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Quantitative evaluation of precautions on chemical tanker operations
process safety and environmental protection 8 7 ( 2 0 0 9 ) 113–120
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Process Safety and Environmental Protection journal homepage: www.elsevier.com/locate/psep
Quantitative evaluation of precautions on chemical tanker operations Ozcan Arslan ∗ Maritime Transportation and Management Engineering Department, ITU Maritime Faculty, 34940 Tuzla, Istanbul, Turkey
a b s t r a c t Large quantities of liquid chemicals are carried by chemical tankers all over seas. Chemical cargoes have different properties and chemical tankers are complex ships that are designed to carry different types of chemical cargoes. Carriage of chemical cargoes contains different hazards both for human life and marine environment. There are several cargo operations that are regularly done on chemical tankers such as loading, discharging, inerting, washing tanks, sampling, and freeing gas. These operations constitute their own risks. Therefore, risk assessment has become a critical issue in maritime industry. The present investigation of this study is attempting to examine the priorities of precautions that are taken by chemical tankers before, during, and after cargo operations. Analytic hierarchy process (AHP) is used for prioritizing the precautions in order to clarify the risk assesment option that will be used for proactive approach to prevent marine casualties. The main aim of this study is to identify an appropriate management tool to increase the level of safety for chemical tankers during cargo operations at a terminal by using the results of AHP application. © 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Keywords: Safety; Chemical tanker; Risk assessment; AHP; Maritime; Transportation
1.
Introduction
Large quantities of liquid chemicals are transported by tanker ships. There are several weaknesses and threats that are increasing risks of chemical cargo transportation by ships (Arslan and Er, 2008). Chemical cargoes have different properties, and many of them represent a health and safety hazard, which is a critical issue for the tanker industry (Karimi et al., 2002). Chemical tankers are under several risks that may occur during the loading, traveling, and unloading. Care should be taken to minimize this risk as far as practicable in each cargo handling case, based upon the best knowledge and technology on the construction and equipment of the ship and the properties of the cargoes that the ships intend to carry (Altuntas, 1997). Chemical tankers are complex vessels that are designed to carry different types of chemical cargoes. Some cargoes need heating, some need refrigerating/freezing, some must be kept under inert conditions, some need to be carried in stainless steel tanks, and some are flammable, explosive, or give off noxious vapor (Hanninen and Rytkönen, 2006).
∗
These properties require careful consideration during the cargo planning process and loading. Cargo loading plan verification needs to be made regarding the chemical ship type, tank coating compatibility, compatibility with other cargo, and the environmental controls required during transportation. In addition, the venting requirements, monitoring equipment, vapor detection, compatible fire protection medium, density limitations of the product in relation to the holding tank construction, and pumping requirements are important criteria for safe cargo handling and navigation of ship (INTERTANKO, 2006). In this study, analytic hierarchy process (AHP) method is used for identifying and prioritizing the safety and environmental precautions’ taxonomy that should be used by chemical tanker operations. Section 2 of this study describes the safety and environmental chemical liquid transportation hazards. Section 3 illustrates brief berthing and cargo operation procedures. Section 4 describes the AHP, Section 5 describes the AHP Application results and Section 6 illustrates the case applications.
Tel.: +90 505 713 47 54; fax: +90 216 395 45 00. E-mail address: [email protected]. Received 22 January 2008; Accepted 30 June 2008 0957-5820/$ – see front matter © 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.psep.2008.06.006
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2. Hazards associated with the transport of bulk chemicals
need different fire extinguishing knowledge for every chemical that will be carried by chemical tankers. (IBC Code, 2007).
2.1.
2.3.
Health hazards
Many chemicals irritate or toxic effect on the skin or on the mucous membranes of the eyes, nose, throat, and lungs in the gas or vapor state (Altuntas, 1997). Impacts of chemicals on health hazards are rated as following: • “0”: no likelihood of producing injury; • “1”: minimum hazard. These chemical threshold limits are above 500 ppm. • “2”: some hazard. These chemical threshold limits are 100–500 ppm. • “3”: moderately hazardous chemicals. These chemical threshold limits are 10–100 ppm • “4”: severely hazardous chemicals. These chemical threshold limits are below 10 ppm. Irritating vapors of chemical materials to the skin or the mucous membranes of the eyes, nose, throat, and lungs are rated as follows: • “0”: chemicals that are non-volatile. • “1”: chemicals that cause a slight smarting of the eyes in cases of high concentration. • “2”: chemicals that cause moderate irritation. • “3”: chemicals that are moderately irritating or volatile. • “4” chemicals that are severe eye or throat irritants, vapors that are capable of coursing eye or lung injury and that cannot be tolerated even at low concentrations. (ISGOTT, 2006).
2.1.1.
Odour threshold
The odour of a potentially dangerous vapor may be hidden by another odour. In addition, a certain vapor is likely to produce olfactory fatigue, which is a deadening of the sense of smell. For these reasons, the sense of smell alone is not a reliable indicator of the presence or absence of a dangerous vapor. The smallest concentration is expressed in parts per million by volume in air and is not an absolute value. It will vary between individuals and will vary from day to day for any person (Kunichkin, 2006).
2.1.2.
Lethal dose: LD50 and LC50
LD50 is a statistical estimate of the dosage necessary to kill 50% of people over 10 months with in 48 h. It is usually expressed in terms of the weight of poison per unit of body weight, most often as mg of chemical/kg of animal (mg/kg). The concentration of about 60 times LD50 is lethal to a person. LC50 is a concentration that, within 40 h is likely to kill 50% of the test animal species. It is usually expressed as ml or mg of chemical gas of vapor/kg of animal (ml/kg or mg/kg) or ppm. The values of LD50 and LC50 are a means of measuring the lethal dose and judging the conditions. Thus, these values are substantially different from the TLV values in the purpose for using (IBC Code, 2006).
2.2.
Fire hazards
Flashpoint, boiling point, flammability limit, and autoignition temperature vary between different liquid chemicals, which therefore have different fire characteristics. Thus, carriers
Pollution hazards
Water pollution hazards are defined in terms of human toxicity, water solubility, volatility, odor or taste, and relative density. The air pollution hazards of chemicals are defined by the emergency exposure limit (EEL), vapor pressure, solubility in water, relative density of liquid, and vapor density. The reactivity hazard of a chemical is defined by reactivity with other products including water and with the product itself (including polymerization). Marine pollution hazards are defined by bioaccumulation with attendant risk to aquatic life, tainting of seafood, damage to living resources, and hazard to human health (IBC Code, 2007).
