bluuebunny/crossref_metadata_2025 huggingface dataset:
Football Helmet Fitting Errors in Wisconsin High School Players
Authors: McGuine T , Nass S
Published: March 2009

The purpose of this study was to evaluate if football helmets were correctly fitted in high school football players from 34 randomly selected Wisconsin public high schools. Helmets were evaluated for correct fit by certified athletic trainers with the consent of the head coach. Helmet fit was assessed by examining seven specific criteria selected from standardized helmet fitting guidelines. The criteria selected for examination were as follows: (1) 1-in. (2.5-cm) clearance above the eyebrows, (2) 2-in. (2.5-cm) minimum clearance from nose to face mask, (3) chinstrap centered and tight, (4) jaw pads snug to face, (5) hear holes aligned and tight, (6) adequate coverage of the posterior cranium, and (7) minimal anterior/posterior movement with pressure. Each of the criterion was visually and manually inspected by the certified athletic trainers while the helmet was being worn by the football player. Other collected information included helmet brand, who fit the helmet, and year in school for the football player. In 1671 helmets 3403 fitting errors were observed for an overall fitting error rate (mean ± SD) of 2.04 ± 1.40, range 0 to 7. Of the helmets, 15.4% (n = 258) had no fitting errors, 23.5% (n = 392) had one or two fitting errors, 22.2% (n = 371) had 3 errors, and 15.4% (n = 258) had 4 or more errors. Bike helmets had the highest fitting error rate (2.34 ± 1.45) and highest percentage of helmets with 4 or more errors, 22.6% (n = 113), but Riddell® helmets had the lowest rate (1.84 ± 1.34) and the lowest percentage of helmets with 4 or more errors, 11.9% (n = 99). Freshman players had the highest fitting error rate (2.56 ± 1.44), while senior players had the lowest rate (1.80 ± 1.29). The most common error, 43.3% (n = 724) was inadequate or excessive clearance above the eyebrows. The least common error, 2.9% (n = 49), was adequate coverage of the posterior cranium. Although football helmets cannot prevent all head injuries in high school football, a correctly fitted helmet may decrease the likelihood of sustaining such an injury. Further study in this area is warranted.
Traction Measurement on Natural Turf
Authors: McNitt AS , Waddington DV , Middour RO
Published: March 2009

An apparatus was developed and field tested to measure traction. The apparatus consists of a framework that supports a leg and foot assembly that can be used to measure both rotational and linear traction using different footwear under various loading weights. The force required to cause foot movement is measured at various degrees of rotation or linear distance traveled. Experiments were conducted to determine the effect of turfgrass and soil conditions on traction of turf areas. Specifically, the influences of species, cutting height, shoe type, and loading weight on traction were determined using this apparatus.

Tall fescue and Kentucky bluegrass provided the highest traction values while perennial ryegrass and creeping red fescue provided the lowest. Higher linear traction values occurred with lower cutting heights. As vertical force increased, traction increased. A studded shoe provided higher linear traction than a molded shoe across all species and cutting heights, while a molded shoe proved higher rotational traction under some conditions.
Strength and Conformance Testing of a GCL Used in a Solid Waste Landfill Lining System
Authors: Merrill KS , O'Brien AJ
Published: March 2009

This paper describes strength and conformance tests conducted on a Bentomat ST geosynthetic clay liner (GCL) used in a composite lining system for the Cells 4 and 5 expansion of the Anchorage Regional Landfill in Anchorage, Alaska. The Cells 4 and 5 lining system included use of an 80-mil, high-density polyethylene (HDPE) liner overlying a GCL on both the sideslopes and base of the cells. The use of this lining system in a Seismic Zone 4 area on relatively steep side slopes required careful evaluation of both internal shear strength of the GCL and interface friction between the GCL and textured HDPE. Laboratory tests were carried out to evaluate both peak and residual GCL internal strengths at normal loads up to 552 kiloPascals (80 pounds per square inch). Laboratory tests also were conducted to evaluate the interface strength between the GCL and Serrot “box and point” textured HDPE. Interface strengths between both woven and nonwoven sides of the GCL and the textured HDPE were evaluated. Considerations related to use of peak or residual strengths for various interim stability cases are described in this paper. Stability analyses using stress-dependent interface and internal strengths for the GCL are addressed. The quality assurance and conformance testing program adopted for the project on GCL is discussed also.
The Effect of Refrigerants in the Mixed Lubrication Regime
Authors: Mizuhara K , Tomimoto M
Published: March 2009

Because of environmental concerns, CFC (chlorofluorocarbon) refrigerants must be replaced with HFCs (hydrofluorocarbons.) As a result, many tribological problems are caused especially in rotary piston compressors. To solve the problem, the effects of refrigerants on friction and wear characteristics of the oil and refrigerant mixtures at the mixed lubrication regime are investigated. The difference in refrigerants are clearly observed not only in boundary but also in the mixed lubrication regime. The effects of operating conditions on sliding conditions and experimental results are also discussed. It is concluded that for practical application where long life is essential, experiments must be conducted under the mixed lubrication regime. Also, the importance of defining the lubrication regime in terms of film parameter is emphasized.
Tribology of Hydraulic Pumps
Authors: Yamaguchi A
Published: March 2009

To obtain much higher performance than that of alternative power transmission systems, hydraulic systems have been continuously evolving to use “high-pressure”. Adoption of positive displacement pumps and motors is based on this reason. Therefore, tribology is a key technology for hydraulic pumps and motors to obtain excellent performance and durability.

