Case Example SIL Classification

Transcription

1 ase Example: SIL lassification of Instrumentation ornelis P. Willig BSc MSc PENDABLE Industrial Automation onsultancy b.v. P.O.Box 42, NL-2110-AA Aerdenhout, The Netherlands facsimile: +31(0) mobile: +31(0) SIL lassification of Instrumentation Objective What is Safety Integrity Level - SIL To introduce SIL classification of a Safety Instrumented System - SIS ontents ase example SIL alculation of Safety Instrumented System - SIS PWillig@diac.nl - fax: +31(0)

2 .Willig VGA Jan 95 DFig1_3P.drw Observations Business & Operations Liability: challenge: Balancing (Governmental) Safety Policy & ompliance After a Major Event: License To Operate : discontinued? Economic & Environmental Loss osts? Business ontinuity after re-build? ompany s Image? Opportunity of today s set of standards: Minimise Liability issues of process automation & safety: audit-able, traceable, systematic & consistent in relation to agreed Tolerated Risks 101 ase: Model Production Plant Layout Disclaimer: any resemblance of this Model Plant with an operating plant is pure coincidental. This model is used for training & presentation purposes only. Feed M M101 Overview of Boiler House and Plant Units. TB101/102 Ethane TB201/202 HP steam V102 Propane V202 V302 Propane Propane MP V101 V201 V301 Ethane HP Steam Boiler M LP M301 Ethane 01 F101 High Joule Low-Joule Fuel Gas V1 Butane V2 V3 Butane Butane Heavy Ends 5+ Heavy Ends UNIT 100 UNIT 200 UNIT 300 Heavy Ends PWillig@diac.nl - fax: +31(0)

3 Mission Of The Production Plant Plant mission definition: Produce at 100% throughput products within specification as scheduled Plant failure definition: Plant has failed if because of this failure the plant is unable to fulfill its mission Safety System Mission Time: 10 years (4 year/ maintenance stop, 4 wk/stop) 25,000.= US$ per lost production hour Initial Risk without protection Increasing Risk Risk Reduction Intermediate Risk influence other risk reduction facilities Necessary Minimum Risk Reduction ATUAL RISK REDUTION Total Risk Reduction Tolerable Risk Actual Remaining Risk Safety Instrumented System + other risk reduction facilities PWillig@diac.nl - fax: +31(0)

4 Vessel Pressure Typical ontrol Layers: Example Gas, Smoke & Fire Detection System: alarms & minimise escalation P-RV P-HH P monitor P - H P - setpoint P - L Mechanical Protection takes action: Relief Valve / Break Disk Safety Instrumented System: takes action and trips the unit/ plant P - Monitor ontrol takes over the normal control P - Normal ontrol RISK Event Principle: Risk Event & Safety Integrity Frequency onsequence Safety Integrity Level - SIL Required to be achieved by the omplete Safety Instrumented System - SIS PWillig@diac.nl - fax: +31(0)

5 S0: No Injury S1: Slight Injury S2: Severe, 1 death Safety Integrity Levels: IE Required SIL at W2: 1 demand / 10y A1 A2 G1: avert G2 G1 G2: No avert SIL 0 - AK - SIL 0 - AK 1 SIL 1 - AK 2 SIL 1 - AK 3 SIL 2 - AK 4 Probability of Failure on Demand PFD - average: < 1/10 < 1/100 S3: >1 death A1: no - min personnel A2: personnel present SIL 3 - AK 5 SIL 3 - AK 6 < 1/1000 S4: atastrophe SIL 4 - AK 7 < 1/10000 E.g % IE-61069: Dependability System s Dependability Availability redibility Reliability Perform for given time Source: IE Maintainability Restorable to required spec Integrity Tasks performed correctly as instructed Security Liability-related!! Unauthorised access = denied PWillig@diac.nl - fax: +31(0)

6 RISK Event Frequency SIS Safety Integrity: Design Principle Standards onsequence Integrity Level Required Hardware & System Software: AK/ Risk lass ompliance onsistent relationship between Risk Reduction requirements & Safety Instrumented System realisation Application Software: Standards Measures & Table of ompliance HP Boiler SIS: Principle System Layout IE 61508: The TOTAL SIS has to achieve the target Safety Integrity Level - SIL Requires: alculation of the Average Probability of Failure on Demand - PFD HZA ESD Logic Solver Safety Instrumented System 20 PT PT PT HP Steam 100 barg High (aloric) Joule Gas Low (aloric) Joule Gas Boiler Feed Water HP Blr ISS Very High Pressure Steam Boiler PWillig@diac.nl - fax: +31(0)

7 Safety Instrumented System: Mission Functional Mission of the SIS: (e.g.. ex HAZOPS) Prevent critical over-pressure in the High Pressure Steam Boiler Upon Demand: close two fuel gas lines Assessment Method: Failure Mode Effects & riticality Analysis, FMEA Fault Tree Analysis, FTA Note: adapted generic & specific failure data are applied for demonstration & training purposes only. The performance of the equipment is likely to vary considerable depending on, for example, service conditions, selection, construction and maintenance practices. SIS onfiguration of ases 1, 2 & 3 PT PT PT Initiators Logic Solver Dependent Failures: Multiple Failure Group: A 20 : Instrument Air 20 analogue electronic P-transmitters Logic Solver HJ Fuel Gas MFG: B 1: AK4 PL Single i/o & PU 2: Solid State E/ Electronic 3: AK5 (6) PL, Red. I/o, PU 1002 Voting LJ Fuel Gas MFG: B Final Elements 1002 Block Valve/ F Gas Line Special ESD Valves 1 Solenoid Valve per Block Valve PWillig@diac.nl - fax: +31(0)

8 SIS Safety PL onfigurations AK4 Single Single I/o & PU AK5 (6) Redundant Double I/o & PU 1002 Voting logic PT PT in in1a in1b PU1 PU1 PU2 o MFG E HJ Fuel Gas LJ Fuel Gas onfiguration ase 4: Duplex System MFG A PT PT PT Logic Solver 1 20 BV1 MFG B BV3 MFG B MFG D PT PT PT 20 Logic Solver 2 BV2 MFG B BV4 MFG B : Instrument Air Initiators 20 analogue Smart P-transmitters Logic Solver 4.1: Solid State E/E 4.2: AK5 PL Redundant, double i/o, 1002 Voting Logic Final Elements 1002 Block Valve/ F Gas Line Special ESD Valves 1 Solenoid Valve/ Block Valve PWillig@diac.nl - fax: +31(0)

9 Assessment Results Summary + For demonstration & training purposes only + ASE SIL MTBF Nuisance Shut Down ost Estimate 1: PL AK 4 Single 1 5 y 400k$/10y 2: Solid State E /E 2 50 y 40k$/ 10y Electric/Electronic 3: PL AK 5 Redundant 2 70 y 30k$/ 10y 4.1: Duplex System Solid State E/E 4.2: Duplex System PL AK 5 Redundant 3 25 y 3 50 y 80k$/ 10y 40k$/ 10y ase Study - Summary Safety Instrumented System design: strategic design achieves SIL, while it minimises nuisance trips, maintenance & testing SIS Life ycle - Business ase to include: System Architecture & required (safety) performance estimated costs of nuisance operations interrupts/ shut downs during mission life of e.g. 10 years estimated OPEX: maintenance & proof testing costs General observation: High performance more APEX expensive instrumentation often achieves lowest Life ycle osts 18 PWillig@diac.nl - fax: +31(0)