Conducting risk analysis and safety-engineering studies before construction of a sour-gas pipeline system will build redundancies into the system and ensure safe operation and maintenance. A recent analysis of a sour gas pipeline built in Texas provides an example of procedures for safety engineering and risk assessment. Oilfield service is a tricky business for a number of reasons. But fluctuating demand driven by commodity prices are the root cause behind a number of the challenges executives in this industry face. US shale production will peak at Equinor has been granted consent by the Norwegian Petroleum Directorate to use the facilities on Tordis and Vigdis fields in the North Sea beyond their respective December and March consents.
Similar records in OSTI. GOV collections:. GOV Book: Risk analysis for process plant, pipelines and transport. Title: Risk analysis for process plant, pipelines and transport. Full Record Other Related Research. Abstract This book gives a detailed description of practical risk and safety analysis methods, tried and tested in over a hundred process industry projects. Authors: Taylor, J. The HAZOP technique [ 36 ] is a structured and systematic examination of a product, process, or procedure—or an existing or planned system.
This is a qualitative technique based on the use of guide words Table 1 that question how design intent or operating conditions may fail to be achieved at each step of the design process or technique. The guide words must always be appropriately selected to the process which is analysed and additional guide words can be used.
Source: ISO [ 27 ]. This technique is applied by a multidisciplinary team during a series of meetings where work areas and operations are defined—and each of the variables that influence the process are applied to the guide to verify the operating conditions and detect design errors or potentially abnormal operating conditions Figure 2. Causal effects are identified deductively and organised in a logical manner and shown using a tree diagram that describes the causal factors and their logical relationships Table 2 with respect to the top event.
Symbols used in fault trees. Source: ISO A fault tree can be used qualitatively to identify potential causes and the ways in which failure the top event occurs or quantitatively, or both, to calculate the probability of the top event from the probabilities of causal events. Construction of the fault tree: From the top event, the possible immediate causes of the failure modes are established and it is possible to identify how these failures can occur at basic levels or in basic events.
Qualitative evaluation: The aim to find the minimum set of faults, establishing a mathematical formulation from the relationships established in the fault tree. Boolean algebra is used. Quantitative evaluation: From the frequency of failure of basic events, the probable frequency of an accident is calculated if it occurs as well as the most critical fault routes i. Quantitative evaluation enables a complete risk analysis before implementing and prioritising actions to improve the safety and reliability of the system under study. A complementary sensitivity analysis can be performed to check the effect of the basic events in the global risk assessment.
These data allow prioritizing the preventive measures and the efforts of the risk control process. The application of the methodology is performed for the jetty and pipe work of the chemical terminal, as well as the connected storage facilities, at the Port of Valencia.
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Both companies work in the reception, storage, loading, and distribution of liquid products—divided into two groups: chemicals and oil. TEPSA stores and distributes gasoline, diesel, methanol, and other chemicals in smaller amounts. Such high-risk plants are required to conduct a risk analysis. Chang et al. The main causes of tanks accidents were in order of importance: lightning Based on this work, Hailwood et al.
They divided the LNG terminals in five areas: LNG tanks, unloading section from ship to tank , send-out section, condenser and outlet pipeline. In tanks section, the main initiating events are boil-off removal malfunction during unloading or during storage , a high temperature in LNG when coming from ship , an excess of external heat in storage tank area, an overfilling of the tank, a rollover during unloading or during storage, an inadvertent starting of additional compressors, a continuation of uploading beyond lower safety level and an increase of send out rate from tank.
In unloading section, the main initiating events are an excess external heat in jetty area, a water hammer in loading arm due to inadvertent valve closure , an inadequate cooling of lading arm and high winds during uploading. In Appendix A , a list of well documented past accidents has been extracted from reports and works available in the literature. The list includes accidents in petroleum and LNG product storage facilities [ 12 , 13 , 43 , 44 ].
The origins of these accidents were leaks or spills 9 , explosions 7 and fire 6.
Leakage in the form of liquid is the most common source of major accidents—leading to fires and explosions that may cause other leaks, thus lengthening the accidental chain. The possible consequences of leakage depend on the flammability and toxicity of the leaked liquids and the environmental conditions in which the leak occurs. Seventeen of the cases originated in storage tanks, two in tanker ships, one in pipes, one in a steam boiler of a LNG plant and in one case there was no specific origin. Factors that may cause an accident are grouped into general and specific.