In this paper the following topics are investigated: 1. The special feature of tribology of hydraulic pumps and motors. 2. Indication of the important bearing/sealing parts in piston pumps and effects of the frictional force and leakage flow to performance. 3. The methods to break through the tribological limitation of hydraulic equipment. 4. Optimum design of the bearing/sealing parts used in the fluid to mixed lubrication regions.
Vickers' 35VQ25 Pump Test
Authors: Johnson HT , Lewis TI
Published: March 2009

In the late 1970's, Vickers, Inc., recognized that their methods of establishing petroleum based fluid recommendations had become inadequate. They provided poor correlation with the field results in the higher pressure and higher speed pumps that had been developed for the mobile hydraulics market. A test procedure based on the high performance VQ product line that had the most severe fluid antiwear requirements was therefore developed.

This paper discusses the resulting 35VQ25 vane pump test; summarizes the rationale used to select test parameters; and presents an interpretation of results with various fluids. The influence of test parameters and variations in production pump components on the overall results are outlined.

Although not developed as a replacement for existing industry standards, the test procedure has become widely used within our industry over the last 15 years. As a result, this paper will attempt to compare the pros and cons of this procedure to other alternatives such as ASTM D-2882.
Energy Efficiency Screening Test for Hydraulic Fluids
Authors: Bronshteyn LA , Smolenski DJ
Published: March 2009

A novel technique for measuring very small variances in friction coefficient due to a change in oil or additive type is presented. A standard pin-on-disk tribometer is used for test oil friction measurement in comparison with a reference oil. The “OCWS” (Oil Change Without Shutdown) test procedure has been used to increase test precision and eliminate the baseline variations that are unavoidable with separate test measurements.
Pump Tests for Hydraulic Fluid Wear Qualification
Authors: Tessmann RK , Heer DJ
Published: March 2009

Modern hydraulic systems are operating at higher pressures and higher temperatures than ever before. In addition, the life and reliability of the hydraulic components and hence the hydraulic system is becoming more and more dependent upon the characteristics of the circulating fluid in the system. The hydraulic component which normally suffers most when the correct fluid is not used in the system is the hydraulic pump. Three different types of hydraulic pumps are widely used in hydraulic systems. Vane pumps have been the dominant type of pump for hydraulic systems. Gear pumps have replaced vane pumps in many applications. Piston pumps are rapidly gaining popularity. Therefore, the pump manufacturers are conducting tests to qualify fluids for use with their pumps and the fluids formulators are conducting tests to show that their formulations are compatible with hydraulic components. Unfortunately, the tests most widely used are either not industry standards or do not address problems encountered with some hydraulic pumps.

This paper presents an overview of the pump tests which are currently available or which are specific to certain hydraulic pumps. Since there are few standard pump tests, many companies have devised their own tests to be confident of the fluids which they qualify. Additional concepts in pump testing are proposed and discussed.
Proposed Hydraulic Pump Testing for Hydraulic Fluid Qualification
Authors: Melief HM
Published: March 2009

The current ASTM D-2882 hydraulic vane pump test does not provide the necessary correlation required for the prediction of the lubricating properties of a hydraulic fluid in various piston pump operations. All too often, a fluid will exhibit excellent wear properties in the Vickers V-104 vane pump used in the ASTM D-2882 test, yet produce catastrophic failure at various wear interfaces in a piston pump which may consist of different material pairs, contact loading, configuration or speed. In this paper, a new piston pump test, which is conducted under cycled pressure testing conditions, is proposed. The new test will provide an excellent assessment of the lubricating properties of a hydraulic fluid under a wide variety of wear conditions.
Tribological Experiences of an Axial Piston Pump and Motor Manufacturer with Todays Available Biodegradable Fluids
Authors: Witte KH , Wills DK
Published: March 2009

Since the late 1970's, biodegradable fluids have been used in hydrostatics with limited success. Performance has not matched expectations during extensive field testing. For example, fluids reported as having excellent lubricating properties, by bench and field testing, produced excessive wear. Design modifications successfully resolved some of these problems, but wear problems with sealing and bearing surfaces still exist, suggesting that fluid properties may need to be modified. New test procedures measureing wear e.g. may need to be developed as well because of the correlation problem between reported fluid properties and axial piston pump performance like good lubricity resulted in excessive wear.
Relating Solid Contaminant Particle Size Distribution to Flow Degradation in Hydraulic Pumps
Authors: Frith RH , Scott W
Published: March 2009

Power hydraulic pump wear is difficult to quantify. Measuring the actual material lost due to wear is impossible in a practical sense. An available simulated procedure is the contaminated sensitivity performance test which measures flow degradation with increasing amounts of contamination in the fluid. It is shown that wear can be related to flow degradation and knowing the mass of contamination causing wear, models for pump wear can be explored. An approach to calculating damaging contaminant mass from particle size distribution is given.
A New Test Method for Determining the Anti-Wear Properties of Hydraulic Fluids
Authors: Priest M , March CN , Cox PV
Published: March 2009

