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- ellipsometry (1)
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- girth welds (1)
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- hydrogen assisted cracking (HAC) (1)
- hydrogen assisted stress corrosion cracking (HASCC), (1)
- hydrogen diffusion coefficient (1)
- hydrogen peroxide (1)
- hydrogen subsurface concentration (1)
- hydroperoxyl radicals (1)
- hydroxyl fictionalization (1)
- numerical modelling (1)
- organic peroxides flame characteristics (1)
- pipeline (1)
- polymer surface chemistry (1)
- post weld heat treatment (PWHT) (1)
- safety distance (1)
- selective monofunctional surface (1)
- sensor layer (1)
- supermartensitic stainless steel (1)
- surface plasmon resonance (SPR) effect (1)
- underwater plasma (1)
Many new technologies are based on applications in extreme conditions, such as at low temperatures or in hydrogen environment. This involves new requirements on material properties, in particular regarding their operability and reliability. To fulfil this demand, the tribological behaviour of PTFE- and PEEK-matrix composites filled with carbon fibres were investigated at cryogenic temperatures and in hydrogen by means of surface analyses. For a better understanding of the tribological behaviour, and because of the temperature-dependent characteristics of polymer materials, thermal and mechanical properties of selected composites were initially investigated at low temperatures. Thermal shock experiments as well as cryo- and hydrogen treatments were carried out. Different coefficients of thermal expansion within the composite lead to debondings of particles, particularly in the case of PTFE materials. Tensile tests indicate that the YOUNG'S modulus increases at T= 77 K compared to room temperature. However, this improvement at low temperatures is moderate for PEEK composite which is already under its glass transition at room temperature. In the main investigation, tribological experiments were carried out at first at T= 77 K to observe the influence of the matrix, fillers and fibres on the material behaviour comparing to room temperature. The reduction of the friction coefficient and wear at low temperatures has been attributed to the low temperature properties of the polymer in particular due to the higher YOUNG'S modulus at T= 77 K. Whereas at room temperature friction and wear depend strongly of the CF content, the quantity of fillers and fibres does not have a significant effect on the tribological behaviour at low temperatures. At T= 77 K, the tribological behaviour of PTFE and PEEK composites is mainly influenced by the matrix. PEEK composites have a better tribological performance than PTFE materials especially regarding the wear resistance. Furthermore, the influence of the cryogenic medium was determined with experiments carried out in LN2 (T= 77 K), LH2 (T= 20 K) and LHe (T= 4.2 K), as well as in helium at T= 77 K and hydrogen at room temperature. The thermal properties of the cryogenic medium have a significant influence on the tribological performances of the composites. Due to the lower frictional heat at low sliding speed, the effect of low temperatures on the tribological behaviour of these composites was more clearly detected in this case, with a change in wear mechanism from mainly adhesive to more abrasive. Experiments in LN2 give the best friction and wear performance at low as well as at high sliding speed. The behaviour of these composites in LHe does not benefit from the low temperature properties of polymers due to the low heat of evaporation of LHe. The influence of hydrogen was particularly seen after the tribological experiments performed in LH2 on the surface of the disc. The reduction effect of hydrogen may have an influence on the tribochemical reactions which appear during sliding, enhancing the formation of iron fluorides, but no influence of the metal fluorides on the tribological performance could be determined in this study.
Low-alloyed heat-resistant steels have a fundamental contribution to the currently applied steel grades in pressurized and temperature loaded components like membrane walls(water walls)or pressure vessels. Here, the main advantages of the low-alloy concept can be used in terms of superior high temperature mechanical properties, workability and decreased amounts of expensive alloy elements. The main challenge for the future is to further increase the power plant thermal efficiency independent of the type of power plant concept, i.e. fossil-fired or nuclear power plant, where the material selection can directly affect reduction of CO2 emissions.
