Mechanical Cleaning Methods Research Articles

Bonding adhesive strength for plasma spray with cathode spots of low-pressure arc after grit blasting and removal of oxide layer on metal surface

Cathode spots of a low-pressure arc can remove oxide layers and evaporate impurities on metal surfaces. Removal of the oxide layer using cathode spots is expected to solve recent obstacles due to chemical and mechanical cleaning methods. Various phenomena of cathode spots have been investigated for pre-treatment of atmospheric pressure plasma spray (APPS). This study treated the surface shapes of oxide and non-oxide samples using a composite pre-treating method: cathode spots after grit blasting. In addition, the samples are compared with conventionally treated cathode spots and mechanical blasted surfaces. Results show that roughness on the sample surfaces becomes higher in concomitance with the initial oxide layer thickness. This fact reveals the factors those dominant bonding strength on the pre-treated surface using cathode spots of a low-pressure arc. Bonding strength becomes higher in relation to the arithmetical mean height of the surface roughness caused by the initial oxide layer thickness. Bonding strength is higher when the mean spacing of profile irregularities is narrower. The bonding adhesive strength after treatment using cathode spots after grit blasting is greater than 90 MPa. However, cathode spot treatment must be limited not to destroy the projection formed by melting after grit blasting in an arc time up to 5 s. And basically the removal characteristics of oxide layer using the cathode spots were discussed on the trace, roughness, number of cathode spots in time and pressure, moving speed on the metal surface, etc.

Effects of process parameters and anti-scalants on scale formation in horizontal tube falling film evaporators

In multiple-effect distillers with horizontal tubes, which are increasingly employed in seawater desalination, scale formation on the heat transfer surfaces has a highly deleterious effect on specific energy consumption and production capacity. The allowance for potential scale formation by over-sizing the heat transfer surface, scale prevention methods, cleaning methods as well as production losses during plant shutdown for cleaning create considerable capital, operating, and maintenance costs. It is therefore essential to incorporate a cost-effective scale control technique. In multiple-effect distillers scale is formed on the outside of the tubes. Mechanical cleaning methods cannot be employed. Achieving effective scale control by suitable anti-scalants is a major challenge for the desalination industry. Scale formation and control in multiple-effect distillers with horizontal tubes for seawater desalination have barely been investigated. The effects of the process parameters and of the anti-scalants on the properties of the scale, e.g., the composition, structure, and morphology, are inadequately understood. Clarifying these aspects of scale formation would facilitate further improvement of anti-scalants and thus the efficiency of multiple-effect distillers. In order to study scale formation and control under conditions that are close to those prevailing in industrial multiple-effect distillers, a horizontal tube evaporator at pilot-plant scale was employed. In the test rig the process conditions in any stage and at various operating conditions of multiple-effect distillers can be provided. Thus, the effects of the thermal field, the flow field, the fluid properties, and the substrate properties can be studied. Experiments with artificial seawater were performed at different operating conditions. Novel aspects of the formation and reduction of scales formed from falling seawater films on the outside of horizontal tubes are presented. The effects of various process conditions such as fluid temperature, heat transfer surface temperature, heat flux, and seawater salinity on the composition and structure of scale layers are shown. The beneficial effects of polymeric anti-scalants on the quantity, composition, and morphology of the scale are discussed. For example, the use of only 0.5 ppm of a specific anti-scalant effectuated a very strong reduction of the calcium carbonate content in the scale as well as a notable decline of the magnesium hydroxide content.

Pre-treatment on metal surface for plasma spray with cathode spots of low pressure arc

The cathode spots of the low pressure arc can remove the oxide layer and evaporate impurities on the metal surface. The removal of the oxide layer by using the cathode spots is expected to solve the recent problems of the chemical and mechanical cleaning methods. The phenomena of the cathode spots for pre-treatment of Atmospheric Pressure Plasma Spray (APPS) have been investigated. In this paper, the surface shapes of oxide and non-oxide work pieces were treated by using a composite pre-treating method: the cathode spots after grid blasting. In addition, they are compared with conventional cathode spots treated and mechanical blasted surfaces. As the results, the roughness on the surface of work pieces is arisen with the initial oxide layer thickness. It reveals the factors dominating bonding strength on the surface pre-treated by using the cathode spots of the low pressure arc. The bonding strength increases with the arithmetical mean height of the surface roughness due to the initial oxide layer thickness. The bonding strength is raised when the mean spacing of profile irregularities becomes narrow. The bonding adhesive strength treated by the cathode spots after the grid blasting is over 90 MPa.