Existing pump test procedures for determining the anti-wear properties of hydraulic fluids are expensive to undertake, have a long test duration and require a large quantity of test fluid. This paper describes a project to develop an alternative low cost bench screening procedure of short duration, requiring only a small quantity of test fluid and using simple reproducible test specimens. A high level of correlation is demonstrated between the new test method and existing vane pump test procedures for a range of hydraulic fluids including mineral oils and water-glycol fluids. The new test procedure is highly suited to the hydraulic fluid development process requiring only ten litres of fluid per test and a maximum total test duration of six hours.
Importance of Mechanical Testing of Hydraulic Fluids
Authors: Reichel J
Published: March 2009

Anti-wear properties of hydraulic fluids are important because hydraulic pump and motor wear is costly. Hydraulic fluid performance specifications represent minimum requirements. International hydraulic fluid performance standards are being developed by ISO/TC28/SC4 committee as draft (ISO DIS 11158 “Specifications for Mineral Oil Hydraulic Fluids”). Performance specifications for non-mineral oil hydraulic fluids are also being developed.

Typically, both the user and fluid manufacturer have insufficient information relating to the anti-wear properties of a new fluid to be used in hydraulic equipment, such as axial piston pumps, vane pumps or radial piston motors. Therefore, pump lubrication and operation requirements, preferably pre-existing in pump manufacturer's specifications, must be determined. The required fluid lubrication properties may be determined by either laboratory pump tests or by a field trial, often at the expense of the customer. More preferably, the lubrication properties of the hydraulic fluid should be determined under mechanical conditions equivalent to field practice. In this paper, the use of both the vane pump test and the FZG Gear Test to predetermine the “recommended“ hydraulic fluid lubrication performance will be discussed. In this way, fluid performance may be determined at significantly lower cost than more expensive large scale hydraulic pump and motor tests which slower and more energy consuming.
An Extensometer for Soft Material Strain Measurement
Authors: Shrive N , Damson E , Frank C , Meyer R , Mejig L , Lucas G
Published: March 2009

The criteria for the design of a device for measuring strain in flexible materials, particularly soft tissues, are described. An extensometer is described which meets the design criteria. The resolution of the extensometer depends on its gage length. With a gage length of 5 mm, a resolution of 20–50 microstrain can easily be obtained. Some preliminary results are presented showing the sensitivity of the results obtained to the contact force between the extensometer and the specimen.
Use of Portable/in situ Stress-Strain Microprobe System to Measure Stress-Strain Behavior and Damage in Metallic Materials and Structures
Authors: Haggag FM , Wang JA , Sokolov MA , Murty KL
Published: March 2009

A novel portable/in situ Stress-Strain Microprobe (SSM) system was used to measure true-stress/true-plastic-strain (σt-ϵp) behavior of several met llic materials, welds, and their heat-affected-zones (HAZs) in various metallurgical and damage conditions. The SSM system utilized an automated ball indentation (ABI) technique to measure elastic modulus, yield strength, σt-ϵp curve, strength coefficient, strain-hardening-exponent (uniform ductility), and to estimate fracture toughness (from the ABI-measured flow properties) in carbon steels, stainless steels, nickel alloys, aluminum alloys, titanium alloys, zirconium alloys, etc. Numerous ABI tests were also conducted on several nuclear pressure vessel steels (NPVSs) in the unirradiated, neutron irradiated, and post-irradiated thermally-annealed conditions. For all these test materials and conditions, the ABI-derived results were in good agreement with those from conventional standard test methods. Furthermore, the nondestructive ABI test results rigorously indicated the various levels of neutron-embrittlement damage and the percentage of ductility recovery following thermal annealing of the NPVS specimens. In situ/nondestructive structural applications of the SSM system and its ABI technique have been demonstrated by testing a circumferentially welded stainless steel pipe and a full-thickness section of a nuclear pressure vessel (using 90° V-blocks and magnetic mounts for temporary attachment of the SSM testing head to the pipe and the steel section, respectively). All SSM localized tests were computer-controlled and conducted in less than 2 minutes per ABI test; depending on the desired strain rate. Example test results on metallic structural components and samples are presented in this paper.
Stress Intensity Measurement via Infrared Focal Plane Array
Authors: Lesniak JR , Bazile DJ , Boyce BR , Zickel MJ , Cramer KE , Welch CS
Published: March 2009

A full-field thermoelastic technique for measuring stress intensity factors in dynamically loaded fatigue crack specimens is outlined. Thermoelastic Stress Analysis (TSA) uses an infrared focal plane array detector and high-speed processing electronics to produce stress images of cyclically loaded specimens. The TSA data is then used in combination with a fitting algorithm to determine stress intensity factors for mode I and mixed mode I and II crack geometries. The technique is non-contacting, fast and accurate, and has the potential to greatly enhance the efficiency of fatigue and fracture testing. An analytical solution for the complete stress state in terms of the first stress invariant is derived in support of the full-field TSA technique. Results using the technique on mode I and mixed mode specimens are presented, and show good agreement with accepted values.
Accelerated Aging and Associated Changes in Ultra-High Molecular Weight Polyethylene (UHMWPE) Microstructure as a Function of Resin Type and Consolidation Variables
Authors: Poggie R , Takeuchi M , Averill R , Nasser S
Published: March 2009