In power plant design, welding is the most applied manufacturing technique in component construction. The necessary weld heat input causes metallurgical changes and phase transitions in the heat affected zone (HAZ) of the base materials and in the deposited weld metal. The weld joint can absorb hydrogen during welding or in later service - This absorption can cause degradation of mechanical properties of the materials, and in certain loading conditions, hydrogen-assisted cold cracks can occur. This cracking phenomenon can appear time delayed due to the temperature dependency of the hydrogen diffusion and
the presence of a “critical” hydrogen concentration. Additionally, each specific weld microstructure shows a certain hydrogen diffusion and solubility that contribute to susceptibility of the cracking phenomenon. Therefore hydrogen cannot be neglected as possible failure effect, which was identified recently in the case of T24 creep-resistant tubeto-tube weld joints. It is necessary to identify and assess the hydrogen effect in weld joints of low-alloyed steel grades for to improve further early detection of possible failures.
For each specific weld joint microstructure, it is necessary to separate the interdependencies between mechanical load and the hydrogen concentration. The
diffusivity and solubility must be considered to identify hydrogen quantities in the material at any given time. In this case, the effects of mechanical loading were dealt with independently. For the characterization of the mechanical properties, hydrogen charged tensile specimens were investigated for the base materials and thermally simulated HAZ
microstructures. The hydrogen diffusion was characterized with the permeation technique at room temperature and at elevated temperature ranges up to 400°C - It was investigated by interpreting the hydrogen effusion behavior with carrier gas hot extraction technique (CGHE). For realistic determination of the hydrogen diffusion coefficients, an improved
method was developed encompassing accelerated specimen heating and hydrogen determination via mass spectrometer (MS). Simultaneously, the corresponding temperature
dependent trapped and total hydrogen concentrations were determined.
The determined experimental results showed increased susceptibility to the hydrogen affected
degradation of the HAZ compared to the base material, which is independent of the investigated alloy composition. In particular, the martensitic coarse grain HAZ is the most susceptible microstructure to hydrogen-affected degradation. The results of the tensile
tests allowed the definition of consistent microstructure specific failure criteria (envelope curves) versus quantified hydrogen concentrations for the reactor pressure vessel 16MND5 steel (20MnMoNi-5-5) and the creep-resistant T24 steel (7CrMoVTiB10-10). The procedure of quantifying hydrogen concentrations in HAZ microstructures is novel and supports a new method of analysis for hydrogen degradation effects. Further investigations with the T22
steel (10CrMo9-10), as compared to the creep-resistant T24 steel (7CrMoVTiB10-10),
confirmed the beneficial effect of Vanadium as an alloying element to improve the resistance to degradation. In general, Mn-Mo-Ni base material grades show a higher resistance compared to Cr-Mo steels that do not include Vanadium alloying.
The investigations showed the decreased diffusion coefficient of the HAZ microstructure compared to the base material microstructure. This is caused by the stronger trapping effects that are present which simultaneously increase the hydrogen solubility as well. In
general, trapping effects above 100°C are negligible. It is noted that after testing the T24 grade, these trapping effects were observed above 100°C and must be considered. At elevated temperatures, the calculated hydrogen diffusion coefficients are sometimes greater than those in literature. This is primarily due to the unique applied specimen heating procedure resulting in a varied hydrogen effusion from the specimen.
The significance of the obtained results can be characterized in three perspectives. First, the direct comparison of the degradation was possible in terms of microstructure-specific hydrogen effects on the mechanical properties. Second, consistent failure criteria were established to quantify degradation vs. the hydrogen concentration. Third, the determination of more accurate hydrogen diffusion coefficients is now available.
From a scientific point of view, important contributions were made to further interpret the hydrogen effects on the macroscopic mechanical properties, with respect to the alloy composition and the microstructure. From a procedural standpoint, the mentioned deviation in the elevated temperature diffusion coefficients can be caused by the calculation method. This can be an explanation for the reported data scatter in the references.
In terms of an economic view, the presented experimental results contribute to a safe and reliable weld workability of the steel grades. Thus, the identified temperature levels of hydrogen trapping can be applied in the definition of minimum preheat, interpass or postheat temperatures. In addition, recommendations for suitable dehydrogenation heat treatment (DHT) procedures, with accurate temperature values and holding times, can be derived from these results. In the future, the application of the mechanical and diffusion data is intended to support numerical analysis methods to provide an improved prediction of hydrogen effects on material degradation in weld microstructures.
