Fault Tree Analsyis for Piper Alpha Disaster

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1. Brief Description of the Piper Alpha Accident The Piper Alpha accident, a major offshore disaster which turned around safety regulations in the oil/gas sector in the United Kingdom thus giving birth to the “Offshore Installation (Safety Case) Regulation 1992 and the transfer of offshore safety from the Department of Energy to the United Kingdom Health and Safety Executive, occurred on the 6th July 1998 in block 15/17; a facility which comprised of module A, B, C and D and was run by Occidental Petroleum (Caledonia) Ltd in the North Sea (Drysdale and SlyvesterEvans 1998, Sam 2012). The accident occurred due to process disruption by production under high pressure, removal of pump A for maintenance, removal of PSV 504 for recertification and set of miscommunication which resulted to release of condensate via leakage from a flange causing series of explosions firstly in module C and through module B. These series of explosions led to the rupture of a gas line, tanks and other structures leading to huge fire invading the gas riser of different platforms connected to the Piper Alpha thus resulted to an uncontrollable fire beneath the platform which burnt across module B and C and even to more important areas of the platform due to the design structure of the upper-side of the platform. This resulted to total damage in the initial phase of the disaster to the control room and the radio room (Pate-Cornell 1993, Sam 2012, Pranav 2013). However, as a result of these series of explosions and other events, tremendous damage which was facilitated by structural failures led to the total loss of the Piper Alpha platform in such that only module A was standing at the end of this disaster. Furthermore, 165 personnel who worked in the platform and 2 rescue workers were killed, and a monetary loss of over $3 billion was estimated (Pate-Cornell 1993, Pranav 2013). 2. Identification, description of hazards and how they cause failure in accident. The Piper Alpha accident occurred due to combination of various hazards that contributed it’s quota thus leading to the accident which happens to be one of the biggest accidents in the oil and gas sector. More so, there is the probability that the extent of loss encountered in this accident would have been minimised whereas efforts had been made to checkmate some of these hazards (Drysdale and Slyvester-Evans 1998). In this section, effort will be made to identify each of these hazards and their relationship with the accident. 1) Condensate leakage from hand tighened flange at site of PSV 504. The leakage of condensate is the product of series of events. These events includes the isolation of pump A, isolation of relif valve A (PSV-504), removal of permit to work of relieve valve A by day shift personnel, lack of update on removal of relieve valve A to night shift personnel and inability of night shift personnel to simply reconnect back power supply to pump A prior to restarting of pump A because these night shift personnel had knowledge that a permit to work had been issued for pump A for maintenance for two weeks and that pupm A has been electrically isolated. These several lapses contributed hugely to the failure in Piper Alpha. This is so because, the ignition which caused the first explosion originated from the point of condesate leakage which occurred when the night shift personnel restarted pump A after several attempt of restarting pump B after it had tripped. The release of condensate from the hand tightened flange on PSV-504 produced a flammable mixture as the condensate gathered in module C where it reacted with an ignition source thus leading to the first explosion. Therefore, this initiated the entire event (Chevron Corporation 2013, Brian 2001). 2) The non-visibility of the digital control system (DCS). The digital control system is a vital equipment in process control and cordincation of all production processes. The visibility of the display screen is extremely important because it aids in the quick identification of any deviation in the production process, but in the cae of the Piper Alpha platform, the display screen which served as the monitoring boards were obviously not visible. This contributed to failure in the case of the Piper Alpha because it led to a situations where the personnel was unable to trace the origin of a warning alarm from the DCS in order for the personnel to initiate the right mitigation in retifying the process disturbance so as to shutting down the alarm, thus preventing any escalation which could lead to any form of faiure event. The inability to trace the origin of the first alarm contributed immersely to the disaster in Piper Alpha (Pate-Cornell 1993, Brian 2001).

