High Pressure Steam Research Articles

A hybrid multi-criteria decision-making approach for analysing operational hazards in Heavy Fuel Oil-based power plants

Hazard identification and prioritisation practices are very important for power plants to continue their operations without disruption. Systematic operational hazard analysis is not a very common practice at the Heavy Fuel Oil (HFO) based power plants in Bangladesh. Hence, a structured hazard evaluation framework can greatly benefit them to ensure their operational safety. This study has been conducted to identify and prioritise the operational hazards of the HFO-based power plants through using a hybrid multi-criteria decision-making (MCDM) approach in a fuzzy environment, and then, to explore the appropriate mitigation methods for the top-ranked hazards and to find the interrelationships that exist among the mitigation methods. First, the most common hazards in HFO-based power plants have been identified from the expert feedbacks. Then, a fuzzy analytical hierarchy process (FAHP) method has been used to determine the weights of the evaluation criteria and a fuzzy technique for order performance by similarity to ideal solution (FTOPSIS) method, has been used for the final ranking of the potential hazards. Afterwards, mitigation methods for the top 25 hazards have been identified and interrelationship among those mitigation methods has been explored through using interpretive structural modelling (ISM) and a matriced impacts croisés multiplication appliquée à un classement (MICMAC) analysis. The study finds that ‘explosion of high-pressure steam drum of the gas boiler’, ‘crankcase explosion and fire hazard due to oil pressure rise’ and ‘explosion of the compressed air reservoir’ are the top three hazards in the hazard ranking. ‘Standard operating procedure (SOP) and training’ have been found to be the most driving mitigation methods for the top-ranked hazards based on the ISM-MICMAC analysis. The findings of this study are expected to provide the managers of power plants with valuable insights, which can help them to prepare sustainable operational strategies to ensure the least hazardous work environment.

Experimental study on steam plume shape characteristics for bevelled spray nozzles exhausting into quiescent water

Steam-water direct contact condensation phenomenon is being widely used in many industries including chemical, thermal and especially in nuclear industry due to its efficient heat and mass exchange capabilities. The present experimental study explores the underlying physics of the steam cavity/plume shapes by condensing supersonic steam exhausting from five different bevelled nozzles into quiescent water tank. Based on the high speed image capturing methodology, the effects of steam pressure, water temperature and nozzle exit inclination angle on the cavity shape characteristics have been studied. Existence of six different plume shapes (oscillatory, conical, expansion–contraction, double expansion contraction, cylindrical and divergent) have been identified. The results show that for a fixed nozzle geometry, with the increase in water temperature and steam pressure, the steam jet becomes lengthy. However, under the same steam pressure and water temperature conditions, the plume shortens with the increase in nozzle exit inclination angle. The dimensionless jet length has been found in the range of 1.26–5.64. Furthermore, it has been observed that steam plume exhausting from bevelled nozzle undergoes deflection from its nozzle symmetry axis possibly due to the pressure difference between upper and lower lip of nozzle. This deflection may either be upward oriented at high steam pressure or downward deflected at lower steam pressure. Additionally, on the basis of findings from 175 No’s of experiments, condensation regime maps have also been developed for bevelled spray nozzle.

Identification and quantification of valuable platform chemicals in aqueous product streams from a preliminary study of a large pilot-scale steam explosion of woody biomass using quantitative nuclear magnetic resonance spectroscopy