The discovery and design of high performance Pd-alloys is of great interest for the use of hydrogen as a future energy carrier. Therefore hydrogen has to be detected, separated from other gases and stored. In this respect this thesis presents the combinatorial synthesis and characterization of the ternary Pd-Ni-Co alloy System over a wide composition range based on so-called thin film alloy libraries. Those libraries are model systems to characterize a large number of alloy compositions at the same time. The sputter-deposition process is optimized for the gradient of the Pd concentration on the surface of the alloy library by the use of electron-excited Auger electron spectroscopy. The scientific goal of this work is the experimental Investigation of adsorbate-induced surface segregation phenomena on alloy libraries.
The surface and bulk compositions of an alloy library are studied after deposition, H2 exposure and H2S poisoning. The co-segregation of Ni and Co to the surface is observed. The segregation process is influenced by the oxidation of Ni and Co due to the contact with ambient air, by H2 and by H2S poisoning. Also at very high Pd concentrations in the range of 87 at.% to 97 at.%, which is interesting for the detection of very low H2-Concentrations in air, the co-segregation of Ni and Co takes place. The poisoning effects were investigated in detail on a pre-selected Pd-Ni-Co alloy by photoelectron spectroscopy (XPS, HAXPES) in addition to AES and EDX. The composition profile of the alloy on the nm scale is acquired and the surface and bulk chemistry is discussed before and after poisoning. The composition of the alloy only changed within the first 3 nm due to H2S exposure. In the ternary Pd-Ni-Co alloy system Pd is present in its metallic state, while Ni and Co show several oxidation states. The presented concepts of ternary alloy development pave the way for the systematic synthesis and characterization of new ternary transition metal alloy systems.
Replacement of expensive duplex stainless steel and conventional carbon steel by a new generation of supermartensitic stainless steel has been taken into account since the last decade corresponding to the "Fitness for Purpose" concept in order to meet the technical- economical challenge for transportation flowlines of unprocessed oil and gas products in offshore technology, in particular. Supermartensitic stainless steels can provide appropriate material properties such as: improved strength-to-weight ratio, enhanced useful corrosion resistance as well as application at relatively low cost. With decreased carbon content and increased molybdenum content compared to traditional martensitic stainless steel, hydrogen assisted stress corrosion cracking (HASCC) problems have been found during service caused by hydrogen being taken up during from sour service environments by cathodic protection. Hydrogen assisted cold cracking in supermartensitic stainless steel can also occur during fabrication welding with hydrogen picked up during welding, since this steel is relatively crack-susceptible by hydrogen. Therefore, effects of hydrogen assisted cracking (HAC), i.e. HASCC and HACC, on characteristic susceptibility of girth welds of supermartensitic stainless steel pipelines are studied in the present thesis by numerical modelling, which is developed using a available commercial finite element program. Firstly, numerical modelling for simulation of HASCC based on the NACE-TM 0177-96 approach is carried out for providing a basic understanding of the crack propagation behaviour. Secondly, a two dimensional finite element according to the gauge length cross-section of the orbitally welded pipeline is created for numerical modelling in order to calculate the time to failure of welded the component exposed to the NACE electrolyte solution with various H2S saturation. Externally applied loads of a series of constant strain rates and of the load history of full scale testing are also taken into account. Finally, numerical modelling is carried out under three specific aspects, i.e. thermal analysis, structural analysis, and hydrogen diffusion analysis, in order to simulate HACC in supermartensitic stainless steel pipelines welded orbitally by four layers of matching filler wires with an interpass temperature of 40°C.
