bluuebunny/crossref_metadata_2025 huggingface dataset:
Coal Dust Explosions in the Cement Industry
Authors: Alameddin AN , Luzik SJ
Published: December 2008

The number of coal fired industrial systems and utility power plants is rapidly increasing because of the high cost and uncertain availability of fuel oil and natural gas. For many cement producers in the United States, the conversion from fuel oil and natural gas to pulverized coal has been difficult, frustrating, and in a few cases, very costly. This study deals mainly with coal safety requirements in the cement industry which accounts for a very small percentage of coal usage in pulverized coal firing systems. It also deals with the safety requirements associated with coal grinding, drying, blending, transporting, and storing. Case histories investigated by the Mine Safety and Health Administration (MSHA) will be discussed, and recommendations will be made for future fire and explosion prevention.
A Sugar Dust Explosion and Some Measures to Limit Its Consequences
Authors: Geysen WJ , Belmans R , Scheys L
Published: December 2008

A dust explosion in a Belgian sugar refinery is described. Using the factory characteristics and the sugar dust parameters as encountered in this plant, and taking into account the results of the accident investigation carried out by the authors, preventive and protective measures are worked out. Adaptions of the installation are proposed and explosion vents in silos, bucket elevators, and dust collectors are introduced. Furthermore, attention was paid to electrical grounding, dustproof electrical equipment, isolation of the equipment with rotary valves, indirect input, and compartmentalization of different production lines. The preventive equipment maintenance program was adapted to minimize spark generation hazards. New regulations were introduced, among others a general no-smoking rule and a general open flame and hot work permit.
Suppression of Maize Dust Explosions
Authors: Moore PE
Published: December 2008

The results of a systematic series of maize (corn) dust explosion suppression trials in vessel volumes of 6.2, 10, and 25 m3 are presented. Tests are reported for explosions of both medium and high turbulence dust clouds. The four suppressants, Halon 1011, ammonium phosphate powder, water, and halon/powder hybrid, were tested. The ammonium phosphate powder proved to be significantly more effective than the other suppressants. In the case of highly turbulent maize dust explosions, the halon suppressant catastrophically failed to suppress the incident. Suppression effectiveness is shown to be more dependent on the speed of deployment of the suppressant agent than on the absolute concentration delivered into the vessel. Thus, deployment of suppressant from a larger number of smaller suppressors results in a lower suppressed explosion pressure. The criteria for the limits of effectiveness of a given suppression system are defined and the experimental results compared with a theoretical estimate of the expected suppressed explosion pressure. It is shown that there is a reasonable correspondence between the theoretical estimate and corresponding experimental measurement and concluded that a theoretical model can be used as a basis for the design of effective explosion suppression systems for industry.
Determination of Metal Sparking Characteristics and the Effects on Explosive Dust Clouds
Authors: Dahn CJ , Reyes BN
Published: December 2008

Of major concern in industry are hazards posed by metal-to-metal sparking in environments where potentially explosive dusts are present. The probability of ignition of a dust cloud by metal sparking is dependent on many factors including the type of metal, the contact speed of the metal surfaces, the contact time of the metal surfaces, the pressure on the contact surface, and the type and concentration of the dust cloud present (per Bowden, F. P. and Thomas, P. H., “The Surface Temperature of Slidings Solids,” Proceedings of the Royal Society of London, Series A, Vol. 223, May 1954, pp. 29–40).

The purpose of the test program was to determine the sparking characteristics of a series of metals and the effects of the sparks produced on several types of hazardous dust clouds. Propellant and black powder dust layers and clouds would be considered as hazardous materials. The test program showed metal sparking could ignite hazardous materials in dust cloud form.
Testing of Electrical Equipment for Use in Class II Hazardous Locations
Authors: Vaickauski RC
Published: December 2008

To prevent dust explosions, electrical equipment in Class II hazardous locations must have special construction features that meet rigid performance criteria. Dust-ignition-proof, dust-tight, and intrinsically safe are types of constructions used.

Underwriters Laboratories (UL) has developed construction and performance standards for these types of equipment. UL's hazardous location equipment test lab is a specially designed facility that provides separation of dust and explosion testing areas from laboratory personnel working areas. The lab has two dust test chambers for conducting dust penetration and dust blanket temperature tests. After each test setup is completed, testing is controlled remotely to protect lab personnel in case of a dust explosion. Testing is conducted using either grain or magnesium dust. Intrinsically safe equipment undergoes spark ignition tests with a specially constructed switching mechanism.

This paper describes Class II hazardous locations, types of protection used for equipment, and how electrical equipment tests are performed.
A Brief History of Dust Explosions
Authors: Verakis HC , Nagy J
Published: December 2008

This paper summarizes the history and early experimental studies of coal and other dust explosions.

In the 1600s, the explosibility of methane, hydrogen, and other combustible gases was recognized by the scientific and industrial community, but few scholars considered the possibility of a dust explosion. (Although a dust explosion could have occurred several centuries earlier, for example in a boat transporting grain from Egypt to Greece, the first recorded dust explosion occurred in an Italian flour mill in 1785.) In Europe, coal mining became an important industry and the dangers from explosions of fire damp (methane) were quickly recognized. However, most miners and many scientists did not accept the explosibility of coal dust.