3. Berthing and cargo operation procedures for chemical tankers 3.1.
Exchange of information before berthing
Before the tanker ship arrives at a berth or a terminal, in addition to any advice on cargo to be loaded or discharged, it is recommended that prior information that could affect the safety of the ship and terminal should be exchanged between terminal and ship. Information should be given from ship to terminal, such as the ship’s draft and trim at arrival; specific characteristics of the cargo any tank; valve or pipeline leaks on the ship that could affect loading or unloading, or cause pollution; necessary repairs (if any) about ship that would cause the commencement of loading or unloading to be late; the standards of size and bolt hole on the flanges at the manifold connections; the standards of size and bolt hole on the flanges at the vapor return line. Using certain information is essential, such as availability of mooring equipment, details of any mooring plan and of any code of visual or audible signals for use during mooring; knowledge about ship’s derrick, depth of water at berth and meteorological information (ISGOTT, 2006).
3.2.
Agreement between ship and terminal
In order to maintain safe and secure cargo operation, a loading plan should be agreed on by the ship’s officer and terminal representative, including the arrangement and capacity of the ship’s cargo line; venting system; shore’s cargo line and the maximum allowable pressure of the ship/shore hoses or loading arms to be used during operation; loading rate and pressure; loading procedures; necessary precautions to avoid static ignitions; atmospheric conditions; ullaging method; system of cargo vapor return to shore installation; overflow control information. (ISGOTT, 2006).
3.3.
Safety precautions and emergency procedures
After berthing, the ship’s officer should contact the terminal representative to provide the information on local safety regulations, to agree on designated smoking spaces, to agree on galley fire and cooking appliance limitations, to advise “Work Permit” and “Hot Work Permit” procedures, and to present and discuss ‘Ship/Shore Safety Check List’ that is identified in Section 5 of this study. After berthing, the ship’s officer and the responsible terminal representative should agree on action to be taken in case fire. Also, these persons should
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agree on a signal system that is indicating “Standby”, “Start loading” or “Start unloading”, “Slow down”, “Stop loading” or “Stop unloading”, “Emergency stop”, and any other necessary signals. (ISGOTT, 2006).
4.
Method used in this study
This section of this study attempted to examine the priorities of precautions that are taken by chemical tankers before, during, and after cargo operations. For this purpose, AHP is used for prioritizing the precautions. The AHP is one of the mathematical methods for analyzing complex decision problems with multiple criteria, and it can deal with qualitative attributes as well as quantitative. It is developed by Saaty (1977). By utilizing the AHP, factors can be weighted and rated quantitatively. AHP is used in many fields, such as planning; selecting the best alternative; resolving conflicts; optimization problems with other techniques, such as linear programming, fuzzy logic, quality function deployment. (Vaidya and Kumar, 2006). Brad used AHP in 1986 as a multi-objective methodology for selecting sub-system automation options (Brad, 1986). Braglia used AHP for analyzing multi-attribute failure mode analysis (Braglia, 2000), and Ceha and Ohta used AHP for evaluating of air transportation network (Ceha and Ohta, 1994). Cheng applied AHP with fuzzy approach for evaluating naval tactical missile systems (Cheng, 1997), and Ghodsypour and Brien applied AHP with linear programming for supplier selection problem (Ghodsypour and Brien, 1998). This study illustrates the pair-wise comparisons are carried out within precautions that can be taken by chemical tanker ships by the master and chief officer who are experienced on chemical tankers more than 5 years, operation manager and safety manager of chemical tanker companies. The comparison making group is consisting with five Unlimited Master and three Chief Officer whom are experinced on chemical tankers; four Operation Manager and three Safety Manager of chemical tanker managing company whom have 5 years experience as well. The comparison scale vary from 1 to 9; 1/1 indicates equal intensity, while 9/1 indicates extreme or absolute intensity. The pair-wise comparison scale is indicated in Table 1. In the pair-wise comparisons, the estimated intensities or priorities can be obtained using the pair-wise comparison matrix as the input of the principal eigenvalue method (Shinno et al., 2006). The intention of this study is to develop strategy action plan for ships, ship operators, ship management companies, and seafarers through AHP with a view to make safer cargo operations at terminals in order to prevent the re-occurrence of marine casualties.
5.
Table 1 – Pair-wise comparison scale Intensity of importance
Definition
1
Equal importance
3
Moderate importance of one over another
5
Essential or strong importance
7
Very strong importance
9
Extreme importance
2, 4, 6, 8
Intermediate values between the two adjacent judgments
Explanation Two activities contribute equally to the objective Experience and judgment strongly favor one activity over another Experience and judgment strongly favor one activity over another An activity is strongly favored and its dominance demonstrated in practice The evidence favoring one activity over another is of tile highest possible order of affirmation When compromise is needed
P1-2 Are emergency towing wires correctly positioned? P1-3 Is there safe access between ship and shore? P1-4 Is the ship ready to move under its own power? P2 Personal and procedural precautions: P2-1 Is there an effective deck watch in attendance on board and adequate supervision on the terminal and on the ship?
Obtained results and considerations
In this study, precautions that should be taken by all chemical tankers were observed from the established ship/shore checklist that is listed below in terms of clusters (ISGOTT, 2006). Then the factors are clustered in hierarchical structure as shown in Fig. 1.
5.1.
Hierarchical structure of precautions
P1 Berthing-related precautions: P1-1 Is the ship securely moored?
Fig. 1 – Hierarchical structure of precautions.
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Fig. 2 – Pair-wise comparison of precautions. P2-2 Is the agreed ship/shore communication system operative? P2-3 Has the emergency signal to be used by the ship and shore been explained and understood? P2-4 Have the procedures for cargo, bunker, and ballast handling been agreed? P2-5 Have the hazards associated with toxic substances in the cargo being handled been identified and understood? P2-6 Has there been agreement regarding the emergency shutdown procedure? P3 Equipment-related precautions on deck:
P3-1 Are scuppers effectively plugged and drip trays in position, both on board and ashore? P3-2 Are unused cargo and bunker connections properly secured with blank flanges bolted? P3-3 Are sea and overboard discharge valves, when not in use, closed and visibly secured? P3-4 Are all cargo and bunker tank lids closed? P3-5 Has the operation of the P/V valves and high velocity vents been verified using the check lift facility, where fitted? P3-6 Are hand torches of an approved type? P3-7 Are portable VHF/UHF transceivers approved type?