This thesis investigated gas sensing by means of surface plasmon resonance enhanced ellipsometry. Surface plasmons were excited in a 40 - 50 nm gold layer by a He-Ne-laser using the Kretschmann configuration, which was arranged on a self-made copper measuring cell. A fixed angle of incidence and the ellipsometric parameter Δ as the measured value were used to monitor changes in the gas phase. Different types of gases were investigated: flammable (hydrocarbons and hydrogen), oxidising (oxygen and ozone), toxic (carbon monoxide) and inert (helium and nitrogen). The gas types can be distinguished by their refractive indices, whereas the sensor responds instantly relative to the reference gas with an increase or a decrease in Δ. Diluting the analyte gas with a reference gas (nitrogen or air) allowed the detection limits to be determined, these lay in the low % range. The sensor stability was also enhanced as well as the sensitivity by modifying the gold layers with a 3-10 nm additional layer. These additional layers consisted of the inorganic materials TiO2, ZrO2, MgF2 and Fe: SnO2 which were deposited by different coating processes. Surface investigations were made of every utilised layer: scanning electron microscope and atomic force microscope measurements for surface topology and spectroscopic ellipsometry mapping to determine the optical constants and the layer thicknesses. All applied materials protected the gold layer from contaminations and thus prolonged the life span of the sensor. Furthermore, the detection limits were reduced significantly, to the low ppm range. The material Fe: SnO2 demonstrates a special behaviour in reaction with the toxic gas carbon monoxide: Due to the iron doping, the response to carbon monoxide is extraordinary and concentrations below 1 ppm were detected. In order to approach a future application in industry, the sensor system was adapted to a stainless steel tube. With this measuring arrangement, pulse and pressure experiments could be performed. The probable mechanisms occuring at the sensor surface and feasible applications in the future are discussed in this thesis.
Plasma chemical methods are well suited for introducing functional groups to the surface of chemically inert polymers such as polyolefins. However, a broad variety of functional groups is often formed. Unfortunately, for further chemical processing such as grafting of molecules for advanced applications a highly dense and monotype functionalized polyolefin surface is needed. Therefore, the main task was to develop a selective surface functionalization process, which forms preferably one type of functional groups at the surface in high and variable concentration. Amongst the novel plasma methods, the under-water plasma process (UWP) is one of most attractive to solve the problem of monotype functionalization. Such plasma is an efficient source of ions, electrons, UV-radiation, high frequency shock waves, radicals such as hydroxyl radical and reactive neutral molecules such as hydrogen peroxide, hydrogen and oxygen. It was found that underwater plasma and the closely related glow discharge electrolysis are interesting new methods for polymer surface functionalization. An effective modification into the topmost surface chemistry of polymer layer was observed by the collective effect of wet-chemistry, electrochemistry, atmospheric gas discharges, irradiation, and shock waves. Underwater capillary discharge was seen more effective in -OH functionalization and was largely seen as a flow dominated process because of the shock wave turbulences. Using such water-based plasma a fraction of 25-40% of all O-functional groups was produced as OH-groups in comparison to <10% OH produced in the oxygen low- pressure plasma. The exact concentration of the OH functionality was studied by TFAA gas phase derivatization and measuring the respective fluorine concentration by photoelectron spectroscopy (XPS). In contrast to established gas phase glow discharge processes, the water phase absorbs and therefore limits the particle and radiation energy and thus the energy input into the polymer. Extensive oxidation, degradation, cross-linking and radical formation in the polymer is more limited than under gas plasma exposure because of the liquid water environment, which moderates high energetic plasma species. The variety of plasma produced species in the water phase is also much smaller because of the limited reaction possibilities of the plasma with water. The possibility to admix a broad variety of chemical additives makes underwater plasma additionally highly attractive for the chemist. At last, the water removes all low-molecular weight oxidized products formed by plasma-induced polymer degradation. Hydrogen peroxide and the catalyst (Fe-ZSM5) should influence or increase the equilibrium concentration of OH radicals in the underwater process. It was supposed that these radicals play the most important role for OH functionalization of polyolefin surfaces. Hydrogen peroxide was believed to be the most prominent precursor for OH group formation in the UWP. The catalyst should modulate the steady state of OH group formation and recombination, and thus accelerate the functionalization. This was confirmed by an increased oxidation rate. Owing to the detection limit of XPS the C-O bond selectivity was defined as clearly resolvable subpeak within the C1s signal assigned to C-OH, C-O-C and other singly C-O bonded species. This bondamounts 47 C-O bonds/100 O atoms with pure UWP system and enhances to a maximum of the 81 C-O bonds/100 O atoms using the Fe-ZSM5 catalyst system. Therefore, this method exhibits a great progress for a start. However, after TFAA derivatization the fraction of desired OH groups could not be significantly increased. In the continuation acetic acid, acrylic acid, maleic and itaconic acid were used as additive monomers. The chemical selectivity in -COOH bond formation using bi-carboxylic additives was seen inferior. Acetic acid is not a chemically polymerizing monomer but it could polymerize by monomer/molecular fragmentation and recombination to a cross linked layer. The other monomers form preferably water-soluble polymers on a preferred chemical way. Only the fragmented fraction of these monomers could form an insoluble coating by cross linking to substrate. The XPS analysis was used to track the alterations in COO- bond percentage on the PP surface. To identify the -COOH groups on substrate surface unambiguously, which have survived the plasma polymerization process, the gas phase derivatization with trifluoroethanol was performed. A much higher yield in COOH groups was achieved using the glow discharge electrolysis and acrylic acid.