It was noted in 1803 that coal dust in passageways had burned and contributed to the flame and violence of a mine explosion in England. In the 1800s, more evidence that coal dust in the absence of fire damp was explosive was obtained by investigators of mine accidents and experimental studies.

The pioneering work during the early 1900s of Taffanel in France and Rice in the United States convinced the mining industry of the danger of coal dust. Full-scale experimental studies of mine explosions began in 1911 in the Bureau of Mines Experimental Mine in Bruceton, PA.

Studies on the explosibility of other industrial dusts followed the recognition of the hazard of coal dust. During the late 1800s, investigations were made to evaluate the explosibility of combustible dusts and the causes of serious dust explosions in U.S. flour mills. Formation of the National Fire Protection Association in 1896 gave impetus to the recognition of the explosion hazard of industrial dusts.

Laboratory experiments on coal and other dusts continue to be made by the U.S. Bureau of Mines, universities, industry, and other research organizations.
Monitoring the Nation's Waters—A New Perspective
Authors: Murray TM
Published: December 2008

Until recently, attempts to monitor the condition of the nation's flowing waters focused on the physical and chemical characteristics of those waters while their biological communities were largely ignored. In addition, data were not collected in a statistically designed fashion. The Environmental Protection Agency (EPA), with the cooperation of the U.S. Fish and Wildlife Service, conducted a statistical survey of the status of the nation's waters, their fish communities, and the limiting factors affecting these fish communities. This study, the National Fisheries Survey, is one tool with which the EPA will continue to monitor national water quality. Among the major findings of the survey are that the majority of the nation's streams (67%) are currently suitable as sport fish habitat, water quality factors adversely affect the fish community in 56% of the nation's waters, and the ability of the nation's waters to support sport fish did not change appreciably during the 5 years which preceded 1982—overall, 91% of the nation's waters maintained a constant ability to support sport fish species during that period.
Innovative Designs for Water Quality Monitoring: Are We Asking the Questions Before the Data Are Collected?
Authors: Perry JA , Schaeffer DJ , Herricks EE
Published: December 2008

Water quality management consists of decisions about the environment; those decisions are usually based on data from monitoring programs. Such data are usually collected following a design which is governed by “bureaucratic risk,” that is, the perceived risk of ire from a superior. We propose the application of a systematic process called the Environmental Audit as a tool for guiding management decision making and for design of monitoring programs. Application of the Audit is shown to produce data which leads directly to real environmental information (in contrast to pure data). Such information is translated into management decisions which incorporate all elements of the broader definitions of environmental risk.
A Review of the Crater Lake Limnological Programs
Authors: Larson GL
Published: December 2008

In response to apparent changes in the water quality of Crater Lake, the National Park Service convened two workshops early in 1982 to evaluate the lake data base and then sponsored the limnological studies the following summer. In September of 1982, Congress mandated the Secretary of the Interior to initiate a ten-year program to develop an adequate data base and an understanding of physical, chemical, and biological characteristics and processes of the lake. Development of the program from 1982 to 1985 is described. The main objective is to stress ecological relationships among trophic levels and environmental conditions to bring a more holistic approach to the baseline data in order to evaluate the hypothesis that the lake has changed.
Coastal Monitoring: Evaluation of Monitoring Methods in Narragansett Bay, Long Island Sound and New York Bight, and a General Monitoring Strategy
Authors: Phelps DK , Katz CH , Scott KJ , Reynolds BH
Published: December 2008

This paper evaluates biological, chemical, and physical monitoring methods and presents a research strategy for coastal monitoring. The purpose of the strategy is to provide a conceptual model for detecting contaminant-induced perturbations of marine systems. The proposed strategy represents a shift in emphasis from analysis of chemical concentrations to an initial biological examination of the effects of contaminants on marine organisms. Evidence of adverse biological effects obtained in this hierarchical strategy would result in the application of chemical and physical techniques to identify the types and sources of contaminants.
Monitoring and Quality Assurance Procedures for the Study of Remote Watershed Ecosystems
Authors: Stottlemyer R
Published: December 2008

The advent of widespread, long-term environmental issues such as atmospheric contaminants requires reassessment of monitoring techniques and procedures to improve field and laboratory quality assurance. We are studying mineral nutrient budgets in mature northern watershed and lake ecosystems which have widely varying inputs of atmospheric contaminants. These sites have been little studied, so consistency and appropriateness of sampling procedure and analysis is critical. We have developed a series of sampling and data quality objectives and procedures which allows us to estimate the accuracy of field methods and sample integrity and to determine analytical bias and precision in the laboratory. The system employs a series of internal and external audits and relies heavily on existing protocols developed by national monitoring and research organizations.
The Application of Ion Exchange to the Determination of Impurities in Aluminum and Aluminum Alloys
Authors: Seim HJ
Published: December 2008