Among the general causes are those that are: external to the plant, human behaviour, mechanical failure, failure caused by impact, violent reactions; instrumentation failure, and failure of services. These general causes include a number of specific causes provided by details of specific accidents. Note that a single accident can occur for more than one general cause, and a general cause may be the result of more than one specific cause. The recorded data on the general causes of accidents shows that the cause was human behaviour in ten cases, instrumentation failure on four occasions, electrostatic spark on two occasions, mechanical failure in two occasions, unknown causes on two occasions, and two accidents were caused respectively by mechanical impact failure and external causes respectively.
Ignition sources provided the energy needed for the combustion of a flammable mixture. These sources can be thermal, electrical, mechanical and chemical. Data shows that in seven accidents the cause was electrical, in three the cause was welding during maintenance works, mechanical in three cases, thermal in two cases, and unknown in seven cases.
The Valencian plant is divided into three systems Figure 3 that correspond to the three activities of the companies: unloading, storage, and loading for distribution.
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These three systems are divided into six sub-systems and these again are divided into specific points or nodes that correspond to the sequence of operational steps in the plant Table 3. As a result of this analysis, it can be seen that, in the areas for loading and unloading liquid products Systems 1 and 3 , the greatest danger is the possibility of an uncontrolled spill.
The occurrence of this event is closely linked to the effectiveness of the staff responsible for handling the tasks.
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Relative to System 2, the risk of a fuel loss in the pipelines and leakage or fuel loss in the storage tanks is noteworthy. The latter event could be caused by overfilling or a partial rupture of the tank.
Special attention must be given to such events because they can cause fires and explosions that may have more serious consequences for the plant and its staff. These events or top events were:.
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The faults and relationships for each top event have been identified and a logical combination of incidents has been deduced that can trigger unwanted events. In this way, each tree contains information about how the combination of certain faults leads to overall failure Figure 4. Appendix B presents the fault trees of the other top events. Once the fault trees have been made, the mathematical expressions are defined ant the probability values are calculated according to the Boolean algebra related to FTA Table 6 and Table 7.
The procedure for calculating the top event 1 is shown in Table 7. In the four analysed top events, some 19 basic events are defined and fault frequencies were determined using data from the Spanish National Institute on Health and Safety at Work [ 45 ] and research on fuel storage [ 12 , 41 , 46 , 47 ]. In the Appendix C similar tables are developed for the others top events. In Table 8 , the results of failure frequency for each of the top events and their ways of failure are presented.
If the basic events are analysed, the main causes for a connection leak are a bad hose connection and a response failure following the detection of an emergency incorrect staff response, failure of the acoustic alarm, or seizure of the manual closure valve. This event occurs following a loss of product caused by a bad connection of the loading arm or damaged parts together with human error.
The probability of occurrence is low since it is one of the most complex operations and involves very strict protocols. A sensitivity analysis has been performed see Appendix D in order to check the effect of the basic events in the global risk assessment. In the top event 1 Table 9 and Figure 5 , the basics events with more influence in the sequence of the accident are in order of importance: operator distracted, operator failure, badly connecting loading arm and collision against jetty during manoeuvres. In the top event 2 are corrosion, operator distracted and with the same importance vehicles collision and fatigue defect.
In the top event 3 are operator failure and with equal importance the failure of the sensor level and the failure of response of the shut-off valve. In the top event 4 are hose incorrectly connected, after with equal importance, the acoustic signal failure and the sticking of the manual shut-off valve, and in the fourth level the operator failures.
These results show the importance in all the sequences of accident of the failure or distraction of the operators, so it should be mandatory a plan for training the staff of the plants. Planning of the maintenance actions of the facility must take into account both the general results from the risk assessment and the results from the sensitivity analysis. HAZOP analysis identifies the risks and their possible causes and consequences. FTA, based on the HAZOP analysis, represents the fault propagation pathways and produces a qualitative and quantitative assessment of the sequences of events that can lead to accidents or serious failures.
Results from FTA allow prioritizing the preventive and corrective measures in order to minimize the probability of failure. An analysis of case study about a fuel storage terminal is performed. HAZOP analysis shows that loading and unloading areas are the most sensitive areas of the plant and where the most significant danger is a fuel spill—tasks that can produce such an event are closely supervised by staff. Tasks related to transferring fuel from ships to tanks and storage tanks are the most automated and so the influence of personnel is reduced—although the consequences are more serious if an accident occurs.