Fig. 3 – Pair-wise comparison scale in verbal.
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P3-8 Are deck seals in good working order? P4 Precautions out of deck: P4-1 Are the ship’s main radio transmitter aerials earthed and radars switched off? P4-2 Are electric cables to portable electrical equipment disconnected from power? P4-3 Are all external doors and ports in the accommodation closed? P4-4 Are window-type air conditioning units disconnected? P4-5 Are air conditioning intakes that may permit the entry of cargo vapors closed? P5 Precautions about probable emergency situations: P5-1 Is there provision for an emergency escape? P5-2 Are all persons in charge of cargo operations aware that discharge operations should cease and that the terminal should be advised in the case of failure of the inert gas plant? P5-3 Are sufficient personnel on board and ashore to deal with an emergency? P5-4 Are ship emergency fire control plans located externally? P5-5 Are fire hoses and fire-fighting equipment on board and ashore positioned and ready for immediate use? P6 Procedural precautions during operation: P6-1 Are smoking regulations being observed? P6-2 Are naked light regulations being observed? P6-3 Have measures been taken to ensure sufficient pump room ventilation? P6-4 If the ship is capable of closed loading, has there been agreement on the requirements for closed operations? P6-5 If a vapor return line is connected, has there been agreement on operating parameters? P7 Condition of cargo system equipment: P7-1 Are cargo and bunker hoses/arms in good condition, properly rigged, and appropriate for the service intended? P7-2 Is the appropriate tank venting system being used? P7-3 Has a vapor return line been connected? P7-4 Is the Inert Gas System fully operational and in a good working order? P7-5 Have the fixed and portable oxygen analyzers been calibrated, and are they working properly? P7-6 Are fixed IG pressure and oxygen content recorders working? P7-7 Are all cargo tank atmospheres at positive pressure with an oxygen content of 8% or less by volume? P7-8 Are liquid levels in P/V breakers correct?
The hierarchical structure has consisted of four clusters. The main cluster is the body of ship/shore check list; the second cluster consists of the precaution groups; third group which indicates sub items, is derived from a check list of requirements; the last cluster is shows the personal and environmental precautions’ weightings.
5.2.
Application of method and results
Pair-wise comparisons have beem done among each precaution as shown in Fig. 2. ‘Super Decisions’ software (www.superdecisions.com) was used for computing the priority of precautions (Super Decisions, 2008).
Table 2 – Priorities of precautions P1 P1-2 P1-3 P1-4
0.26828 0.01828 0.05430 0.04606
P2 P2-1 P2-2 P2-3 P2-4 P2-5 P2-6
0.19900 0.08771 0.02012 0.00916 0.02449 0.04711 0.01041
P3 P3-1 P3-2 P3-3 P3-4 P3-5 P3-6 P3-7 P3-8
0.12390 0.00980 0.01057 0.00843 0.01436 0.02794 0.01455 0.02421 0.01406
P4 P4-1 P4-2 P4-3 P4-4 P4-5
0.04977 0.00565 0.01296 0.01190 0.00649 0.01278
P5 P5-1 P5-2 P5-3 P5-4 P5-5
0.07029 0.01052 0.00552 0.03749 0.00447 0.01228
P6 P6-1 P6-2 P6-3 P6-4 P6-5
0.09661 0.02002 0.01866 0.02208 0.01972 0.01613
P7 P7-1 P7-2 P7-3 P7-4 P7-5 P7-6 P7-7 P7-8
0.19215 0.05880 0.02171 0.01751 0.01930 0.01841 0.01601 0.02371 0.01668
Environmental Personal
0.45442 0.54558
Scale, which is indicated in Table 1, is used to make pair-wise comparison between alternatives and the simple intensity of importance illustration is mentioned in Fig. 3. The results of AHP computation is summarized in Table 2. According to the results of berthing-related precautions, personal and procedural precautions, and checks about condition of cargo system equipment are more important criteria that will mitigate potential risks during cargo handling. Therefore, the weighting of second cluster in respect to the third cluster is shown in Fig. 4. Similarly the weighting of the third cluster is shown in Fig. 5. According to the results, the following items are proposed. Securely mooring of the ship is the most important precaution to mitigate risks at the terminal. Maintaining effective deck watchkeeping and understanding the potential
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5.3.
Fig. 4 – Percentage of precaution groups’ priorities.
Fig. 5 – Priorities of precautions. hazards about carried cargo are the two important precautions among personal and procedural precautions. Providing enough personal precautions both on board and at the terminal in case any emergency situation, keeping cargo and bunker hoses/arms in good and appropriate condition, and properly rigging them are other important precautions to mitigate potential risks during cargo operations. Fig. 6 indicates the overall analyzed results of precautions’ weighting rates in regard to the percentage that the precaution is related with personal safety and environmental protection. According to the results, precautions that are taken by chemical tanker ship and the terminal are related to more personal safety in the means of occupational health and safety than environmental awareness.
Fig. 6 – Percentage of environmental and personal precautions.
Practical strategies for risk mitigation
Taking into account the AHP computation results mentioned in the previous subsection this study, the following practical results are suggested. The human-related precautions weightings are more than equipment-related precautions. This result directly signifies the importance of the human factor engineering including ergonomics. Consequently, the precautions that are offered in this study will directly focus on how knowledge and skills of officers and crew members should be developed. In advance, situational awareness is the key factor to breaking the error-fault chain, so crew members should share their knowledge, skill, and awareness with all. Workloads of chemical tanker crews are more than those of any other ships, so an adequate number of qualified officer and a rating should be employed on board. Efficient workload management is extremely important on chemical tankers because fatigue is responsible for many human errors. The ergonomic aspects should be taken into account while designing pipelines, pumps, pump rooms, loading/discharging units, and onboard accommodation places. Equipping chemical tankers with fully automated loading and unloading systems and monitoring systems will have an efficient risk reducing strategy.
6.
Case study and results
6.1.
Case-1: fire at manifold area
A “flash” fire aboard a chemical tanker happened after finishing discharge operation at cargo manifold connection area resulting in two injuries. The incident occurred at 11:15 a.m. and the ship was due to sail that day. A flash fire occurred at the vessel’s manifold area while shore and ship staff were disconnecting cargo arms. As a result, two crew were injured. At about 11:15 a.m. there was a sudden ignition at the manifold area. This ignition produced a flash fire. There was an immediate response to the alarm by the ship’s crew. and the fire was extinguished in few minutes. Thus, the fire was caused by the ignition of spilled oil that sparked used equipment from manifold connection area. A contributory factor of the incident could have been the incorrect fitting of the coupling and using unsuitable equipment.