Methods are described for the determination of low percentages of gallium and lead in aluminum alloys using anion exchange chromatography and atomic absorption spectrophotometry. Limits of quantitation can be lowered by at least an order of magnitude over methods without preconcentration. With minor modifications, the method for gallium can be applied to the determination of trace levels of iron, zinc, and cadmium. The lower limits of measurement using 1-g samples are 0.001% for both gallium and lead. Using larger sample weights, the limits for both elements can be lowered to at least 0.0005%.
Novel Sample Preparation Techniques for Chemical Analysis—Microwave and Pressure Dissolution
Authors: DeMenna GJ , Edison WJ
Published: December 2008

As the capabilities of an analytical laboratory expand to meet the increasing demand for tighter specifications and lower detectability, one must be cautious not to let the chemistries involved be a limitation to the analysis. This becomes particularly true when sophisticated, multi-element analytical capability in an instrument allows over 800 elemental determinations per hour, and the typically labor-intensive preparation of the samples prevents utilizing such capability. Classical preparation techniques involve multiple steps and introduce contamination and error into the analysis. Some procedures involve costly equipment or slow dissolution times, which further reduce the laboratories throughput. There are many techniques: some very old that have been forgotten through lack of use and others that are so unconventionally new that analysts usually do not consider them, which are applicable to the preparation of many types of samples. This report reviews a selection of the techniques themselves and the results obtained from the analysis of several types of samples.
Laser Damage in Plastics at the Frank J. Seiler Research Laboratory (FJSRL)
Authors: O'Connell RM , Saito TT , Deaton TF , Siegenthaler KE , McNally JJ , Shaffer AA
Published: December 2008

In order to study ways to improve the laser damage resistance of transparent polymers and thereby realize their advantages for high power laser system applications (e.g., they are lightweight, inexpensive, and castable), a laser damage program has been established at FJSRL. In this paper we describe the damage facility and present the results obtained during the initial year of the program.

The heart of the damage facility is a 1.06-micron wavelength Q-switched Nd:YAG laser capable of providing 300 mJ, 8 nsec FWHM pulses at repetition rates up to 10 pps. For the results reported here, the beam was focused to a 46 micron 1/e2 spot diameter.

Extensive single and multiple-shot bulk damage studies were made of several commercially available materials including polymethylmethacrylate (PMMA), three grades of polycarbonate (PC), and cellulose acetate butyrate (CAB). Measured single-shot damage thresholds were, respectively, 41 J/cm2, 15 J/cm2, and 15 J/cm2, which correlates with the relative “dirtiness” of the materials. Of the three materials, PMMA also had the greatest multiple-shot damage resistance. However, at fluence levels ≤ 0.1 times its single-shot threshold, CAB appears to be remarkably damage resistant.

Preliminary measurements were also made on PMMA which was synthesized in-house from both unpurified and moderately purified monomers, both with and without unpurified plasticizers. The single-shot damage threshold of the material made from purified monomers (no plasticizer) was 1.6 times that of the material made from unpurified monomers. The multiple-shot behavior of the purified material as compared to that of the unpurified material was even more remarkable.
Strengthening of Calcium Fluoride
Authors: Willingham CB , Spears MA , Graves GA , Knecht WL
Published: December 2008

Improvements in the fracture and grain boundary strengths in fusion cast calcium fluoride are discussed. A fluorocarbon cleaning process that successfully improved the fracture strength was scaled to an apparatus capable of treating 30-centimeter diameter CaF2 ingots. Mean fracture strengths of 132 MPa (19 ksi) were obtained. Diffusion of strontium ions into CaF2 failed to strengthen the material because stress relaxation effects eliminated the induced stresses.
Bulk Absorption Measurements Using Prism-Shaped Samples for Laser Calorimetry
Authors: Temple PA , Arndt DP
Published: December 2008

A method is described where low absorption samples are cut in the shape of prisms. The prism angles are chosen to allow the (polarized) laser beam to enter the prism at normal incidence and exit the prism at Brewster's angle. This configuration eliminates internal reflections and allows for easier analysis. Measurements are then made at various positions along the prism to obtain the total absorptance for several path lengths through the sample. The method has the advantage of simplified analysis and minimal surface absorption fluctuation. The disadvantages are special sample shape and a need for a special calorimetric setup allowing sample translation. Representative data will be shown for single-crystal and fusion-cast CaF2 at HF and DF wavelengths.
The Effect of Surface Finish on the Laser-induced Damage Thresholds of Gold-coated Copper Mirrors
Authors: Wood RM , Waite P , Sharma SK
Published: December 2008

Gold-coated copper mirrors with both diamond-turned and conventionally polished substrates have been evaluated in terms of their laser-induced damage thresholds (LIDT) at 10.6 μm. A detailed study of the surface finish on each component has revealed that a log-inverse log relationship exists between LIDT and substrate preparation.
Damage Threshold of Fused Silica at 3ωo
Authors: Mengue JF , Friart D
Published: December 2008

