Boiler Shell Research Articles

Analysis of Three-Dimensional Modeling and Simulation of Boiler Shell and Tube Heat Exchanger Baffles

The goal of this research is to model a three-dimensional steam-producing plant heat exchanger for industrial operations. With a certain tube bundle structure, inlet temperatures and the velocity of the tube and shell sides are used as input factors in the current investigation. The heat transfer study takes hot flue gas inside the tubes and steam on the shell side into account. The model was designed and simulated using ANSYS 2020 fluent for the analysis, which was authenticated by contrasting the output results to actual in-house operating data. According to the computational results, the proposed design allowed for a 9oC rise in shell-side fluid temperature. It has been discovered that installing more baffles in the steam flow channel increases the fluid pressure moving through the heat-exchanger. When compared to the WKX110 model, the velocity along the PMX110 length was more uniform. The velocity distribution indicates that the velocity is particularly high at the baffle turns. This is helpful because the high velocity encourages high convection transfer of heat in the region; therefore, the installation of this baffle improves heat exchange efficacy. The numerical PMX110 and WKX110 findings were validated with experimental data and found to be in good agreement.

Comparative assessment and numerical simulation of boiler shell materials

Boilers are prone to both longitudinal and circumferential stresses. Hence, the need for better materials has been constant. Corrosion and stress failure due to extreme temperature conditions are common threats. Therefore, in the present research, numerical simulation and mechanical properties of various boiler shell materials have been highlighted. The results and conclusions have been obtained using the finite element analysis software ANSYS for commonly used boiler materials. The materials selected were Stainless Steel, Aluminum Alloy, and Composite materials. The Equivalent Stress (Von-Mises Stress) and Maximum Stress Failure criterion were used to identify the ultimate strength of all three materials. Findings indicated Structural Steel as safer when compared to other materials in terms of Equivalent Stress (Von-mises Stress). In addition, Titanium Alloy is extremely resistant to corrosion. As far as weight consideration, Aluminum alloy was the lightest among all three.

Investigations on mechanical properties and microstructural examination of activated TIG-welded nuclear grade stainless steel

Nuclear grade austenitic stainless steel 321 contains titanium for severe corrosive conditions and is used for process equipment, aircraft exhaust manifolds and boiler shells. Taguchi-based grey relational analysis technique has been considered to optimize the input parameters for welding SS321 material using activated tungsten inert gas welding process. The optimized input parameters were identified from the multiple output responses, i.e. arc length of 3 mm, welding current of 220 Amps and welding speed of 120 mm/min (A1B3C1). The analysis of the variance table was performed to calculate the importance of the input parameters in the weldment quality. Also, the influence of the heat input on the depth of penetration and bead width at different arc lengths has been studied. The mechanical integrity is evaluated in terms of tensile strength for base metal (BM) (621 MPa) and weld metal (WM) (624 MPa) specimens by conducting the uniaxial tensile test. The 180° bend test with WM sample revealed the ductility level and was free from fissures and cracks. Charpy impact test results depicted the toughness values of BM (123.17 J) and WM (113.46 J) samples. Microstructural investigations at the SS321 WM highlighted the existence of columnar and equiaxed dendrites in the fusion zone. Moreover, the formation of titanium carbide reduces the chances of weld decay. Ferrite number measurement shows that the amount of delta ferrite is higher in WM (5.9) than in BM (1.2). The existence of dimples and voids in the fractographic analysis of the failed specimens (tensile and impact) confirms the ductile type of failure.

A study method for possible breakdown of boiler tank for dangerous goods in an emergency collision

An impact to the boiler of a railway tank car in an emergency in the event of a car derailment and falling onto a track has been considered. In this case, boiler breakdown, spillage of the transported cargo and fire can occur. When developing a method, the following objectives have been solved: development of a method for determining a stress-deformed state (SDS) of a cylindrical shell at the initial elastic stage of deformation; - development of a method for calculating the deformation energy for the boiler shell when the yield point in the impact zone is reached; - development of a method for estimating the conditions for the beginning of the limiting state (shell destruction). For the shell behavior to be modeled, a moment theory of shells has been used with taking into account the nonlinear terms in stress-strain deformations. The energy principles in the form of the Lagrange principle have been applied to compile a resolving system of equations. The onset of the limiting state is taken according to the condition of a cut along the striker perimeter. A system of the nonlinear equations at the first stage and a transcendental equation at the second one has been solved using numerical methods. The proposed method makes it possible to develop methods of protection in terms of the choice of methods for attaching add-on elements to the boiler.

