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USING RISK MATRIX AS AN INHERENT RISK TOOL AT PRELIMINARY DESIGN STAGE FOR INHERENTLY

SAFER DESIGN

Dzulkarnain Zaini, Universiti Teknologi PETRONAS

31750 Tronoh Perak Malaysia E-mail address: coltvr4@gmail.com

AP Dr Azmi Mohd Shariff,

Universiti Teknologi PETRONAS 31750 Tronoh Perak Malaysia

E-mail address: azmish@petronas.com.my

Abstract - Safety should be considered and addressed in the whole life cycle of a process system or facility. They are many established methodologies to identify, analyze, prioritize and manage risks arising from different stages. One of the design methodologies to reduce and eliminate root causes of hazards during design stage is known as Inherent Safety (IS). The principles to defining IS were formalized by Prof. Trover Kletz and were further developed into guidelines that are more definitive by a number of researchers. An inherently safer process plant could be designed if the information on risk levels, likelihood and severity could be known earlier at the preliminary design stage. The risk levels, likelihood and severity could be reduced or eliminated by applying the principle of inherent safety in the design. However, process designers normally lack of information on risk levels, likelihood and severity from process plant during preliminary design stage. This information is available once Quantitative Risk assessment (QRA) study is completed at the end of detail design stage prior to plant construction as required by law. Therefore, this research aims to overcome this problem by developing an inherent risk tool that can determine the risk levels, likelihood and severity early in the preliminary process design stage and at the same time to provide the opportunity for process designers to apply inherent safety principles for inherently safer process design.

Keywords: inherent risk, inherent safety, preliminary design, risk matrix.

I. INTRODUCTION AND BACKGROUND

A hazard is any unsafe condition or potential

source of an undesirable event with potential for harm or damage [1][2]. Inherent safety is one of the concepts to reduce or eliminate the root causes of the hazards rather than to control it by modifying the process design such as raw materials, unit operations and operating conditions. These principles aim to reduce or eliminate hazards by modifying the design (using different chemicals, hardware, controls and operating conditions) of the plants itself. Plants that apply inherently safer design concepts are believed to be simpler in design, easier, more friendly to operate and more tolerant of errors [3].

The inherent safety application in process plant design can lead to improve safety and lower capital and operating costs [4][5][6]. Khan and Amyotte [7] replicated similar findings in their works, which stated that considering the lifetime costs of a process and its operation, an inherently safer approach is a cost-optimal option. This is further validated by their work showing that inherent safety can be integrated at any stage of design and operation. However, its application at the earliest possible phase of process design (i.e process selection and conceptual design) gives in the best result [8][9][10]. In term of cost, any re-design done after the detailed design stage of the process life cycle would be very expensive compared to the alteration in the early stage (i.e. during conceptual design stage) [11]. Overton and King of Dow Chemical Company [12] proved several examples on the application of inherently safer design concept that result in lower capital cost, lower operating costs, greater reliability and faster start times for a new and existing plant. Referring to Crawley [13] and Warwick [14], the largest recompenses are attained by applying the inherent safety principle in the preliminary process and engineering design stages. Inherently safer options are also economically and technically practicable for operation stage of the plant life cycle [15].

From the technical point of review, the extent of the risks and the effects, of risk reducing measures can be quantified in a quantitative risk assessment (QRA). In order to estimate risk, QRA has gained a wide acceptance as a powerful tool to identify and assess the significant sources of risk and evaluate alternative risk control measures in the chemical process. However, conventional Quantitative Risk Assessment (QRA) as shown in Figure 1 is applied after a detailed engineering design has been completed when Process & Instrumentation Diagram (P&ID) is fully available. It has been observed that by the time QRA is carried out, much of the design work has been completed. For example, equipment layout has been determined and to a large extent, some already have the operating philosophy been set. At this juncture, one of the most common methods to mitigate risk and its consequences is by means of adding protection devices such as instrumented protective functions or mechanical protection devices such as relief valves, etc. These protective measures which are added late in the design often require regular preventive maintenance to detect revealed failures. The preventive maintenance throughout the life of the plant, adds to the operating cost as well as necessitating repetitive training and documentation

upkeep. The lifetime preventive maintenance coupled with good plant operation and management could prevent catastrophic events. Even though the added protective functions can reduce the risk, the hazards still exist. [16]

In order to detect hazards proactively in the preliminary design stage and to allow for the opportunity to proactively reduce their magnitude or likelihood of occurrence, this work proposes an evolution of technique to evaluate inherent risk. This technique is possible by utilizing the integrated risk matrix quantification tool with process design simulator. With the integration, process design engineers can assess the risk which is inherent to their design from the beginning of the design stage. This technique is named as inherent risk matrix evaluation (IRME) which is an evolution from inherent risk assessment (IRA) [16] (see Figure 2 and 3) as an alternative to conventional QRA that will be discussed in the next chapter.