The purpose of this investigation was to characterize the consolidation structure of several types of commercially available, medical-grade ultra-high molecular weight polyethylene (UHMWPE) before and after accelerated oxygen aging. The observations were correlated to the following: (1) UHMWPE resin molecular weight, 2 to 4 versus 4 to 6 million; (2) presence versus absence of calcium stearate; (3) two consolidation methods, ram extrusion versus sheet molding; (4) gamma radiation (2.5 to 3.0 Mrads) versus as-consoli- dated; and (5) consolidation process parameters (manufacturer controlled, “A” versus “B”). Accelerated aging was performed at 70°C, 5 atm pressure, and pure oxygen for 20 days. Optical microscopy was performed on 90-μm-thick sections, with FTIR analysis performed on selected samples. The results of this investigation showed: (1) calcium stearate slightly decreased resistance to oxidation; (2) for a specific resin and manufacturer, compression-molded sheet was more resistant to oxidation than ram-extruded rod; (3) oxidation was not observed for some gamma sterilized UHMWPE while others were significantly oxidized; and last and most important, (4) the resistance to oxidation of a specific UHMWPE resin is most dependent on optimal process parameters (time, temperature, pressure, and cooling, dependent on manufacturer) during resin consolidation, regardless of method. For this study, the most degradation resistant UHMWPE was optimally processed compression-molded GUR 1020 sheet.
Characterization of Solid Products of Corrosion Generated by Modular-Head Femoral Stems of Different Designs and Materials
Authors: Urban RM , Jacobs JJ , Gilbert JL , Rice SB , Jasty M , Bragdon CR , Galante JO
Published: March 2009

This paper reviews the microanalytic and histopathologic findings from studies reported previously by our laboratory describing the nature and significance of solid products of corrosion generated at modular junctions of femoral components for hip replacement. A total of twenty-five retrieved, corroded modular junctions with surrounding tissues were examined from a variety of component designs and material combinations, including head/neck couples of CoCr/CoCr, CoCr/Ti6Al4V, and Al2O3/CoCr. The products were examined using electron microprobe with energy dispersive x-ray analysis, x-ray diffraction, and Fourier-transform infrared spectroscopy.

The products of corrosion identified at the modular junctions of all of the various prostheses examined were similar regardless of the implant design or materials coupled, even when a ceramic head was employed. The most prevalent corrosion product was characterized as an amorphous chromium orthophosphate hydrate-rich material. Particles of this material were identified throughout the periprosthetic tissues of most of the cases studied and at the polyethylene bearing surface of several cases. The multitude of particles generated by fragmentation of the corrosion products and the finding that they migrate to sites distant from their origin are of concern because of their potential to increase the production of polyethylene wear debris by a three-body wear mechanism and their direct participation in particle-induced, macrophage-mediated osteolysis.
The Mechanical and Electrochemical Processes Associated with Taper Fretting Crevice Corrosion: A Review
Authors: Gilbert JL , Jacobs JJ
Published: March 2009

Implant modularity has become a primary implant design concept used in total hip replacement procedures. However, over the last 5 years evidence of corrosion attack in taper crevices formed at the junction of these components has come to light from retrieval analyses. The goals of this paper are to summarize the results of retrieval studies and to discuss the material properties and the mechanical and electrochemical processes which are hypothesized to govern the corrosion attack observed. This paper will review several test methodologies developed by the authors to evaluate aspects of the proposed mechanism of mechanically assisted crevice corrosion. Retrieval studies have shown that both mixed-alloy (Ti-6Al-4V stems and Co-Cr-Mo heads) and similar-alloy (Co-Cr-Mo stems and Co-Cr-Mo heads, and Ti-6Al-4V stems and Ti-6Al-4V heads) couples demonstrate corrosion attack in-vivo. These results indicate that this corrosion process is not due solely to the mixing of dissimilar metals but may occur as a result of mechanical-electrochemical interactions in the taper crevice. Oxide film fracture due to mechanical fretting and the restricted crevice environment of the taper combine to cause changes in the solution chemistry of the fluid inside the taper including pH drops and increases in chloride concentrations. Furthermore, the potential of the implant can become significantly more negative causing the oxide film which reforms to be thinner than the original film and moves the implant's potential toward the active range for corrosion attack. The role of solution chemistry, sample potential and the mechanical tenacity of the oxide films and the test methods used to evaluate these factors will be discussed as they effect the corrosion attack observed.
Corrosion Testing of Modular Hip Implants
Authors: Goldberg JR , Buckley CA , Jacobs JJ , Gilbert JL
Published: March 2009

Flexibility in sizing, lower inventory requirements, and the ability to choose materials with optimum physical properties for each component have made modular hip implants the design of choice for most orthopedic surgeons. However, the presence of surface asperities and angular mismatch between the head and neck components can result in the formation of a crevice between the taper surfaces of the assembled couple. This crevice may be large enough to allow fluid ingress and fretting to occur which can lead to crevice and fretting corrosion.