Our laser-matter interaction program requires the conversion of our OCTAL laser from 1.06 μm to 0.355 μm. Fused silica is used to realized the focusing lens and the last optics (KDP windows, debris-shield, etc). A damage test facility at 3ωo was build in CEA Limeil in order to compare the performance of the different French manufacturers production (polished fused silica was provided by SORO, REOSC, BERTIN ESO, STIGMA-OPTIQUE, ELECTRO-QUARTZ).
Development of RF-Sputtered Laser Coatings at Burleigh Northwest
Authors: Lunt DLJ
Published: December 2008

Complex dielectric coatings, with up to forty-three layers have been deposited using RF diode sputtering techniques. Deposition parameters have been established for ZrO2, SiO2 and Al2O3. Fabrication consistency has been high in both material properties and spectral response, and the coatings have shown useful damage, loss and environmental attributes, for laser applications, in the realms so far investigated.
Comparison of Optical Coatings Deposited by Novel Physical and Chemical Techniques
Authors: Wodarczyk FJ , Strauss DR , Harker AB
Published: December 2008

We have undertaken a systematic study of various methods of depositing good quality thin films of optically interesting materials by different physical and chemical methods in an effort to identify promising techniques for producing low-absorbing, low-scatter, high damage-threshold coatings. The deposition methods studied include e-beam deposition in a UHV environment, sol-gel processes utilizing hot isostatic pressing (HIP) to densify the films, photochemical deposition using organometallic reagents entrained in inert or potentially reactive gas flows, and ion-beam deposition in a reactive environment. The deposited single-layer films were analyzed using various surface analysis techniques to provide information on film composition, stoichiometry, and impurity level.
Optical Characterization of Low-Scatter, Plasma-Deposited Thin Films
Authors: Partlow WD , Choyke WJ , Bennett JM , Silva RM
Published: December 2008

Plasma-deposited thin films, sometimes called plasma CVD or plasma-enhanced CVD, are deposited in a low pressure gas phase reaction that is controlled by a glow discharge plasma. Substrate temperatures of 200 – 300°C, low compared to conventional CVD processes, are typical for plasma-coating processes. This new coating method has wide possible applications in the optics area. In this paper we will describe studies that have been made to determine if the films are suitable for critical optical applications requiring highly uniform, low-scatter films that, for example, could be used as mirror coatings or as graded index antireflection coatings. We have evaluated the surface quality of SiO2 and Si3N4 films approximately 1000 Å thick, plasma-deposited onto silicon and silicon carbide substrates. Evaluation techniques have included surface profiling using a Talystep instrument, Nomarski microscopy, and total integrated scattering. In all cases, comparisons have been made between the coated and uncoated substrates. The best Si3N4 films have been found to contour the very smooth surfaces onto which they were deposited, while the SiO2 films added only a minimal additional roughness, of the order of 2.8 Å rms. Some problems have been encountered, however, with particulates contained in the films; techniques for minimizing these effects will be discussed.
Optical Properties of Ion-Beam Sputtered TiO2 Films
Authors: Demiryont H , Kerwin DB , Sites JR
Published: December 2008

Ion-beam sputtered TiO2 films were simultaneously deposited onto Corning 7059 and silicon substrates for ellipsometric and spectrophotometric investigation of optical parameters. Film thicknesses ranged from 5 to 500 nm, and spectrophotometer wavelengths from 400 to 2500 nm. Results from the two techniques agree well at the 632.8 nm wavelength used for ellipsometry.

At thicknesses above 100 nm and wavelengths above 1 μm, the TiO2 refractive index was insensitive to changes in thickness or wavelength. It increased, as expected, at shorter visible wavelengths, and it decreased markedly for films below 100 nm in thickness. The index varied with the oxygen to argon ratio of the ion beam, showing a maximum value of 2.52 for 632.8 nm wavelength light. The extinction coefficient was too small for spectrophotometric measurement in the infrared; previous calorimetric measurements for half wave films at 1.06 μm showed absorption below 100 p/m. The extinction coefficient, however, increased in the visible, typically reaching values corresponding to a few tenths percent absorption at 0.4 μm.
Improvement of the Damage Threshold of High Reflectivity Multidielectric Coatings 1.06 μM
Authors: Geenen B , Malherbes A , Guerain J , Boisgard D , Friart D , Garaude F
Published: December 2008

Development of new high power laser for laser-matter interaction in C.E.A. Limeil requires the realization of H.R. coatings with damage thresholds above 8 J/cm2.

MATRA's laboratory “couches minces optiques” (thin optical layers) production commercial mirrors was around 3.5 J/cm2 in 1982. In order to obtain better results we decided to improve the control of evaporation parameters such as:

– vacuum and regulation of oxygene pressure by means of a mass spectrometer

– better measurements of evaporation temperature and regulation of evaporation rate

– measurement and control of substrate temperature by pyrometric observation and to automatize the process.

These different measurements and controls enable us to establish new processing operations giving better evaporation condition.