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3) Failure of permit to work system The permit to work is a vital system in industries because it helps to keep in view works which are ongoing onsite and helps to relate each of these work where necessary. In Piper Alpha, the system of permit to work was poor. This is because, there was no reference of the the 24 months ongoing maintenance work on pump A and the recertification work of PSV 504 by the night shift personnel. More so, after the end of the day shift, the return of the permit to work which had been assigned to PSV 504 did not follow the laid down rules thus breaching thee permit to work system. Besides, the permit to work for pump A and PSV 504 did not make reference to each other. Therefore, upon failure of pump B, the night shift personnel decided to start pump A which would not have happened if the personnel has seen the permit to work of PSV 504 or even been aware of it removal for recertification. This to a great extent caused failure in Piper Alpha (David 2013, Oil and Gas n.d.). Moreover, the failure of the permit to work system as regards disaster was not formally in the procedures but was rather in the practical applications (M 1991, Brian 2001). 4) Operation of the fire fighting system Fire fighting system is a very vital system which has to be highly effective and always functional in any offshore facility especially one like the Piper Alpha. The reason been that, unlike onshore facilities where emergency services whenever needed arrives within minutes, offshore facilities need to handle any form of emergency on the facility using the available and installed equipments on board with crew members while waiting for arrival of emergency services. Besides, the platform had a fire fighting ship which could pump water onto it, but had minute effect to curtail the disaster and there was a deluge system which happened to be the main fire fighting equipment which sprayed certain amount of water across equipment areas that contained hydrocarbons (Pate-Cornell 1993, Brian 2001). Furthermore, the deluge system was supplied sea water by sets of electrical pumps which were rendered inactive at the onset of the first explosion which damaged the mai unit responsible for power supply. Athough, the risk of the electrically powered pumps been non-functional had been analysed with backup automatic diesel pumps provided to mitigate this risk. However, these diesel pumps were on manual operation mode on the night of the disaster, so they could not start automatically to pump water to the deluge system which could have curtailed the pump (Pate-Cornell 1993, Brian 2001). Moreover, the probability of the deluge system been efficient in curtailing this disaster had the automatic diesel kick started was unlikely. This is because part of the system had probably been damaged by the first explosion. Also, the entire heads of system had been blocked due to corrosion of the pipe by sea water and the disposition of corroded particles on the spray heads. Several attempts has been made to solve this problem but to no avail, so a decision to replace the pipes was reached but had not been totally replaced when the incident happened. Therefore, the lack of a properly functional deluge system contributed immersely to the failure. Besides, if it had been functional, the extent of loss would have been curtailed by the spray of high pressure water on the platform (Leal-Valias n.d., PateCornell 1993, Brian 2001). 5) Low level of safety training The low level of training in Piper Alpha contributed to the failure event. This is because personnel were supposed to be trained but often times this trainings are waived once personnel admits to have work offshore in the past. This practice by management helped to bring to the barest minimum the safety culture amongst personnel thus leading to a situation where the right procedure of carrying out production tasks were often neglected. This was evident in the personnel response of not been able to work over time when they knew that PSV 504 was an important valve in the facility that should be fixed in the shortest time possible since there is always the possibility of a breakdown of the other functional pump. More so, this neglience due to low safety training is also seen in the aspect of supervisors who failed to take actions like caution personnel or even report personnel negligent to safety to management. More so, this is evident in the the flange on the PSV 504, was only hand tightened without by personnel who did not deem it necessary to perform a leak test after tightening the flange. More so, the low level of safety training was evident because personnel failed to understand the need to properly communicate all ongoing work during shift change over and also failed to access the link between every on-going job on site in Piper Alpha (Chevron Corporation 2013, Brian 2001, LealValias n.d., Pate-Cornell 1993, Sam 2012). The low level of safety training thus contributed hugely to

