Large Diameter Tanks Research Articles

Моделирование тушения пожаров нефтепродуктов в резервуарах с применением водопенных огнетушащих веществ

The decisive parameter in the design of automatic fire extinguishing systems in the depots for storing oil and oil products, the organization of fire extinguishing in the tanks with mobile equipment is the standard (critical) foaming agent supply rate. The purpose of this work is to evaluate the influence of the scale of model fire centers and their design on the values of critical intensity of the foam solution supply. The article presents the results of the analysis of the scientific studies of the process of oil products combustion and approaches to determining the standards for supplying a foaming agent solution to extinguish fires in the tanks. It is shown that the existing fire extinguishing modeling methods in the tanks do not fully take into account the effect on the extinguishing process of the following factors: the  change in the rate of oil products burn-up depending on the tanks sizes, the transformation of the aerodynamic characteristics of the medium in the vicinity of the combustion zone, the scale and design of model combustion centers, means and methods of foam supply. The analysis of the work on estimating the burn-up rate of flammable liquids in the tanks of various diameters does not allow to conclude what the minimum size of the experimental tank should be, so that the results obtained for determining the critical intensity of the foam solution supply would not cause anyone doubts. The paper presents the results of mathematical modeling of changes in the heat flux density on the surface of burning gasoline in the tanks with a diameter of 3 m, 5 m and 21 m. It is shown that combustion in small-diameter tanks does not simulate the thermal regime of a fire implemented on the large-diameter tanks. Consequently, the foaming agent solutions critical on intensity supply for small and large tanks differ from each other.  The combustion source used in a number of documents do not simulate the conditions for heating the side of a real tank, which explains the failure to extinguish fires in the large tanks. It is proposed to determine the intensity of the foaming solution supply, evaluate the efficiency of means and methods for producing foam in full-scale tanks or their mock-ups, which is economically justified and ensures the results reliability.

Spherical Dome Buckling With Edge Ring Support

Spherical dome roofs are widely used on large diameter tanks and silos, as they provide high strength for very limited amounts of material: buckling normally controls the design. Their design is currently based on very simple rules that were devised many decades ago. In particular, existing design is based on very simple boundary condition assumptions that cannot be realised in practice. This paper presents the first thorough study of the influence of realistic boundary conditions, in the form of a ring at the eaves, on the linear bifurcation of these domes. The outcome is a clear documentation of one of the key reference resistances required for a design description in the terminology of the Eurocode on shell buckling EN 1993-1-6. The complete study explored a very wide range of parameters, so only a sample of the findings is presented here. The complete results are expected to form the basis of future rules in the ECCS Recommendations on Buckling of Shells.

Numerical evaluation on shell buckling of empty thin-walled steel tanks under wind load according to current American and European design codes

Liquid storage steel tanks are vertical above-ground cylindrical shells and as typical thin-walled structures, they are very sensitive to buckling under wind loads, especially when they are empty or at low liquid level. Previous studies revealed discrepancies in buckling resistance of empty tanks between the design method proposed by the American Standard API 650 and the analytical formulas recommended by the European Standard EN1993-1-6 and EN1993-4-2. This study presents a comparison between the provisions of current design codes by performing all types of numerical buckling analyses recommended by Eurocodes (i.e. LBA-linear elastic bifurcation analysis, GNA-geometrically nonlinear elastic analysis of the perfect tank and GNIA-geometrically nonlinear elastic analysis of the imperfect tank). Such analyses are performed in order to evaluate the buckling resistance of two existing thin-walled steel tanks, with large diameters and variable wall thickness. In addition, a discussion is unfolded about the differences between computational and analytical methods and the conservatism that the latter method imposes. An influence study on the geometric imperfections and the boundary conditions is also conducted. Investigation on the boundary conditions at the foot of the tank highlights the sensitivity to the fixation of the vertical translational degree of freedom. Further, it is indicated that the imperfection magnitude recommended by the EN1993-1-6 is extremely unfavorable when applied to large diameter tanks. Comments and conclusions achieved could be helpful in order to evaluate the safety of the current design codes and shed more light towards the most accurate one.

120 tonne GRP tanks shop fabricated

Two large diameter tanks for hydrochloric acid (HCl) and nickel chloride (NiCl2) storage have been fabricated in Mexico and shipped to the Pacific Rim. GRP construction offered lower cost than high-end alloys for this application and is relatively friendly for repairs and modifications, given the remote location of the jobsite. Alfred L. Newberry of Fiberglass Engineering Mechanics discusses the project.

263 センターポンツーン付きシングルデッキ形浮屋根式タンクのスロッシング

The floating roofs are widely used to prevent evaporation of content in large oil storage tanks. The 2003 Tokachi-Oki earthquake caused severe damage to the floating roofs due to liquid sloshing. Several damaged floating roofs in large diameter tanks were the single deck type with center pontoon. This paper presents the sloshing characteristics of a single deck floating roof with center pontoon in cylindrical storage tank. The hydrodynamic coupling of fluid and floating roof is taken into consideration in the axisymmetric finite element analysis. It is assumed that the fluid is incompressible and inviscid, and the floating roof is linear elastic while the sidewall and the bottom are rigid. The basic vibration characteristics, natural periods and vibration modes and so on, of the floating roof due to the sloshing are investigated. These will give engineers important information on the design.

