LPG Tanks Research Articles

Modeling the behavior of LPG tanks exposed to partially engulfing pool fires

Accident scenarios leading to full or partial fire engulfment represent a serious threat to tanks used for the transportation and storage of dangerous goods. The present study focuses on the impact of partial engulfing fire scenarios on an LPG tank. An experimentally validated CFD modeling approach was further developed and applied to perform a parametric study by varying the exposure mode and the filling degree. The results of the simulations show that both these factors have a strong influence on the pressurization rate, the energy accumulation, and the high-temperature mechanical weakening of the tank structure. Fire scenarios where the flame zone is at the top or at the end of the tank are particularly critical when the liquid filling degree is low or medium. Liquid thermal stratification is evident in all the case studies analyzed and, in most of them, it strongly affects the vessel pressurization curve. The comparison to the results obtained using a lumped model showed that this provides non-conservative pressurization results for high filling levels (80%). The results show that a validated CFD approach can be used as a virtual workbench to support tank design within a digital twinning approach.

Three dimensional CFD simulation of LPG tanks exposed to partially engulfing pool fires

The availability of accurate and robust models for the prediction of the behavior of pressurized tanks under fire exposure is a key requirement to improve the design of fire protection systems. Most of the models present in the literature take into consideration fully engulfing pool fire scenarios only. In the present study, a CFD modelling approach previously validated against full engulfing pool fire tests is used to simulate partial engulfment conditions. The model allowed analyzing local flow field promoting thermal stratification, which in turn drives internal pressurization of the tank. Comparison with fire test results shows good agreement with experimental measurements both in terms of temperature and pressurization curves. The results obtained represent a valuable source of information to support risk management, planning of emergency response and improve fire protection systems design.

Development of a predictive accident model for dynamic risk assessment of propane storage tanks

Investigation of past accidents has shown that LPG tank accidents cause significant damage to the industry due to the storage of large volumes of flammable materials in them. This study aimed for developing a predictive accident model for dynamic risk assessment of propane storage tanks of the refinery. Hazards and safety barriers were identified using MIMAH methodology. The basis of MIMAH methodology is Bow-tie method. To construct the Bow-tie diagram, first, accidents that occurred on LPG tanks were extracted from the databases of accidents and valid sources. The top events of the accidents were identified and analyzed by the fault tree. The Bow-tie diagrams were constructed and the barriers on the diagrams were identified and verified by refinery experts. According to the SHIPP model, safety barriers were categorized into seven main barriers. The failure rates of the fault tree basic events were extracted from reliable sources and the prior probability of barriers was calculated. Based on the failure or success of safety barriers, 6 levels of severity of consequences, safe, near miss, mishap, incident, and catastrophic accident were considered. Using the prior probability of failure of the barriers, the probability of occurrence of each level of severity of consequences was calculated with the event tree. In the next step, this paper employed LPG storage tanks past accidents to construct a likelihood function and update prior probability using the Bayesian equation. Finally, the posterior probability of occurrence of the consequences was calculated using the posterior probability of failure of the barriers. Because LPG accidents occur with low probability and high severity, predicting accidents dynamically helps people to always be prepared to prevent their occurrence.

A Study of Brittle Crack Arrestability Test Method

This study evaluated the brittle crack arrest temperature (CAT) through an isothermal crack arrest test. The concept of evaluating CAT by an isothermal crack arrest test was proposed by C. Wiesner for application to low temperature steels for LPG tanks. The proposed test method consists of arresting a double-tension-type brittle crack with EB melt-run, which acts as a crack initiator and crack runway. There are some disadvantages when evaluating CAT with electron beam welding (EBW), which requires a local brittle zone to initiate a brittle crack. A local temperature gradient (LTG) system is developed to overcome the limitations of the EBW method. LTG systems do not require additional EBW to develop a brittle zone to initiate brittle crack. Recently, brittle crack arrest (BCA) steels are being used in large container ship such as in the upper deck or hatch side coaming of 22,000 twenty-foot equivalent units to prevent fatal brittle fracture accident of those ships. The International Association of Classification Societies (IACS) defined BCA steels using Kca requirement or CAT requirement in their unified rule (UR) S33. Therefore, when a shipyard uses BCA steel in the construction of large container ships, CAT or Kca should be evaluated. In this study, a new CAT test method is introduced to evaluate brittle crack arrest temperature more easily. Furthermore, both test methods were compared for the same specimens to verify the validity of the test method. Key words: Brittle fracture, Crack Arrest Temperature (CAT), Electron Beam Welding (EBW), Embrittled zone, Local Temperature Gradient (LTG)