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the event of Piper Alpha because of the negligence exhibited by personnel because no appropriate safet training was provided 6) Lack of blast walls installed between modules The importance of blast walls in an oil rig cannot be undermined. This is because it help to a greater extent in preventing fatalities in the case of any failure event which ivolves explosion or even fire outbreak in the facility. In Piper Alpha the firewalls were made up of bolted lattice-work construction. These fire walls were not designed to withstand explosion so when the first and second explosions occurred, B/C and C/D firewalls were all blow off causing tremendous increase in damage. More so, the damage of the firewalls also affected the destruction of the control. Hence, if there had been blast wall that could withstand the first and second explosion, the degree of damage and loss of life in Piper Alpha would have been minimal. Moreover, a risk assessement conducted earlier had suggest the subsequent installation of blast walls when it considered the effect of failure of a high pressure gas pipeline. This recommendation was once again neglected by management thus on the eventual failure of a high pressue gas pipeline, devasting event as seen in the loss of Piper Alpha was the result of management negligence (Chevron Corporation 2013, Pate-Cornell 1993, Brian 2001, Mohamad 2013). 7) Siting of extraction equipments in close proximity tothe control room The building of process equipments near the control to great extent contributed massively to the event of Piper Alpha which happens to be the “ location where all production activities are monitored, controlled, coordinated and information sent out to personnel as regards production status and conditions on site constantly”. But, the initial explosion totally destroyed the control room and killed personnel who had mad efforts to intiate mitigation through the DCS. Therefore, the nearness of the control room to production facilities was totally a hazard in waiting (Leal-Valias n.d., Pate-Cornell 1993, Brian 2001). 8) Lack of communication amongst personnel The issue of communication is very relevant in the offshore facilities. In Piper Alpha, communication was tolled with amongst personnel. For example, the day shift personnel failed to inform the night shift personnel about the status of PSV 504, the supretendient failed to ask the technicians about the status of PSV 504 at the end of day shift. This situations clearly shows that the lack of communication is a hazard which contributed to the accident (Pate-Cornell 1993). 9) Management lapses Management failed to perform trainings for newly recruited personnel, it also operated a situation of promotion whereby unqualified personnel are assigned task which they have no capacity to perform. More so, the number of crew members on board the Piper Alpha were not enough, this entails that management failed to employ as many as needed personnel in the operation of the platform. Thus, giving room to a situation where a personnel need to perform tasks such personnel never had a prior knowledge on. More so, the head of the deluge system which had been recommendation for change due to corrosion effects even after several years was not totally changed. More so, the failure of management to immediately switch the diesel fire pump back to automatic mode even after 24 hours that divers had stopped work in the waters close to the platform. Therefore, management lapses is hazard that caused the accident (Chevron Corporation 2013, Leal-Valias n.d., Pate-Cornell 1993, Brian 2001). More so, the methanol system which helps prevent hydrate formation on pipeline in the facility had problems and was neglected by management. Therefore causing pump B to trip as hydrate had accummulated in the line (Mohamad 2013). All these are management lapses which if had been properly controlled, maybe the incident of Piper Alpha would have been prevented. 10) Installation of the gas conservation module close to the utility module The gas conservation module in the platform was too near to the utility module. This contributed tremendously to the disaster because it the gas conservation module provided fuel for massive fire thus leading to several explosion that resulted to the ruputring of several facilities on the Piper Alpha. More so, it was the main source of the smoke that prevented emergency workers from accessing the platform and also assisted in the formation of the jet fire after the rupturing of the Tartan riser, Claymore riser and MCP01 riser (Leal-Valias n.d., Pate-Cornell 1993, Brian 2001).

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11) The restructure of the platform Piper Alpha was initially an oil rig but was modified later on into a gas production facility. The conversion of the facility to oil and gas facility posed as huge hazard because the change was not managed effectively and efficiently. More so, this change implied that both oil and gas pipelines will be in close proximity thus no inherent safety practice was put in place to curtail any issues which might arise. (Mohamad 2013) 3. Fault-tree analysis. The use of fault tree to analyze the Piper Alpha disaster is relevant.The reason been that it helps to explicitly provide the relationships that exist between the series of events that led to the disaster. More so, it provides for an opportunity to fully qunatify the events. In the construction of the fault tree for Alpha various events is considered and linked together to show their role in the accident. Furthermore, the use of fault tree will provide an opportunity to prioritize the events thus showing the event which played high contributory role that led to the event. Table 1: Description of Keys to Fault Tree Event Description of event Events Description of event TE

Loss of Piper Alpha due to explosions and massive fire Rupture of higly pressurized LPG pipeline Bursting of Claymore riser

