New protective clothing materials for working with handheld ultra-high-pressure water jet guns

The effect of a crown-shaped nozzle on cavitation is studied experimentally in the near-field of a 25 mm diameter (D) water jet at ReD=2×105 using particle image velocimetry (PIV) and high speed shadowgraphy recorded with a 5000 fps digital camera. The objectives are to passively control the jet flow structure and to examine its consequences on the physical appearance of cavitating bubbles. The experiments are performed in a closed-loop facility that enables complete optical access to the near-nozzle region. The cavitating and noncavitating mean velocity fields are obtained up to three nozzle diameters downstream and compared to those of a companion round nozzle. PIV measurements are taken in two distinct azimuthal planes passing through the tip and bottom points of the crown nozzle edge. The data include shear layer momentum thickness and vorticity thickness, spanwise vorticity distribution and streamwise normal Reynolds stress. Significant deviation from an axisymmetric shear layer is observed in the noncavitating flow consistently up to one diameter downstream, after which identical asymptotic conditions are achieved in both round and crown-shaped nozzles. Maximum magnitudes of spanwise vorticity and streamwise normal Reynolds stress are the highest downstream of the nozzle tip edges under noncavitating conditions. Significant modifications in trends and magnitudes are observed for the shear layer momentum thickness under cavitating conditions up to one diameter downstream. Qualitative flow visualization reveals that bubble growth occurs at different conditions depending on azimuthal location. Bubbles, in the form of elongated filaments, are the dominant structures produced downstream of the valley edges of the nozzle with an inclination of 45 deg with respect to the direction of the flow, and are observed to persist with significant strength up to two diameters downstream. These filaments are stretched between periodic larger-scale, spanwise bubbly clusters distorted in the shape of the nozzle outlet. The tip edges produce cavitating bubbles under conditions similar to that of a classical round nozzle. In summary, it was demonstrated that passive control of turbulent structures in the jet does impact the cavitation process.

In this study, for the plunging water jet aeration system using various inclined nozzle types, bubble penetration depth, air entrainment rate, water jet expansion, effect of water jet circumference at impact point, oxygen transfer coefficient and oxygen transfer efficiency which changed depending on the water jet velocity, were researched in an air-water system. Numerous studies were conducted with circular nozzles. The present study describes new experiments performed with different nozzle types. Three types of nozzles were examined, i.e., those with circular, ellipse and rectangle duct with rounded ends. Experimental results showed that water jets produced with ellipse and rectangle duct with rounded ends nozzles have very different flow characteristics, entrainment patterns on free water jet surface, and submerged water jet region within the receiving tank. Higher air entrainment rate and oxygen transfer efficiency was observed in the rectangle duct with rounded ends nozzle due to water jet expansion. Bubble penetration depth, however, is lower for the rectangle duct with rounded ends nozzle than for the other nozzles. The ellipse nozzle provided the highest bubble penetration depth. These results showed that it is appropriate to use ellipse nozzle in aeration of deep pool and rectangle duct with rounded ends nozzle in the applications where high bubble concentration is desirable.

Laser and water-jet manufacturing processes are independently used to cut monolithic and composite ceramics. While these processes offer many advantages over diamond sawing and other abrasive processes, the energy efficiency, precision, cutting speed, and environmental threats remain as barriers to their continued success. This is partly attributed to the material removal mechanisms, which are melting, and subsequent evaporation (laser) and energy-intensive erosive wear (water jet). In this paper, we describe a novel laser and water-jet (LWJ) hybrid manufacturing process that enables the synergistic effects of CO2 laser and pressurized pure water jet, facilitating precise material removal by thermal shock-induced fracture and overcoming the deficiencies listed above. Experiments of the LWJ effects on the cutting of aluminum nitride, an electronic ceramic substrate, are presented. The most exciting results are very narrow kerf dictated by the crack width; the absence of thermally affected zone, slag formation, chemical decomposition; and controlled thermal cracking, implying that the LWJ process is far superior to conventional laser cutting of ceramics. The LWJ process also improved the surface finish while reducing energy losses in the process. The practical realization of the LWJ manufacturing process could be a potential alternative to diamond saw, high-power laser, and high-pressure abrasive water-jet methods for machining hard and brittle ceramics.