Analysis of the impact of wildland-urban-interface fires on LPG domestic tanks

Managing Wildland-Urban-Interface (WUI) fires is a challenging task due to the inherent complexity of the WUI environment. To ensure the success of strategies for the protection of population and structures, safety measures have to be implemented at different scales (landscape, community and homeowner). The present study is focused on the homeowner scale and deals with the threat related to the presence of LPG domestic tanks in a WUI fire scenario. Recent accidents have demonstrated that the risk associated with this type of installation is real, but often disregarded by residents. A methodology was developed, providing a set of indicators that may easily be compared with risk acceptance criteria, assessing whether the integrity of an LPG tank exposed to WUI fire scenarios is compromised or not. The methodology is applicable to a vast range of situations and at a different level of detail according to available data. A number of case studies were carried out, showing that WUI fire scenarios impacting on domestic LPG tanks complying with regulations currently adopted in several Mediterranean countries cannot be deemed safe. The methodology proposed represents an advanced tool to assist on safety distances sizing to be prescribed by standards, driving regulators towards better-informed decision-making.

Research on Safety Spacing of Chemical Storage Tanks Based on Accident Consequence and Risk Analysis

The placement of chemical storage tanks is an important topic in industrial safety, and its placement method is based on the study of the safety spacing of storage tanks. This paper takes LPG and LNG storage tanks as examples. It uses vapor cloud explosions, pool fires, pressure vessel explosions, boiling liquid expansion vapor explosions and other fire and explosion accident consequences models and risk probability analysis methods to analyze. It is proved that the transfer of storage tanks from ground to underground can significantly reduce the scope of impact of explosion accidents, thereby increasing the utilization rate of industrial land.

Static and Time History Earthquake Analysis of LPG Spherical Steel Tanks in Iraq

Spherical storage tanks are widely used in Iraq for store hazardous liquid petroleum gas LPG which, thus it must be adequately designed for seismic actions. This paper present static and time history analysis of LPG tanks in Iraq using UBC97 code. The time history analysis accomplished by using three artificial earthquakes generated using SIMQKE_GR program in additional to El Centro earthquake records scaled according to PGA. The investigations were performed on the tank in Maysan province which was selected to be representative the other tanks in Iraq due to recently seismic activity in Maysan. The study comprised finite element modeling using STAAD Pro program for the estimation of the dynamic and static responses of the tank structure. The study is performed for both conditions of empty tank and at operating with 100% fill of LPG. The description of the properties and allowable stresses LPG tank used in Iraq is presented. Its concluded that time history analysis govern the tank behavior. The dynamic magnification factor of 1.4 for displacements and stresses was obtained which reflect the importance of dynamic analysis. The stresses of columns and sphere are within allowable limits except at sphere/column connection which slightly exceed the allowable limit, while the stresses in diagonal bracings are exceed the yielding limit thus double angle section is inadequate

LPG vessels exposed to fire: Scale effects on pressure build-up

Fires may induce the thermal failure of LPG storage and transport vessels, leading to severe escalation scenarios. In the present study, an innovative CFD modeling approach was developed to investigate the thermal behavior of LPG tanks exposed to fires to support the prevention of catastrophic scenarios. For the first time, several data-sets were used to assess the model predictions considering different vessel scales, fire geometries and configurations. Comparison with experimental results demonstrates the predictive capabilities of the approach. The model allowed analyzing the role of different key phenomena, such as: the effect of free convection and thermal boundary layer forming in the near wall region, the thermal stratification, both in the liquid and the vapor phases, and the liquid thermal expansion. In addition, the influence of the vessel geometry on such phenomena was investigated. The results obtained may drive the design of emergency response, improving the safety of hazardous materials storage and transport systems.