6.2.
Case-2: entering unsafe cargo tank
After a chemical tanker discharged the cargo cyclohexane that was waiting for a pilot, the chief officer entered the cargo tank
Fig. 7 – Comparison between general results and case studies.
process safety and environmental protection 8 7 ( 2 0 0 9 ) 113–120
for controlling purpose under the supervision of pumpman of the ship. When the pumpman saw that the chief officer had fallen into the cargo tank, he informed other crew on board and immediately entered into the cargo tank. The chief officer and the pumpman were taken from the cargo tank, but they died at hospital. It was understood that the nitrogen in cargo tank was coming from a vapor return line that connected with the vessel and remained in the tanks as blanketing. After examination, it was determined that the victims did not realize that they had breathed nitrogen (Arslan and Er, 2008).
Table 3 – Obtained Results from Cases General
Case-1
Case-2
P1 P1-1 P1-2 P1-3 P1-4
0.26828 0.14964 0.01828 0.05430 0.04606
0.03224 0.01623 0.00242 0.01232 0.00127
0.00000 0.00000 0.00000 0.00000 0.00000
P2 P2-1 P2-2 P2-3 P2-4 P2-5 P2-6
0.19900 0.08771 0.02012 0.00916 0.02449 0.04711 0.01041
0.21360 0.04324 0.06243 0.00310 0.00920 0.09332 0.00231
0.16320 0.04362 0.01624 0.00640 0.03232 0.06400 0.00062
P3 P3-1 P3-2 P3-3 P3-4 P3-5 P3-6 P3-7 P3-8
0.12390 0.00980 0.01057 0.00843 0.01436 0.02794 0.01455 0.02421 0.01406
0.25018 0.01604 0.08132 0.02836 0.10892 0.00883 0.00326 0.00225 0.00120
0.08862 0.00460 0.03136 0.01640 0.02160 0.00164 0.00240 0.00198 0.00864
P4 P4-1 P4-2 P4-3 P4-4 P4-5
0.04977 0.00565 0.01296 0.01190 0.00649 0.01278
0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
P5 P5-1 P5-2 P5-3 P5-4 P5-5
0.07029 0.01052 0.00552 0.03749 0.00447 0.01228
0.08225 0.00112 0.00112 0.03264 0.00525 0.04212
0.14232 0.01024 0.04215 0.08024 0.00720 0.00249
P6 P6-1 P6-2 P6-3 P6-4 P6-5
0.09661 0.02002 0.01866 0.02208 0.01972 0.01613
0.16146 0.04240 0.08548 0.01032 0.00966 0.01360
0.18262 0.00357 0.00640 0.01624 0.10360 0.05281
P7 P7-1 P7-2 P7-3 P7-4 P7-5 P7-6 P7-7 P7-8
0.19215 0.05880 0.02171 0.01751 0.01930 0.01841 0.01601 0.02371 0.01668
0.27027 0.14984 0.06265 0.03232 0.01454 0.00630 0.00210 0.00162 0.00090
0.42324 0.12601 0.10360 0.08667 0.07270 0.02484 0.00628 0.00232 0.00082
Environmental Personal
0.45442 0.54558
0.24325 0.75675
0.11250 0.88750
6.3.
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Results of AHP application
Pair-wise comparisons have been done among each precaution that should be taken before each case that is described in Section 5 of this study. ‘Super Decisions’ software (www.superdecisions.com) was used for computing the priority of precautions and the following results were obtained (Fig. 7 and Table 3).
7.
Conclusion
It is clear that the hazards associated with the carriage of liquid chemicals in tankers are more complex and dangerous when compared to other types of ships. Due to the nature of transportation, operation of tankers is more complex than the operation of other ship types; therefore, working on a tanker requires extra knowledge, skills, and precautions. The operation of chemical tankers causes more incidents and accidents when compared to other types of ships as a direct result of the behavior of the chemicals being carried. The aim of this study is directly concerned with the utilizing analytic hierarchy process identification to show the importance of precautions on reducing casualties during cargo operations that have not been used in the risk mitigation approach yet. Therefore, the originality of this research appears in the following manner. Potential risks should be identified with observing the frequencies of incidents and with observing the consequences in case the accident/incident happens. After observing the frequencies and consequences, the risk can be monitored. In maritime industry, accidents and incidents are generally the results of error-fault chains, and many times it is difficult to identify the frequencies of accidents and incidents because of secrecy and inadequate history records. Accidents and incidents occur in the maritime industry in spite of the latest navigational technologies and strict precautions. This study proposes that the use of the AHP method is an acceptable basis for analyzing the precautions that are developed to guard against to potential dangers during chemical cargo operations for observing the frequencies and consequences. Therefore, an appropriate management tool can be considered to increase the level of safety for chemical tankers during cargo operations at a terminal by using the results of AHP application. Then, strategy making could be designed to minimize accidents, incidents, and defects for shipboard operations. Well-operated cargo operations enable a chemical tanker ship safer and more profitable. It is clear that if the importance of precautions is understood well, the safety of the working environment will be improved for both occupational health and safety and environmental protection.
Acknowledgement The author gratefully acknowledges supports and data that is given Sener Petrol Maritime Company during preparation of this study.
References Altuntas, H., 1997, Chemical Tanker Training Manual, Aksay, Istanbul. Arslan, O. and Er, I.D., 2008, SWOT analysis for safer carriage of bulk liquid chemicals in tankers. J. Hazard. Mater., 154(1–3): 901–913.
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Brad, J.F., 1986, A multi-objective methodology for selecting sub-system automation options. Management Science, 32(12): 1628–1641. Braglia, M., 2000, MAFMA: multi-attribute failure mode analysis. International Journal on Quality and Reliability management, 17(9): 1017–1033. Ceha, R. and Ohta, H., 1994, The evaluation of air transportation network based on multiple criteria. Computers and Industrial Engineering, 27(1–4): 249–252. Cheng, C.H., 1997, Evaluating naval tactical missile system by fuzzy AHP based on grade value of membership function. European Journal of Operational Research, 96(2): 343–350. Ghodsypour, S.H. and Brien, C.O., 1998, A decision support system for supplier selecting using an integrated analytic hierarchy process and linear programming. International Journal of Production Economics, 56–57(1–3): 199–212. Hanninen, S., Rytkönen, J., 2006, Transportation of Liquid Bulk Chemicals in the Baltic Sea, Helsinki. IBC Code, 2006, International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk, Hazards of Liquid Chemicals, London [Chapter 1.2].