This paper describes several test methods used to duplicate the fretting behavior of modular taper components and determine the electrochemical changes that occur as the result of fretting corrosion. Mixed and similar metal modular taper junctions were tested in phosphate buffered sahne solution with and without the application of a cyclic load. Fretting currents, open circuit potential (OCP), and pH, pO2, and [Cl-] of solution trapped inside the spaces between the head and neck components were measured. Metal ion concentrations in fluid trapped inside similar metal taper junctions were measured. The effects of load magnitude on OCP and fretting currents were determined. Test components and trapped solution were inspected and analyzed for signs of corrosion. Results of testing support a hypothesis of mechanically assisted crevice corrosion and are presented.
Oxygen Piping Code—Where Knowledge Becomes Practice: Keynote Address
Authors: Koch UH
Published: March 2009

The principles of oxygen safety have been well known for many years, but oxygen fires—most having the same technical causes—continue to occur. This paper reviews several typical oxygen fire incidents. The author points out that, despite the best efforts of the ASTM G-4 Committee and others to inform and educate, existing knowledge about oxygen system safety does not reach the people who need it most, such as architects, engineers, contractors, building inspectors, and insurance underwriters. The author suggests that the ultimate solution is a national oxygen piping code and that the ASTM G-4 Committee should take an active role in its development.
Total Water Demand for Suppression of Fires in Hypobaric Oxygen-Enriched Atmospheres
Authors: Beeson HD , Forsyth ET , Hirsch DB
Published: March 2009

NFPA 99B Standard for Hypobaric Facilities defines an oxygen-enriched atmosphere to be any atmosphere in which the concentration of oxygen by volume is greater than 23.5 percent. It further defines an atmosphere of increased burning as any atmosphere containing a percentage of oxygen, or oxygen and nitrous oxide, greater than the quotient of 23.45 divided by the square root of the total pressure in atmospheres. Atmospheres of increased burning are required by the NFPA to be protected with a water fire-extinguishing system capable of delivering 305.6 L/min/m2 (7.5 gal/min/ft2). This requirement was developed by the NFPA using results from testing in 100 percent oxygen. This paper describes testing performed to determine the total water demand required to suppress fires in atmospheres of less than 100 percent oxygen. Testing was accomplished in a 7.1 m3 (250 ft3 ) hypobaric chamber using polyurethane foam and cotton fabric in atmospheres from 6.9 to 101.3 kPa (1 to 14.7 psia) and oxygen concentrations from 21 to 100 percent. The results indicate that the maximum water demand required to extinguish the fires was well below the NFPA requirement.
Inclusion of Oxygen Equipment Training in Workplace Basic First Aid Curricula
Authors: Starr LM
Published: March 2009

Occupational Safety and Health Administration (OSHA) regulations require that employers provide first aid training and supplies to ensure that employees have a safe and healthy workplace. To comply, some workplaces have acquired portable oxygen devices as part of their first aid supplies, and have completed nationally promoted oxygen training classes. However, as there has been no objective national curriculum for first aid courses or for oxygen training, course content varies. This paper reviews a newly proposed curriculum, and describes how national oxygen training courses and first aid programs can integrate mechanical, safe handling, and emergency care objectives into their courses. Recommendations for programs which appropriately describe first aid procedures and the control of hazards associated with use of oxygen equipment by first aiders are provided.
Use of Oxygen-Enriched Mixtures in Recreational SCUBA Diving -- Is the Public Being Informed of the Risks?
Authors: Gabel H , Janoff D
Published: March 2009

The use of enriched air mixtures, often called nitrox, has been getting more and more attention in the recreational diving community. This is especially true since major recreational diving organizations are starting to certify non-technical divers for oxygen-enriched nitrox diving. The decompression physiologists have explained both the risks and benefits of oxygen-enriched nitrox use in the diving literature. However, there are other risks that divers need to know about when using oxygen-enriched air. There is a belief in some groups in the diving community that any mixture less than 40 percent oxygen can be handled in the same manner as high pressure air.

This approach would include the use of materials are that are not very oxygen compatible, and little or no cleaning or contamination control. In this article, the authors would like to assert that this approach carries with it an unacceptable risk to the users of this equipment. To support this position, industry and professional society guidelines from ASTM, Compressed Gas Association, and The National Fire Protection Association are cited, as well as the results of research and testing. Recreational divers need to understand that as they increase the oxygen concentration in the mix, they also increase the chances of having a fire incident in their equipment. The recommendation is made that everyone involved in the design, use, servicing and refilling of oxygen-enriched diving gases must be aware of the additional hazards involved. This awareness will empower divers with the knowledge to make more informed choices about their equipment, and how it is maintained.
Failure of Stainless Steel Check Valve in Oxygen Service
Authors: Rago JJ
Published: March 2009

Past fires in check valves in oxygen service have yielded clear internal damage. In a recent failure, most of the valve internals, including polymers, were undamaged and evidence of fire was confined to an O-ring and groove that was downstream of threads. An apparent key causal factor was evidence of silicone grease present.
Failure of PTFE-Lined Flexible Hose in Oxygen Service
Authors: Rago JJ
Published: March 2009

