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This paper is intended to be the first study to discuss the fire suppressing performance of the four most common extinguishing media under the same reproducible conditions. The tests were performed in bench-scale and used standardized 5A wood cribs as well as a miniature extinguishing system with a liquid flow rate of 1.4 lmin−1. The tests results present a consistent overview of the fire suppression efficacies of water, water with a foaming agent, nozzle-aspirated foam and compressed air foam. Depending on their jet types, the cooling capabilities of the extinguishing media water and water with a foaming agent were compared to the cooling capability of a full Jet of wet, general and dry foams. The results show that compressed air foam suppressed fire most effectively under the test conditions. Because of the convoluted crib structure, water and water with foaming agents used from a distance are more effective in the form of a full jet rather than a spraying jet. At close range, spraying jets multiply their effectiveness. A slight difference can be observed in the cooling performance of extinguishing foams that use foaming agents from different manufacturers. The paper establishes a link between the foaming agent's cooling capability and its wetting power by relating the results of wood crib fire tests according to DIN EN 3–7 and findings from laboratory immersion tests compliant with DIN EN 1772.
Compressed natural gas (CNG) is a widely used automotive fuel in a variety of countries. In case of a vehicle fire where the safety device also malfunctions, a failure of the CNG automotive cylinder could occur. Such a cylinder failure is associated with severe hazards for the surrounding environment. Firstly, a comprehensive analysis is given below, summarizing various accidents involving CNG automotive cylinders and their consequences. In an extensive experimental program, 21 CNG automotive cylinders with no safety device were tested. Of the 21, burst tests were carried out on 5 Type III and 5 Type IV cylinders. Furthermore, fire tests with 8 Type III and 3 Type IV cylinders were conducted. Apart from cylinder pressure, inner temperature and cylinder mantle temperature, the periphery consequences, such as nearfield blast pressure and fragmentation are documented. The maximum measured overpressure due to a Type III cylinder failure was p = 0.41 bar. Each traceable fragment was georeferenced. All-in-all, fragment throw distances of d > 300 m could be observed. As one key result, it can be stated that the tested Type IV CNG cylinders showed less critical failure behavior then the Type III cylinders under fire impingement.
This study evaluates the efficacy of compressed air foam (CAF) in comparison to common fire extinguishing media. Newly developed mixed-material burning cribs were used as a normative fire load for extinguishing tests to accurately represent the significantly elevated utilization of synthetic materials in everyday life. A series of outdoor experiments was carried out to analyze the effectiveness of the fire extinguishing medium CAF using synthetical class-A foaming agents from two different manufacturers, and compared them to water and waterfoam solution as a function of the extinguishing distance. In a second series, performed inside a fire room, the efficiency of CAF-usage in indoor fires was evaluated. Moreover, the results of the indoor test series provided information about the composition of smoke gases based on the kind of extinguishing tactic used to suppress the fire. The results showed that under the tested conditions CAF suppressed fire more effectively than both water and water with foaming agents. CAF was able to wet areas hardly accessible to other extinguishing media, and due to its various simultaneously occurring effects and its compact jet with high kinetic energy, it cooled down temperatures more efficiently than water or water-foam solution.
In laser machining with ultrashort laser pulses unwanted X-ray radiation in the keV range can be generated when a critical laser intensity is exceeded. Even if the emitted X-ray dose per pulse is low, high laser repetition rates can lead to an accumulation of X-ray doses beyond exposure safety limits. For 925 fs pulse duration at a center wavelength of 1030 nm, the X-ray emission was investigated up to an intensity of 2.6 × 10^14 W/cm2. The experiments were performed in air with a thin disk laser at a repetition rate of 400 kHz. X-ray spectra and doses were measured for various planar target materials covering a wide range of the periodic table from aluminum to tungsten. Without radiation shielding, the measured radiation doses at this high repetition rate clearly exceed the regulatory limits. Estimations for an adequate radiation shielding are provided.
Steel tension rod systems consist of tension rods, fork connectors and associated intersection or connecting plates. They are used for truss systems, bracings or suspensions owing to slender design and increased economic efficiency. In case of fire, beside the tension rods themselves, the connection parts require appropriate fire protection. The use of intumescent fire protection coatings prevents a rapid heating of the steel and helps to ensure the load-carrying capacity of the structures. Because the connection components of the tension rod systems feature surface curvature as well as a complex geometry, high demand is placed on the intumescence and thermal protection effectiveness of the reactive fire protection coatings. Experimental studies were carried out to investigate the performance of intumescent coatings applied to the components of tension rod systems. The examined aspects include the foaming and cracking behaviour of the intumescent coatings, the influence of different dry film thicknesses (DFT), the heating rate of the steel connecting parts in comparison to the tension rods, as well as the mounting orientation of the tension rods together with their associated fork connectors. The results show that a decrease in the surface curvature and/or an increase in the mass concentration of the steel components lead to a lower heating rate of the steel. Moreover, the performance of the intumescent coating on tension rod systems is influenced by the mounting orientation of the steel components.