INTERTANKO, 2006, The Revision to MARPOL Annex II, A Practical Guide, London. Karimi, I.A., Srinivasan, R. and Por, L.H., 2002, Unlock supply chain improvements through effective logistics. Chem. Eng. Prog., 98(5): 32. Kunichkin, V., (2006). Chemical Tanker Notes. (Seamanship International, Lanarkshire). ISGOTT, 2006, International safety guide for oil tankers and terminals/International Chamber of Shipping, Oil Companies International Marine Forum, International Association of Ports and Harbors, Witherby, London. Saaty, T.L., 1977, Scaling method for priorities in hierarchical structures. Journal of Mathematical Psychology, 15(3): 234–281. Shinno, H., Yoshioka, H., Marpaung, S. and Hachiga, S., 2006, Quantitative SWOT analysis on global competitiveness of machine tool industry. Journal of Engineering Design, 17(3): 251–258. Super Decisions, 2008. The website for Super Decisions Software for Decision-making. http://www.superdecisions.com. Vaidya, S.O. and Kumar, S., 2006, Analytic hierarchy process: an overview of applications. European Journal of Operational Research, 169: 1–29.
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Quantitative evaluation of precautions on chemical tanker operations Ozcan Arslan ∗ Maritime Transportation and Management Engineering Department, ITU Maritime Faculty, 34940 Tuzla, Istanbul, Turkey
a b s t r a c t Large quantities of liquid chemicals are carried by chemical tankers all over seas. Chemical cargoes have different properties and chemical tankers are complex ships that are designed to carry different types of chemical cargoes. Carriage of chemical cargoes contains different hazards both for human life and marine environment. There are several cargo operations that are regularly done on chemical tankers such as loading, discharging, inerting, washing tanks, sampling, and freeing gas. These operations constitute their own risks. Therefore, risk assessment has become a critical issue in maritime industry. The present investigation of this study is attempting to examine the priorities of precautions that are taken by chemical tankers before, during, and after cargo operations. Analytic hierarchy process (AHP) is used for prioritizing the precautions in order to clarify the risk assesment option that will be used for proactive approach to prevent marine casualties. The main aim of this study is to identify an appropriate management tool to increase the level of safety for chemical tankers during cargo operations at a terminal by using the results of AHP application. © 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Keywords: Safety; Chemical tanker; Risk assessment; AHP; Maritime; Transportation
1.
Introduction
Large quantities of liquid chemicals are transported by tanker ships. There are several weaknesses and threats that are increasing risks of chemical cargo transportation by ships (Arslan and Er, 2008). Chemical cargoes have different properties, and many of them represent a health and safety hazard, which is a critical issue for the tanker industry (Karimi et al., 2002). Chemical tankers are under several risks that may occur during the loading, traveling, and unloading. Care should be taken to minimize this risk as far as practicable in each cargo handling case, based upon the best knowledge and technology on the construction and equipment of the ship and the properties of the cargoes that the ships intend to carry (Altuntas, 1997). Chemical tankers are complex vessels that are designed to carry different types of chemical cargoes. Some cargoes need heating, some need refrigerating/freezing, some must be kept under inert conditions, some need to be carried in stainless steel tanks, and some are flammable, explosive, or give off noxious vapor (Hanninen and Rytkönen, 2006).
∗
These properties require careful consideration during the cargo planning process and loading. Cargo loading plan verification needs to be made regarding the chemical ship type, tank coating compatibility, compatibility with other cargo, and the environmental controls required during transportation. In addition, the venting requirements, monitoring equipment, vapor detection, compatible fire protection medium, density limitations of the product in relation to the holding tank construction, and pumping requirements are important criteria for safe cargo handling and navigation of ship (INTERTANKO, 2006). In this study, analytic hierarchy process (AHP) method is used for identifying and prioritizing the safety and environmental precautions’ taxonomy that should be used by chemical tanker operations. Section 2 of this study describes the safety and environmental chemical liquid transportation hazards. Section 3 illustrates brief berthing and cargo operation procedures. Section 4 describes the AHP, Section 5 describes the AHP Application results and Section 6 illustrates the case applications.
Tel.: +90 505 713 47 54; fax: +90 216 395 45 00. E-mail address: [email protected]. Received 22 January 2008; Accepted 30 June 2008 0957-5820/$ – see front matter © 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.psep.2008.06.006
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2. Hazards associated with the transport of bulk chemicals
need different fire extinguishing knowledge for every chemical that will be carried by chemical tankers. (IBC Code, 2007).
2.1.
2.3.
Health hazards
Many chemicals irritate or toxic effect on the skin or on the mucous membranes of the eyes, nose, throat, and lungs in the gas or vapor state (Altuntas, 1997). Impacts of chemicals on health hazards are rated as following: • “0”: no likelihood of producing injury; • “1”: minimum hazard. These chemical threshold limits are above 500 ppm. • “2”: some hazard. These chemical threshold limits are 100–500 ppm. • “3”: moderately hazardous chemicals. These chemical threshold limits are 10–100 ppm • “4”: severely hazardous chemicals. These chemical threshold limits are below 10 ppm. Irritating vapors of chemical materials to the skin or the mucous membranes of the eyes, nose, throat, and lungs are rated as follows: • “0”: chemicals that are non-volatile. • “1”: chemicals that cause a slight smarting of the eyes in cases of high concentration. • “2”: chemicals that cause moderate irritation. • “3”: chemicals that are moderately irritating or volatile. • “4” chemicals that are severe eye or throat irritants, vapors that are capable of coursing eye or lung injury and that cannot be tolerated even at low concentrations. (ISGOTT, 2006).
2.1.1.
Odour threshold
The odour of a potentially dangerous vapor may be hidden by another odour. In addition, a certain vapor is likely to produce olfactory fatigue, which is a deadening of the sense of smell. For these reasons, the sense of smell alone is not a reliable indicator of the presence or absence of a dangerous vapor. The smallest concentration is expressed in parts per million by volume in air and is not an absolute value. It will vary between individuals and will vary from day to day for any person (Kunichkin, 2006).
2.1.2.