Purpose. The purpose of this study is to provide scientific and experimental substantiation of the principles for designing effective thermal protective special clothing (TPSC) equipped with an utonomous life support system, based on the integrated mplementation of passive and active thermal rotection methods under conditions of extreme and ultra-high temperature exposure. The research is aimed at establishing thermophysical regularities of heat transfer within multilayer material assemblies and developing a predictive model for temperature distribution and protective performance time under convective heat removal conditions. Methods. The research methodology is based on a combination of theoretical modeling, experimental determination of thermophysical characteristics, and engineering design approaches. The theoretical framework relies on the theory of non-stationary heat transfer and the method of regular thermal regime, employing analytical solutions of differential equations describing heat conduction and convective heat exchange processes in porous multilayer systems. The thermophysical parameters of aterials and material assemblies were determined using a flat bicalorimeter and a regular regime rocalorimeter. The study encompassed material packages omposed of metallized heat-reflective outer layers, heat-esistant fabrics, membrane materials, thermal nsulation interlayers, and lining materials. In addition, a nanostructured textile material modified with silver nanoparticles synthesized via a green echnology approach was developed and mplemented as a hygienic underwear layer. A comparative analysis of various package configurations was conducted in order to identify optimal combinations according to thermal resistance, density, and ergonomic performance criteria. Results. It was established that the exclusive use of passive thermal protection under ultra-high temperature conditions is ergonomically inefficient due to the necessity of significantly increasing garment thickness and mass. The integration of an active convective cooling system ensures a ubstantial increase in the effective thermal resistance of the multilayer structure. A mathematical model describing temperature distribution within a porous thermal insulation layer under forced air filtration conditions was developed. An efficiency coefficient of active thermal protection was introduced and analytically determined, enabling quantitative evaluation of cooling system performance. xperimental results confirmed that optimized aterial packages incorporating metallized outer layers and advanced thermal insulation materials provide enhanced thermal resistance while maintaining acceptable weight and dimensional characteristics. The application of the nanomodified textile material in the inner layer ensures compliance with hygienic requirements, ultraviolet radiation protection, and improved environmental sustainability of the production process. Scientific novelty. For the first time, a comprehensive physical model of heat transfer in thermal protective clothing combining passive multilayer thermal insulation with active convective cooling has been theoretically substantiated. An analytical solution to the problem of temperature distribution within a porous thermal insulation layer under convective filtration conditions was obtained, enabling determination of the heat flux penetrating toward the human body as well as calculation of the efficiency coefficient of active thermal protection. The approach to the classification of heat-resistant materials according to their thermophysical characteristics and functional role within multilayer assemblies has been further developed. The use of a nanostructured textile material containing silver nanoparticles synthesized through an environmentally safe method is proposed as an integral component of combined thermal protection systems. Practical significance. The obtained theoretical relationships and experimental results provide the possibility of predicting the protective performance time and ergonomic characteristics of thermal protective special clothing at the pre-design stage. The developed design principles contribute to the creation of competitive, high-technology products intended for fire-rescue units and professionals operating under extreme temperature conditions. The implementation of nanomodified textile materials enhances the hygienic properties of garments, ensures ultraviolet rotection, reduces energy consumption in the manufacturing process, and improves the environmental safety of the technology. The proposed approach establishes a methodological foundation for the further evelopment of adaptive and autonomous life support systems in the design of modern protective clothing.

While working in a fire incident, firefighters are protected by thermal protective clothing and equipment (e.g., helmet, gloves). The protective clothing and equipment mainly help to avoid injuries and fatalities by providing them proper protection and comfort. In the last few decades, extensive research and development has been carried out to develop different types of firefighters' protective clothing (station uniform and turnout gear) and equipment (helmet, flash hood, gloves, boot, and breathing apparatus). This chapter gives an overview and discusses different types of existing firefighters' protective clothing and equipment as well as the scientific features associated with materials and designs. The discussion on the clothing features revealed several critical factors related to the firefighters' protection and comfort such as fibre, yarn, and fabric characteristics as well as garment designs. The ergonomically fit, comfortable design aspects and protective materials used for the development of firefighters' protective equipment are also considered. These discussions on types and features could help to develop a better understanding of the combined protection and comfort properties for achieving the best possible clothing and equipment performance. In the final section of this chapter, various key issues related to firefighters' protective clothing and equipment are highlighted. It has been found that these key issues are mainly related to the improper designs (non-ergonomically fit) and materials (heavy weight woven/nonwoven fabrics, impermeable fabrics) used in firefighters' protective clothing and equipment. By improving these design and material issues in the near future, it is possible to provide better occupational health and safety for firefighters.