Polymer lined flexible hoses can be vulnerable in high-pressure oxygen systems. Ignition within a hose occurred after pressurization. The hose was not protected with a distance piece. However, a key factor appears to have been the presence of contaminants of hydrocarbons. The trail of contaminants leading from the ignition point and following the path of flow is shown in the analysis of this failure.
A 6000 psig Gaseous Oxygen Impact Test System for Materials and Components Compatibility Evaluations
Authors: Newton B , Porter A , Hull WC , Stradling J , Miller R
Published: March 2009

Over the last several years, the International Standards Organization (ISO) has developed standards which require pneumatic impact testing on valves, regulators, and other oxygen components used in Europe in medical, industrial, and commercial applications. The several standards involved all reference a test system designed by BAM and presented in ASTM STP 1267 by Binder, et. al. in their paper “A 500 BAR Gaseous Oxygen Impact Test Apparatus For Burn-Out Testing Of Oxygen Equipment.” This paper discusses another gaseous oxygen impact test system designed to conform to the ISO standards, and presents its performance characteristics in pneumatic impact testing. This paper also discusses the value of a component test method and considers some of the critical parameters that should be maintained in order to produce consistent test results with different test systems.
Ignition Resistance of Hard (Type III) Anodized Aluminum to Particle Impact
Authors: Forsyth ET , Stoltzfus JM
Published: March 2009

The ignition resistance of hard (type III) anodized aluminum alloy to particle impact in pure oxygen was investigated. Test samples with aluminum oxide film thicknesses of 3 μm (0.12 mils), 5 μm (0.20 mils), 20 μm (0.79 mils), and 50 μm (1.97 mils) were tested at six different temperatures ranging from 239 K (-28 °F) to 672 K (750 °F). These anodized test samples were placed in a supersonic particle impact chamber with the impact surfaces directly exposed to the impacting particles. Aluminum alloy particles of 2000 μm (0.078 in.) diameter were used to promote ignition upon impact. The event of ignition was recorded on standard video. The test results are plotted as Logistic Regression curves showing the ignition frequency over the temperature range tested. The results are compared to previously tested soft anodized (type II) aluminum alloy and bare aluminum alloy. The results indicate that the hard (type III) anodized coating offers increased resistance to particle impact ignition as compared to bare aluminum. The data is inconclusive as to which anodization process (type II or type III) provides better protection from ignition.
Configurational Effects on the Combustion of Several Alloy Systems in Oxygen-Enriched Atmospheres
Authors: Janoff D , Pedley MD
Published: March 2009

The promoted combustion resistance of many metals and alloys have been evaluated using 3 mm (0.13 in.) diameter rods. Although the rod configuration has been useful in ranking alloys for combustion resistance, the threshold pressures determined are usually not directly applicable to configurations used in the actual design and fabrication of oxygen systems. This is especially true for configurations that have a higher surface area to volume ratio than a 3 mm diameter rod. Investigators have tested alloys for promoted combustion resistance in higher surface area to volume ratios and various configurations, such as small diameter wires, sheet, wire mesh, sintered filters, structured packings, tubing, and in the current investigation, metallic sponge. The effects of these various configurations on the promoted combustion resistance of several alloy systems will be reviewed. Alloy systems that will be reviewed are copper alloys, nickel alloys, stainless steels, and aluminum alloys.
Flammability Limits of Stainless Steel Alloys 304, 308, and 316
Authors: Werley BL , Hansel JG
Published: March 2009

More than 100 specimen combustion tests suggest that stainless steel thresholds of sustained propagation depend to a great degree on diameter, tubing wall thickness, positive burn criterion, presence of flow through tubing, and alloy, and to a smaller extent on surface finish and oxygen concentration.
Thermodynamics and Kinetics of Burning Iron
Authors: Wilson DB , Steinberg TA , Stoltzfus JM
Published: March 2009

Macroscopic kinetic analysis of the burning of 0.1 and 0.2-cm-diameter iron rods in pure oxygen at pressures between 0.3 MPa and 10 MPa, and 0.32-cm- diameter iron rods in pure oxygen at pressures between 0.3 MPa and 5 MPa indicates that the kinetic reaction occurs at the phase boundary between the molten oxide product and the liquid iron core. An apparent activation energy of 246.8 kJ/mol Fe(l) is consistent with this analysis. The surface area of the liquid oxide/liquid iron phase-boundary is appropriate for describing the reaction. An enthalpy of reaction of -365.2 kJ/mol Fe(l) at 298K is consistent for the burning of iron. The Langmuir-Hinshelwood- Hougen-Watson mechanism is consistent with the flammability data for iron. In the linear range of that mechanism an appropriate rate equation is: RFe = 7.05E3exp(-2.9684E4/T)Po21/2gm cm-2s-1
Modeling of Promoted-Ignition Burning: Aluminum
Authors: Wilson DB , Stoltzfus JM
Published: March 2009