Glass has different outstanding material-specific properties which offer theoretically the application of thin-walled hollow fibers in the field of high pressure gas storage. Especially the storage of hydrogen as renewable and environmental friendly energy carrier is possible. Glass is an amorphous material which is characterized by a theoretical tensile strength much higher than this of other materials. However, in practice the tensile strength is decreased significantly by defects on the glass surface or in the material and its network structure. As part of this thesis the burst pressures of hollow glass fibers were determined. The burst pressure correlates very well with the tensile strength of hollow glass fibers. By using the Weibull statistic the results of different test series were evaluated in respect to failure probabilities and compared to each other. Thereby the influence of various parameters on the pressure resistance was investigated. Beside the influence of the chemical composition of the material the aging by environmental and their effect on the pressure resistance was investigated. Additionally hollow glass fibers were loaded dynamically and statically with different gases. Afterwards the burst pressure was determined and the effect of used gas on the pressure resistance could be determined as well as the impact of method and duration of loading. A further influence of the dimension of hollow glass fibers on their resistance against inner pressure load is the ratio between wall thickness and inner diameter which was investigated as well as the combination of different glasses and the utilization of their disparate coefficient of thermal expansion which lead to prestressing of the hollow glass fiber. Finally, the impact of the variation of several production parameters on the pressure resistance was determined experimentally as like as the influence of surface coatings. These shall protect the glass surface from subsequently procured defects and, hence, increase the pressure resistance. As essential part of current thesis the defect analysis of test samples of various series was done whereby the differentiation between material and production dependent defects was important. Not only a light microscope but a scanning electron microscope was used for the investigation, as well. Beside volume defects like bubbles or inclusions surface defects in the form of scratches or spalling can be detected and observed. A calculation of the failure-causing defect size from measured burst pressure is possible. Dependent on the dimension and determined burst pressure value of each single fiber defect sizes of less than one micron were calculated. Particularly the geometry of the test samples inappropriate for many examination methods and the fact that the calculated defect size occurs only under loaded conditions at actual burst pressure the local detection of corresponding defect rendered impossible. In the end, the present thesis shows the pressure resistance of hollow glass fibers and their potential to store safely gases under high pressure.