Failure of deluge system

Rupture of MCP01 riser

Removed PSV 504 for recertification

First explosion in Module C that housees process oil and gas

Unable to complete recertication work of PSV 504 before shift change

Condensate leakage from PSV 504 of pump A Hand tightened flange on PSV 504

Misplace permit to work of PSV 504

Restart of pump A

Permit to work of pump A kept in different location

Closure of permit to work of pump A

Failure of personnel to reconnect power to pump A

Need to continue production

Hydrate formed in pipeline resulting to tripping of pump B

Rupture of 120 atm Claymore riser

Pump A was marked for maintenance

Second Explosion in Module B due to rupture of 55 tonne oil tank

Permit to work of pump A was with no reference to PSV 504

Light weitgh condensate rupture Loss of C/D firewalls

Failure of Tharos fire equipment

pipeline

Continuous operation of Pump A Process disturbance (production under high pressure

Misplace permit to work of PSV 504

Jet fire from broken riser

Loss of Control Room

Huge leakage of crude oil in Module C which gathered on the grates

Loss of main power supply

Failure of B/C firewall

Failure of emergency shutdown system

Spread of fire across Module C

Failure of gas detector

Continued supply of oil and gas from Claymore and Tartan platform

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Figure 1: Hand Drawn Fault Tree of Piper Alpha Disaster

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4. Explanation of logic leading to accident using Boolean Logic The Boolean loogic is used to explain th logic behind this event considering the fault tree from top to down  The destruction of Piper Alpha was the result of combination of either of three (3) intermediate events that were aftermaths of series of intermediate and basic events. The combination of these events, which includes, the “rupture of highly pressurized LPG pipeline ” “bursting of Claymore riser ” “rupture of The . Besides, either of these failures led to the loss of Piper Alpha platform which slipped into the North Sea at the end of the sequence of events albeit Module A which survived the disaster. More so, out of the 226 personnel onboard the Piper Alpha, 165 personnel lost their lives and 2 other persons from the rescue team were killed.  However, “rupture of the highly pressurized LPG pipeline caused by the “loss of C/D firewall “loss of Control Room “loss of main power supply “failure of emergency shutdown system failure of gas detectors “failure of deluge system “first explosion in Module C which houses processed oil and gas combine to initiate the onset of the devastating intermediate event. However the occurrence of intermediate event triggered the onset of series of basic events , which simultaneously combined, resulting into applicable because these events uniquely combined with each contributing its quota. 



Furthermore, the “rupture of the claymore riser ” occurred due to, “failure of Tharos fire equipment ” “jet fire from the broken riser ” “the rupture of the Tartan riser ”. The Tharos firefighting equipment been an equipment put in place for mitigation of any fire incident on the Piper Alpha platform began to melt at the inception of the first explosion and massive fire thus resulting into a situation where the equipment was unable to perform its duties, thus allowing the formation of huge jet fire, hence contributing to the rupture of the Claymore riser due to formation. Moreover, “the rupture of the Tartan riser ” which helped transport oil and gas in the Piper Alpha for onward onshore transportation for processing resulted from “the huge leakage of crude oil in module C which gathered on the grates which had been kept on the platform by divers

“failure of B/C firewall ”, an aftermath of the first explosion, “second explosion on module B due to the rupturing of 55 tonnes oil tank ” “spread of fire module C ”. The rupture of the Tartan riser supplied fuel to the fire which was already burning in the Piper Alpha. 

In addition, “the second explosion



Furthermore, “rupture of ” resulted from the, “failure of Tharos fire equipment ” “jet fire from the broken riser ” “the rupture of the Tartan riser ”. . The rupturing of the , resulted into the release of gas into the atmosphere thus resulting into the formation of huge flames. Also, “first explosion in Module C ” occurred due to the an intermediate event and two basic events, “the leakage of condensate from the PSV 504 of pump A ” “continual operation of



” which occurred in the Piper Alpha was the effect of the “light weight condensate pipeline rupturing ” “the continued supply of oil and gas from Claymore and Tartan platform ”. On the onset of the accident, the two platform that transported oil and gas to Piper Alpha for onward transportation to onshore facility continued this cycle of fluid transportation, thus providing more fuel for the already massive fire that have developed in the platform. . Also, the“light weight condensate pipeline ruptures ” happened bcause of “the leakage of condensate from the PSV 504 of pump A ” “continual operation of pump A ” “process disturbance as a result of production been performed under high pressure ”.