Steam explosion breaks down the polymeric matrix and enables the recovery of valuable compounds from lignocellulosic feedstock. In the steam explosion process, biomass is treated with high-pressure steam which subsequently generates large quantities of a condensed aqueous liquid (process effluent) and a filtered aqueous liquid (filtrate) that contain furfural, 5-hydroxymethylfurfural, 5-methylfurfural, methanol, and acetic acid as major constituents. This study addresses the identification and quantification of value-added chemicals in the aqueous product streams using quantitative analytical nuclear magnetic resonance spectroscopy with water suppression. This work reports a screening study for two different types of sawdust (Norway spruce and birch) at two different scales (4 L and 10 L reactors) using different reaction temperatures (190–223 °C) and corresponding pressures (13–24 bar), with and without the addition of SO2 gas. The duration of all experiments was 8 min. The process effluents contained acetic acid, methanol, formic acid, 5-methylfurfural, and furfural. Acetic acid (0.5 g/kg dry input biomass) and furfural (1.0 g/kg dry input biomass) were more abundant than methanol, formic acid, and 5-methylfurfural for both feedstocks. The addition of SO2 increased the furfural yields, indicating more efficient hydrolysis of hemicelluloses under acidic conditions. Filtrate samples also contained 5-hydroxymethylfurfural, with the highest concentrations (5.7–6.0 g/kg dry input biomass) in the filtrates from spruce. The different feedstocks and steam explosion temperatures strongly influenced the overall yields of the target compounds, in some cases tripling the concentrations. The results can be used to improve the profit margins in a pellets and chemicals biorefinery, as demonstrated in the ArbaOne pellets plant.

Pulsed FCAW of Martensitic Stainless Clads onto Mild Steel: Microstructure, Hardness, and Residual Stresses

The low carbon martensitic stainless AWS 410NiMo steel has in its chemical composition 13% chromium, 4% nickel, and 0.4% molybdenum (wt.%) and is used in turbine recovery, rotors, and high-pressure steam pump housings due to its resistance to impact at low temperatures, as well as to corrosion and cavitation. Those applications of the AWS 410NiMo steel frequently demand repair, which is performed by welding or cladding. Arc welding is a well-established technique for joining materials and presents several parameters that influence the mechanical performance of the weld bead. Although numerous welding processes exist, optimizing welding parameters for specific applications and materials is always challenging. The present work deals with a systematic study to verify the correlation between the pulsed fluxed core arc welding (FCAW) parameters, namely pulse current and frequency, welding speed, and contact tip work distance (CTWD), and the bead morphology, microstructure formation, residual stress, and hardness of the martensitic clad. The substrate used was the AISI 1020 steel, and the AWS 410NiMo steel was the filler metal for clad deposition. From the initial nine (9) samples, three (3) were selected for in-depth characterization. Lower heat input resulted in lower dilution, more elevated hardness, and lower compressive residual stresses. Therefore, the results highlight the need for selecting the proper heat input, even when using a pulsed FCAW procedure, to achieve the desired performance of the clad. In the present case, a higher heat input appears to be more advantageous owing to the lower convexity index, smooth hardness transition between fusion and heat-affected zones in addition to more elevated compressive stresses.

The influence of energy output and substitution on the environmental impact of waste-to-energy operation: quantification by means of a case study

A life cycle assessment (LCA) was conducted to evaluate the total environmental impact of state-of-the-art waste-to-energy (WtE) in Belgium with respect to recovered energy utilization and addition of carbon capture and storage (CCS). Four energy output scenarios were modeled on Umberto LCA software using primary data of mass and energy flows surrounding the six incinerators at the considered WtE plant and predefined processes from the Ecoinvent 3.6 database. The normalized LCA results suggest that by utilizing all the recovered energy as high-pressure steam, the WtE plant can avoid an equivalent annual environmental impact value of approximately 21200, 36800, 6700, 15800, 37000, and 6900 average European citizens in the impact categories ‘climate change,’ ‘freshwater and terrestrial acidification,’ ‘freshwater eutrophication,’ ‘photochemical ozone creation,’ ‘respiratory effects, inorganics,’ and ‘terrestrial eutrophication,’ respectively. The ‘Electricity and Steam with CCS’ scenario resulted in the most avoided environmental impact in the impact category ‘climate change.’ However, in all other impact categories, it resulted in less avoided environmental impact compared to the ‘Steam’ scenario. The comparative analysis showed that 19 out of the 24 LCA results varied by more than 50% between a region-specific and a region- and fuel-specific model, thus quantifying the influence of scenario uncertainty, introduced by the normative choice of substituted processes in LCA modeling. This study exemplifies the environmental benefit WtE technology can realize by substituting conventional energy production processes that are reliant on fossil resources, while performing its primary function that is reducing the volume of non-recyclable waste, destroying hazardous organic components it contains, and recovering useful materials from it.