Simple SummaryProcess operators have an important monitoring role in the petrochemical industry. In the event of process disruptions and incidents, a process operator is often the first responder and takes measures to diminish the effects of an incident. Thus, a process operator can be exposed to dangerous circumstances, and therefore personal protective equipment has to be worn. In case of fire, the operator may be exposed to high heat radiation levels. Previous studies have established maximum acceptable heat radiation levels for long- (>15 min) and short-term exposures (<5 min), these being 1.0 kW/m2 and 1.5 kW/m2, respectively. These limits were based on manikin measurements and physiological models. The validation of the protection of operators’ clothing in human trials is lacking. Therefore, twelve professional firefighters were exposed to three different heat radiation levels in process operators’ clothing. The experiments showed that the majority of the operators can be exposed for 5 min to 1.5 kW/m2, up to 3 min to 2.0 kW/m2, while exposure to 2.5 kW/m2 or above must be avoided. Due to a slower skin temperature rise, loose-fitting protective clothing was related to longer exposure times. We speculate that additional long-armed/legged (under)clothing may offer more protection and extend the exposure time to heat radiation.During the early stage of a fire, a process operator often acts as the first responder and may be exposed to high heat radiation levels. The present limit values of long- (>15 min) and short-term exposure (<5 min), 1.0 and 1.5 kW/m2, respectively, have been set using physiological models and manikin measurements. Since human validation is essentially lacking, this study investigated whether operators’ protective clothing offers sufficient protection during a short-term deployment. Twelve professional firefighters were exposed to three radiation levels (1.5, 2.0, and 2.5 kW/m2) when wearing certified protective clothing in front of a heat radiation panel in a climatic chamber (20 °C; 50% RH). The participants wore only briefs (male) or panties and a bra (female) and a T-shirt under the operators’ clothing. Skin temperatures were continuously measured at the chest, belly, forearm, thigh, and knee. The test persons had to stop if any skin temperature reached 43 °C, at their own request, or when 5 min of exposure was reached. The experiments showed that people in operators’ clothing can be safely exposed for 5 min to 1.5 kW/m2, up to 3 min to 2.0 kW/m2, and exposure to 2.5 kW/m2 or above must be avoided unless the clothing can maintain an air gap.

A review on continuous and pulsed water jet machining

The goal of this project was to develop chemical protective clothing for use by DOE decontamination and decommissioning workers that is sufficiently water vapor permeable to keep the workers cool, thereby enhancing their productivity. This report describes the results of Phase II of a two-phase project to complete development of the novel permselective material and to test protective clothing made from the fabric. In Phase I a novel material incorporating a nonporous hydrophilic polyvinylacohol (PVA) layer, which is water vapor permeable but relatively impermeable to organic vapors, was developed. The results of the Phase I tests showed that the chemical resistance of the MTR material is comparable to that of Saranex/Tyvek materials, and that the comfort properties are closer to those of Tyvek (as measured in terms of CLO and permeability). Chemical resistance was measured using permeation tests against liquid dichloromethane. Comfort properties were ascertained by measuring the water vapor transmission of the material and by sweating manikin tests on whole protective suits. In addition, a cost/benefit analysis demonstrated that use of MTR's material technology could result in significant improvements in work productivity and cost savings if protective clothing items made from the new material were used more than once. In Phase II, MTR undertook a program to optimize the performance and production engineering for the new material technology. A partnership was formed with Kimberly-Clark Corporation to assist with a detailed evaluation of the MTR technology, and MTR used the services of Mr. Jeff Stull, President of the consulting firm International Personnel Protection, Inc., who conducted a detailed economic and application analysis for the developed fabric. The protective fabric manufacturing steps were simplified significantly, resulting in a 30% reduction in manufacturing costs and eliminating the necessity for capital investment in production equipment. Protective suits were prepared in collaboration with Kimberly-Clark Corporation and heat stress testing with human test subjects was carried out by the International Union of Operating Engineers (IUOE). The tests confirmed that the MTR protective fabric is significantly more comfortable than non-breathable materials. A cost analysis was developed from the properties of the optimized protective fabric and the results of the of the IUOE field study to determine the potential for the MTR material technology within the chemical protective clothing market. A detailed assessment of the specific chemical protective clothing applications for which the material can be used and its competitiveness with existing material technology, based both on expected performance and material/end item costs, was prepared. Three specific market opportunities identified for the novel protective fabric are: (1) liquid splash protective clothing for hazardous waste site operations, (2) liquid splash protective clothing for emergency response, and (3) Class 3 NFPA 1994-compliant protective clothing for civilian use during chemical terrorism incidents.

Perfluorocarbons (PFCs) have been adopted for plasma etching and chemical vapor deposition process in semiconductor manufacturing. Among the other exhaust gases, PFCs have longer residual time in air and higher global warming potential. To remove PFCs, water jet gliding arc plasma was designed and prepared. Water jet gliding arc plasma has received the attention as a PFCs decomposition technique due to the formation of OH radical and wide range of plasma. Using water jet gliding arc plasma, the efficacy on the decomposition of CF4, one of the major PFCs, was evaluated. As the results of experiments, the amount of water jet increases the decomposition efficiency of CF4. From the experimental results, a combination of plasma and water jet is considered to be effective for the decomposition of CF4. Regarding the parametric researches, input feed of water jet, input concentration change, variation in input power, electrode gap, and electrode length were selected for experiments. The highest decomposition efficiency of CF4 was achieved with 2.1% of input concentration, 7200 kJ/m 3 of specific energy input (SEI), 1.53×10 -4 m 3 /s of total gas amount, and 4.25×10 -7 m 3 /s of water jet feed.