Laser-induced alteration of contaminated papers

Cleaning of paper objects represents one of the most complex cases of laser ablation, since low volumes of dispersed material phases are evaporated while a sensitive and fragile fibrous organic matrix has to be preserved. Conventional chemical and mechanical cleaning methods suffer from the common phenomenon that the foreign matter is diluted into the substrate rather than removed. The application of a laser beam allows highly localized and optically specific interaction. However, the occurrence of extreme temperatures and light intensities may cause irreversible alteration of the paper matrix. Further, incomplete removal and/or chemical conversion of contaminations may result in insufficient cleaning or affect the ageing behaviour. Laser treatments were performed by Q-switched Nd:YAG lasers at three wavelengths (355 nm, 532 nm, and 1064 nm). Papers contaminated with inks and adhesive-tape remnants served as model samples. Multispectral imaging and colorimetric results served to quantify and systematize the results.

Er:YAG laser: an innovative tool for controlled cleaning of old paintings: testing and evaluation

A cleaning method based on an Er:YAG laser system at 2.94 μm, highly absorbed by OH bonds, was tested for removal of over-paintings, varnishes and patina top-layers from various painted surfaces, including laboratory paint models and old paintings. The aim was to evaluate the efficiency, selectivity and safety of the laser cleaning method using various pulse energies and various OH containing wetting agents to enhance the efficacy and limit the penetration of the laser beam. A large number of paint models were prepared with known characteristics (type and number of layers, thickness, composition) simulating old masters’ techniques. A set of diagnostic controls was designed to study the effects of the laser radiation on the surface components, including morphological, optical and chemical examination and analyses. The aim was also to compare the laser method with the traditional solvent based procedures. Thresholds of safe energy were found for each type of surface layer such as varnishes and over-paintings. The results confirmed the suitability of the Er:YAG laser when used by qualified and expert conservators, especially in combination with traditional chemical and mechanical cleaning methods.

The South African early fossil hominids and John Talbot Robinson (1923–2001)

Bone is a primary source of information in prehistoric contexts. In many cases, this type of material cannot be studied without prior cleaning, which is further conditioned by the state of preservation and deposits found on it. This experimental study applies a new method that can be used to evaluate the possible modifications that mechanical cleaning can cause on archaeological bone materials. These modifications have been objectively identified through the use of artificial crusts and statistical analyses. Microhardness testing also made it possible to consider how variability in the state of preservation of the archaeological material can influence cleaning. The study presents an initial classification of the modifications and an evaluation of the effectiveness of mechanical cleaning methods. Our conclusions advise caution in the use of these cleaning methods and support the need for further research to better evaluate cleaning processes and the modifications they can induce in archaeological bone material.

Transplantation of allogenic anterior lens capsule to the subretinal space in pigs.

To investigate the consequences of transplantation of a new basement membrane to the subretinal space (SRS) as a substitution of Bruch's membrane. Porcine anterior lens capsules (ALC) were transplanted to the subretinal space of 20 eyes from 19 young Danish landrace pigs. All pigs underwent a three port localized pars plana vitrectomy. Seventeen eyes received naked ALC. In three experiments the ALC was embedded in gelatine, in order to prevent curling of the ALC. The observation period varied between zero and 49 days. The pigs were examined by ophthalmoscopy and fundus photography. Histopathological examination of enucleated eyes was performed at the end of the experiment. ALCs transplanted to the subretinal space were well-tolerated and caused no inflammation when Bruch's membrane was left undamaged. After 11 days host RPE and glial cells started to cover the ALC in a competitive fashion. When Bruch's membrane was damaged, ingrowths of choroidal vessels and fibroblasts was prominent. The use of gelatine to flatten the ALC did not prevent curling, and gelatine caused pronounced inflammation. It is possible to transplant porcine ALC to the SRS of the pig. ALCs are well-tolerated in the SRS and are covered with well-differentiated monolayers of host RPE-cells, if Bruch's membrane is left intact.

A METHOD FOR RAPID ANALYSIS OF BIOFILM MORPHOLOGY AND COVERAGE ON GLASS AND POLISHED AND BRUSHED STAINLESS STEEL

A tool for the rapid analysis of biofilms, using epifluorescence microscopy and image analysis was developed. The tool allows the evaluation of overall biofilm coverage and biofilm patch morphology. It will provide a quantitative method for identifying relationships between biofilms and their substrates and for identifying the morphology of patches of damaged bacteria. The coverage percentage allows evaluation of the growth of biofilms and will allow the evaluation of the effectiveness of sanitizers and mechanical cleaning methods in removing biofilms from food processing surfaces. The patch morphology is useful for investigating the relationships between surface morphology and biofilm growth and for determining the surface morphology, biofilm shape, and sanitizer effectiveness. The software was tested and validated using biofilms of E. coli K12 on glass, polished 316 stainless steel, and brushed 316 stainless steel. The biofilms were stained with both propidium iodide and SYTO–16. After performing digital image analysis of both overall coverage and biofilm patch morphometrics, it was found that the percentages of living or total biofilm were independent of the substrate material. However, the absolute area of individual biofilm patches varied depending on the substrate material. These areas also showed changes over time. The circularity of the biofilm patches was investigated. At the end of the studies, the shape of most of the biofilm patches in this group was nearly circular.