Failure Analysis of Abnormal Bulging and Cracking for High-Pressure Steam Pipe

Failure Analysis of Abnormal Bulging and Cracking for High-Pressure Steam Pipe

Intelligent sterilizable self-cleaning membranes triggered by sustainable counterion-induced bacteria killing/releasing procedure

The separation efficiency of currently developed bacteria-removal membrane system will be limited and lost due to the chemical cleaning and regeneration procedure. The main innovation of this research is the development of a novel intelligent bacterial filtration process to produce a polycationic membrane separation system that continuously kills and releases bacteria even after a 121 °C sterilization procedure. This work breaks through the possibility of introducing medical-grade sterilization procedures for clinical applications while providing the implementation of self-cleaning techniques that can be facilitated by sustainable cycle operation. The polycationic membrane was prepared by the vapor-induced phase separation (VIPS) process to control the membrane formation of polyvinylidene difluoride (PVDF) blended with a new copolymer of poly(butyl methacrylate-co-(trimethylamino)propyl methacrylamide chloride) (PVDF/PBTP). The tested hypothesis is to validate the effect of the chemical-segment substitution of methacrylamide for methacrylate on the bacteria-killing/releasing functions. The reversible molecular interaction between the membrane and microorganisms is driven by controlling the electrostatic attraction adjusted by a multivalent negatively charged ions. The PVDF/PBTP membrane can sustainably provide more than 80% bacteria-killing efficiency after the high-pressure steam sterilization process. The results of multiple bacterial separation cycles show that the PVDF/PBTP membrane can exhibit a bacteria-killing level of more than 82% and an average bacteria-releasing level of 75% without aging under 5 repeated membrane filtrations. The significant results show that PVDF/PBTP membrane exhibit excellent bacteria-killing/releasing function proved through multiple cycles of bacterial isolation. The new self-cleaning membrane developed in this study can provide a potential strategy to effectively remove potentially harmful microorganisms in domestic water and industrial wastewater, and significantly reduce its environmental pollution and bacterial pathogenicity.

Optimal operating strategy of ash deposit removal system to maximize boiler efficiency using CFD and a thermal transfer efficiency model

Ash deposits generated during the combustion process on the outer tube surface of a boiler reduces the boiler’s efficiency. In most boilers, ash deposits are physically removed with high-pressure steam using an ash deposit removal system, sootblower. However, most sootblowers spray steam with excessive pressure, without considering the characteristics of the ash deposit, resulting in problems such as waste of steam energy and damage to equipment. In addition, an optimal operation strategy based on the position of the sootblower and the injection angle of the steam nozzle are not considered, leading to a lowered efficiency of ash deposit removal and steam waste. Hence, this study proposes a novel method to determine the optimal operating conditions of a sootblower using computational fluid dynamics (CFD) and a thermal transfer efficiency model considering the properties of the ash deposits. This method was developed based on a commercial recovery boiler, and consists of (i) a sootblowing steam velocity model that considers the ash deposit characteristics, (ii) a three-dimensional CFD model considering the interior design of the boiler, and (iii) a thermal transfer efficiency model that calculates the thermal resistance depending on the amount of ash deposit removed.Case studies were performed to calculate the amount of ash deposit removed for various ash deposit thicknesses, and sootblower positions and angles using this methodology. The boiler heat transfer efficiency was calculated using the calculated ash deposit removal amount and thermal transfer efficiency model, and the optimum operating conditions for the sootblower with the optimum heat transfer efficiency were derived. This study presents a guideline for efficiently operating sootblowers according to the ash deposit characteristics, and can be applied not only to recovery boilers but also to other boilers in which ash deposits are generated.

