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International Conference on the 20th Anniversary of Bhopal Gas Tragedy
“Bhopal and its Effects on Process Safety”
The Indian Institute of Technology, Kanpur, India, December 1 to 3, 2004
Hazardous Material Storage Installations
Steps to address concerns on Safety and build Public Confidence
D.C Sorte, Director (Technical)
Dr M.P Sukumaran Nair*, Dy Chief Engineer (Corp Planning)
Fertilizers And Chemicals Travancore (FACT) Ltd
Cochin, India
Abstract.
Much public concern is raised on hazardous material bulk storages at vulnerable locations that cater the requirements of basic industries. This concern has grown into alarming proportions after the ‘Bhopal’. Over these years considerable improvements have taken place in almost all aspects relating to the design, construction, operation, maintenance and troubleshooting, assessment and mitigation of risk from such installations. Relying on concepts of inherent safety and with the help of modern instrumentation and renewed operating philosophy such units are operated today with a high degree of safety and reliability. Competent Emergency Management and Response Plans are also in place to tackle emergencysituations that are likely to crop up even with the remotest probability. This paper attempt to trace the course of developments in increasing process safety to reasonably address public concerns on the risk to the neighboring community emanating from units with a particular review in the case of port based refrigerated atmospheric pressure ammonia storage tank which store and handle large quantities of ammonia imported for fertilizer manufacturing.
Industrial accidents remain a major concern before the Governments consequent to the loss of lives, damage to property and environment that is inflicted on the society besides upsets in tranquil and a heavy economic strain. Along with the growth of the processing industry, the problem of accidents caused in the industry poses a big question with its regional and global implications and efforts are also underway to minimize the damages and ensure all safer working environments around industrial installations. Known experiences of accidents caused in the industry over and again caution us that the price of process safety is increasingly becoming a concern on the profitability of the unit, morale of its employees and the public image of the institution. Still, the growth and development of the processing industry is not deterred by occasional mishaps. At the same time these lessons from past industrial accidents urge industry operators to continue efforts to better their safety standards and enhance pubic perception of the industry. Incidents like Flixborough, Sevaso, Bhopal, Chernobyl, North Sea and recently Toulouse etc have taught us where do we stand with regard to achieving an accident free operating environment in the chemical processing industry, which direction we are to go, and what commitment is needed for future. Everywhere and especially in the matter of process safety, Murphy’s Law holds good and it also provide the impetus for continuous research and improvement to unearth , identify and overcome the hidden and the unknown through a process of elimination.
Key Words: hazard, risk, ammonia
The safety and environmental concerns are often shared by public interest groups, which lead to outcries, litigations and in certain cases even closure of units. The loss to the society on account of such closures is enormous and thus it is in the interest of the industry and the community that dialogues to address the conflict between them are always maintained. This prescription, though looks simple, is difficult to practice in the real operating environment of the industry. More often, a cultural change is needed to understand and effectively address the community’s rights to know and Government’s concern on public health and safety. Efforts are to be organized from the side of the industries to empower the public understand what is happening with in the processing facilities and effectively communicate the risk from such operations. Major industries have a specific role in this regard in building public understanding as a first step to enhancing public confidence and build a better community perception on the industry. At the State level, there shall be efforts to organize effective mechanisms to ensure public safety through well-defined policy prescription and legislation. In the past 20 years since Bhopal, there is an increasing concern and resurgence of public interest in the matter and so also the efforts to address them have increased considerably.
Major contributory factors to accidental releases in the hydrocarbon –chemical industries are mechanical failures and operator error. Today, industries use a predictive maintenance strategy based on condition monitoring of equipment to overcome the shortcomings of preventive maintenance. It is also possible to most satisfactorily assess the integrity of equipment and structures with the help of modern inspection tools and methods and predict likely failure situations well in advance to enable them to take effective remedial action. A recent development in ultrasonic technology with its patented equipment and technology eliminates the use of hazardous chemicals associated with radiographic examination commonly used for flaw detection. Better training, simplified procedures and work practices and a ready access to vital information help to reduce human error and enable the operator to spot exact locations in the plant where problems are likely to crop up and take corrective actions before the situation go out of control. Thus with the currently available technology and skill it is possible to operate and maintain hazardous installations with a very high degree of safety and environmental protection standards.
The following case study illustrates the success of the above approach.
The Willington Island Ammonia Import Terminal belonging to the major fertilizer producer and Govt Company, Fertilizers And Chemicals Travancore (FACT) Ltd came under suspicion that it posed a serious threat to safety the local community of Cochin. A Public Interest Litigation (PIL) initiated by a local NGO before the High Court.