The result was an increase of damage threshold from 3.5 J/cm2 to 8 J/cm2.
Characterization of Micron-Sized, Optical Coating Defects by Photothermal Deflection Microscopy
Authors: Abate JA , Schmid AW , Guardalben MJ , Smith DJ , Jacobs SD
Published: December 2008

Information about the localized absorbing defects in optical thin films is required for a better understanding of laser-induced damage. Photothermal deflection microscopy offers a nondestructive optical diagnostic which can yield spatially resolved absorption data on simple and multiple-layer AR and HR dielectric coatings. This paper describes the computer-controlled apparatus used to generate absorption maps of dielectric thin films and an experiment in which a partial correlation between localized absorption sites and damage caused by nanosecond laser irradiation at 351 nm is established.

An absolute calibration of absorption for our measurement technique is presented here. Micron-sized absorbtive defects of Cu were introduced into our coatings to provide a means of calibration. Also presented here are some preliminary data on the modification of the absorption signatures measured by photo-thermal deflection as a function of the location of the defect within the coating layers.
Plasma Deposited Inorganic Thin Films for Optical Applications
Authors: Partlow WD , Heberlein JVR
Published: December 2008

Plasma deposited thin films, widely used in semiconductor processing, have begun to be used in optical applications such as anti-reflective coatings and optical waveguides. Amorphous films of refractory materials such as SiO2, SiC, and Si3N4 have been applied with high optical perfection on substrates at 200—300°C with this process. Control of index of refraction has been achieved by selecting appropriate deposition parameters.

We describe the plasma deposition process and the properties of these coatings. We present applications and discuss how these coatings may be applied to more demanding optical applications in the future such as graded index films, rugate coatings, and vacuum UV reflecting films. We see that hydrogen inclusion in the films is a factor that must be controlled, and we propose methods to accomplish this.
Laser-Induced Emission and Laser Damage of Optical Components
Authors: Nichols DB , Morris DJ , Bailey MP , Hall RB
Published: December 2008

The role of point defects in the failure of high-power laser optical components has been the subject of many analytical and experimental studies. We describe a related surface effect, newly observed, which is visible-wavelength emission from component surfaces undergoing exposure to infrared laser radiation at levels far below the visible damage threshold. This effect has been observed on a variety of optical components, including coated reflectors and uncoated window materials. In large-spot tests, the total emission amplitude exhibits strong time dependence. Spatial imaging shows distinct point sources of the visible emission, some of which recur during multiple-shot tests. Spatial correlations between (a) microscopic surface defects visible before damage, (b) emission points due to laser irradiation, and (c) damage points due to high-power laser irradiation, have been studied using spatial mapping techniques with indexing uncertainties of ∼25 μm. For dielectric coatings, a strong correlation is observed between the recurrent visible emission points, and pulsed laser damage points.
Laser Damage Threshold Predictions Based on the Effects of Thermal and Optical Properties Employing a Spherical Impurity Model
Authors: Lange MR , McIver J , Guenther AH
Published: December 2008

The influence of the thermal and optical properties of thin films on the damage threshold for pulsed laser induced damage is studied via the spherical impurity damage model. A previous study employing the geometric cross section of the impurity as the absorption cross section of the incident laser predicted several scaling laws. Those scaling laws gave the damage threshold as a function of the laser pulse parameters along with the thermal properties of the thin film and impurity. That model neglected the effect of the optical properties of the thin film and impurity and the wave nature of the incident laser. These are incorporated in the present study by utilization of Mie scattering theory resulting in somewhat modified scaling laws. The absorption cross section results from Mie theory are presented and discussed along with a comparison of the scaling laws with each other and with experimental data. No simple scaling laws for the optical properties are apparent and, as such, a numerical study of these are conducted and the trends suggested by the analysis are compared with experimental observation.
“Analytical Model for Evaluating Transient, Steady-State, Coating Damage Threshold, Optical Distortion, and Axial Gradient for Externally Cooled Laser Mirrors.”
Authors: Palmer JR
Published: December 2008

There are a number of requirements in high energy laser systems to provide optical elements that are not integrally cooled. However, there are many instances where a cooling gas, such as helium or nitrogen, may be used to cool the front and back surfaces in order to reduce optical distortion.

In order to evaluate the response of an optic to this type of cooling, first order analytical techniques have been generated to determine transient and steady-state temperature distributions through a fully irradiated optic, an irradiated spot on a large optic, and a toroidal shaped beam (i.e., hole in the beam), on a large optical element.

Cooling temperatures and damage relationships coupled with optical path differences of the flowing gas are treated for evaluation. Optical distortion of the element due to radial and axial temperature gradients are treated for both transient and steady-state conditions and for various gas flow dynamics.
Catastrophic versus Microscopic Damage: Applicability of Laboratory Measurements to Real Systems
Authors: Foltyn SR , Jolin LJ
Published: December 2008

At ultraviolet wavelengths, damage to both coatings and bare surfaces is dominated by the presence of discrete localized defects. During multiple-shot irradiation, the overwhelming majority of these defects are damaged by the first or first few shots. Initially, damage morphology is that of a crater of approximately 10 μm in diameter; however, upon continued irradiation, one of two events can occur: either the crater grows to catastrophic dimensions or it remains unchanged. In the latter case, the damage is only observable under a microscope, it may be indistinguishable from cosmetic defects present before irradiation, and it is likely that any related degradation in optical performance is unmeasurable.