The burning of aluminum in NASA/ASTM flammability tests is examined for establishing a probable mechanism. Similarity between oxidation of pure solid and pure liquid aluminum surfaces suggest that a phase-boundary reaction occurs and that a Langmuir-Hinshelwood model is appropriate. Consistent evaluation of available data confirm that a phase-boundary reaction is highly probable. Vacuum evaporation and thermal energy considerations support this contention.
Experimental Study of Flame-Spreading Processes Over Thin Aluminum Sheets
Authors: Yeh C-L , Johnson DK , Kuo KK
Published: March 2009

An experimental study of flame-spreading behavior over thin aluminum (99% Al and 1% Mn) sheets was conducted in oxygen-enriched environments. This subject is of great interest since the occurrence of violent energy release (VER) phenomena in promoted ignition and combustion tests of brazed aluminum heat exchangers (BAHX) seems to be strongly coupled with flame-spreading processes. The objective of this study is to determine the dependency of flame-spreading rate of aluminum sheets as a function of oxygen pressure, oxygen purity, oxygen flow condition, sample thickness, and multiple layer configuration.

The flame-spreading rate over aluminum sheets was measured by an array of fast-response lead-selenide (Pb-Se) IR photodetectors. The overall transient event of the ignition and flame spreading of aluminum sheets was recorded by both a high-speed movie camera and a CCD video camera. The initial chamber pressure was varied from 0.1 to 10 MPa. Two grades of oxygen gas were used with purities of 99.996% and 99.75%. Tests were conducted either with stagnant oxygen or under a continuous oxygen flow with oxygen velocity ranging from 5 to 15 m/s. The dimension of aluminum samples with three different thicknesses (0.15, 0.20, and 0.40 mm) was 2.5 cm by 43 cm. Besides tests with single aluminum sheets, tests were conducted using three sheets mounted with a controlled gap width of 1.6 mm.

As the initial chamber pressure was increased, the flame-spreading rate was found to increase to a maximum, decrease to a minimum, and then increase again. The flame-spreading rates under high-purity oxygen (99.996%) environments are greater than those in commercial grade oxygen (99.75%). The threshold pressure for self-sustained flame propagation is lower under high-purity oxygen environments and also for samples with a smaller thickness. The oxygen flow can enhance the flame-spreading rate to some extent. There exists an optimum oxygen velocity beyond which the flame-spreading rate decreases with the increase of oxygen velocity. The mechanisms associated with aluminum combustion and VER phenomenon are also discussed.
Oxygen Compatibility of Polymers Including TFE-Teflon®, Kel-F® 81, Vespel® SP-21, Viton® A, Viton® A-500, Fluorel®, Neoprene®, EPDM, Buna-N, and Nylon 6,6
Authors: Chou TC , Fiedorowicz A
Published: March 2009

Ten polymeric materials including EPDM, Nylon 6,6, Buna-N and other materials marketed* as TFE-Teflon® (PTFE), Kel-F® 81 (PCTFE), Vespel® SP-21, Viton® A, Viton® A-500, Fluorel®, and Neoprene® were systematically evaluated for their oxygen compatibility property. The specific properties examined included: (1) autoignition temperature (AIT), (2) heat of combustion, and (3) liquid-oxygen (LOX) mechanical impact sensitivity. Test methods and procedures employed for the evaluations were in compliance with those prescribed in the ASTM and BSI standards. Additionally, a BOC in-house high-pressure autoigniticn test rig (HP-AIT) was used for a detailed study on the materials' autoignition behavior. This high-pressure vessel is capable of probing the AIT of a material up to 450°C and at oxygen pressure (prior to a thermal excursion) up to 5000 psig (∼34.5 MPa).

According to the test results, fluorinated polymers including TFE®, Kel-F® 81, Viton® A, Viton® A-500 and Fluorel® exhibited superior oxygen compatibility property. Specifically, they possessed relatively high autoignition temperatures and reasonably low heat of combustion values. Among them, TFE® possessed the best property by showing the highest autoignition temperature (>450°C), lowest heat of combustion (1517 cal/g), and qualified (pass) LOX impact sensitivity. Vespel® SP-21 (15% graphite-filled polyimide) exhibited an autoignition temperature higher than fluorinated elastomers like Fluorel® and Viton® A, but lower than Kel-F® 81 as well as TFE®. The variation of oxygen pressure, ranging from 1800 psig (∼12.4 MPa) to 5000 psig (∼34.5 MPa), was found to exert little influence on the autoignition temperature of the polymers.

The autoignition behavior of Kel-F®81, Viton® A, Vespel® SP-21, and Nylon 6,6 was further investigated, using HP-AIT, as a function of sample quantity and surface area at different oxygen pressure. On the one hand, variation of sample quantity exerted a more pronounced effect on the AITs of Viton® A, Nylon 6,6 and Kel-F® 81 at various pressures than on Vespel® SP-21. A higher autoignition temperature was generally observed from samples with smaller quantities. On the other hand, changes in sample surface area had little influence on the autoignition temperature of the materials in 1800 psig (∼12.4 MPa) oxygen.
Relative Performance of Elastomeric Materials in the Seal Configuration Test Apparatus
Authors: Yentzen MJ , Powell BA , Jordan S
Published: March 2009

Although perfluoroelastomers were designed for high temperature and severe service, they have become the preferred elastomeric material for high pressure oxygen applications. The main reason for their widespread use in oxygen is that perfluoroelastomers typically perform better in most ASTM standard test methods designed for evaluating oxygen compatibility. The principal disadvantage of the use of perfluoroelastomers is that they are prohibitively expensive — approximately 50 times the cost of most other elastomeric materials.