The facts came under judicial scrutiny are
In the case of a catastrophic accident to the storage tank resulting in a major crack or rupture it would lead to disastrous and devastating consequences of annihilating all living beings inverting the city of Cochin a city of dead and nearby places a morbid graveyard.
The catastrophic failure of the tank is not an unreal or remote possibility but a credible and contingent possibility to be reasonably anticipated on the facts unfolded in the case.
Though the catastrophic event is only a possibility and when it would happen is unpredictable it is unwise to forget or slur it. Once it happens it is irreversible so prudence dictates not complaisance, but positive action.
The Ammonia tank
The 10000 MT double wall double integrity refrigerated atmospheric ammonia tank was built as per API Code 620 including Appendix R in the year 1976 by UHDE GmbH , Germany to receive imported ammonia consignments for the phosphatic fertilizer plants of FACT located at Ambalamedu 30 kilometers from the Cochin Port. The tank has 41.6 metre in diameter and is 17.4 metre tall. Thickness of the bottom plate 5 millimeters and that of the annular plate is 8mm. The inner cup shell consists of six courses , design thickness varying from 8 mm to 11.2 mm .Outer shell consists of 14 courses and the design thickness varying from 5 mm to 22 mm. Roof is constructed with built up support beams in the spherical segments and with connection between the roof plates and the beams. The thickness of the roof plate is 5 mm. The outer tank is anchored to the reinforced concrete foundation with tie rods.
During the construction phase while the tank was tested hydraulically, at a water load of 8000 MT 6 piles (among 217 ) in the outer row was found cracked. A detailed investigation was done by Central Building Research Institute (CBRI), Roorkee and a thorough rectification was done. Subsequently water load test was conducted at a maximum of 10000 MT plus 1600 MT of over pressure load. Thus the tank was tested at a water load of 11600 MT after the repairs and the differential settlement was found to be with in acceptable limits. Clearance for loading ammonia was also given. Since then the tank continued to be in operation till 1985.The tank was decommissioned and inspected thoroughly in 1985 . During this time FACT engaged Indian Institute of Technology (IIT) Chennai to ascetain the soundness of the foundation and integrity of the tank. After exhaustive studies IIT , Chennai concluded that the foundation was in sound condition after operation of 10 years. The tank and associated facilities were got inspected by the world-renowned inspection agency M/s TUV, Netherlands. They suggested certain measures to avoid normal deterioration of the tank while in service FACT implemented their recommendations and the tank was serviced back to operation.
The tank is insulated by poly urethane foam and bottom of the tank by poly styrene foam board. The tank is protected against over pressure and vacuum by two relief/vacuum valves. Other associated facilities included two large capacity refrigeration compressors (for use during tank loading), two pressure holding compressors (one driven by motor and the other diesel engine), a diesel generation set to take care of power failure situations, three pumps for loading rail wagons and barges, three sets of wagon loading and one set og barge loading arms, connected piping, cooling tower, instruments and a flare system.
Liquid ammonia at -33 deg C is moved in rail wagons to the plant. The tank terminal is a self contained facility with provisions for emergency supplies and is guarded round the clock by security personnel. It was operated and maintained by competent personnel with all mandatory inspections, tests and certifications.
Based on its finding that ‘the catastrophic failure of the tank is not a remote possibility, but a credible and contingent possibility to be reasonably anticipated on the facts unfolded in the case’, the High Court
ordered to decommission, empty and close down operations of the installation.
Against the verdict FACT appealed to the Supreme Court of India for reconsidering the case.
The Supreme Court appointed Engineers India Limited (EIL), a consulting group of international repute to re-examine the issues and submit a report.
Following the Supreme Court directive, EIL conducted extensive inspection and tests to ascertain the present condition of the tank. It included
1). Visual examination
2). Non-Destructive Test (NDT) methods such as Schmidt Hammer test (as per IS 13311 Part II) on piles, beams and slabs to assess strength of concrete
3). Ultrasonic Pulse Velocity Test to assess condition of structures as cracks, voids etc.
4). Carbonation Test for assessing alkaline protection of reinforcement steel
5). Test of Compressive strength for concrete (IS 456:2000)
6). Half-Cell Potentiometer Test to assess corrosion of steel reinforcements and
7). Chemical analysis of soil samples.
From the above analysis EIL inferred that the foundation of the tank is in a sound condition.
EIL also evaluated the heath and integrity of the tank through visual inspection and with the help of a series on NDT methods.