Glass is an amorphous material. When compared to steel, both its density and weight is three times lower. Its high theoretical strength makes it stand out as a premier material for a variety of applications. One such application is acting as a pressure resistant vessel for gas storage. Because glass has a high theoretical strength this makes it potentially suitable to withstand much higher pressures than steel or composite vessels. As a result of its brittle character, glass breaks when reaching a critical stress level. Therefore, the stress distribution during pressure load needs to be homogeneous without local stress peaks. At those peaks an initial crack will occur and the material will break. This PhD thesis is primarily concerned with the determination of the strength of several structures made of single hollow glass fibers during inner pressure treatment. Therefore, different kinds of hollow glass structures with varying parameters of shape and dimension were examined concerning their strength by determining the burst pressure. The burst pressure method was compared to the tensile test method, which poses the common test method for examining the strength of a material. The conclusion reached was that both test methods lead to comparable results and therefore, the burst pressure method poses an adequate tool for examining the strength of a hollow material against inner pressure. Another tool used in this thesis is the Finite Elements Method (FEM) simulation of internal stress and expansion of glass structures during pressure treatment. FEM was used to validate the burst pressure test results. A few selected material parameters needed to be incorporated, most notably the Young’s Modulus. Therefore, the expansion of single glass fibers was measured with light microscope during pressure load. Within the parameters of expansion, wall thickness and applied pressure, the Young’s Modulus was calculated with the Barlow’s Formula. According to the results, different two-dimensional models from single fibers to complex structures with up to 1000 single fibers were constructed and simulated with the CFD software Comsol Multiphysics. The expansion as well as the principal stress during pressure load was calculated. Different dimensions as well as different geometries of the glasses were considered to find a structure with the highest possible free volume and at the same time as less stress peaks as possible. This calculation was made in order to determine the best structure for gas storage. For this purpose the calculations were done with different dimensions of round single fibers right up to hexagonal structures consisting of more than one thousand round single fibers, which resulted in constant expansion of the structure. Furthermore, the problem of occurring interspaces between round single fibers, regarding their burst pressure-decreasing influence, was approached. Closing these interspaces with glass or other materials to avoid unsolicited pressure load led to increased strength of the structure and low storage capacities due to the increased weight and less free inner volume. The behavior of hexagonal fibers was determined as single fiber as well as in bundled condition. The walls between two hexagonal single fibers with applied inner pressure showed homogeneously distributed stress. Merely the outer walls without counter pressure showed high deformation and high structural stress. Based on that knowledge, several structures were modeled varying in different aspects. The fibers with hexagonal shape showed optimal stress distribution and high storage capacities because of high free inner volume, provided that these fibers are surrounded by additional fibers with identical inner pressure. Reducing the wall thickness for even higher free inner volume led to similar distribution but higher stress and expansion. To overcome the problem with the high stress at the outer fibers, the influence of outer fibers with different shape and dimension was simulated as well as the influence of solid glass fibers at the outer layer of the structure. The results showed that a structure with hexagonal thin-walled fibers should be surrounded by round fibers with higher wall thickness. This way the high stress peaks at the outer fibers are lowered. The examined practical strength of glass is about 100 to 1000 times lower than the theoretical strength. This is caused by defects, which may occur at the glass surface by handling or inside the material by defective production. Since the modeled results are based on the theoretical strength, the optimal wall thickness with a good compromise of strength and free inner volume needs to be found in practical tests. If further handling of the structures is necessary, an outer layer of solid fibers works as a protection layer against damages at the outer hollow glass fibers and increases the strength. Additionally, the influence of collapsing fibers inside a structure on the remaining system has been modeled as well as the influence of defects like holes or cracks at the surface or manufacturing induced defects inside the material. Any kind of defect leads to areas of high stress, whereby failure occurrence will be encouraged. In order to approve the theoretical results, the simulated structures were compared to the previously manufactured and tested ones. Due to the burst pressure test results, the tested structures showed low strength compared to the theoretical strength. This was primarily caused by the existence of defects in the material and on the surface of the glass structures. Therefore, the production process needs to be optimized in order to prevent such defects. Furthermore, an additional protection against outer influence like air humidity or the physical contact to other materials is required.