Lethal dose: LD50 and LC50
LD50 is a statistical estimate of the dosage necessary to kill 50% of people over 10 months with in 48 h. It is usually expressed in terms of the weight of poison per unit of body weight, most often as mg of chemical/kg of animal (mg/kg). The concentration of about 60 times LD50 is lethal to a person. LC50 is a concentration that, within 40 h is likely to kill 50% of the test animal species. It is usually expressed as ml or mg of chemical gas of vapor/kg of animal (ml/kg or mg/kg) or ppm. The values of LD50 and LC50 are a means of measuring the lethal dose and judging the conditions. Thus, these values are substantially different from the TLV values in the purpose for using (IBC Code, 2006).
2.2.
Fire hazards
Flashpoint, boiling point, flammability limit, and autoignition temperature vary between different liquid chemicals, which therefore have different fire characteristics. Thus, carriers
Pollution hazards
Water pollution hazards are defined in terms of human toxicity, water solubility, volatility, odor or taste, and relative density. The air pollution hazards of chemicals are defined by the emergency exposure limit (EEL), vapor pressure, solubility in water, relative density of liquid, and vapor density. The reactivity hazard of a chemical is defined by reactivity with other products including water and with the product itself (including polymerization). Marine pollution hazards are defined by bioaccumulation with attendant risk to aquatic life, tainting of seafood, damage to living resources, and hazard to human health (IBC Code, 2007).
3. Berthing and cargo operation procedures for chemical tankers 3.1.
Exchange of information before berthing
Before the tanker ship arrives at a berth or a terminal, in addition to any advice on cargo to be loaded or discharged, it is recommended that prior information that could affect the safety of the ship and terminal should be exchanged between terminal and ship. Information should be given from ship to terminal, such as the ship’s draft and trim at arrival; specific characteristics of the cargo any tank; valve or pipeline leaks on the ship that could affect loading or unloading, or cause pollution; necessary repairs (if any) about ship that would cause the commencement of loading or unloading to be late; the standards of size and bolt hole on the flanges at the manifold connections; the standards of size and bolt hole on the flanges at the vapor return line. Using certain information is essential, such as availability of mooring equipment, details of any mooring plan and of any code of visual or audible signals for use during mooring; knowledge about ship’s derrick, depth of water at berth and meteorological information (ISGOTT, 2006).
3.2.
Agreement between ship and terminal
In order to maintain safe and secure cargo operation, a loading plan should be agreed on by the ship’s officer and terminal representative, including the arrangement and capacity of the ship’s cargo line; venting system; shore’s cargo line and the maximum allowable pressure of the ship/shore hoses or loading arms to be used during operation; loading rate and pressure; loading procedures; necessary precautions to avoid static ignitions; atmospheric conditions; ullaging method; system of cargo vapor return to shore installation; overflow control information. (ISGOTT, 2006).
3.3.
Safety precautions and emergency procedures
After berthing, the ship’s officer should contact the terminal representative to provide the information on local safety regulations, to agree on designated smoking spaces, to agree on galley fire and cooking appliance limitations, to advise “Work Permit” and “Hot Work Permit” procedures, and to present and discuss ‘Ship/Shore Safety Check List’ that is identified in Section 5 of this study. After berthing, the ship’s officer and the responsible terminal representative should agree on action to be taken in case fire. Also, these persons should
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agree on a signal system that is indicating “Standby”, “Start loading” or “Start unloading”, “Slow down”, “Stop loading” or “Stop unloading”, “Emergency stop”, and any other necessary signals. (ISGOTT, 2006).
4.
Method used in this study
This section of this study attempted to examine the priorities of precautions that are taken by chemical tankers before, during, and after cargo operations. For this purpose, AHP is used for prioritizing the precautions. The AHP is one of the mathematical methods for analyzing complex decision problems with multiple criteria, and it can deal with qualitative attributes as well as quantitative. It is developed by Saaty (1977). By utilizing the AHP, factors can be weighted and rated quantitatively. AHP is used in many fields, such as planning; selecting the best alternative; resolving conflicts; optimization problems with other techniques, such as linear programming, fuzzy logic, quality function deployment. (Vaidya and Kumar, 2006). Brad used AHP in 1986 as a multi-objective methodology for selecting sub-system automation options (Brad, 1986). Braglia used AHP for analyzing multi-attribute failure mode analysis (Braglia, 2000), and Ceha and Ohta used AHP for evaluating of air transportation network (Ceha and Ohta, 1994). Cheng applied AHP with fuzzy approach for evaluating naval tactical missile systems (Cheng, 1997), and Ghodsypour and Brien applied AHP with linear programming for supplier selection problem (Ghodsypour and Brien, 1998). This study illustrates the pair-wise comparisons are carried out within precautions that can be taken by chemical tanker ships by the master and chief officer who are experienced on chemical tankers more than 5 years, operation manager and safety manager of chemical tanker companies. The comparison making group is consisting with five Unlimited Master and three Chief Officer whom are experinced on chemical tankers; four Operation Manager and three Safety Manager of chemical tanker managing company whom have 5 years experience as well. The comparison scale vary from 1 to 9; 1/1 indicates equal intensity, while 9/1 indicates extreme or absolute intensity. The pair-wise comparison scale is indicated in Table 1. In the pair-wise comparisons, the estimated intensities or priorities can be obtained using the pair-wise comparison matrix as the input of the principal eigenvalue method (Shinno et al., 2006). The intention of this study is to develop strategy action plan for ships, ship operators, ship management companies, and seafarers through AHP with a view to make safer cargo operations at terminals in order to prevent the re-occurrence of marine casualties.
5.
Table 1 – Pair-wise comparison scale Intensity of importance
Definition
1
Equal importance
3
Moderate importance of one over another
5
Essential or strong importance
7
Very strong importance
9
Extreme importance
2, 4, 6, 8
Intermediate values between the two adjacent judgments
Explanation Two activities contribute equally to the objective Experience and judgment strongly favor one activity over another Experience and judgment strongly favor one activity over another An activity is strongly favored and its dominance demonstrated in practice The evidence favoring one activity over another is of tile highest possible order of affirmation When compromise is needed
P1-2 Are emergency towing wires correctly positioned? P1-3 Is there safe access between ship and shore? P1-4 Is the ship ready to move under its own power? P2 Personal and procedural precautions: P2-1 Is there an effective deck watch in attendance on board and adequate supervision on the terminal and on the ship?
Obtained results and considerations
In this study, precautions that should be taken by all chemical tankers were observed from the established ship/shore checklist that is listed below in terms of clusters (ISGOTT, 2006). Then the factors are clustered in hierarchical structure as shown in Fig. 1.