Fire fighters' protective clothing provides a limited amount of thermal protection from environmental exposures produced by fires. This level of thermal protection varies with the design, materials, construction, and fit of the protective garments. Limits of thermal protection may be analyzed using the thermophysical properties of garment materials. However, little information is currently available for analyzing and predicting protective garment thermal performance. To address this need, a research effort was begun to measure the thermal properties of fire fighters' protective clothing materials. This report presents thermal conductivity data for ten materials used in fabricating fire fighters' protective clothing. These materials included: (a) outer shell fabrics, (b) moisture barriers, and (c) thermal liner battings. The thermal conductivity data for each material was obtained twice. Once when the material was new and once after the material had undergone a conditioning process of five washings and dryings by a contract cleaner that specializes in cleaning, decontaminating and repair of fire fighters' protective clothing. The thermal conductivity of individual protective clothing materials was measured using the test procedure specified in ASTM C 518 Standard Test Method for Steady-State Thermal Transmission Properties by Means of Heat Flow Meter Apparatus. Measurements producing estimates of thermal conductivity for a single layer of materials were carried out at mean test temperatures of 20 C (68 F), 48 C (118 F), 55 C (131 F), and 72 C (162 F). No visible physical changes were observed with any of the materials tested at these temperatures. For unconditioned materials, the thermal conductivity estimates ranged from 0.034 W/m K to 0.093 W/m K. For the conditioned materials the thermal conductivity estimates ranged from 0.033 W/m K to 0.089 W/m K. Thermal conductivity values increased for all materials as mean test temperatures were increased.

1 - Overview of protective clothing

Increased likelihood of armed forces operations occurring in hostile climatic regions have increased the need for highly specialized protective clothing systems. Protection is needed under a variety of conditions which often present conflicting requirements. Protective military clothing provides broad design possibilities and stimulates research for new textile materials and equipment. Development of protective gear provides the possibility for interdisciplinary teaching and research. Disciplines such as textile engineering, electrical engineering, industrial engineering and design, clothing design, textile science, and physiology can all be combined to provide satisfactory solutions to design problems presented by protective clothing systems. Current requirements for protective military clothing, problems with gear, and critical factors which can be addressed by clothing and textiles research are included.

Guest Editorial

The manipulation of the trajectory of high-pressure micro water jets has the potential to greatly improve the accuracy of water jet related manufacturing processes. An experimental study was conducted to understand the basic static and dynamic responses of high-pressure micro water jet systems in the presence of nonuniform electric fields. A single electrode was employed to create a nonuniform electric field to deflect a high-pressure micro water jet toward the electrode by the dielectrophoretic force generated. The water jet's motions were precisely recorded by a high-speed camera with a 20× magnification and the videos postprocessed by a LabVIEW image processing program to acquire the deflections. The experiments revealed the fundamental relationships between three experimental parameters, i.e., voltage, pressure, and the distance between the water jet and the electrode and the deflection of the water jet in both nonuniform static and dynamic electric fields. In the latter case, electric signals at different frequencies were employed to experimentally investigate the jet's dynamic response, such as response time, frequency, and the stability of the water jet's motion. A first-order system model was proposed to approximate the jet's response to dynamic input signals. The work can serve as the basis for the development of closed-loop control systems for manipulating the trajectory of high-pressure micro water jets.

Part 1 Materials and design: Overview of protective clothing Standards for protective textiles Fashion and function - factors affecting the design and use of protective clothing Steps in the selection of protective clothing materials Fibres and fabrics for protective textiles Technical textiles for protection Intelligent textiles for protection Surface treatments for protective textiles Evaluation of protective clothing systems using manikins Interactions between protection and thermal comfort Modelling thermal burn injury protection. Part 2 General protection requirements and applications: Civilian protection and protection of industrial workers from chemicals Textiles for UV protection Textiles for protection against cold Thermal (Heat and fire) protection Microorganism protection Textiles for respiratory protection Electrostatic protection Ballistic protection Chemical and biological protection. Part 3 Case studies: Military protection Fire fighters protective clothing Protection against knives and other weapons Flight suits for military aviators Protection for workers in the oil and gas industry Motorcyclists.