The ASTM standard test methods that are used to evaluate oxygen compatibility of elastomeric materials do not necessarily measure the resistance to ignition in oxygen of o-ring materials in their use configuration. The seal configuration tester (SCT) simulates a typical dynamic o-ring application and is therefore a better method for comparing the relative wearability and oxygen sensitivity of various elastomeric o-ring materials. while data from the ASTM standard test methods suggest that perfluoroelastomers may be less oxygen sensitive than other materials, data from the seal configuration test demonstrate that fluoroelastomers are superior to perfluoroelastomers in a dynamic o-ring use configuration. Seal configuration test data were also compiled for other elastomeric materials such as butadiene nitrile and silicone. This data are compared to the test data for perfluoroelastomers and fluoroelastomers and are discussed in the paper. The seal configuration test data provide additional information to aid in the selection of elastomeric materials for high pressure oxygen o-ring applications.
Oil Migration on the Structured Packing by Evaporation and Recondensation During the Defrosting Operation in the Air Separation Unit
Authors: Egoshi N , Kawakami H , Fujita I
Published: March 2009

Structured packing has been applied to the cryogenic distillation of air. The specific surface areas of packing are higher than that of conventional sieve trays. The lubrication oils are used for manufacturing of the packing and some oils remain on the packing surface, which results in introducing a larger amount of the total remained oil in the structured packed columns than that in the sieve trays. In the oxygen enriching section of the low pressure column of the air separation unit, the accumulation of the oil should be avoided for safety. High level local accumulation may be caused by the migration which is due to evaporation and recondensation of the oil during the defrosting operation, which occurs in start-up and shut-down procedures of the air separation unit. An allowable oil film limit of 50–100mg/m2 is recommended by CGA. It is confirmed that oil migration by gravity and cold chipping does not occur at this oil level. However, there is no experimental or theoretical study of the migration mechanism by evaporation and recondensation.

The purpose of this study is to determine whether the evaporation and recondensation causes a high accumulation level in the structured packed column under the initial condition of 100mg/m2 oil level. The correlation on mass transfer for evaporation and recondensation of oil (Shell Talpa 30) was developed by the laboratory-size experiments. By using the mass transfer correlation, the behavior of the oil migration was simulated for the low pressure column. The simulation results showed that the accumulation of the lubrication oil (Shell Talpa 30) was less than 1 mg/m2 during the defrosting operation, hence an unfavorable oil accumulation did not occur under the initial condition of 100mg/m2 oil level. On the other hand, it was found that the accumulation of hexadecane (light oil) was higher than that of Shell Talpa 30 (heavy oil) at a same time within the defrosting operation.
A Database for Metallic and Nonmetallic Materials Commonly Utilized in Oxygen Service
Authors: Newton B , Hull WC , Stradling J
Published: March 2009

This paper presents the design, structure, and use of a materials database for metallic and nonmetallic materials commonly utilized in oxygen service. Also discussed is the need for a widely accessible and easily searched database of materials compatibility test data for general use within the oxygen community. Over the last two decades, the ignition and combustion properties of metallic and nonmetallic materials exposed to oxygen-enriched environments have been widely studied by both government and commercial industry. However, to our knowledge, these data have never been compiled into a comprehensive and easily accessible database for general utilization and cross-comparison. Consequently, collecting the necessary data for hazards analyses on materials and components is difficult and time consuming, when done in accordance with the procedures advanced by ASTM Guide G-63, “Standard Guide for Evaluating Nonmetallic Materials for Oxygen Service,” and ASTM Guide G-94, “Standard Guide for Evaluating Metals for Oxygen Service.” This paper presents a database of materials test data and discusses the utilization of these data in a computerized hazards analysis that generally follows the guidelines of ASTM G-63 and G-94 and the “good practices” of ASTM G-88. The relational structure of the database is presented and the advantages of this type of data structure are discussed.
Flammability of Intestinal Gases During Nitrous Oxide Anesthesia
Authors: Sidebotham GW , Cantelmi F , Stoffa DM , Fried E , Wolf GL
Published: March 2009

Typical intestinal gas mixtures created during nitrous oxide anesthesia are shown to be flammable. Flammability limits of mixtures of fuel (hydrogen or methane), oxidizer (nitrous oxide) and inert (nitrogen) were measured and compared to compositions expected during nitrous oxide anesthesia. When hydrogen is the predominant fuel component, flammable mixtures are produced in approximately 30 minutes, regardless of the fuel concentration, and the concentration of nitrous oxide delivered. When methane is the fuel, the time at which flammability is achieved is longer than for hydrogen. Further, the time increases with decreasing concentrations of nitrous oxide delivered, and increasing methane concentration. It is recommended that nitrous oxide not be used as an anesthetic if a potential ignition source is used in the vicinity of the intestines.