5.1.
Hierarchical structure of precautions
P1 Berthing-related precautions: P1-1 Is the ship securely moored?
Fig. 1 – Hierarchical structure of precautions.
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Fig. 2 – Pair-wise comparison of precautions. P2-2 Is the agreed ship/shore communication system operative? P2-3 Has the emergency signal to be used by the ship and shore been explained and understood? P2-4 Have the procedures for cargo, bunker, and ballast handling been agreed? P2-5 Have the hazards associated with toxic substances in the cargo being handled been identified and understood? P2-6 Has there been agreement regarding the emergency shutdown procedure? P3 Equipment-related precautions on deck:
P3-1 Are scuppers effectively plugged and drip trays in position, both on board and ashore? P3-2 Are unused cargo and bunker connections properly secured with blank flanges bolted? P3-3 Are sea and overboard discharge valves, when not in use, closed and visibly secured? P3-4 Are all cargo and bunker tank lids closed? P3-5 Has the operation of the P/V valves and high velocity vents been verified using the check lift facility, where fitted? P3-6 Are hand torches of an approved type? P3-7 Are portable VHF/UHF transceivers approved type?
Fig. 3 – Pair-wise comparison scale in verbal.
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P3-8 Are deck seals in good working order? P4 Precautions out of deck: P4-1 Are the ship’s main radio transmitter aerials earthed and radars switched off? P4-2 Are electric cables to portable electrical equipment disconnected from power? P4-3 Are all external doors and ports in the accommodation closed? P4-4 Are window-type air conditioning units disconnected? P4-5 Are air conditioning intakes that may permit the entry of cargo vapors closed? P5 Precautions about probable emergency situations: P5-1 Is there provision for an emergency escape? P5-2 Are all persons in charge of cargo operations aware that discharge operations should cease and that the terminal should be advised in the case of failure of the inert gas plant? P5-3 Are sufficient personnel on board and ashore to deal with an emergency? P5-4 Are ship emergency fire control plans located externally? P5-5 Are fire hoses and fire-fighting equipment on board and ashore positioned and ready for immediate use? P6 Procedural precautions during operation: P6-1 Are smoking regulations being observed? P6-2 Are naked light regulations being observed? P6-3 Have measures been taken to ensure sufficient pump room ventilation? P6-4 If the ship is capable of closed loading, has there been agreement on the requirements for closed operations? P6-5 If a vapor return line is connected, has there been agreement on operating parameters? P7 Condition of cargo system equipment: P7-1 Are cargo and bunker hoses/arms in good condition, properly rigged, and appropriate for the service intended? P7-2 Is the appropriate tank venting system being used? P7-3 Has a vapor return line been connected? P7-4 Is the Inert Gas System fully operational and in a good working order? P7-5 Have the fixed and portable oxygen analyzers been calibrated, and are they working properly? P7-6 Are fixed IG pressure and oxygen content recorders working? P7-7 Are all cargo tank atmospheres at positive pressure with an oxygen content of 8% or less by volume? P7-8 Are liquid levels in P/V breakers correct?
The hierarchical structure has consisted of four clusters. The main cluster is the body of ship/shore check list; the second cluster consists of the precaution groups; third group which indicates sub items, is derived from a check list of requirements; the last cluster is shows the personal and environmental precautions’ weightings.
5.2.
Application of method and results
Pair-wise comparisons have beem done among each precaution as shown in Fig. 2. ‘Super Decisions’ software (www.superdecisions.com) was used for computing the priority of precautions (Super Decisions, 2008).
Table 2 – Priorities of precautions P1 P1-2 P1-3 P1-4
0.26828 0.01828 0.05430 0.04606
P2 P2-1 P2-2 P2-3 P2-4 P2-5 P2-6
0.19900 0.08771 0.02012 0.00916 0.02449 0.04711 0.01041
P3 P3-1 P3-2 P3-3 P3-4 P3-5 P3-6 P3-7 P3-8
0.12390 0.00980 0.01057 0.00843 0.01436 0.02794 0.01455 0.02421 0.01406
P4 P4-1 P4-2 P4-3 P4-4 P4-5
0.04977 0.00565 0.01296 0.01190 0.00649 0.01278
P5 P5-1 P5-2 P5-3 P5-4 P5-5
0.07029 0.01052 0.00552 0.03749 0.00447 0.01228
P6 P6-1 P6-2 P6-3 P6-4 P6-5
0.09661 0.02002 0.01866 0.02208 0.01972 0.01613
P7 P7-1 P7-2 P7-3 P7-4 P7-5 P7-6 P7-7 P7-8
0.19215 0.05880 0.02171 0.01751 0.01930 0.01841 0.01601 0.02371 0.01668
Environmental Personal
0.45442 0.54558
Scale, which is indicated in Table 1, is used to make pair-wise comparison between alternatives and the simple intensity of importance illustration is mentioned in Fig. 3. The results of AHP computation is summarized in Table 2. According to the results of berthing-related precautions, personal and procedural precautions, and checks about condition of cargo system equipment are more important criteria that will mitigate potential risks during cargo handling. Therefore, the weighting of second cluster in respect to the third cluster is shown in Fig. 4. Similarly the weighting of the third cluster is shown in Fig. 5. According to the results, the following items are proposed. Securely mooring of the ship is the most important precaution to mitigate risks at the terminal. Maintaining effective deck watchkeeping and understanding the potential
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5.3.
Fig. 4 – Percentage of precaution groups’ priorities.
Fig. 5 – Priorities of precautions. hazards about carried cargo are the two important precautions among personal and procedural precautions. Providing enough personal precautions both on board and at the terminal in case any emergency situation, keeping cargo and bunker hoses/arms in good and appropriate condition, and properly rigging them are other important precautions to mitigate potential risks during cargo operations. Fig. 6 indicates the overall analyzed results of precautions’ weighting rates in regard to the percentage that the precaution is related with personal safety and environmental protection. According to the results, precautions that are taken by chemical tanker ship and the terminal are related to more personal safety in the means of occupational health and safety than environmental awareness.
Fig. 6 – Percentage of environmental and personal precautions.