Transient Evaporation Simulation of the Forced Circulation Hot Water Boiler

This paper presents a comprehensive analysis of the water vaporization in a hot water boiler system. The Computational Fluid Dynamics (CFD) technology was adopted to simulate the transient water evaporation in the boiler termed as DZL14-1.25/115/70-AⅡ under the assumption of extreme conditions such as the water pump failure. The results indicated that the average pressure in the pipeline increased from 0.57Mpa to 0.66Mpa (the setting pressure of the safety valve) within 1050s. The pressure increased rapidly with the time increase. The average temperature of hot water changed linearly with time, and the internal thermal deviation of the hot water pipeline in the boiler decreased with time. The internal vaporization phenomenon of the hot water boiler became significant under the extreme condition. The steam flowed upward and accumulated in the upper part of the boiler shell. At 1050s, the vapor volume fraction in the hot boiler was 1.05%, which indicated that the safety valve above the stream shell need to be opened in time after 1050s to ensure the safety of the boiler.

Напряженно-деформированное состояние в зоне увода сварного шва котла цистерны с учетом переменной толщины обечайки

The article presents the results of theoretical studies of the strain-stress state in the breakaway zone of boiler shell ring. According to the developed analytical method, the refined results of the strain-stress state in the breakaway zone of tank boiler welded seam are obtained, taking into account the local thickening of the cross profile of the boiler shell ring.

Studies on the weldability, mechanical properties and microstructural characterization of activated flux TIG welding of AISI 321 austenitic stainless steel

The presence of titanium in AISI 321 austenitic stainless steel, mitigates the corrosion when deployed in specific applications such as boiler shells, aircraft exhaust manifolds and process equipment. Using Commercial flux purchased from Edison Welding Institute (EWI), studies were conducted to note the effect of Activated Tungsten Inert gas (A-TIG) welding on the surface morphology of type 321 austenitic stainless steel welds and compared with conventional TIG welding. A thin flux layer was applied to the surface of the 6 mm thick plate, followed by a conventional TIG welding process. The bead on trial results shows that compared with the TIG welding process, the flux causes the weld depth to increase, weld bead width to decrease and weld area to increase. This incredible depth of penetration (DOP) has been accomplished by the mechanisms of reversal of Marangoni flow and Arc constriction. From various experimental trials, arc length of 3 mm, welding current of 220 Amps and welding speed of 120 mm min−1 were found to be optimal and subsequently used as input parameters to produce a good quality A-TIG welded butt joint. The welded joint is subjected to transverse and longitudinal tensile and bend tests, charpy impact toughness tests, microhardness, optical microscope, x-ray diffraction analysis, ferrite number measurement and Scanned electron fractography. The welded joint exhibited improved tensile strength, bend and charpy impact toughness and hardness. The weld metal microstructure was observed to be austenite, delta-ferrite and TiC intermetallic compounds (Titanium carbides). The XRD pattern indicates that austenite and ferrite phases are present in both base and weld metal. The results of Fischer Feritscope FMP30 (ferrite measurement) show that the content of delta-ferrite in the weld metal (5.9 FN) is much higher than the parent metal (1.2 FN) and shows excellent mechanical properties in the A-TIG welded joint. Scanned electron fractography indicates that the failure of weld metal and base metal occurs in the ductile mode of fracture.

Design a Refractory Boiler Shell for Optimum Weight

Design a Refractory Boiler Shell for Optimum Weight

English

English

Modelling and Analysis of Power Plant Boiler with the use of Functionally Graded Materials

The focus is led on understanding the best combination of material to be used for a low capacity power plant boiler shell; a comparative study has been done which includes two different materials, a conventional material (SS301) and Functionally Graded Material (WC-SS) is implemented. The work involves modelling the basic structure of boiler shell and the analysis phase involves the study of the structural, thermal and vibrational outputs for both the materials. The analysis would highlight the advantages in change of material while keeping the same shell thickness.