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” ”

pump A pressure 

In addition, “condensate leakage from PSV 504 of pump A ” resulted from the “hand tightened flange on PSV 504 ” “the restart of pump A which was due for maintenance by night shift

”.

personnel 

Moreover, the “hand tightened flange on PSV 504 ” was done by personnel who have earlier “Removed PSV 504 for recertification work ” was “unable to complete the recertification before shift

change 







“process disturbance as a result of production been performed under high

”

“misplaced the permit to work of PSV 504

)”.

Also, the “restart of pump A ” is the onset for the disaster in Piper Alpha. The combined nature of the “misplaced the permit to work of PSV 504 )” the fact the “permit to work of pump A was kept in different location ” the fact that the “permit to work of A was closed as a result of miscommunication and misconception ” . The restart of pump A after several attempt to restart pump B. Furthermore, the “permit to work of A was closed as a result of miscommunication and

misconception ” was as a result of the intermediate event, that is “need to continue production a basic event which “failure of personnel to reconnect power to pump A which had earlier been isolated. The permit to work of pump A was closed because it started that the work for which the permit to work was open will be started on the 7th July, 1988. ” . Besides, the “need to continue production resulted from the production situation that arouse when “hydrate formed in production pipeline resulting to tripping pump B t as “pump A was marked for maintenance the “permit to work of pump A was with no reference to PSV 504 Moreover, the intermediate event

are connected to intermediate event to through intermediate event the . This implies that the various events that occurred from intermediate event to contributed to the occurrence of intermediate event as shown on the fault tree.

Therefore, it is the “rupture of highly pressurized LPG pipeline ” “bursting of Claymore riser ” “rupturing of combined with the various intermediate and basic events. 5. Actions to prevent future failure In regards to the Piper Alpha disaster, there are several actions which could be taken to prevent the reoccurrence of such disaster in the future. These actions include 1) Ensuring to put in place a proper auditing and monitoring system A proper auditing and monitoring system is a relevant step which must be taken to ensure that future failure does not occur. The reason why this is necessary is because, this ought to be one of the key areas of the safety management system of any organisation that really want to prevent to the lowest minimum the occurrence of failure event which could put workers safety and the environment at a loss. In the case of Piper Alpha, it is evident that there was safety audit and monitoring but it was not of right standard and quality as many of the deficiencies could have been picked up it the auditing and monitoring was of standard. Therefore, it is reason to perform a standard and proper auditing./monitoring so as to ensure that no casaultive agent of event failure is left unidentified. More so, the need for a proper auditing and monitoring system is to ensure that the right mitigation and actions are put in place in to avert failure. 2) Ensure proper safety training for all personnel including contractors and sub-contractors. There is need for proper training to be regularly conducted for all personnel. The reasons to perform such training is to ensure that personnel are always aware of the need to be safety conscious while carrying out their jobs. In addition, all new recruits should be exposed to training such as fire training, emergency response training before ever resuming work. This will to a great