The direct synthesis of dimethyl ether (DME) from landfill gas: A techno-economic investigation

The use of fossil fuels is primarily responsible for the increasing amounts of greenhouse gas emissions in the atmosphere and, unless this issue is quickly addressed, the effects of global warming will worsen. Synthesis gas (syngas) is an attractive target chemical for carbon capture and utilisation and dry reforming of methane (DRM) enables the conversion of methane (CH4) and CO2, the two most abundant greenhouse gases, to syngas. This paper presents a techno-economic analysis of a syngas-to-dimethyl ether (DME) process, by utilising landfill gas as feedstock. The process developed herein produces DME, methanol and high-pressure steam as products, resulting in an annual income of €3.49 m and annual operating expenses of €1.012 m. Operating profit was calculated to be €2.317 m per year and the net present value (NPV) was €11.70 m at the end of the project’s 20-year lifespan with a profitability index of 0.83€/€. The process was expected to have a payback time of approximately 10 years and an internal rate of return of 12.47%. A key aspect of this process was CO2 utilisation, which consumed 196,387 tonnes of CO2 annually. The techno-economic analysis conducted in this paper illustrates that greenhouse gas utilisation processes are currently feasible both in terms of CO2 consumption and profitability.

Film condensation heat transfer of high-pressure and low-mass-flux steam in inclined tube

High pressure conditions with a compact condensation system are used for high efficiency. In this regard, we present herein an experimental study on the film condensation heat transfer under low-mass-flux high-pressure steam in an inclined tube. The effect of each parameter on the film condensation was analyzed based on the average heat transfer coefficients determined by the logarithmic mean temperature difference method for different steam mass fluxes (27, 54, and 82 kg/m2 s), pressures (0.5 and 2.0 MPa), and inclination angles (−37.5°, −15°, 0°, +7.5°, and +30°). Condensation heat transfer coefficient generally tends to decrease as the steam quality decreases, however, we found regions where Nu in one direction is higher than that in other directions. We expect this is caused by different flow pattern transition points for flow directions and discuss local heat transfer changes for the flow patterns based on the effect of vapor-liquid interfacial wave and film curvature. The obtained reference data for high-pressure steam in inclined condensation tubes and is expected to contribute toward the design of advanced energy systems involving high-pressure condensation components.

Improve the mechanical durability of superhydrophobic/superamphiphobic coating through multiple cross-linked mesh structure

Superhydrophobic/superamphiphobic coatings have attracted extensive attention because of their unique liquid repellency, but their poor durability hinders their large-scale application in the market. This paper designs and synthesizes a mesh structure that uses covalent bonds to link the roughness-building nanoparticles, film-forming polymer, and the substrate together, which significantly improves the stability and durability of the coating. Firstly, the acrylate copolymer (FHA) containing silicon monomer and fluorine monomer was synthesized by free radical polymerization. Then FHA, SiO2/TiO2 nanoparticles, and self-made crosslinker (AG) were connected to form a meshwork structure by Si-O-Si bond through a hydrolysis condensation reaction. Finally, the curing agent (HDI) was added before dip-coating, and the coatings were firmly linked to the substrate through secondary cross-linking. The single-factor experiment showed that when silicon monomer was 12 wt%, fluorine monomer was 5 wt% and FHA content was 16 wt%, the coatings displayed the 5B adhesion. The contact angle (CA) to water, diiodomethane, soybean oil， rapeseed oil, hexadecane, kerosene, waste engine oil on the FAFH-SiO2 coating (consists of the mesh structure and SiO2 nanoparticles) were 158.7° ± 1.5°, 151.1° ± 1.6°, 150.1° ± 1.7°, 150.4° ± 1.5°, 141.1° ± 1.6°, 142.2° ± 1.9°, and 144.7° ± 1.8°, respectively. The coatings could maintain WCA (water contact angle) > 150° after immersion in HCl (PH = 1), toluene, ethanol, and acetone for 84 h. The sandpaper abrasion, water flow scouring, high-pressure steam cooking, machine washing, and environmental exposure tests proved that the coatings have excellent stability and durability. This method for enhancing the durability of the coatings is suitable for particles and substrates containing active hydrogen or hydroxyl groups, which has a wide range of application prospects.