Results of Static Loading Tests on Single Piles and on Pile-Supported LPG Tanks

Full-scale static loading tests on eight single test piles and hydrotests on two 50-m diameter tanks supported on 849 piles intended for storing refrigerated gas were performed at Cai Mep Industrial Park approximately 90 km southeast of Ho Chi Minh City, Vietnam. The test piles were precast concrete piles installed through 21 m of soft clay into dense sand to about 45 m depth below ground surface. Four piles were installed by driving and four by jacking. The maximum pile test loads were 3000 kN, which was well below any ultimate resistance, but showed that the tank-foundation piles (to be installed by jacking) could expect to shorten about 3 mm for the 750-kN working load. Each tank was hydro-tested to 636-MN maximum service load, which load was held constant for 1 week, while monitoring the tank settlement at benchmarks placed along the tank perimeters. The records showed the tank perimeters to settle about 15 mm in addition to an about 3-mm pile shortening. Back-analysis of the tank foundation modeled as flexible equivalent rafts at the pile toe level showed that the settlement of the tank center was about three times larger than that of the perimeter. Analysis of long-term settlements indicated that, under service loading, the tank perimeters and centers will settle an additional about 100 mm and 300 mm, respectively. Due to a 3 m thick fill placed over the site causing the clay to consolidate, the ground surface is expected to settle more than 1 m over the long-term. The general subsidence will affect the perimeter piles and transfer load to the interior piles. However, because the pile neutral plane is located in the sand below the clay, downdrag is not an issue for the piled foundation. The drag force will be well below the limit of the pile axial structural strength.

A study to design the emergency reaction plan for LPG tanks in 5<sup>th</sup> refinery, south pars gas-condensate by using phast software

Outcome Assessment is a tool applied by safety engineers in order to evaluate the risk resulting from industrial activities and determine the level of risk and damage arising from work-related accidents. After identifying and evaluating the risks, it is essential to estimate the intensity and consequences of the risks because the intensity of adverse effects and the likelihood of occurrence determine the risk. On the other hand, today, with increased density and proximity of industrial units, the adverse consequences of an accident cannot be limited to one unit. The damaging effects can spread to adjacent units or the surrounding residential area. This study aims to identify the risks in LPG storage unit, 5 th South Pars Gas Refinery and possible events in the process by using PHAST software. In order to enhance the modeling accuracy, Pseudo-Component Method was replaced with Multi-Component Method and it was employed to model combined hydrocarbons such as LPG. The results show that sudden explosion of tank is more dangerous than others, leaving irreparable financial and human damages. LPG export pipeline requires more protection due to the radiation radius as a result of fire induced by fracture. Keywords: Outcome analysis; phast software; accident modeling; risk assessment; safety

Requalification of LPG tanks in Europe: Verifying the structural integrity by monitoring the pressure test with acoustic emission

Requalification of LPG tanks in Europe: Verifying the structural integrity by monitoring the pressure test with acoustic emission

BLEVE를 고려한 LPG 시설 Siting 분석

In previous studies on LPG siting in Korea, the scope have not included the probability of the secondary events of adjacent LPG tanks or structures from an explosion source. Therefore, it is essential to first identify the phenomenon which can be caused by BLEVE and then, properly assess their effects to each target including secondary event. In this study, we calculated the effects from a potential BLEVE of 15 ton LPG tank causing damages of storage tanks (LPG), structures and human using Phast ver. 6.7 and then suggested three risk zones (Zone I, II, III) assuming the consequences such as overpressure, heat radiation and missile effect by fragments. Zone I and II are divided at the line of 50% occurrence of the secondary event. Zone II and III are divided by Individual Risk(IR). The zone approach in this study can be used for more effective and safer Land Use Planning (LUP) for the future.