IARJSET - Science, Engineering and Technology

Boiler is an important practical application in heat transfer devices.Its function is to transfer the heat produced by the combustion of fuel to water, and ultimately to generate steam.This paper was carried out by taking data of Pulverized fuel boiler which is a water tube boiler having pressure 138 bar and temperature 540 0 C.The fuel used in this boiler is low grade bituminous coal having a calorific value of 4204kcal/kg.The performance of this boiler was conducted by calculating thermal efficiency and heat losses of pulverized fuel boiler by indirect method. Gross calorific value of fuel, wind velocity, surface temperature of boiler shell, and ambient temperature, humidity of air, fuel firing rate, specific heat of flue gas and steam are taken as input parameters. Thermal efficiency, heat losses such as heat losses due to dry flue gas, evaporation of water formed due to H2 in fuel, moisture present in fuel, moisture present in air, incomplete combustion, radiation and convection and unburntfuel in fly ash and bottom are calculated.

Experience gained from automation of starting operations in a 200-MW two-boiler single-turbine power unit equipped with once-through coal-fired boilers

Results obtained from a large set of investigations, search for, and perfection of the technology for starting 200-MW two-boiler single-turbine power units from different thermal states are presented. An algorithm for automated starting of the boiler shell from its hot state is given as an example.

Feasibility Study of Modified Three Pass Dry Back Reversal Chamber Fire-Tube Boiler

A well designed, operated and maintained boiler is the heart of an efficient steam plant. Research data shows that extensive research work on improving the efficiency and to quicken the steam formation from fire-tube boilers has been done all across the globe. Steam once formed cannot be stored in any container; it has to be simultaneously regulated in the required section of the plant. So a continuous and constant input of steam is desired in industries. The existing three pass dry back reversal chamber industrial boiler consists; well defined passes of fire tubes surrounded all over by water within a boiler shell. The authors have proposed another set of tubes inside the boiler shell; which introduces water inside the shell upon the fire tubes. Researchers have come up with the designs of fire-cum-water tube boilers; in which water in tubes is present in the fire chamber of the fire tube boilers to increase efficiency, minimise losses and to quicken the steam formation. The authors have mainly focused on developing a three pass fire tube boiler which compiles to minimise water loss and quicken steam formation as stated above.

Fatigue Failure of 321 Stainless Steel Superheater Tubes from a Thermal Incinerator

Several boiler superheater tubes showed circumferential cracking at weld seams after 2 years in noncontinuous service (several shutdowns). On-site inspection revealed that several tubes were cracked and leaked; while many others were cracked, however, the severity was less pronounced. Two types of superheater tubes samples were collected: one with butt-welded tubes and the other with fillet-welded sleeve. The latter was found to be out of the boiler fireplace, and the sleeve was used as tubing support to the boiler shell. Detailed investigation showed that the butt-welded tubes contained circumferential fatigue cracks that initiated from the internal surface. The cracks initiated in the heat-affected zone and propagated as a result of tube vibration. The variations in the tube internal diameter and tube wall thickness are expected to play a role in tube fatigue failure. On the other hand, tubes with fillet-weld sleeve showed circumferential cracking as a result of fatigue crack initiation from weld defects on the tube external surface. The high vibration during several unscheduled shutdowns in addition to several other factors such as variations in tube inside diameter, wall thickness, and weld defects resulted in the initiation and propagation of fatigue cracks and premature failure. White deposits, similar to those observed when boiler tubes failed by caustic exposure, were seen in the vicinity of the tube cracks. Therefore, it was difficult to confirm whether the boiler tubes failed because of the fatigue cracks or because of the caustic salts (pH control chemical).

Finite element analysis of residual stresses in a letter-box excavation repair weld for Chapelcross Power Station

A routine inspection on the heat exchanger 6 boiler in Chapelcross Nuclear Power Station revealed the existence of a crack in the bottom dome of the boiler. A ‘letter-box’ repair procedure was developed to repair the damage and justify the return to service of the boiler. Due to the location of the repair, it was undesirable to conduct post weld heat treatment (PWHT) because this could result in damage to neighbouring components. A full residual stress programme was conducted in order to justify a non-PWHT repair to the boiler using a temper bead technique on a boiler shell section of up to 44 mm. This paper describes the work conducted during the project and subsequently regarding residual stresses in letterbox excavation repairs.