A sensitivity analysis of the FTA results shows the importance of the human behaviour in all sequences of the possible accidents. In future research, we will apply a similar analysis to other type of plant, as LNG plants or storage of chemical products at a process plant, in order to improve the use of the combined method and to compare results from the risk assessments. National Center for Biotechnology Information , U. Published online Jun Jason K. Levy, Academic Editor.
Author information Article notes Copyright and License information Disclaimer. Received May 10; Accepted Jun Abstract The size and complexity of industrial chemical plants, together with the nature of the products handled, means that an analysis and control of the risks involved is required. Introduction Technological and social development has led to an increase in the size and complexity of chemical plants.
The Regulatory Framework The disastrous accident at Seveso Italy in led to European Union legislation intended to prevent accidents in certain industries using hazardous substances and thus limit the impact on employees, the general population, and on the environment.
Methodology Risk assessment is the process of identifying, analysing, and evaluating the hazard posed by an industrial plant and the main aim is the prevention and mitigation of accidents in potentially hazardous facilities [ 26 , 27 ]. Open in a separate window. Figure 1. More is produced than intended In addition of the amount of water of the process was added. Figure 2. Table 2 Symbols used in fault trees. Symbol Meaning Description Logic gate AND The output event happens only if all input events happen Logic gate OR The output event occurs if any of the input events happen Basic event Failure of a component that has no identifiable primary cause.
It is the highest level of detail in the tree Undeveloped event Failure of a component with a primary cause undeveloped because of lack of information Intermediate event A fault event that occurs because of one or more antecedents causes acting through logic gates. Application to a Case Study: The Chemical Terminal at the Port of Valencia The application of the methodology is performed for the jetty and pipe work of the chemical terminal, as well as the connected storage facilities, at the Port of Valencia. Historical Analysis of Accidents Chang et al. HAZOP Analysis The Valencian plant is divided into three systems Figure 3 that correspond to the three activities of the companies: unloading, storage, and loading for distribution.
Figure 3. System Sub-System Nodes 1 Unloading ship 1. ID: Identity. Node 2. Bad earth grounding. Possible risk of explosion if difference in electrical potential occur. The faster the speed of flow, the greater charge generated. Valves and flanges that are completely painted should be conductively bridged and earthed. More Corrosion More corrosion of materials than expected Exposure to corrosive environment. Attack of impurities at points with imperfections or fatigue. Lack of maintenance. Uniform deterioration of surface of valve general corrosion. Reduction in the useful life weakening.
The best way to avoid corrosion is to select the most resistant alloy for the valve— depending on the corrosive nature of the fluids. When damage is minor and possible to repair the body of the valve—at least provisionally—with a metal weld or with epoxy resin for low pressures and temperatures. Incorrect valve setting. Supervisor failure to recognise problems. Product over flow. Spill of liquid down external tank walls.
Formation of inflammable atmosphere as fuel hits floor. Activate tank vents to reduce or stop emissions of vapour. Staff training. Renewal of level sensors.
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Verification of state of all valves. Automatic level alarms as operator activated redundant safety devices. Use of indicators that measure volume to avoid confusion with specific weight. Spill containment berm system should have a capacity greater than the tanks including safety percentage. More Static electricity Accumulation of static electricity than expected Liquid projected by jet. Liquid enters tank being filled. Movement of liquid in tank causing turbulence and splashing.
Production of electrostatic sparks with sufficient energy to cause ignition. As a safety measure, it is recommended that the filling tube is always below the liquid surface level meaning that it reaches the floor , or if not possible, the flow should be reduced. Fluids should slide along the walls of tanks so that charges can dissipate through the earthed protective coverings. Figure 4. Table 6 Qualitative evaluation of top event 1. Table 7 Top event failure frequencies 1. Table 8 Results of quantitative analysis. Figure 5. Table 9 Sensitivity Analysis for the Top event 1.
Appendix A. The most probable ignition source is an electrostatic discharge. The first explosion took place in a tank where the base—shell weld ruptured and the upper part of the tank was launched up in the air and landed in the north-eastern corner of Tank Farm II. Subsequent explosions and fires destroyed the other tank farm. There were no casualties in the accident.
This accident occurred during purification of coker gasoline reduction of the content of mercaptans. The investigation found that addition of hydrochloric acid during the process reduced the solubility of mercaptans in the solution, leading to the build-up of a flammable mixture.