In view of the generally accepted definition of laser damage (i.e., any visible change in the surface), it is important to consider the implications for real systems. These are discussed in the context of ultraviolet test results for both coatings and surfaces.
Toward Improved Accuracy in Limited-Scale Pulsed Laser Damage Testing Via the “Onset Method”
Authors: Seitel SC , Porteus JO
Published: December 2008

A recently reported method for determining the defect damage onset (minimum intensity for defect initiated damage) in optical surfaces offers certain advantages over more conventional methods. First of all, the onset is a more reliable and useful indication of operational performance than conventionally measured thresholds, which may depend strongly on the size of the tested area. Secondly, measurement of damage frequency vs intensity provides valuable information on defect densities. This permits more effective use of a limited test area and provides a basis for defect classification. Effective limited-scale testing is becoming increasingly important as larger optical surfaces and reduced defect densities are made possible by improved coating technology.

In this paper, the onset method is mainly applied to 1.06 μm coatings, tested with a 40 μm (D-1/e2) Gaussian focal spot and 2.7 μm coatings, tested with a 67 μm spot. Comparisons are made between onsets and conventionally measured thresholds, including a demonstration of convergence with large-spot thresholds from other laboratories. Examples of damage frequency distributions indicating the presence of more than one class of defect will also be shown. Finally, the onset model is extended to include flat-topped spatial profiles, and possible advantages over Gaussian profiles are noted.
Simple Direct Measurements of n2
Authors: Williams WE , Soileau MJ , Van Stryland EW
Published: December 2008

A simple direct method for measurements of n2 is described. The method involves measurements of beam distortions in the transmitted, time-integrated spatial profile using an optical multichannel analyzer. A model is described which allows extraction of n2 from fits of experiment to computer generated theoretical spatial profiles. The results for picosecond pulses at 1.06 μm and 0.53 μm are presented for three materials: fused quartz, NaCl, and CS2. Little dispersion in n2 is seen for each material over the wavelength range studied.
Perspectives on 100% Solid Spray-Applied Polyurethane Elastomers
Authors: Oechsle SJ
Published: December 2008

This paper offers an overview of technological progress in polyurethanes—in particular, their use as a protective coating. The physical characteristics of the coatings are discussed, with special emphasis on the new 100% solid spray-applied polyurethane systems. A breakdown of advantages, commitments, and market opportunities is presented.
Precision Reactivation of Antifouling Paints
Authors: Poretz I
Published: December 2008

Present-day operation of commercial and military ships requires smooth ship bottoms in order to minimize the ship's frictional resistance as it moves through the water. The hydrodynamic advantage of the smoother hull results in lower fuel consumption, which, at current fuel prices, significantly lowers operating costs.

Frequent drydockings to renew antifouling coatings are intended to maintain ship-bottom smoothness. However, they are expensive, interfere with the flexibility of ship operations, are not always completely successful, and do not permit full realization of the economic potential of smooth bottoms for long periods. Recognizing the need to overcome these limitations, the Norwegian Ship Research Institute, with the support of the maritime industry and in close cooperation with paint manufacturers, has developed a successful underwater reactivation technology for an antifouling paint. This technology is described and compared with conventional coatings and another advanced type of coating. Ship-bottom roughness requirements for optimal fuel economy are discussed in numerical terms. The cumulative roughness of underwater hull surfaces during periods between drydockings is compared for conventional and advanced reactivatable antifouling coatings. Finally, a typical program for a ship on a five-year drydocking cycle that is consistent with U.S. regulatory and certification requirements is illustrated.
Minimum Film Thickness for Protection of Hot-Rolled Steel: Results after 23 Years of Exposure at Kure Beach, North Carolina
Authors: Morcillo M
Published: December 2008

This study was initiated by Dr. Wouter Bosch, University of Missouri at Rolla, in 1957, more than 25 years ago, under the direction of the Corrosion Committee of the Federation of Societies for Paint Technology. It has been continued by the Steel Structures Painting Council (SSPC) from 1966 to the present, under the sponsorship of the Federation.

Originally, the purpose of this study was to determine the optimum film thickness for a few representative coatings in typical atmospheres, with the hypothesis that there were likely to be some differences in film thickness requirements among coatings, surface preparation grades, and atmospheres of varying severity.

Four progress reports have been published, the most recent in 1969 by the Steel Structures Painting Council. This 10-year SSPC report showed clearly (1) an increase of about 20 months of paint life for each additional mil of paint thickness, applicable to all oil-based and alkyd paints in three environments (industrial, marine, and rural); (2) a critical minimum thickness for each generic type of paint; and (3) the value of applying sufficiently heavy films at the beginning rather than undertaking more frequent maintenance painting.

The results given in this work refer only to panel exposure tests in the marine environment of Kure Beach (800-ft lot), North Carolina, while previous studies also considered rural and industrial environments.