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extent alight the new recruit of the importance of always been safety reliant while performing their jobs. 3) Provision of temporary safe shelter In the case of Piper Alpha, most fatalities occurred as a result of suffocation from inhalation of smoke. Therefore, it is necessary for operators to always provide a temporary safe shelter where all onboard personnel outside the accommodation platforms can always take refuge during emergency with proper instruction followed while doing so prior to evacuation. This temporary safe shelter could be in the accommodation or production platform and constant safety drills should be performed to always keep personnels alert on how to evacuate to the temporary safe shelter when necessary. More so, there should be total protection against the enterance of smoke or fumes of any form into the temporary shelter and provision should be made in the design to ensure that ventilation dampers of such shelter do not shoot on high temperature as was the case of the accommodation block in Piper Alpha. 4) Strong safety culture should be inculcated There is need to inculcate a strong safety culture at all levels to prevent a repitition of the Piper Alpha disaster. In Piper Alpha the safety culture was poor thus giving room to situation of “I do not care attitude”. This is evident in the ways the facility was been handled, personnel with low qualification promoted to occupy key positions by management, inability to adhere to recommendations for change of head of deluge system, unwillingness to perform safety training. Inculcating a strong safety culture will help to prevent future accident failure because, personnel and management will always perform work practices in ways that controls hazards effectively, there will be a much more high level of positive attitude in managing risks and compliance to laid down rules of prodction thus providing personnel and maanagement the opportunity to learn from failure events and near misses which will help prevent future reoccurrence. 5) High quality safety management should be practiced High quality safety management is relevant to prevent the reoccurence of the Piper Alpha disaster. In Piper Alpha, the decision to always switch the diesel fire pumps to manual mode each time divers were on the water was right but it lacked quality in that it did not put in place a procedure that will immediately turn on the diesel fire pumps back to automatic mode immediately divers leave the water. Quality safety management is necessary because it ensures that standards are not broken thus providing a quality system where lives of personnel and even the equipment are highly safe. Moreso, quality safety management will help prevent future reoccurence because the right safety system will be provided to enure high quality safety management. More so, this will reflect in the safet culture of personnel. 6) Thorough Hazard and Operability Study (HAZOP) should be conducted. It is essential that a proper HAZOP should be carried out during the design stage of platform to prevent the future reoccurence of the Piper Alpha disaster. In doing this, the possible hazards will be identified and mitigation measures rightly put in place to eithere eleminate those hazards or curtail its tendencies to cause harm. 7) Proper positioning of emergency shutdown valve (ESV) The position of emergency shutdown valve is essential because it helps prevent the onset of failures. In Piper Alpha, the ESV was not properly installed along the Claymore, Tartan and MCOP-01 risers which resulted into the rupturing of these risers. For example, the ESV of the Tartan raiser was far from were the Tartan riser ruptured. However, if the ESV’s were properly located close to the sea level, it would have shut down these risers at the onset of the first explosion thus curtailing the effect of the failure event. Therefor, it is recommended that the ESV be properly positioned in production faciltie so as to avoid repeatition of the Piper Alpha disaster. 8) A proper permit to work system should be put in place A proper permit to work system unlike that found in the Piper Alpha will help prevent a disaster of this magnitude in the future. This is because the permit to work will provide an effective means of communication between personnel especially during shift handovers. A proper permit to work

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system will be made possible by making the procedure from opening to closing a permit to work as easy as possible and also providing trainig to personnel on how best to perform work practices with the work permit. Moreso, the work permit system should include a practice whereby padlocks should be used to lock isolated units with red flags been placed on them and such isolated units permit to work been rightly kept in the designated places in the control room. More so, the following can be done to prevent the reoccurence of future events  The setting up of a system which must be included as part of normal operating management for the timely resolve of faults in safety critical equipments must be available.  There should an interactive effect system set up to resolve emergencies between linked operating system.  A proper evacuation and escape system should always be set up.  The installation of a susbsea isolation valve should be provided and installed on a case to case basis on facilities.  Personnel should only be promoted and assigned duties to key positions only by merit and prove of having adequate exposure and experience to handle such key positions.  Personnel should be empowered to always stop any workr on site which deviates from the laid down safety rules and regulations  Mock evacuaton muster should always be conducted to enlighten personnel on the evacuation routes and safety measures to be applied during evacuation. 6. Quantification of the fault tree and probability of the top event The quantification of the fault tree analsysis drawn for the Piper Alpha disaster is to determine to what extent did each of the basic and internediate event contribute to the event failure. In this process, the Boolean algebra will be used and necessary calculation perfom from the top event. In addition, all the basic event are denoted as , intermediate events as and the top event as More so, in qunatifying the fault tree analysis, certain probabilities have been used and justification are as fellows. 1) Loss of control room: The probability was chosen because the personnel chose to abandon the control thus failure to act correctly in the first 60 seconds of an extremely high stress condition which lead to devasting effects (P 2002). 2) Failure of C/D and B/C firewalls: The probability of 0.5 was selected because according the firewalls of the modules of Piper Alpha were not built to withstand explosion (Pate-Cornell 1993). Also, because the level of explosion was not properly outlined, it became imperative that a 50:50 situation be applied in selection of the probability. This implied that the explosion could be high explosion that will destroy the firewalls or a low explosio which will not destroy the firewalls. 3) Failure of Emergency shutdown system: The probability of 0.00055 was selected because of the potential of multiple fatalities which was present in Piper Alpha and also based on Safety Integrity Level 3 (SIL 3), (Magnetrol 2009). 4) Incomplete recerticaition of PSV 504, Removal of PSV 504 for recertification and misplacement of permit to work of PSV 504: The probability of 0.3 is chosen because of the lack of safety training of personnels in Piper Alpha which led to negligence. Moreover. This probability was chosen because to a greater extent human error is a contributory factor because these personnel could have been under general high stress condition due to limited crew members on board. (P 2002) 5) Oil leak and gathered on grates kept: The probaility selected is 0.3904.Here, the probability is considered to be as a result of two factors, deficient safety training and inefficeint emergency plan. The grates where oil gathered was kept on the platform by divers. This grates ought to be kept in the store house but beause there was deficient trainging whose probability is 0.0487 (Yan, et al. 2011) and inefficient emergency plan with probability of 0.0862. These probability were considered because the divers could have kept these grates because of either reasons. However, all other probabilities were obtained from relevant journals.

