Expert System for LOPA - Incident Scenario Development -

Transcription

1 Expert System for LOPA - Incident Scenario Development - Adam Markowski a, Jaffee Suardin b, and M.Sam Mannan b a Process and Ecological Safety Division, Technical University of Lodz, Poland b Mary Kay O Connor Process Safety Center (MKOPSC), Texas A&M University 2006 MKOPSC International Symposium Oct 25th, 2006

2 Agenda Background Objective Definition: LOPA and Expert System LOPA Expert System Demo Q&A

3 Incident Scenario Unplanned event or sequence of events that results in undesired consequences

4 Background Incident scenario development: Most critical element in LOPA Unique for variety of processes and equipment Complex (Initiating event consequences) thus leads to inconsistency Usually done by PHA No integrated tool to identify incident scenario within LOPA framework

5 Objective To build expert system to develop incident scenario for LOPA

6 Layer of Protection Analysis Main goal: To identify layer of protection required for having sufficient risk reduction

7 LOPA event tree model The LOPA assumes that no layer of protection is perfect; every layer has some probability failure on demand (PFD). Therefore the risk of occurrence of unwanted consequences depends on the failure of the Independent Protection Layers-IPLs.

8 Expert System Computer program that attempt to represent knowledge from well defined and usually highly specialized domain and hence solve problems that would otherwise require additional human expertise A collection of necessary knowledge accompanied by a collection of rules of using them Inference engine to find appropriate solution based on IF THEN logic

9 Proposed Expert System Proposed Expert system

10 LOPA Expert System - Flow Sheet -

11 1. Selection of Target Process Focus on selection of process concerned for LOPA Based on classification of: Equipment (5 groups) 20 typical process units Activities (6 activities) Substance, based on SEVESO II directive Selection of release Consequence

12 Logic diagram for selection of target process Input Data No Target Process Equipment Selection no no no no no SE PE PPE TE OE yes yes yes yes yes Activity Type no no no ChO ElO PhO yes yes yes Substance Class no no no no no T OX EX FL D yes yes yes yes yes Release Size I no II no III no IV no V no yes yes yes yes yes Target Process

13 2. Loss Event Selection Each process could lead to several potential loss event 13 categories

14 Loss Event (expert opinion) No Loss Event Short Description Code 1 Fire Combustion of flammable substance with thermal radiation effects 2 Explosion Rapid combustion of flammable vapor with generation of heat radiation as well as overpressure effects 3 Physical explosion Release of physical energy with generation of overpressure as result of rupture of system under pressure 4 Dust explosion Rapid combustion of flammable dust with generation of heat radiation as well as blast wave and overpressure effects 5 Internal fire/explosion Fire and/or explosion inside the equipment/piping LE 5 6 Runaway/ decomposition Explosion due to runaway chemical reaction or decomposition of an unstable material which usually generate the blast wave and overpressure effects 7 Pipe leak/rupture Release of substance as a result of loss of containment of the pipe 8 Tank leak/rupture Release of substance as a result of loss of containment of the tank 9 Vessel collapse Structural damage of the vessel due to internal or external forces 10 Tank roof collapse Destruction of tank roof as a result of external load or internal explosion 11 Release substance to water 12 Release substance to ground Loss of containment and direct release of substance to water bodies Loss of containment and direct release of substance to ground LE1 LE 2 LE 3 LE 4 LE 6 LE 7 LE 8 LE 9 LE 10 LE 11 LE Other Any other event leading to losses LE 13

15 3. Identification of Initiating Event Each loss event could be caused by more than one initiating event Classified into 5 categories: Process upsets (15 causes) Technical failures (13 causes) Human error (7 causes) Management oversight (10 causes) External event (8 causes)

16 4. Severity of Consequence Five severity consequences categories based on: Release size Qualitative Personnel Community Environment Facility

17 Release properties 1-10 kg kg Size of release ( beyond a plant) kg kg kg Above Very toxic Toxic Flammable below BP Flammable above BP Highly flammable Extremely flammable

18 5. Layers of Protection Identification Based on: Loss event Initiating event

19 Logic diagram for LOP identification Lo ss Event (LE) Select Initiating Ev e nt (IE) no no no no PU TF HE MO EE yes yes yes yes yes no Prevention Layer no no no BPCS Operator Other yes yes yes Protection Layer no no no SIS PhP Other yes yes yes Mi tigation Layer AC no CR no Other no yes yes yes yes Is more IE possible? no Loss Event Selected No Los s Event

20 RESPONSE NO YES ACTIVE SYSTEM NO YES PASSIVE SYSTEM NO YES LOP PHYSICAL PROTECTION NO YES SIS NO YES OPERATOR NO YES BPCS NO YES IE SAFE OUTCOME SD / ESD SAFE OUTCOME BUT UNDESIRED LOSSES MINOR LOSS EVENT MAJOR LOSS EVENT CATASTROPHY NEAR MISS SCENARIO LOPA SCENARIOS

21 Documentation for LOPA Event tree Provides user review form LOPA form Compatible with LOPA calculation

22 Case Study Storage spherical tank for liquefied pressurised isobutane, 300 m Isobutane sphere P=35 o C P=3,27 bar V=300 m Storage sphere 2. Heat exchanger 3. Transfer pump 4. BPCS 5. Safety Valve 6.Water sprinkler 7. Detectors 7

23 Step 1. Hazardous process selection 1. Selection of hazardous process 1.1. Storage equipment SE-EQ2 (pressure storage) 1.2. Classification of activity Storage-OnS 1.3. Classification of substance (F+, R12) Step 2. Loss event selection 2.1. Physical explosion Release of physical energy with generation of overpressure as result of rupture of system under pressure LE Tank leak/rupture Release of substance as a result of loss of containment of the tank LE 8

24 Step 3. Identification of initiating events for LE3 PHYSICAL EXPLOSION PU1 Overheating (Increase temperature/ pressure) PU2 overfilling, or HR1 (exceeding prescribed limits) or HR6 (no reaction on alarms) for LE8 TANK LEAK/RUPTURE TF1 (TF11-TF15) Loss of physical integrity or/ and external accidental event

25 4. Estimation of severity of consequences for LE3 PHYSICAL EXPLOSION release of full content of isobutane (ca. 200 tons), cloud of vapor, ignition, VCE S category V (catastrophic) for LE8 TANK LEAK/RUPTURE release of kg, S category V (catastrophic)

26 5. Identification of independent protection layers, IPL for LE3 PHYSICAL EXPLOSION pressure safety devices (PSH, PSL, and PSV) level safety devices (LSH and LSL) water sprinkler system for LE8 TANK LEAK/RUPTURE pressure safety devices (PSH, PSL, and PSV) level safety devices (LSH and LSL) detectors and operator action

27 6. Documentation event tree

28 Conclusions 1. Incident scenario can be developed not only through PHA, BOW-TIE method but also with EXPERT SYSTEM method. 2. An expert method can be carried out on the basis of the general knowledge on type of the hazardous process, hazardous loss event, safety layers of protection used in that process and kind of the dangerous substance involved. It provides a comprehensive methodology and seems to be simpler than any particular PHA method. 3. An expert method will extend capabilities for Layer of Protection Analysis which may become a rather general risk assessment method than particular tool used for determination of necessary level of SIL for the Safety Instrumented System.

29 Demo Demonstration of LOPA expert system

30 Future Work Improve databases Expert system for specific system

31 Thank You Question?