The Influence of Multiple Fouling and Cleaning Cycles upon the Membrane Processing of Lignosulphonates

Although the application of pressure-driven membrane technology continues to grow, fouling remains a major unsolved problem. Despite the success achieved with mechanical cleaning methods such as backfluushing and backshocking, chemical cleaning-in-place remains the major way to tackle fouling 1–3 . This paper investigates the relationship between fouling and cleaning processes, and how they influence each other over a number of operational cycles. Results are reported for the ultrafiltration of lignosulphonates, which simulates a real industrial filtration problem in the pulp and paper industry. Cleaningwas undertaken with both an acid and a commercial aqueous cleaning formulation. Results are presented which show that cleaning performance is strongly dependent upon the nature of the foulant. Results also illustrate the importance of examining membrane performance over several fouling and cleaning cycles.

Isolation and Determination of Starch from Amaranth (Amaranthus cruentus) and Quinoa (Chenopodium quinoa)

From the seeds of Amaranthus cruentus and Chenopodium quinoa the starch was gained by the means of mechanical cleaning methods and their starch content was found out by four different methods: by subtractiv determination; polarimetrically with the CaCl2-method and with two enzymatic methods. The results of the subtractiv method were used to calculate the Ewers-factor (hydrochloric acid method).

Investigation of low fouling surface alloys made by ion implantation technology

Despite numerous investigations and industrial mitigation strategies, formation of deposits on the heat transfer surfaces is still the major problem in design and operation of industrial heat exchangers. This article describes the development of stainless steel surfaces with low surface energy by ion implantation, which experience considerably reduced fouling without the inherent disadvantages of surface coatings, chemical additives and mechanical on-line cleaning methods. Fouling experiments during pool boiling of CaSO 4 solutions demonstrate that thermal fouling is significantly reduced for all investigated conditions of heat flux and CaSO 4 concentration.

Stability of Mass Standards Made of XSH Alacrite: Gravimetric Study of the Influence of Cleaning

Some fifteen years ago, the Institut National de Métrologie (France) opted to produce its secondary mass standards in XSH alacrite and adopted a mechanical cleaning method using ethanol and isopropanol. This paper concerns the influence of this cleaning method and presents some of the results obtained on two alacrite kilograms. The influence of the cleaning process is not the same on the two standards which are nevertheless as similar as possible from the manufacturing point of view. Alcohol cleaning leads to mass variations of several tens of micrograms causing the standard to be unstable for several months. It finally reaches a mass value that is stable, but is not reproducible.

Cleaning of metal-contaminated graphite tiles of the TEXTOR ALT-II pump limiter blades

Graphite is the preferred material for plasma facing components in today's fusion experiments and it is a prime candidate material also for coming fusion devices. At least in the existing tokamaks it cannot be excluded that the graphite surface will become contaminated, e.g. with metals, which leads to undesired effects on the plasma. Instead of an expensive exchange for new graphite parts, an appropriate cleaning method should be applied. This paper describes comparative tests of different mechanical cleaning methods applied to metal contaminated graphite tiles of the ALT-II toroidal belt pump limiter in the TEXTOR tokamak. Scanning electron microscope techniques have been used to characterize the cleaning efficiency. Best results have been obtained by sandblasting the graphite surface with boron carbide grains, which proves to be a very effective, inexpensive and fast cleaning method. After reassembly of the tiles, in-situ tests by exposure to tokamak discharges showed undetectably low (≤10 −5) metal concentrations in the TEXTOR plasma.

Asphaltene deposition: a survey of field experiences and research approaches

The paper reviews the experiences]of the oil industry and the progress and direction of the research community in their efforts to provide solutions to the asphaltene deposition problem. The oil industry, basically, seems to be combating the problem through remedial rather than preventive methods. Mechanical and chemical cleaning methods are being improvised to maintain production at economical levels. The research community, currently, is rather split in the approach to model the asphaltene deposition problem. One school of thought considers the asphaltenes dissolved in the oil in a true liquid state and dwells upon thermodynamic techniques to predict their phase behavior. Another considers asphaltenes to exist in oil in a colloidal state, as minute suspended particles, and utilizes colloidal science techniques, among other, to predict their phase behavior. Experimental work over the last 40 years suggests that asphaltenes may exist in a colloidal state in the crude oil and further pursue of the subject in this direction by both the industrial and research communities is warranted.