Figure 1: Quantitative Risk Assessment (QRA)

II. METHODOLOGY

There is a need to develop a framework for the best possible integration of preliminary risk at preliminary process design stage. Recently, Shariff and Zaini [17] have proposed a framework to integrate the consequence analysis with process design simulator in preliminary design stage. They developed a prototype tool know as toxic release consequence analysis tool (TORCAT), which use iCON process simulation engine to provide process information to consequence analysis model in a Excel spreadsheet. They have showed that the toxic release consequence estimation can be easily done in the preliminary design stage to produce inherently safer design with TORCAT. Nevertheless, there was no evidence to show that TORCAT

Figure 2: Inherent Risk Assessment (IRA)

Likelihood

of Occurrence

Severity

Catastrophic Critical Marginal Negligible

Frequent

Probable

Occasional

Remote

Improbable

Figure 3: Inherent Risk Matrix Evaluation (IRME)

is capable to quantify risk at preliminary design stage since they only presented the case studies limited to consequence due to toxic release. The challenge of the current work is to address these shortcomings by integrating an inherent safety quantification system with risk calculations for inherently safer design options focus on the application at preliminary design stage.

Thus, a new alternative framework is proposed in order to address this issue as given by a block diagram in Figure 4. The present framework consists of 3 major components, i.e TORCAT [17], Integrated Probability Estimation Module (IPEM) [18] and Inherent Risk Matrix. These components are linked with iCON process design simulator for fast data transfer. The models used for all three components are developed in Microsoft Excel spreadsheet. The Visual Basic Application (VBA) available in the Microsoft Excel is used for the development of user interface between the program and the users. Information from the iCON process design simulator is linked with the integrated risk assessment model in Microsoft Excel through an interface that is developed using object, linking and embedded (OLE) automation.

The risk unacceptable zone

The risk acceptable zone

Figure 4: Framework of Inherent Risk Matrix Tool

III. RESULTS AND DISCUSSION In this chapter, as soon as the hazards have been

acknowledged, it is very significant to note that likelihood and severity consequence estimates should be considered and performed very well by experienced process engineer [1] to conduct a risk assessment which is according to relation Risk = Severity x Likelihood [22]. Therefore, it has been developed based on evolution of IRA [16] and modification from Department of Occupational Safety and Health (DOSH) Malaysia [19] risk matrix, the work from Markowski [20] and MIL-STD-882C [21] as shown in Figure 3. Eventually, the result and framework given in Figure 3 and 4 are currently under the development stage or underway.

CONCLUSION

This paper proposed an evolution of concept to

quantify risk which is inherent to the process plant at preliminary in design stage. It is done by using a risk matrix as an alternative that can determine the risk levels in

preliminary process design stage and the same time to provide the opportunity for process designers to apply inherent safety principles for inherently safer process design at preliminary design stage which is economically and technically practicable for the process plant life cycle as well. This concept would also provide the industries a relatively simpler methodology that readily integrated with process design simulator to quantify levels of inherent safety.

ACKNOWLEDGEMENT

The authors would like to thank Ministry of Science, Technology and Innovation (MOSTI), Malaysia for providing e-Science Fund 03-02-02-SF0050 for this project. By the meantime, a part of this work has been accepted for publication in Hazardous Material Journal (HAZMAT) Elsevier.

A.M.Shariff, D.Zaini, Toxic release consequence analysis tool (TORCAT) for inherently safer design plant,J.Hazard.Mater.(2010),doi:10.1016/j.hazmat.2010.06.06

REFERENCES

[1] Reniers, G. L. L., Dullaert, W., Ale, B. J. M., & Soudan, K., Developing an external domino prevention framework: Hazwim. Journal of Loss Prevention in the Process Industries, 18, 172-138, Elsevier, 2005 [2] The use of current risk analysis tools evaluated towards preventing external domino accidents, Journal of Loss Prevention in the Process Industries, 18, 769-773, Elsevier, 2005 [3] R. Rusli, A. Mohd Shariff, Qualitative assessment for inherently safer design (QAISD) at preliminary design stage, Journal of Loss Prevention in the Process Industries 22, 1-9, Elsevier, 2009 [4] C.T. Leong, A.M. Shariff, Process Route Index (PRI) to assess level of explosiveness for inherent safety quantification, Journal of Loss Prevention in the Process Industries 22, 216-221, Elsevier, 2009 [5] Leong, C.T., Shariff, A.M., Inherent Safety Index Module (ISIM) to assess inherent safety level during preliminary design stage, Process Safety and Environmental Protection, 86(2). 113-119, Elsevier, 2008 [6] Shariff, A. M., Rusli, R., Chan, T.L., Radhakrishnan, V.R., & Buang, A., Inherent safety tool for explosion consequence study. Journal of Loss Prevention in the Process Industries, 19/5, 409-418, Elsevier, 2005 [7] F.I. Khan, P.R Amyotte, Inherent safety in offshore oil and gas activities : a review of the present status and future directions, Journal of Loss Prevention in the Process Industries 15, 279-289, Elsevier, 2002 [8] Hassim, M.H., Hurme, M., Inherent occupational health assessment during process research and development stage,

