Journal of Loss Prevention in the Process Industries 48 (2017) 41e47
Contents lists available at ScienceDirect
Journal of Loss Prevention in the Process Industries
journal homepage: www.elsevier.com/locate/jlp
An improved layer of protection analysis based on a cloud model:
Methodology and case study
Fang Yan a, Kaili Xu a, *, Zhikai Cui b, Xiwen Yao a
a
School of Resources and Civil Engineering, Northeastern University, Shenyang 110819, PR China
b
Jacobs Schools of Engineering, University of California, San Diego, CA 92093, USA
a r t i c l e i n f o a b s t r a c t
Article history: The LOPA is a semi-quantitative assessment method. If the assessment of risk is not precise, then a
Received 4 February 2017 reasonable assessment may not be made. Human factors affect assessment results because expert
Accepted 5 April 2017 judgments are involved in the LOPA assessment. This paper proposes an improved layer of protection
Available online 8 April 2017
analysis (LOPA) called the cloud model layer of protection analysis (CM-LOPA). A cloud model (CM) is
used to improve the LOPA. Expert judged risk is processed by the CM, the quantified risk is presented as
Keywords:
the cloud model risk (CMR), and the algorithm of the CMR is developed. A case study of gas leakage in a
Layer of protection analysis
biomass gasification station is developed based on the CM-LOPA. A risk-matrix-based LOPA is introduced
Cloud model
Risk
and compared with the proposed method. Assessment and comparison results show that the random-
Randomness ness and fuzziness of the CM make assessment results obtained by CM-LOPA more precise and
Fuzziness reasonable.
Normal cloud © 2017 Elsevier Ltd. All rights reserved.
1. Introduction industry as well. According to Khalil's study (Khalil et al., 2012),
industrial accidents in the natural gas industry can be prevented or
Risk analysis and assessment are useful in risk control and risk limited by the adoption of LOPA. LOPA can also be used to identify
management of plants that have large quantities of hazardous scenarios relating to dust explosion accidents (Weirick and
materials (Ramirez-Marengo et al., 2013). Risk analysis and Manjunath, 2009); potential hazardous dust explosion scenarios
assessment are divided into qualitative and quantitative methods. can be identified by a five-part methodology based on LOPA. Better
Quantitative methods focus on the calculation of numerical prob- preparation can be made for protection of people and property.
abilities of possible consequences, while qualitative methods LOPA can also be applied in the chemical industry (Tong et al.,
concentrate on the determination of severity (Rausand, 2011). 2016), offshore industry (Chang et al., 2015), quantification of hu-
Various methods are involved in risk analysis; they include fault man error (Schmidt, 2014), etc. Various kinds of improved LOPA
tree analysis (FTA), event tree analysis (ETA), Bayesian network have been proposed. Torres-Echeverria adopted a LOPA associated
(BN), set pair analysis (SPA; Guo et al., 2014), hazard and operability with risk graphs to determine the safety integrity level (SIL; Torres-
analysis (HAZOP), failure model effect criticality analysis (FMECA), Echeverria, 2016). A more detailed and objective consideration of
probabilistic risk assessment (PRA) and layer of protection analysis protection layers can be made in the decision-making process.
(LOPA). Because LOPA is a simple and effective method for risk Ramirez-Marengo improved computational use of a LOPA by pro-
analysis and assessment (Jin et al., 2016), it is widely used in risk posing a mixed integer nonlinear programming (MINLP) model
analysis and assessment for hazardous plants. Yun took advantage (Ramirez-Marengo et al., 2013), thus using the proposed model to
of LOPA to develop risk assessment for the LNG industry (Yun et al., optimize risk reduction during the LOPA process. The LOPA can also
2009). In their study, the potential risks of LNG terminals were be integrated with other assessment methods. In Cui's study (Cui
estimated by LOPA so that effective safety protections could be et al., 2012), the LOPA was integrated with HAZOP, safety require-
installed. LOPA can be used in risk assessment of the natural gas ment specification (SRS), and SIL by an intelligent software plat-
form named HASILT so that information loss was reduced. Because
the LOPA is a semi-quantitative method (Jin et al., 2016), the
research trends are aimed at quantification of the LOPA. The
* Corresponding author.
theoretical basis of quantification of the LOPA was analyzed in Jin's
E-mail address: kaili_xu_neu@126.com (K. Xu).
http://dx.doi.org/10.1016/j.jlp.2017.04.006
0950-4230/© 2017 Elsevier Ltd. All rights reserved.