Analysis of Loads for Nozzles in API 650 Tanks

The analysis of tank nozzles for API 650, (American Petroleum Institute, 1998, API Standard 650, 10th ed.) tanks is a complex problem. Appendix P of API 650 provides a method for determining the allowable external loads on tank shell openings. The method in Appendix P is based on two papers, one by Billimoria and Hagstrom, 1997, ASME Paper No. 77-PVP-19 and the other by Billimoria and Tam 1980, ASME Paper No. 80-C2/PVP-5. Although Appendix P is optional, the industry has used it for a number of years for large diameter tanks. For tanks less than 120feet(33.6m) in diameter this Appendix is not applicable. In previously published papers, the authors used finite element analysis (FEA) to verify the experimental results reported by Billimoria and Tam for low-type nozzles. The analysis showed the variance between stiffness coefficients and stresses obtained by FEA and API 650 methods for tanks. In this paper, the authors have expanded the scope to include almost any size of nozzle as well as tank size. Stress factors for nozzles at different elevations on the shell are provided. Nozzles located away from a discontinuity are analyzed based on the method provided by the Welding Research Council (WRC), New York, Bulletin No. 297, 1987. Stress reduction factors have been developed using FEA for nozzles located closer to a discontinuity. Mathematical equations are provided together with the curves for the stress factors. The results of this paper have been incorporated into Appendix P of API 650 with the Addendum 3 of the 10th edition which was issued in 2003.

FOAMSPEX: Large scale foam application-modelling of foam spread and extinguishment

Engineering models have been developed to predict foam spread and extinguishment under fire conditions on liquid fuels in a research project called FOAMSPEX. A large number of experiments have been performed to generate input data and to generate data for verification of the theoretical models. The experiments include laboratory measurements of foam properties, foam spread tests in various geometries, field trials of foam monitors, and full scale validating fire tests. This paper gives a brief description of the model. Emphasis is put on the part of the project related to the foam spread experiments and the final application of the model to large-scale tank fires. The main driving force of the foam spread is due to differences in the hydrostatic pressure within the foam while the dominating resisting force is due to viscous friction between the foam blanket and the fuel beneath for a pool fire. For foam spread in channels the friction between the foam and the sidewalls dominate. Account is taken to the influence of ordinary drainage, radiation-induced drainage, and evaporation. The foam spread experiments were conducted both in a channel and a pool configuration. Some experiments were designated to determine friction coefficients between the fuel and foam and between foam and sidewalls. These coefficients have then been scaled and used for other fuels to calculate the foam spread in a number of different scenarios, both with and without fire. Finally, the model has been used to indicate the foam spread in large-scale tank fire situations and the results have been compared with observations from some real scale tank fires. The results of the modelling support some of the existing recommendations according to NFPA 11 although it is clear that large diameter tanks will require higher application rates than presently stated. It is also found that the approximations introduced in the present models i.e. neglection of the consumption of foam due to the fire results in an underestimation of the time necessary to control the fire.

Large diameter FRP tanks mark progress in Mexico

This case study follows the construction of two large diameter tanks, which are believed to be the largest tanks ever fabricated in Mexico by a domestic company. Alfred L. Newberry of FEMech Engineering describes the project.

Theoretical and experimental studies of stratified thermocline storage of hot water

A theoretical calculation of the degradation of heat in stratified thermocline storage has been carried out based on a conduction model. Since this neglects mixing, eddy currents and other degradation mechanisms, it provides an upper limit to the performance of a stratified thermocline storage tank. The calculation can be carried out for any selection of dimensions, temperatures, and choice of insulation. The results indicate that heat conduction through the insulation to the ambient can be a larger loss mechanism than conduction across the thermocline, except in large diameter tanks with very heavy insulation. With a properly designed tank (length/diameter > 10, diameter > 1.5 ft, insulation resistance > 20 hr ft 2 °F/B.t.u.) efficient storage of heat through a daily cycle should be routinely simple based on conduction. Experiments were carried out in static and dynamic modes. In the static experiments, a fixed thermocline was established, and temperatures were monitored at spatial intervals above and below the thermocline. Some mixing occurred during formation of the thermocline, which caused an initial broadening not present in the calculations. Aside from this, it was found that the spreading of the thermocline was only slightly faster than predicted by conduction theory. If a thinner wall tank had been available, agreement between experiment and theory probably would have been closer. Dynamic experiments were conducted with a moving thermocline (both upward and downward). The results indicate preservation of the initial thermocline was excellent at linear flow rates below about 0.2 ft/min. It is believed that stratified thermocline storage has been shown to be technically viable.