Ye

iCON Process Simulator

NO

TORCAT This tool

estimates consequence of undesired toxic release event

IPEM This tool calculates

the probability of the undesired event

happening based on established database

iCON – MS Excel Interface Using object linking and

embedding (OLE) codes from MS Excel VBA to link the process simulator for data transfer and

analyse in spreadsheet

Input from User

Modification based on

Inherent Safety principle

Inherent Risk Matrix

This tool evaluates the inherent risk

level.

Risk Acceptable?

User proceed with design

YES

Journal of Loss Prevention in the Process Industries 23 (1), 127-138, Elsevier, 2010 [9] Hassim, M.H., Hurme, M., Inherent occupational health assessment during preliminary design stage, Journal of Loss Prevention in the Process Industries 23 (3), 476-482, Elsevier, 2010 [10] Hassim, M.H., Hurme, M., Inherent occupational health assessment during basic engineering stage, Journal of Loss Prevention in the Process Industries 23 (2), 260-268, Elsevier, 2010 [11] Gupta, J.P., & Edwards, D. W., A simple graphical method for measurement of inherent safety, Journal of Hazardous Materials, 104(1), 15-30, Elsevier, 2003 [12] T. Overton, G.M. King, Inherently safer technology: an Evolutionary approach, Process Safety Progress 25 (2) 116-119, American Institute of Chemical Engineers/Wiley Inter Science, 2006 [13] P. Crawley, Offshore Loss prevention, The Chemical Engineer (July), 23-25, 2005 [14] A.R. Warwick, Inherent safety design of floating production, storage and offloading vessels (FPSOs), in: Proceedings of Off-shore Mechanics and Artic Engineering Conference, Lisbon, Portugal, 1998 [15] G.I.J.M Zwetsloot, N. Askounes Ashford, in : A. Amendola, D. Wilkinson (Eds.), Encouraging Inherently safer production in European firms : a report from the field [Special Issue], Risk assessment and environmental decision making, Journal of Hazardous Materials, 78,1-3, pp. 123-144, Elsevier, 1999 [16] A.M. Shariff, C.T. Leong, Inherent Risk Assessment (IRA) – new concept to evaluate risk in preliminary design stage, Process Safety and Environmental Protection, Elsevier, doi : 10. 1016/j.psep.2009.08.004 [17] Shariff, A.M., Zaini, D., Toxic release consequence analysis tool (TORCAT) for inherently safer design plant, Journal of Hazardous Materials 182, 394-402, Elsevier, 2010 [18] Hussan, N.A., Shariff, A.M., Fault Tree Analysis Using Microsoft Excel: A Case Study of Offshore Compression Platform, Hazardous Area Conference – IDC Technologies, 2008 [19] Jamil, M., Integrating risk-based inspection into the oil & gas industry: authority's perception & roles, Prepared for the Department of Occupational Safety & Health, Malaysia, 2009 [20] Markowski, A.S., exLOPA for explosion risk assessment, Journal of Hazardous Materials 142, 669-676, Elsevier, 2007 [21] US Department of Defense, System Safety Program Requirement, DC US Department of Defense, MIL-STD-882C

[22] Woodruff, J.M., Consequence and likelihood in risk estimation: A matter of balance in UK health and safety risk assessment practice, Safety Science 43, 345-353, Elsevier, 2005

AUTHOR BIOGRAPHIES

AP Dr Azmi M Shariff is an Assoc. Professor in Chemical Engineering Department of UTP. He received a Doctoral Degree from Leeds in UK in 1995. He has experienced in conducting QRA for oil and gas related companies. He is also an invited technical committee member of Environmental

Impact Assessment for Department of Environment, Perak. He can be reached at azmish@petronas.com.my

Dzulkarnain Zaini is a Research Officer in Chemical Engineering Department of UTP. Currently he is completing his PhD in Chemical Engineering Process Safety at Universiti Teknologi Petronas and he is an Associate Member of IChemE UK. He can be reached at coltvr4@gmail.com