Techno-Economic Analysis for the Production of 2,3-Butanediol from Brewers’ Spent Grain Using Pinch Technology

2,3-Butanediol (BDO) is a versatile platform chemical with great potential as the precursor for various value-added derivatives across different industrial sectors. This work thus presents a techno-economic feasibility study for microbial BDO production from C5 and C6 sugars derived from brewers’ spent grain (BSG). Water-soluble carbohydrates obtained from pretreatment were further utilized for the biogas generation. Besides, the solid residue generated after fermentation and biogas were used to generate high-pressure steam and electricity. The process integration was carried out using pinch technology for various BDO titers and plant capacities. The pinch analysis helped in the reduction of hot and cold utility consumption by about 34 and 18%, respectively. The minimum hot and cold utility consumption was 4.59 and 10.97 MW for 100 MT BSG per day with 100 g/L BDO titer, respectively. The cooling water consumption was decreased, and electricity generation was increased with the increase in BDO titer, while the BDO production cost reduced marginally. For 100 MT BSG per day, the BDO production cost was US$1.84, US$1.76, and US$1.74/kg for BDO titers of 80, 100, and 120 g/L, respectively. However, the unitary BDO production cost was only US$1.07 for 2000 MT BSG per day. For 100 g/L BDO titer, the minimum BDO selling price was US$3.63 and US$2.00/kg for 100 and 2000 MT BSG per day, respectively, with 8.5% return on investment and 5 years as the payback period.

Decarbonisation of steel mill gases in an energy-neutral chemical looping process

The iron and steel industry is the largest industrial carbon dioxide emitter. More than 70% of their emissions originate from conventional combustion of steel mill gases. In this work, a strategy for carbon capture from the steel mill gases is laid out, using a combination of emerging technologies employing oxygen carrying nickel oxide, carbon dioxide accepting calcium oxide, and dioxygen uncoupling manganese(III) oxide. The process combination was simulated and analysed using Aspen Plus. By applying the proposed strategy, up to 85% of carbon dioxide emitted from the combustion of blast furnace gas and coke oven gas can be captured and compressed for storage or utilisation without external heat and electricity supply. The chemical energy in the steel mill gases is used for the reduction of nickel oxide to nickel and the exothermic capture of carbon dioxide by calcium oxide to form calcium carbonate. Auto-thermal conditions for the energy-intensive carbon dioxide release by the endothermic decomposition of calcium carbonate at 1173 K are achieved by combining it with the exothermic oxidation of nickel by dioxygen, thereby regenerating nickel oxide and calcium oxide for another cycle while efficiently using the chemical energy stored in the steel mill gases. The dioxygen necessary for nickel oxidation to nickel oxide is produced by using a fraction of the product carbon dioxide stream at 1173 K for the endothermic manganese(III) oxide reduction to manganese(II,III) oxide, operated between 1100 and 1140 K, making use of the sensible heat of the carbon dioxide product stream and shifting the equilibrium towards dioxygen uncoupling of manganese(III) oxide. Air is used to re-oxidise manganese(II,III) oxide to manganese(III) oxide and complete the process cycle. Self-sufficiency of electrical power for carbon dioxide compression is obtained by recovering high temperature heat and converting it into electricity via high pressure steam in a steam turbine assembly. A proof of concept is obtained in a laboratory scale fixed bed reactor and the effect of operating conditions is experimentally explored.

A natural gas-based eco-friendly polygeneration system including gas turbine, sorption-enhanced steam methane reforming, absorption chiller and flue gas CO2 capture unit