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Calculations From the fault tree, Solving for

Solving for

Solving for

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7. Prioriting of accident contributory factors In prioritizing the contributory factors that led to accident, the minimal cuts sets are determined for the fault tree using the Fussell - Vesely Algorithm. Thereafter, calculation are made to prioritize. 1 2 T

Table 2: Cut sets for Fault Tree Using Fussell-VeselyAlgorithm 4 5

3

6

7

8

9

10

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Table 3: Minimal Cut Sets for Fault Tree Minimal Cut Sets

Table 4: Faulty Tree Analysis showing priority of minimal cut set No Q

W Events in minimal cut sets

1

0

2

0

3

0

Considering table 4, it is seen that the cut set that will contribute to the fast occurrence of the event failure comprises mainly of events which results from flaws in design of the Piper Alpha and negligence of

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management. Hence, it is recommened that thorough efforts should be put in in the areas of identification of hazards and mitigation measures provided during design stage of platforms so as to avoid a repetition of the Piper Alpha. More so, management need todo the right things so as to avoid a situtaiton whereby personnel neglect safety measures while performing production tasks on platforms. However, huge funds are involved in doing this as such it is adviceable that while taking into consideration ways to eliminate design flaws the measures and funds put into doing this should be proportionate thus the “principle of ALARP” should be the key while doing this. Solving for priority of each basic event by replacing each with

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From the above calculations, it is concluded that three groups of basic events can identified and prioritized by values when probability of each basic events was taken as 0 and replaced into the cut sets 0 Table 5: Priority of Basic events group according to top event value (TE) value Basic Events Priority Priority explanation 1

Each of these basic event had equal effect on the top event, therefore they have high priority to cause failure

2

Each of these basic event have equal effect on the top event, therefore, they have low priority to cause failure

0 3

Each of these basic event have equal effect on the top event, the have very low effect to cause failure

From table 5, The contributory factors have been grouped into three categories with each group having same contributory effect on the top event. From the table, it can be concluded that design flaws are the huge contributors to the failure event. These design flaws are such that could have been eliminated if inherent design stragegy was thoroughly applied during the design phase of the platform. Thus, adequate measures which considers safety from the design stage of platfroms should be taken to eliminate the replicate of the Piper Alpha disaster or any disastrous event in the future. This measures should be those that include HAZOP, fire and explosion modelling as sregards how both will affect the real-life platform etc. More so,the principle of “ALARP” need to be the foremost determinant while doing this.

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8. Conclusion The event of Piper Alpha disaster turned around the oil and gas industry especially in the UK where it gave birth to new offshore regulations. Moreover, it is always relevant for operators to always ensure that safety is paramount in whatsoever activities which concerns the drilling, production and operation of oil and gas facilities. Furthernore, it is recommended that the various actions which has been carefully outlined in this report be taken into consideration in present and future practice of industries so as to avoid a reoccurence of event such as the Piper Alpha or any resemblence to it. More so, government should monitor the promotion and employment of personnel in the oil and gas industries especially offshore facilities so as to ensure that only competent hands are employed and trained. However, safety should be more of proactive then reactive as this will safe huge capitals that are paid as compensation in situations of accidents.

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