AT on Buried LPG Tanks Over 13 m3: An Innovative and Practical Solution

In Italy, since 2005, techniques based on Acoustic Emission have been introduced for testing of underground LPG tanks up to 13 m3, according to the European standard EN 12818:2004.The testing procedure for these tanks plans to install one or more pairs of sensors inside the “dome” suited for the access to the valves and fittings of the tank, directly on the accessible metal shell.This methodology is not applicable for the underground LPG buried tanks, where it is necessary to install a larger number of AE sensors, in order to cover at 100% the whole tank shell, even at very deep positions.Already in 2004, the European standard EN 12820 (Appendix C - Informative)give the possibility to use Acoustic Emission testing of LPG underground or buried tanks with a capacity exceeding 13 m3, but no technique was specified for the application.In 2008, TÜV AUSTRIA ITALIA – BLU SOLUTIONS srl - Italian company of TÜV AUSTRIA Group - has developed a technique to get access at tank shell, where tank capacity is greater than 13 m3 and its’ diameter greater than 3,5 m.This methodology was fully in comply with the provisions of the European Standard EN 12819:2010, becoming an innovative solution widely appreciated and is used in Italy since this time.Currently, large companies and petrochemical plants, at the occurrence of the tank's requalification, have engaged TÜV AUSTRIA ITALIA – BLU SOLUTIONS to install such permanent predispositions, which allow access to the tank shell - test object – with diameters from 4 to 8 m. Through this access, you can install the AE sensors needed to cover at 100% the tank surface and then to perform AE test.In an economic crisis period, this technique is proving a valid and practically applicable answer, in order to reduce inspection costs and downtime by offering a technically advanced solution (AT), increasing the safety of the involved operators, protecting natural resources and the environment.

Impact of Wildfires on LPG Tanks

Research on wildland fires focused traditionally on two main objectives: the prediction of the velocity at which a fire will spread and the estimation of the released heat from the flame front of the wildland fire. Both topics are key points in order to evaluate the gravity of the fire and to organize firemen intervention to fight the fire (Alexandridis et al., 2011). The wildland-urban interface (WUI) may be defined as a contact zone between a natural zone such as a forest and a heavy or light urbanized area. At this interface, the threat to homes and their destruction during wildland fires, with associated concerns for life safety, are significant problems for emergency managers throughout the world. Due to the increasing urbanization of the surrounding countryside, the number of these areas is growing rapidly. In the last ten years, wildfires resulting in residential destruction occurred in Australia, Canada, Mediterranean countries and the United States. The WUI areas are complex systems, difficult to manage, especially in the context of wildfire prevention. (Butler, 1974) contributed the first description of urban wildland interface not in geographic terms but in terms of fire process. He defined that interface as the occurrence of fire spreading from wildland fuel (vegetation) to urban fuel (homes), in terms of the wildland fire becoming close enough for its flames and (or) its firebrands (lofted burning embers) to contact flammable parts of a home or the home’s immediate surroundings. The main question of his description is “How close is close enough for home ignition ?”. Well know operational models of fire spreading (for example BEHAVE, FIRE CODE, FORE FIRE models) are no longer valid in the urban interface. Some authors coupled wildfire dynamics with structure ignition models. (Cohen, 2000) proposed the Structure Ignition Model (SIAM). This model is based on strong assumptions, as the flame is assumed to be a uniform parallel-plane black body emitter. The flame-tostructure distance does not allow for flame contact. This model overestimates the heat received by the structure, as reported by (Porterie et al., 2007). These latter authors developed a three-dimensional physics-based model able to describe the near-field dynamics of a wildland fire, as well as its impact on structural elements. This model was validated by a prescribed burning and fire tunnel experiments. (Zarate

Finite Element Analysis of LPG Gas Cylinder

The present work involved the Finite Element Analysis of existing LPG gas cylinder to verify the burst pressure. The LPG gas cylinder is manufactured from low carbon steel. The LPG tanks are subjected to incremental internal uniform pressure in the FEA model. 2D nonlinear plane models are developed and evaluated under non-uniform and axis symmetric boundary conditions. For the analysis, the required actual shell properties including weld zone and thickness variation are investigated. Therefore the stress distribution has been analyzed using ANSYS 11 software for which maximum shear stress, equivalent shear stress at critical area has been calculated. Therefore 3D solid model has been chosen in order to predict the detailed stress.

Modeling the performance of coated LPG tanks engulfed in fires

The improvement of passive fire protection of storage vessels is a key factor to enhance safety among the LPG distribution chain. A thermal and mechanical model based on finite elements simulations was developed to assess the behaviour of full size tanks used for LPG storage and transportation in fire engulfment scenarios. The model was validated by experimental results. A specific analysis of the performance of four different reference coating materials was then carried out, also defining specific key performance indicators (KPIs) to assess design safety margins in near-miss simulations. The results confirmed the wide influence of coating application on the expected vessel time to failure due to fire engulfment. A quite different performance of the alternative coating materials was evidenced. General correlations were developed among the vessel time to failure and the effective coating thickness in full engulfment scenarios, providing a preliminary assessment of the coating thickness required to prevent tank rupture for a given time lapse. The KPIs defined allowed the assessment of the available safety margins in the reference scenarios analyzed and of the robustness of thermal protection design.

