42 Pascual06

Intervalos entre inspecciones para sistemas de protección Dr. Rodrigo Pascual Departamento de Ingeniería Mecánica Universidad de Chile http://www.ing.uchile.cl/~rpascual Pressure vessel lu 1 lu 2 pt 1 pt 2 pt 3 v 1 v 2

Motivación ,[object Object],[object Object],[object Object],[object Object],Dormant systems Systems in storage Spares Weapons Standby equipment Safety systems

[object Object],Fuente: J. Moubray, RCM, 1997.

Motivación Medical Expose dose control in radiotherapy systems Air transport Flight-by-wire control systems Automotive Airbags Antilock brake systems Process Emergency shutdown systems Military/Law enforcement Gas detectors Railway Automatic train stop systems Applications

Motivación Industria de proceso (34 accidentes) Source: Bell (2003) http://www.iee.org/Oncomms/pn/emc/Paper03.pdf Conception Design Implementation Operation & maintenance

Balance No disponibilidad Frecuencia de inspecciones Global Desconocida Conocida (inspecciones, reparaciones, reemplazos) Costos Modelo de confiabilidad

IEC 61508 (2004) Functional safety of electrical/electronic/programmable electronic safety-related systems ,[object Object],[object Object],4 3 1 1,E-05 1,E-04 1,E-03 1,E-02 1,E-01 2 Probability of failure on demand Safety integrity level IEC 61508 (2004) Nuclear IEC 61513 (2001) Machinery 62061 (2005) API 670 (2000) Generic ISO 14224 (2004) Railway EN 50126 (1999) EN 50128 (2001) Process IEC 61511 (2003) ANSI 84.01 (2004 )

Objetivo para la fase operacional ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Conception Design Implementation Operation & maintenance

Consideraciones del modelo ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Sensor 1 Sensor 2 Sensor 3 Logic 1 Logic 2 2/3 1/2 1/2 Actuator 1 Actuator 2 Pressure Temperature Leak … Valve Break Fire extinguisher … Electronic unit Valve spring …

Ocasiones de inspección ,[object Object],[object Object],[object Object],[object Object]

Fallas en sistemas de protección IEC 61508 Detectada en inspecciones No detectada en inspecciones Failure “ Random” Systematic Aging (component) Stress (subsystem) Design (specification) Interaction (human error)

Inspecciones imperfectas ,[object Object],Goble, W.M., Periodic inspection and test: requirements and benefits, Hydrocarbon Processing, 81(6), 117, 2002.

Inspecciones parciales y completas instantaneous

Disponibilidad global & de seguridad * ✔ ✔ ? ? ? ✔

Modelo simplificado Overall availability Partial inspections Full inspections Probability of failure on demand Safety availability overall safety

Consideraciones Tasa de falla de componentes (standard databases) Tasa de fallas del sistema (plant information system) Modelo Multi-componente Modelo simple Conception Design Implementation Operation & maintenance

Redundancia y fallas con causa común ,[object Object],[object Object],Causa común Independientes ,[object Object],[object Object],[object Object],1- β 1- β β Comp. 1 Comp. 2    Conception Design Implementation Operation & maintenance

Ejemplo 2 de 3 Pressure vessel lu 1 lu 2 pt 1 pt 2 pt 3 v 1 v 2

Ejemplo single component safety system ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object], Time Instantaneous availability Partial insp. Partial insp. Full inspection Overall Availability 0 2 4 6 8 10 No. of partial inspections before renewal

Sistema complejo Failure rate (  10 6 hours) Common Cause Factor From:Hauge, S., et al., Reliability Prediction Method for safety Instrumented Systems; PDS Method Handbook, 2006 Edition.,SINTEF, Trondheim, Norway, 2006

Diagrama de bloques de confiabilidad

Resultados Disponibilidad de seguridad Partial coverage Full coverage  =0.7  =1.0

Número de inspecciones parciales en un ciclo de renovación N

Análisis de sensibilidad Nr of partial inspections Period between Partial inspections Optimal overall availability Attained safety availability

Comentarios ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Conception Design Implementation Operation & maintenance

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