The variables studied include type of paint (oil, alkyd, phenolic, vinyl, chlorinated rubber, and epoxy ester), surface condition of steel before and after surface preparation, and a wide range of film thicknesses (primer and topcoat).

The main conclusions of the study are:

• For surface preparation, the degree of cleanliness is much more important to the performance of chemical-resistant coatings than to the performance of conventional coatings.

• Total dry film thickness (primer and topcoat) is the most important factor. Obviously, the minimum paint film thickness required for an effective protection is a function of the required protection duration.

• Nine mils of oil paint film thickness (primer and topcoat) do not afford protection for more than 10 to 12 years (until Rust Grade 8, SSPC-Vis 2/ASTM D 610, Evaluating Degree of Rusting on Painted Steel Surfaces, is reached).

• With other paint systems, film thicknesses of 10 to 12 mils, or even less, afford effective protection after more than 23 years.
A View of the Mackay and Labofina Laboratory Tests for Assessing Dispersant Effectiveness with Regard to Performance at Sea
Authors: Byford DC , Green PJ
Published: December 2008

A comparison has been made of the Mackay and Labofina tests for evaluating oil spill dispersants, in terms of showing correlation with effectiveness at sea. Both tests have been found to provide repeatable data on the efficiency of dispersants. Good agreement was obtained between the two tests for the efficiency ratings of five commercially available dispersants as well as for the identification of optimum surfactant combinations. When differences occurred between the two methods in the selection of optimum formulations, the cause was found to be the onset of wave damping affecting the Mackay test results. The major advantages of each test were speed and simplicity in the case of the Labofina test and the simulations of wind shear and wavemixing action on dispersant-treated oil at sea for the Mackay test. While both methods showed significant disadvantages, both were considered useful in predicting dispersant performance at sea.
The Drop-Weight Interfacial Tension Method for Predicting Dispersant Performance
Authors: Rewick RT , Sabo KA , Smith JH
Published: December 2008

The drop-weight test is an improved interfacial tension method for predicting the relative effectiveness of oil-spill dispersant products. The test is based on the relationship between the weight of a drop of oil detached from a capillary beneath a dispersant-in-seawater solution and the lowering of the interfacial tension between oil and water. A modified test procedure, based on measuring the time for a drop detachment rather than the weight, significantly reduces the test time and simplifies the apparatus. Another modification permits the determination of relative diffusion rates of dispersants through an oil column. Seventeen water-based dispersant products were evaluated with light Arabian crude oil and, in some cases, with No. 6 fuel oil using the modified procedures. The results were interpreted in terms of data reliability and compared with information obtained by a standard test.
Effectiveness of Oil Spill Dispersants at Low Salinities and Low Water Temperatures
Authors: Lehtinen CM , Vesala A-M
Published: December 2008

The effect of ambient low salinity and low temperature in the Baltic Sea on the effectiveness of dispersants was investigated in the laboratory using a Mackay-Nadeau-Steelman apparatus. Three dispersants were tested on two oils (fresh and weathered crude) at different water temperatures (4, 12, and 15°C) and different salinities (3, 7, and 12‰). The results show a strong dependency on water temperature for all the dispersants tested, although one chemical was less sensitive than the others in this respect. The dispersants showed significant differences between their sensitivity to changes in salinity and in the relationships between effectiveness and dosage. The stability of the dispersion obtained seems to be influenced by both type of oil and water temperature, and some difference between the chemicals could be found also in this respect. The parameters studied strongly affected the performance of the dispersants. It is therefore essential to make a careful choice of dispersants for use in low salinity environments such as the Baltic Sea.
Chemical Oil Dispersion in Trials at Sea and in Laboratory Tests: The Key Role of Dilution Processes
Authors: Bocard C , Castaing G , Gatellier C
Published: December 2008

To minimize the ecological impact of oil at sea, dispersants are used to spread the spill across a large amount of water and thus make hydrocarbon levels low enough to be sublethal. Such an objective demands two correlative conditions: (1) that an oil-in-water emulsion can be obtained by adding the dispersant and (2) that rapid dilution conditions are provided by a downward motion of oil droplets and wind-induced velocity shear between surface and subsurface. In September 1981, two 6-m3 slicks in the Mediterranean Sea were treated by two concentrated dispersants. More than 1500 samples were taken at different depths during several hours following treatment and were analyzed by a differential method to measure separately oil and dispersant. Direct measures were also recorded by a continuous flow of water through a nephelometer and a spectrofluorometer. Despite apparently complete emulsification of the slick, the most efficient dispersant did not preclude some of the oil from resurfacing 6 h after treatment. The short-term fate of dispersed oil was therefore under the control of the sea conditions, which limit dilution processes. Because any laboratory test in closed vessel cannot duplicate dilution factors, a new approach is being developed to measure simultaneously the rate of dispersion and the behavior of test marine animals submitted to variable concentrations of potentially toxic substances during the flow of dispersed oil through a continuous system.
Recommended Methods for Testing the Fate and Effects of Dispersed Oil in Marine Sediments
Authors: Anderson JW , Vanderhorst JR , Kiesser SL , Fleischmann ML , Fellingham GW
Published: December 2008