To save weight and resources lightweight tanks with complex geometries made of glass-fibre reinforced plastics (GFRP) are a promising innovation for the transportation of dangerous goods. To realise the use of polymer tanks for such applications, their fire safety must be guaranteed. This paper presents solutions to protect fibre-reinforced plastic tanks from fire. The fire resistance of six GFRP tanks with different fire protection systems was tested in an outdoor full-scale fire test facility according to the regulation stipulated in the ADR (European agreement concerning the national carriage of dangerous goods by road). All tanks feature a complex geometry and a holding capacity of 1100 litres. The fire protection systems are composed of specialised resins as well as two intumescent coatings. All systems had a protective impact. The best results were achieved by the epoxy based intumescent coating, which was able to prolong the time needed to reach 150 °C inside the tank by 20 min. The emergence of a temperature holding point inside the tank due to condensation effects was observed at temperatures around 100 °C.
The present study aims to investigate the use of geopolymer mortars as passive fire protection system for steel structures. Coal fly ashes were used as aluminosilicate source and perlite was employed as aggregate to obtain a lightweight system. In addition, a geopolymer mortar containing quartz aggregate was produced for comparison. The geopolymer mortars were applied on stainless steel plates and exposed to both, cellulosic and hydrocarbon standard fire curves, according to ISO 834-1 and EN 1363-2, respectively. Acoustic emission measurements were conducted to analyze cracking phenomena during the high temperature exposure. The resulting temperature-time curves showed that the investigated system is effective in retarding the temperature rise of the steel plates. When the cellulosic fire curve was applied, a 20 mm [0.79 in.] thick layer of lightweight geopolymer mortar protected the steel substrate from reaching the critical temperature of 500 °C [932 °F] for at least 30 minutes, avoiding the rapid decrease of its mechanical properties and thus representing an important safety measure against accidental fires. No spalling phenomena on heating were detected; however, significant cracking was observed on cooling.
In case of a vehicle fire, an installed LPG (liquefied petroleum gas) tank with a malfunctioning safety device poses severe hazards. To investigate the consequences in case of tank failure, we conducted 16 tests with toroidal shaped LPG vehicle tanks. Three tanks were used for a Hydraulic Burst Test under standard conditions. Another three tanks were equipped with a statutory safety device and were subjected to a gasoline pool fire. The safety device prevented tank failure, as intended. To generate a statistically valid dataset on tank failure, ten tanks without safety devices were exposed to a gasoline pool fire. Five tanks were filled to a level of 20 %; the re-maining five were filled to a level of 100 %. In order to gain information on the heating process, three tem-perature readings at the tank surface, and three nearby flame temperatures were recorded. At distances of l = (7; 9; 11) m to the tank, the overpressure of the shock wave induced by the tank failure and the unsteady tem-peratures were measured. All ten tanks failed within a time of t < 5 min in a BLEVE (boiling liquid expanding vapor explosion). Seven of these resulted directly in a catastrophic failure. The other three resulted in partial failure followed by catastrophic failure. A near field overpressure at a distance of l = 7 m of up to p = 0.27 bar was measured. All ten tests showed massive fragmentation of the tank mantle. In total, 50 fragments were found. These 50 fragments make-up 88.6 % of the original tank mass. Each fragment was georeferenced and weighed. Fragment throwing distances of l > 250 m occurred. For the tanks with a fill level of 20 %, the average number of fragments was twice as high as it was for the tanks that were filled completely.
Commercial grade-1 titanium samples (Ti, 99.6%) were treated using three alternative methods, (i) femtosecond laser processing, (ii) thermal heat treatment, and (iii) electrochemical anodization, respectively, resulting in the formation of differently conditioned superficial titanium oxide layers. The laser processing (i) was carried out by a Ti:sapphire laser (pulse duration 30 fs, central wavelength 790 nm, pulse repetition rate 1 kHz) in a regime of generating laser-induced periodic surface structures (LIPSS). The experimental conditions (laser fluence, spatial spot overlap) were optimized in a sample-scanning setup for the processing of several square-millimeters large surface areas covered homogeneously by these nanostructures. The differently oxidized titanium surfaces were characterized by optical microscopy, micro Raman spectroscopy, variable angle spectroscopic ellipsometry, and instrumented indentation testing. The tribological performance was characterized in the regime of mixed friction by reciprocating sliding tests against a sphere of hardened steel in fully formulated engine oil as lubricant. The specific tribological performance of the differently treated surfaces is discussed with respect to possible physical and chemical mechanisms.
The application of lightweight materials for tanks for transportation appears promising. Besides saving weight and therefore transportation costs, new complex geometries that depart from common cylindrical shapes of steel tanks can be manufactured. For transportation of dangerous goods, fire and explosion safety must be maintained to prevent accidents with serious consequences. In this work the fire behavior of lightweight tanks made from glass fiber reinforced plastics (GFRP) with complex geometries is investigated. Pretests on intermediate scale GFRP plates are conducted to identify suitable fire protection systems and surface treatments for composite tanks. The fire resistance is shown to be improved by addition of fire protective coatings and integrated layers. Finally, a complex rectangular GFRP tank with a holding capacity of 1100 liters is fire protected with an intumescent fire coating. The tank is filled up to 80 % with water and burned under an engulfing fully developed fire. It was shown that the intumescent layer could expand before the decomposition of the resin occurred. Furthermore, the adhesion between tank surface and coating was maintained. The structure could withstand a fire for more than 20 min.