synthetic leachate on the structure of four different bentonites used in the manufacturing of GCLs. The preparation of bentonite dispersions increased the interaction between the bentonites and the various liquids. The hydraulic properties of the dispersions also were tested using filter press tests to obtain flow curves. Results of these tests were correlated with the cationic concentration, electrical conductivity and pH of the dispersions, swell indexes of the bentonite extracted from the GCLs, and permittivities of the intact GCLs determined in oedopermeameter tests. The results showed that one bentonite was more sensitive to the synthetic leachate than the other bentonites. For example, the permittivities of the more sensitive bentonite based on the oedopermeameter tests and filter press tests were respectively 2.11 × 10 −8 s −1 and 5.6 × 10 −8 s −1, whereas the permittivities for other bentonites, including a natural sodium bentonite and two sodium-activated calcium bentonites, were respectively 5.7 to 6.5 × 10 −9 s −1 and 3.2 to 3.5 × 10 −8 s −1. The filter press test served as a quick and easy-to-use test to compare the performance of the various bentonites in containing a given liquid. However, the oedopermeameter test or direct permeation test is preferable to filter press tests or fluid loss tests for evaluating the long-term impact of a liquid on a bentonite.

Heat capacities of aqueous solutions of sodium hydroxide and water ionization up to 300 °C at 10 MPa

A commercial (Setaram C80) calorimeter has been modified to measure the heat capacities of highly caustic solutions at temperatures up to 300 °C and pressures up to 20 MPa. The improvements have allowed more accurate determination of the isobaric volumetric heat capacities of chemically aggressive liquids at high temperatures. Test measurements with aqueous solutions of sodium chloride showed a reproducibility of about ±0.1%, with an accuracy of ∼0.3% or better, over the whole temperature range. Heat capacities of aqueous solutions of sodium hydroxide at concentrations from 0.5 to 8 mol/kg were measured at temperatures from 50 to 300 °C and a pressure of 10 MPa. Apparent molar isobaric heat capacities of NaOH(aq) were calculated using densities determined previously for the same solutions by vibrating-tube densimetry. Standard state (infinite dilution) partial molar isobaric heat capacities of NaOH(aq) were obtained by extrapolation using an extended Redlich–Meyer equation. Values of the standard heat capacity change for the ionization of water up to 300 °C were derived by combining the present results with the literature data for HCl(aq) and NaCl(aq).

Playing safe with dangerous and corrosive liquids

Pumping aggressive liquids such as sulphuric acids, nitric acids, solvents and fuels requires extra care and attention, since some chemicals can crystallize or ignite if they are released into the atmosphere. Hakan Ekstrand of Tapflo AB explains how its recently developed air-powered diaphragm pump handles this situation.

Design of a scanning probe microscope with advanced sample treatment capabilities: An atomic force microscope combined with a miniaturized inductively coupled plasma source

We describe the design and performance of an atomic force microscope (AFM) combined with a miniaturized inductively coupled plasma source working at a radio frequency of 27.12 MHz. State-of-the-art scanning probe microscopes (SPMs) have limited in situ sample treatment capabilities. Aggressive treatments such as plasma etching or harsh treatments such as etching in aggressive liquids typically require the removal of the sample from the microscope. Consequently, time consuming procedures are required if the same sample spot has to be imaged after successive processing steps. We have developed a first prototype of a SPM which features a quasi in situ sample treatment using a modified commercial atomic force microscope. A sample holder is positioned in a special reactor chamber; the AFM tip can be retracted by several millimeters so that the chamber can be closed for a treatment procedure. Most importantly, after the treatment, the tip is moved back to the sample with a lateral drift per process step in the 20 nm regime. The performance of the prototype is characterized by consecutive plasma etching of a nanostructured polymer film.

Wear behaviour of low-temperature gas nitrided austenitic stainless steel in a corrosive liquid environment

The paper presents the results of an investigation into the wear behaviour of gas nitrided austenitic steel in a corrosive liquid representing conditions appropriate to the manufacture of soft drinks. The layers were obtained by low temperature (400 and 450 °C) gas nitriding and were predominantly composed of a phase known as expanded austenite. Non-treated austenitic stainless steel was used as a reference material and tests in deionised water were also carried out for comparison. The layers were characterised by XRD, optical microscopy, roughness and hardness measurements, and stationary potential tests. Wear and friction tests using an alumina ball as the counter-surface were used to characterise the tribological behaviour. For all samples, the wear performance in the aggressive liquid was superior to that in water, mainly due to a lubricating transfer layer formed on the alumina ball under these conditions.