Experimental investigation and CFD simulation of organic peroxide pool fires (TBPB and TBPEH)
(2010)
Time averaged mass burning rate (m˙′′f ), flame length (H), temperature (T ), irradi- ance (E) and surface emissive power (SEP ) of TBPB (tert -butyl peroxybenzoate) and TBPEH (tert-butyl peroxy-2-ethylhexanoate) pool fires are measured for six pool di- ameters (d = 0.059 m, 0.107 m, 0.18 m, 0.5 m, 1 m and 3.4 m) at BAM in house and outside test facility. The measured heats of combustion (–Δhc) of TBPB and TBPEH are 30113 kJ/kg and 34455 kJ/kg and the specific heat capacities at constant pressure (cp) are 1.8 kJ/(kg K) and 2.1 kJ/(kg K) respectively. The measured m˙′′f of TBPB and TBPEH pool fires are in the range of 0.37 kg/(m2 s)≤ m˙ ′′ f ≤ 0.83 kg/(m2 s) and show little dependence on the pool diameter d, and are four to sixty times higher (for d = 1 m) than that of hydrocarbon pool fires. It is shown that the mass burning rates of the investigated organic peroxides can be represented as an exponential function of the self-accelerating decomposition temperature (SADT). Low SADT implies that the organic peroxide pool fires burn at a much higher m˙′′f than hydrocarbon pool fires. Fuel Froude numbers (Frf) of TBPB and TBPEH are 5 to 100 times (depending on d) higher than for hydrocarbon pool fires. Due to higher Frf the H of TBPB and TBPEH (measured with a S-VHS Videocamera) are found to be two times larger (d = 1 m) than corresponding pool fires of hydrocarbons. Heskestads flame length correlation predicts the Hd (d = 3.4 m) of TBPB and TBPEH pool fires much better than Thomas and Fay correlations. The measured time averaged flame temperatures T (d = 3.4 m) for TBPB and TBPEH pool fires are in the range of 1400 K ≤ T ≤ 1500 K and are 200 K to 300 K higher than for JP-4, kerosene and gasoline. The irradiances of the TBPB and TBPEH pool fires measured by radiometers are E (Δy/d = 0.3) = 45 kW/m2 and E = 98 kW/m2 which are two to ten times higher in comparison to the corresponding n-pentane, super gasoline and diesel pool fires. So the thermal safety distances for organic peroxide pool fires are larger by a factor four in comparison to the hydrocarbon pool fires. An infrared thermography system is used for the determination of SEP of TBPB and TBPEH pool fires. The values of surface emissive power for TBPB and TBPEH are SEP (d = 3.4 m) = 196 kW/m2 and SEP = 258 kW/m2 and thus the SEP are by a factor of approximately two higher than for hydrocarbon pool fires. A self-sustained pulsating Hd (’W’-Effect) is found in TBPB pool flames and is further analysed to explain the reason of occurance on the basis of chemical structure of the fuel and discontinuous heat flux back from flame to the liquid pool. CFD simulations of TBPB and TBPEH pool fires at d = 0.18 m, 0.5 m, 1 m, 3.4 m and 8 m are carried out using the Unsteady Reynolds Averaged Navier Stokes (URANS) equa- tions. The three-dimensional geometries have been discritized with unstructured hybrid grids, with the number of cells in the range of 1 million. Depending on the grid resolu- tion and the pool diameter time steps of 0.0001 s ≤ Δt ≤ 0.01 s for the CFD simulations are used. For solving the discritized equations a finite volume based implicit solver AN- SYS CFX has been used. For modelling the combustion, stoichiometric combustion for both peroxides are assumed. The temperature dependence of the reaction rate has been determined by the Arrhenius approach. For modelling the combustion eddy dissipation concept (EDC) model has been used. For turbulence buoyancy modified k- � and SAS (Scale Adaptive Simulation) turbulence models are used. For the thermal radiation and soot mass fraction discrete transfer radiation model and Magnusson soot model have been used. A new method is suggested for the prediction of mass burning rate (m˙′′f ) by CFD simula- tion. Both peroxide pool fires show approximately constant mass burning rate indepen- dent of d whereas m˙′′f of TBPEH are under predicted at the beginning but show relatively good agreement with measurements for large pool diameters (d = 1 m). In case of TBPB the CFD simulation over predicts the mass burning rate m˙′′f of small TBPB pool fires and shows a continuous decrease with d. CFD predicts the flame length H close to the measured data provided that the constants in Thomas equation are modified. The CFD predicted time averaged surface emission flame temperatures of TBPB and TBPEH pool fires (d = 3.4 m, 1437 K and 1542 K) are in good agreement with the measured time averaged flame temperatures. The CFD predicted SEP for TBPB and TBPEH pool fires (d = 3.4 m, 217 kW/m2 and 288 kW/m2) are also in agreement with the measured values. From the CFD predicted irradiance ECFD it is possible to determine the thermal safety distances from large pool fires of hydrocarbons and organic peroxides.