Acoustic emissions: small underground LPG tanks – analysis of the results pertaining to the first inspection campaign applied to the ISPESL AE procedure

Acoustic emissions: small underground LPG tanks – analysis of the results pertaining to the first inspection campaign applied to the ISPESL AE procedure

Experimental and analytical investigation of thermal coating effectiveness for 3 m 3 LPG tanks engulfed by fire

Two large-scale diesel pool fire engulfment tests were carried out on LPG tanks protected with intumescing materials to test the effectiveness of thermal coatings in the prevention of hot BLEVE accidental scenarios in the road and rail transport of LPG. A specific test protocol was defined to enhance reproducibility of experimental tests. The geometrical characteristics of the test tanks were selected in order to obtain shell stresses similar to those present in full-size road tankers complying to ADR standards. In order to better understand the stress distribution on the vessel and to identify underlying complicating phenomena, a finite element model was also developed to better analyze the experimental data. A non-homogeneous and time-dependent effectiveness of the fire protection given by the intumescing coating was evidenced both by finite element simulations and by the analysis of the coating after the tests. The results of the fire tests pointed out that the coating assured an effective protection of the tanks, consistently increasing the expected time to failure. The data obtained suggest that the introduction of fire protection coatings may be a viable route to improve the safety of the LPG distribution chain.

EVALUATION OF ACCIDENTS WITH DOMINO EFFECT IN LPG STORAGE AREAS

The term domino effect denotes a chain of accidents, or situations, in which a fire/explosion load generated by an accident in one unit in an industry causes secondary and higher order accidents in other units. Such chains of accidents have a greater propensity to cause damage than stand-alone accidents. Most of the past risk assessment studies deal with accident in a single industry, more so in one of the units of an industry. But, often, accident in one unit causes a secondary accident in a nearby unit, which in turn may trigger a tertiary accident, and so on. The probability of occurrence and adverse impacts of such ‘domino’ or ‘cascading’ effects are increasing due to increasing congestion in industrial complexes and increasing density of human population around such complexes. Accidents with domino effect are seldom studied. LPG storage areas could produce the worst possible consequences in the event of an unforeseen incident. This work illustrates the application of models to evaluate the impacts of events with fire and explosion in LPG tanks on other similar units in the park and the possibility of occurrence of a domino effect. The criteria for occurrence of accidents with domino effect adopted in this work were 37.5 kW/m2 in case of fire radiation and an overpressure of 0.7 atm in explosion cases in a receptor body. The spacing between LPG tanks was evaluated. The results show that such spacing is minimal and does not represent, as it should, a parameter indicating a safe distance able to prevent the propagation of an accident with domino effect.

EVALUATION OF ACCIDENTS WITH DOMINO EFFECT IN LPG STORAGE AREAS

The term domino effect denotes a chain of accidents, or situations, in which a fire/explosion
load generated by an accident in one unit in an industry causes secondary and higher order
accidents in other units. Such chains of accidents have a greater propensity to cause damage
than stand-alone accidents. Most of the past risk assessment studies deal with accident in
a single industry, more so in one of the units of an industry. But, often, accident in one unit
causes a secondary accident in a nearby unit, which in turn may trigger a tertiary accident,
and so on. The probability of occurrence and adverse impacts of such ‘domino’ or
‘cascading’ effects are increasing due to increasing congestion in industrial complexes
and increasing density of human population around such complexes. Accidents with domino
effect are seldom studied. LPG storage areas could produce the worst possible consequences
in the event of an unforeseen incident. This work illustrates the application of models to
evaluate the impacts of events with fire and explosion in LPG tanks on other similar units
in the park and the possibility of occurrence of a domino effect. The criteria for occurrence
of accidents with domino effect adopted in this work were 37.5 kW/m2 in case of fire
radiation and an overpressure of 0.7 atm in explosion cases in a receptor body. The spacing
between LPG tanks was evaluated. The results show that such spacing is minimal and
does not represent, as it should, a parameter indicating a safe distance able to prevent the
propagation of an accident with domino effect.