Poly-generation systems have attracted a lot of attention due to the increment of efficiency as well as reducing energy penalties, costs and pollutants. Extensive research has been done on these systems in recent years. The current work is done with the aim of simulating an environmentally friendly poly-generation system in the power plant of Shahrood city in Iran. In this way, a poly-generation system is simulated in Aspen Plus software which consists of: I) a gas turbine (GT) for power generation with natural gas fuel of Shahroud power plant, that its flue gas is utilized to supply heat for other cycles and streams, II) a sorption-enhanced chemical looping reforming (SECLR) which simultaneously generates H2 by steam methane reforming (SMR) and uptakes produced CO2 by calcium adsorbent during the carbonation/calcination reactions. In this section, there is also a chemical looping combustion (CLC) based on redox reactions of Ni/NiO to provide heat of the reactors, III) a NH3/H2O absorption refrigeration system to yield the cooling demand, IV) a high-pressure steam generation unit and V) a MEA-based post-combustion CO2 capture unit (PCC) for flue gas. In this system, an attempt has been made to prevent heat loss by internal streams, especially gas turbine exhaust gas, so that energy loss is minimized. Moreover, environmental issues are also prioritized to reduce the CO2 emissions as much as possible. The proposed process is capable of producing 133.3 MW power, 9.875 MW cooling, 50 kg/s high-pressure steam and 0.384 kg/s hydrogen. The mass flow rates of CO2 captured in the SECLR and PCC sections are 2.6 kg/s and 15.35 kg/s, respectively. Moreover, the total energy efficiency of the integrated system is 68.74%. Ultimately, a sensitivity analysis was performed to identify the key parameters and their influence on the process performance.

Microstructure understanding of high Cr-Ni austenitic steel corrosion in high-temperature steam

The microstructure and microchemistry of the oxide scales formed on Fe-21Cr-32Ni and Fe-17Cr-9Ni steels after exposure to deaerated high-temperature high-pressure steam at 600 °C for 1500 h have been analysed and compared by several advanced characterization techniques. By comparing the oxide scales formed at different-stages of exposure, it is shown that Fe-21Cr-32Ni steel was internally oxidized at the early-stage, and then an external oxide scale was developed together with an inner chromia band under the internal oxidation zone. In comparison, Fe-17Cr-9Ni steel was internally oxidized together with an external Fe-rich oxide scale during the entire experimental period. The thicknesses of the internal oxidation zone of Fe-21Cr-32Ni and Fe-17Cr-9Ni steels were ∼7 and ∼70 µm, respectively. Further characterisation revealed that the internal oxidation zone contained (Cr, Fe, (Ni))3O4 and nanoscale nickel networks, together with numerous nano-pores. The effects of these structures on mass transfer and reaction product formation were discussed, in connection with the alloy composition and the formation of the chromia layer.

Hospital cleaning

The aim of this narrative review is to present up-to-date facts concerning hospital cleaning (HC). HC is essential in the prevention of healthcare associated infections (HAI). If a proper HC is followed by a proper use of disinfectants even the HAI caused by the most dangerous nosocomial pathogens like methicillin-resistant Staphylococcus aureus, vancomycin- resistant Enterococcus, carbapenem-resistant Pseudomonas aeruginosa and multidrug-resistant Acinetobacter baumannii may be stopped without closing the ward or placing the patients in isolation. Critical hospital surfaces that may be highly contaminated with pathogens include toilet seats and bowels, toilet flush handles, doorhandles, furniture, hospital equipment, linen, clothes, buttons, switches, computers, printers, shelves, cellphones, curtains, patient chairs, nurse call-buttons and bed rails. Hand-touch sites at bedside pose the highest risk of HAI for patients and these should be targeted with continuous and detail cleaning. The most used methods for the assessment of hospital cleanliness are visual inspection, aerobic colony counts, adenosine triphosphate (ATP) bioluminescence and fluorescent markers. Together with soaps and detergents the environmental-friendly disinfectants like hydrogen peroxide, high-pressure steam, electrolyzed water, ozone, probiotic cleaners and microfiber cloths have a priority in hospital cleaning. Recent advances in the methods of hospital cleaning together with the continuous education of cleaning staff and nurses significantly contribute to the prevention and control of hospital outbreaks.