Application of nanoindentation technique for structural characterisation of weld materials

Nanoindentation, a modern technique for investigation of mechanical properties of materials using a modified scanning force microscope (SEM), has been employed to examine two different types of boiler shell weld materials from nuclear power plants. These weld materials differ mainly in their manganese content and temperature treatment. The nanoindentation technique allows very small regions in grains to be investigated and different phase structures are distinguished using this technique. It is shown that a difference exists between the microhardness values, which integrate over several grains compared to the nanohardness measurements for weld materials made over smaller regions. The difference between the phase structures of these small regions is determined by a combination of both SFM imaging and the characteristic properties of force–depth curves which allow specific values of hardness and Young's modulus to be determined. Detailed measurements of the nanohardness and Young's modulus for various weld materials are given and these values are related to the material properties. It has been found that the hardness of the grains is always less in the centre and increases towards the grain boundary.

Grain boundary segregation of phosphorus, manganese, and carbon in boiler shell weld material

Submerged arc weld materials have been employed in a study of the effects of manganese and carbon on phosphorus segregation and intergranular embrittlement. The equilibrium grain boundary segregation behaviour of these elements during aging has been studied in two different boiler shell weld materials, which differ mainly in the manganese concentration and operating temperature during service. The materials have seen temperatures above 300C during operation of the boiler in service, at which temperature thermally induced segregation and embrittlement occurs. A new co-segregation model has been compared with the existing site competition model. The microstructure shows fine and coarse grained regions. The effects of manganese and carbon on the grain boundary segregation of phosphorus have been examined. Thermally induced grain boundary segregation during full service life up to 50 years as a function of temperature is described. To evaluate the free matrix concentration of a given element, equilibrium thermodynamic software was used to allow for the tendency to form precipitates within the alloy matrix. The predicted results reveal the dependence of the grain boundary concentration on temperature and show that manganese and carbon decrease the phosphorus segregation by site competition. The final segregation consists of non-equilibrium and equilibrium segregation, which occur during quenching after welding, post-weld heat treatment, and service. The microstructure has been investigated by optical microscopy and transmission electron microscopy to show carbide formation at the grain boundaries and intergranular precipitation of MnS. Preliminary analysis of the grain boundary has been made and the results compared with theoretical segregation predictions.

Stress analysis of a repair weld to boiler in a nuclear power station

A routine inspection on Hex No. 6 boiler at Chapelcross nuclear power station revealed the existence of a crack in the bottom dome of the boiler. To enable continued operation of the boiler, it was required that the crack be repaired. Due to the position of the repair in the boiler it was undesirable to carry out post-weld heat treatment (PWHT) as the process could cause damage to neighbouring components and attachments. MBEL was engaged by BNFL to take part in a programme to investigate a non-PWHT repair methodology which would not compromise the structural integrity of the vessel and would satisfy the stringent safety requirements of the Nuclear Installations Inspectorate. Using the latest finite-element modelling techniques, in conjunction with experimental measurements made both on specimens and on the boiler shell, a full residual stress analysis of the repair was carried out which showed that the tolerable defect size in the repair was increased to a level within the non-destructive testing detection range. The employment of the foregoing methods has enabled the BNFL programme to justify a non-PWHT repair to the boiler.

CARPENTER PROJECT 70 STAINLESS TYPE 347

Abstract Carpenter Project 70 stainless type 347 is a modified version of type 347 stainless steel with improved machinability when compared to conventional type 347. The alloy is a nonhardenable austenitic chromium-nickel steel that is particularly adaptable for parts for use at temperatures between 427 and 899 C (800 and 1650 F). It is nonmagnetic in the annealed condition but is slightly magnetic in the cold-worked condition. Among its many applications are aircraft-engine exhaust manifolds, boiler shells, and high-temperature handling equipment. This datasheet provides information on composition, physical properties, and elasticity. It also includes information on corrosion resistance as well as forming. Filing Code: SS-730. Producer or source: Carpenter. Originally published October 1998, corrected November 1998.

CRUCIBLE 347

Abstract CRUCIBLE F347 is a non-hardenable austenitic chromium-nickel steel that is particularly adaptable for use at temperatures between 800 and 1650 F. It is non-magnetic in the annealed condition but is slightly magnetic in the cold-worked condition. Among its many applications are aircraft-engine exhaust manifolds, boiler shells and high-temperature handling equipment. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SS-436. Producer or source: Crucible Specialty Metals Division, Colt Industries.