Practical strategies for risk mitigation
Taking into account the AHP computation results mentioned in the previous subsection this study, the following practical results are suggested. The human-related precautions weightings are more than equipment-related precautions. This result directly signifies the importance of the human factor engineering including ergonomics. Consequently, the precautions that are offered in this study will directly focus on how knowledge and skills of officers and crew members should be developed. In advance, situational awareness is the key factor to breaking the error-fault chain, so crew members should share their knowledge, skill, and awareness with all. Workloads of chemical tanker crews are more than those of any other ships, so an adequate number of qualified officer and a rating should be employed on board. Efficient workload management is extremely important on chemical tankers because fatigue is responsible for many human errors. The ergonomic aspects should be taken into account while designing pipelines, pumps, pump rooms, loading/discharging units, and onboard accommodation places. Equipping chemical tankers with fully automated loading and unloading systems and monitoring systems will have an efficient risk reducing strategy.
6.
Case study and results
6.1.
Case-1: fire at manifold area
A “flash” fire aboard a chemical tanker happened after finishing discharge operation at cargo manifold connection area resulting in two injuries. The incident occurred at 11:15 a.m. and the ship was due to sail that day. A flash fire occurred at the vessel’s manifold area while shore and ship staff were disconnecting cargo arms. As a result, two crew were injured. At about 11:15 a.m. there was a sudden ignition at the manifold area. This ignition produced a flash fire. There was an immediate response to the alarm by the ship’s crew. and the fire was extinguished in few minutes. Thus, the fire was caused by the ignition of spilled oil that sparked used equipment from manifold connection area. A contributory factor of the incident could have been the incorrect fitting of the coupling and using unsuitable equipment.
6.2.
Case-2: entering unsafe cargo tank
After a chemical tanker discharged the cargo cyclohexane that was waiting for a pilot, the chief officer entered the cargo tank
Fig. 7 – Comparison between general results and case studies.
process safety and environmental protection 8 7 ( 2 0 0 9 ) 113–120
for controlling purpose under the supervision of pumpman of the ship. When the pumpman saw that the chief officer had fallen into the cargo tank, he informed other crew on board and immediately entered into the cargo tank. The chief officer and the pumpman were taken from the cargo tank, but they died at hospital. It was understood that the nitrogen in cargo tank was coming from a vapor return line that connected with the vessel and remained in the tanks as blanketing. After examination, it was determined that the victims did not realize that they had breathed nitrogen (Arslan and Er, 2008).
Table 3 – Obtained Results from Cases General
Case-1
Case-2
P1 P1-1 P1-2 P1-3 P1-4
0.26828 0.14964 0.01828 0.05430 0.04606
0.03224 0.01623 0.00242 0.01232 0.00127
0.00000 0.00000 0.00000 0.00000 0.00000
P2 P2-1 P2-2 P2-3 P2-4 P2-5 P2-6
0.19900 0.08771 0.02012 0.00916 0.02449 0.04711 0.01041
0.21360 0.04324 0.06243 0.00310 0.00920 0.09332 0.00231
0.16320 0.04362 0.01624 0.00640 0.03232 0.06400 0.00062
P3 P3-1 P3-2 P3-3 P3-4 P3-5 P3-6 P3-7 P3-8
0.12390 0.00980 0.01057 0.00843 0.01436 0.02794 0.01455 0.02421 0.01406
0.25018 0.01604 0.08132 0.02836 0.10892 0.00883 0.00326 0.00225 0.00120
0.08862 0.00460 0.03136 0.01640 0.02160 0.00164 0.00240 0.00198 0.00864
P4 P4-1 P4-2 P4-3 P4-4 P4-5
0.04977 0.00565 0.01296 0.01190 0.00649 0.01278
0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
P5 P5-1 P5-2 P5-3 P5-4 P5-5
0.07029 0.01052 0.00552 0.03749 0.00447 0.01228
0.08225 0.00112 0.00112 0.03264 0.00525 0.04212
0.14232 0.01024 0.04215 0.08024 0.00720 0.00249
P6 P6-1 P6-2 P6-3 P6-4 P6-5
0.09661 0.02002 0.01866 0.02208 0.01972 0.01613
0.16146 0.04240 0.08548 0.01032 0.00966 0.01360
0.18262 0.00357 0.00640 0.01624 0.10360 0.05281
P7 P7-1 P7-2 P7-3 P7-4 P7-5 P7-6 P7-7 P7-8
0.19215 0.05880 0.02171 0.01751 0.01930 0.01841 0.01601 0.02371 0.01668
0.27027 0.14984 0.06265 0.03232 0.01454 0.00630 0.00210 0.00162 0.00090
0.42324 0.12601 0.10360 0.08667 0.07270 0.02484 0.00628 0.00232 0.00082
Environmental Personal
0.45442 0.54558
0.24325 0.75675
0.11250 0.88750
6.3.
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Results of AHP application
Pair-wise comparisons have been done among each precaution that should be taken before each case that is described in Section 5 of this study. ‘Super Decisions’ software (www.superdecisions.com) was used for computing the priority of precautions and the following results were obtained (Fig. 7 and Table 3).
7.
Conclusion
It is clear that the hazards associated with the carriage of liquid chemicals in tankers are more complex and dangerous when compared to other types of ships. Due to the nature of transportation, operation of tankers is more complex than the operation of other ship types; therefore, working on a tanker requires extra knowledge, skills, and precautions. The operation of chemical tankers causes more incidents and accidents when compared to other types of ships as a direct result of the behavior of the chemicals being carried. The aim of this study is directly concerned with the utilizing analytic hierarchy process identification to show the importance of precautions on reducing casualties during cargo operations that have not been used in the risk mitigation approach yet. Therefore, the originality of this research appears in the following manner. Potential risks should be identified with observing the frequencies of incidents and with observing the consequences in case the accident/incident happens. After observing the frequencies and consequences, the risk can be monitored. In maritime industry, accidents and incidents are generally the results of error-fault chains, and many times it is difficult to identify the frequencies of accidents and incidents because of secrecy and inadequate history records. Accidents and incidents occur in the maritime industry in spite of the latest navigational technologies and strict precautions. This study proposes that the use of the AHP method is an acceptable basis for analyzing the precautions that are developed to guard against to potential dangers during chemical cargo operations for observing the frequencies and consequences. Therefore, an appropriate management tool can be considered to increase the level of safety for chemical tankers during cargo operations at a terminal by using the results of AHP application. Then, strategy making could be designed to minimize accidents, incidents, and defects for shipboard operations. Well-operated cargo operations enable a chemical tanker ship safer and more profitable. It is clear that if the importance of precautions is understood well, the safety of the working environment will be improved for both occupational health and safety and environmental protection.
Acknowledgement The author gratefully acknowledges supports and data that is given Sener Petrol Maritime Company during preparation of this study.
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