Flow meter for high-purity and aggressive liquids

We describe a new kind of flow sensor for liquids, which is based on a balance between hydrodynamic and magnetic forces. A floating body, containing a permanent magnet, is kept at constant position in a tube by an external solenoid. The current in the solenoid required to compensate the hydrodynamic force by a magnetic force is used as a measure for the flow rate in the tube. An integrated viscosity and density measurement allows an autocalibration, if liquids of unknown density or viscosity have to be measured. The only material in touch with the liquid is teflon, which allows measurements of highly aggressive media or such with high requirements to hygiene or purity. The prototype covers a range of 20–250 ml/min and has a repeatability of ± 0.5 % full scale and an accuracy of ± 1 % full scale. The simple and modular design should lead to production costs which are significantly lower than those for other devices while offering the same performance.

Optical-fibre sensor system for monitoring the performance of the gas–propellant centrifuge separator of a spacecraft

An optical-fibre sensor system is presented for monitoring void fraction distribution in a spacecraft's gas and propellant centrifuge separator. The system could be used at the separator development stage or for monitoring, during ground tests, the elements of the spacecraft propulsion system. Our sensor system employs an array of point optical-fibre refractometric transducers installed in the form of several linear radial arrays on the separator rotating blades. We employed a small-size hemispherical optical detection element as the transducer and we optimized its parameters through numerical ray-tracing. The aim is to minimize the effect of the thin film of liquid that forms on the transducer's surface in this application. The features of this sensor system are: (1) an efficient matrix-type multiplexing scheme, (2) the installation of the main optoelectronic unit of the sensor in a hermetically sealed container inside the separator tank located on the rotating shaft and (3) the spark-proof and explosion-proof design of the sensor circuits and elements. The sensor is simple, reliable, low-cost and is capable of withstanding the factors involved during operation of the propulsion system such as cryogenic temperatures and chemically aggressive liquids. The novel elements and design concepts implemented in this sensor system can also find applications in other sensors for spacecraft propulsion systems and also in a variety of optical-fibre sensors used in scientific research and industry.

Increasing the life efficiency of oil and gas pumps

In oil and gas pumping, corrosion is the ultimate dirty word. It leads to a waste of natural resources and creates problems where aggressive liquids and ecologically damaging toxins are being handled. Alan Brown, Sales Manager at Arc Energy Resources, discusses the benefits of weld overlay cladding to protect the internal surfaces of oil and gas pumping equipment from corrosion; and reviews the options available using corrosion resistant alloys.

Effect of Aggressive Liquid Media on the Durability of Polystyrene foam under Load

Effect of Aggressive Liquid Media on the Durability of Polystyrene foam under Load

Mechanical and electrochemical interactions during liquid–solid impingement on high-alloy stainless steels

The erosion–corrosion behaviour of three high-alloy stainless steels (UNS S31245, UNS S32654 and UNS S32750) under aggressive liquid–solid impingement conditions has been assessed using a combination of electrochemical tests and weight-loss analysis. The material loss occurring under conditions of varying solid loading (900 mg/l), and at a temperature of 18°C, velocity of 17 m/s and impingement angle of 90° has been scrutinised as a function of time. Post-test examination has identified material loss mechanisms and the physical relevance of erosion and corrosion interactions has been illustrated. In this paper it has been shown that the resistance to material loss for the three materials does not follow the expected trend of increasing resistance as hardness increases. Through electrochemical measurements the pure corrosion component of the material can be isolated and it has become clear that corrosion (through direct and indirect effects) plays an important role in the erosion–corrosion process of even high-grade stainless steels due to depassivation–repassivation events corresponding to solid impact in the corrosive medium. Although the pure corrosion process (direct corrosion effect) constitutes only a small part of the total material loss, there is an important synergistic factor defined as the effect of corrosion on erosion which means that corrosion-related processes can be significant in erosion–corrosion.