Energy performance assessment of a novel zeolite-water direct contact adsorptive heat pump for waste heat recovery

• The low-grade industrial waste heat can be recovered using adsorption heat pumps. • The direct contact adsorption heat pumps guarantee simple configurations. • The water inlet downward flow configuration shows excellent thermal performances. The adsorption heat pumps are a promising technology suitable for the industrial waste heat recovery. In particular, the direct contact configuration can be used to generate high pressure steam for industrial applications limiting the design complexities. In this paper, a numerical simulation of the adsorption phase of an original configuration of a direct contact water/zeolite heat pump is presented and discussed. Two different models have been developed and compared using experimental data. Different sensitivity analyses were carried out with the aim of understanding the process of steam generation. The mass flow inlet results to be one of the most relevant parameters of the process and, consequently, an innovative process configuration is proposed. A descendent inlet water flow is implemented and compared with the classical ascendent process. The simulations on this configuration demonstrated that it is possible to obtain higher steam production and better process performances doubling the generated steam mass flow.

К применению низкотемпературных рабочих тел и сверхкритических флюидов для снижения углеродного следа при производстве карбамида и в пиролизе углеводородов

Low-temperature working fluids and supercritical fluids for use in compressor equipment drives in a number of areas are considered: production of urea, pyrolysis of hydrocarbons in the production of olefins. In the existing technologies, the energy consumption in the form of high-pressure steam for compression is very high. The use of closed gas turbine cycles will significantly reduce the consumption of such high-temperature energy while simultaneouslyusing the heat of intermediate technological flows, saturated low-pressure steam and additional low-potential heat discharged under existing conditions to cooling towers or leaving with flue gases.

Dissimilar metal weld failure of steam piping in a hydrogen unit of petroleum refinery

Steam generation from hot reformer effluent in a hydrogen unit of a petroleum refinery increases the refinery margin. Upstream and downstream piping in hydrogen plant were constructed by SA335 P22 (AS) and type SS304L (SS) materials, respectively. This paper reports failure of dissimilar pipe weld after six months of high pressure steam service. Visual inspection indicates several ratchet marks initiated from outer wall surface at heat affected zone (HAZ) of AS pipe accompanied with brittle fracture. Further, failed samples were examined for chemical analysis, micro-hardness, fractography & elemental analysis and microstructural analysis. Fractographic results indicated that the dissimilar weld was failed due to thermal fatigue. Moreover, microstructural analysis revealed the presence of martensite in AS HAZ region with higher micro-hardness. In-spite of fixed operating temperature at 600 °C, there was a difference in thermal expansion that induced large strain gradient at interface and result in low cycle thermal fatigue failure. Type 308L filler metal was directly employed for dissimilar welding without buttering at interface layer was the main cause of failure. The principal factors that were responsible for Dissimilar Metal Weld (DMW) failure are discussed with respect to Schaeffler diagram and correct welding procedure for failure prevention is proposed. It is further recommended to employ 309/309L filler metal at interface layer according to ASME codes & standards to avoid DMW failure.

Comparison of the fabrication process and macro and micro properties of two types of crack-free, flatten bamboo board

The crack-free flattened bamboo board can be fabricated by using high-pressure saturated steam followed by a flattening process. With the application of “notched flattening technology”, the flattened bamboo board can be obtained with a large width and limited length. However, this technology causes the formation of nail holes in the bamboo surface, resulting in the deformation concerning the appearance and mechanical properties of bamboo products. On the other hand, “non-notched flattening technology” can yield flattened bamboo board with a 3.5-m total length without nailing holes on bamboo surface. The present study investigates the fabrication processes, chemical composition, microstructure, cell-wall mechanical properties of bamboo boards, and their practical applications. The obtained results showed that the contents of hemicellulose and cellulose were decreased due to heat treatment. Moreover, the flattening process caused the compression and squeezing of parenchyma cells that were evident through microstructure analysis. Thus, the density and EMC improved due to the flatting process. The improved density and crystallinity degree had a positive impact on the nano-mechanical properties of the bamboo cell wall. The modulus of elasticity and hardness of the control had been increased from 17.3 GPa and 0.49 GPa to 21.2 GPa and 0.73 GPa (non-notched flattened bamboo board), respectively. The improvement in the bamboo cell-wall mechanics had contributed positively to the macro and physical properties of the flattened bamboo board. Furthermore, the introduction of these two types of manufacturing processes of the crack-free flattened bamboo board demonstrates their applications in producing the different types of flattened bamboo board.