Tests have been conducted to determine the extent of dispersed oil sorption on sediments and retention of this association when seawater is flushed through the substrate. Sediment beds were prepared where dispersed oil in seawater was allowed to percolate down through the sand. Water concentrations of dispersed oil were determined before and after percolation. Distribution of oil in sediments was shown to be very patchy and not suitable for quantitating effects on benthic species. Eighty-three percent of the oil remained in the top 3 cm during this process. Additional tests in special cores showed that sediments containing dispersed oil would release about 40% of the oil when seawater flowed from the bottom of the core up through the bed of sand. Based on the fact that most of the dispersed oil is held in the top 3 cm of sub-strate when water is drained completely through the sediment, it is recommended that exposure systems be designed with a layer (2 to 3 cm) of contaminated substrate on top of clean sediment. Fiberglass trays (with mesh bottoms) were prepared in this manner and exposures initiated in both subtidal and intertidal areas in Sequim Bay, Washington. The alterations in hydrocarbon component composition during the exposure periods will be described. Biological responses measured in these studies were the growth of small clams and the recruitment of multiple benthic species.
Comparison of the Fate and Ecological Effects of Dispersed and Nondispersed Oil in a Variety of Intertidal Habitats
Authors: Baker JM , Crothers JH , Little DI , Oldham JH , Wilson CM
Published: December 2008

Field experiments were carried out to compare the littoral fate and ecological effects of chemically dispersed oil and nondispersed oil. The basic experimental design was a series of treatments applied to marked plots on rocky shores, a salt marsh, an intertidal sea-grass bed, and sand and mud flats. The treatments included a variety of oils and the dispersants BP 1100 WD, BP 1100X, Corexit® 8667, and Corexit 7664, applied directly to the intertidal plots. Results from treatments on intertidal rock suggested that oil deposition or oil deposition followed by dispersant cleaning had a greater effect than dispersant cleaning alone on limpets (Patella spp.) and small winkles (Littorina spp.). On the salt marsh, oil or oil followed by dispersant cleaning significantly reduced the density of the perennial grass Spartina anglica C.E. Hubbard and the annual plant Salicornia spp. Dispersant alone had relatively little effect on the vegetation. On the sea-grass bed, although variability was high, all treatments reduced the percentage cover of the sea-grass Zostera noltii Hornem. Sediment hydrocarbon analysis indicated little long-term retention of applied oil (whether dispersant treated or not) in the salt marsh mud and in muddy sand on a waterlogged intertidal flat. However, in the sea-grass bed sediments and in the fine sands on freely draining intertidal flats, dispersant-treated oil was, in some cases, retained at greater concentrations than untreated oil. The results are discussed with reference to the rocky shore Exposure Scale of Ballantine, to the shoreline Vulnerability Index of Gundlach and Hayes, and to factors such as the behavior of the water table, particle size, and depth of disturbance of sediments.
The Comparative Fate of Chemically Dispersed and Untreated Oils in an Arctic Nearshore Environment
Authors: Boehm PD
Published: December 2008

The distribution and environmental fate of petroleum hydrocarbons introduced into the nearshore environment of Cape Hatt, Baffin Island, Canada, during two controlled experimental discharges of a Venezuelan (Lagomedio) crude oil have been studied. An analytical program based on a combination of ultraviolet/fluorescence studies, high resolution gas chromatography, and computer-assisted gas chromatographic mass spectrometry has been used to examine several hundred oil, seawater, sediment, sediment trap, surface floc, and benthic animal (seven species) samples to determine the distribution, transport, and weathering of oil spilled in two scenarios: as untreated oil on the surface and as chemically dispersed oil discharged below the surface. Conclusions are drawn about the weathering of oil in the two scenarios, transport of low and high molecular weight hydrocarbons into the water column and their persistence, the sedimentation of oil, the incorporation of oil into the sediment via sedimentation onto the surface floc and direct penetration of the sediment/water interface, and the uptake and depuration of untreated and chemically dispersed oils by seven species of filter feeders and deposit feeders in the subtidal benthos.
Ecological Considerations for the Use of Dispersants in Oil Spill Response
Authors: Lindstedt-Siva J , Albers PH , Fucik KW , Maynard NG
Published: December 2008

A multidisciplinary task force with membership from government agencies, academia, and industry is developing ecologically based guidelines for dispersant use in marine and estuarine environments. The guidelines are organized by habitat type (e.g., coral reefs, rocky shores, bird habitats) and consider dispersant use to protect the habitats from impact, to mitigate impacts, and to clean the habitats after a spill. Each guideline contains a description of the habitat type covered, recommendations for dispersant use, and a background section reviewing the relevant literature. The goal is to minimize the ecological impacts of oil spills. Aesthetic, socioeconomic, and political factors are not considered, although it is recognized that these are important concerns during spill response. Use of dispersants is considered along with other appropriate countermeasures and compared with the “no cleanup” alternative.