These methods involved use of
1). Wet Fluorescent Magnetic Particle Testing (WFMPT) to ensure that weld joints are free from cracks and discontinuities,
2). Liquid Penetrant Testing (LPT) for weld joints in the annular area not accessible to WFMPT 3). Ultrasonic thickness measurement (UTT) of shell, plates, piping, nozzles,
4). Ultrasonic flaw detection (UFD) to detect sub surface defects in T joints of shell plates of inner cup,
5). Hardness testing of weld heat affected zones to know degradation of parent material,
6). In-situ metallographical examination by advanced replication technique,
7). Vacuum box leak test to ensure that there is no leak through bottom plates of inner cup and annular plates of inner and outer tanks,
8). Water load test at 10000 MT ,
9). Hydro pneumatic test by pressurizing to 1000 mm WG for one hour to see any settlement and then maintaining a vacuum of 50 mm WG for 30 minutes .
All these tests were satisfactory and it was considered that the tank is in sound condition.
EIL further evaluated the probabilities of leaks and other failures from accessories and connected systems. Reviewing the chronology of the history of leaks occurred in the installation EIL opined that the leaks had developed outside the storage tank and can be handled effectively by proper monitoring and maintenance.
Safety audit
FACT conducted a full fledged safety audit and Hazard and Operability (HAZOP) study in 1988 engaging M/s Cremer & Warner Ltd (CWL) , London, UK who are specialists in the field. The idea was to identify the potential hazards involved in the plant and their likelihood of occurring and its effect on the local population. They reviewed site safety policies, safety responsibilities, design standards and guidelines, operating procedures, safety checks, inspection and maintenance, modifications, detection systems, disaster management plans, training facilities, fire fighting, emergency shut down systems etc and identified areas of concern
Results of the above study showed that generally the leaks from the plant would not appear to affect the surrounding population to a significant extent. However, reduction of the potential effects of some of the release cases can be achieved by the use of automatic shut off facilities. Additionally containment of the spill and hence boil off rate will reduce the distance of the cloud travel and hence the risk to the local population. Comprehensive inspection , testing and maintenance routines will also help in minimizing likelihood of any failure leading to the release of ammonia and therefore these procedures should continue to be carried out on a regular schedule with periodic review of maintenance frequencies. Following the report the recommendations were implemented by FACT.
CWL concluded that ‘the management and organization structure appears to be well balanced and efficient with good back up from the technical services, maintenance and inspection groups. Due to the sensitive siting of the tank the management have taken every effort to ensure the integrity of the facility is not undermined and that it is operated by well trained, competent staff Everyone interviewed at ite had a good working knowledge of the plant and how to react in an emergency situation. All senior operations staff were qualified engineers and had long experience of the operation of a chemical plant’.
Expert opinion
During the course of the hearing, the High Court sought the opinion of Dr John M.Campbell of CHERRYROSE Ltd, UK to go into the merits of the PIL. Dr Campbell after studying of the documents made available to him suggested that the issue is not limited to leakages that can be contained and which may not cause major hazards. He was of the opinion that worst cases like tank rupture, terrorist attack , aircraft crash, extreme high speed wind or cyclone and earthquake should have been considered. CWL has not addressed these issues, he pointed out. Later EIL carried out a separate HAZOP study and Quantitative Risk Analysis covering all these issues.
Risk assessment study by EIL
M/s Engineers India Ltd (EIL) conducted another HAZOP study and quantitative risk assessment (QRA) covering the tank, ammonia ship unloading facilities, barge and rail loading facilities, storage tank and associated facilities and flare and other utilities. The recommendations arisen out of the above studies intended to improve safety during operation were listed. The QRA identified the type of hazards that could emanate from the facilities, likely failure scenarios and evaluated the potential hazards, their damage effects and risk posed to the surrounding population in the event of an unforeseen release of ammonia. The likely hood of a catastrophic failure as an an air crash on to it was also evaluated. EIL suggested certain mitigation measures also to reduce the hazard and its risk potentials.
Major observations and recommendations of the study are
Catastrophic failure of the tank can be considered as a remote possibility considering the fact that the storage is a double containment type of construction.
The failure frequency associated with the catastrophic failure of such storage tank indicates that this event may be classified as an unforeseeable scenario.
Possible causes that could lead to this remote scenario are earthquakes, because of terrorism or air crash on to the tank.
Latest prevalent seismic data has been already considered during the design of the tank.
Sabotage is an issue that cannot be predicted and it can cause disaster at any time and to any place even with the best of safety measures. A properly tight security and surveillance of the installation is the answer in this case.
The study also assessed the air crash rates and compared the assessed crash rates with that of the inherent failure frequencies associated with such failures. It is observed that the assessed crash rate on to the tank with respect to one of the runways, is 1.36 per million years which is of the same order of magnitude as that due to inherent failures. The assessed crash rate due to second runway is estimated about 0.67 times that due to inherent failures. Thus the possibility of air crash on the tank can be considered as remote and pose a low level of risk.