仪表安全系统简介sis英文学习资料.pdf

abb - page 1 e x t e n d e d a u t o m a t i o n s y s t e m 8 0 0 x a functional safety engineering - intro to sis abb - page 2 functional safetyintro to safety instrumented system ?safety instrumented system definition ?safety instrumented system purpose ?safety instrumented function ?sis equipment ?terms and abreviations abb - page 3 functional safetysafety instrumented system definition ?safety instrumented system = sis ?iec 61511 defines the safety instrumented system as: ?“instrumented system used to implement one or more safety instrumented functions. a sis is composed of any combination of sensor(s), logic solver(s) and final elements(s) ?iec 61508 does not use the term safety instrumented system (sis) and instead use the term safety related system (srs) to mean the same thing. ?this may change in next release of 61508 abb - page 4 functional safetysis definition from iec 61511 ?safety instrumented systems ?reduce risk by decrease the likelihood of a potential hazard ?decrease risk by reducing the magnitude of the consequence ?a sis may be responsible for ?shutdown function ?permissive function ?and consequence reduction (mitigation) functions ?all these functions reduce risk abb - page 5 functional safetysis definition ?a more functional definition of sis such as: ?“a sis is defined as a system composed of sensors, logic solvers and final elements designed for the purpose of ?1. automatically taking an industrial process to a safe state when specified conditions are violated ?2. permit a process to move forward in a safe manner when specified condition allow (permissive functions) ?3. taking action to mitigate the consequences of an industrial hazard ?sis = ”automatic risk reduction systems abb - page 6 functional safetysis purpose ?the purpose of a sis is to reduce the risk that a process may become hazardious to a tolerable level, ?the amount of risk reduction that an sis can provide is represented by its safety integrtity level (sil), which is defined as a range of probability of failure on demand. ?safe state; state of the process when safety is achieved ?a sis sences hazardious conditions and then take action to move the process to a safe state, preventing an unwatned accident from occuring abb - page 7 functional safetysis safety instrumented system temperature transmitter temperature transmitter level switch logic solver solenoid shut-off valve pump safety instrumented system with multiple sifs flow transmittersolenoid sif 1 sif 2 sif 3 sif 4 globe valve abb - page 8 functional safety safety function and safety integrity from iec 61511 ?safety function ?function to be implemented by an e/e/pe safety-related system, other technology safety related system or external risk reduction facilities, which is intended to achieve or maintain a safe state for the euc, in respect of a specific hazardous event (see 3.4.1) ?safety integrity ?average probability of a safety instrumented system satisfactorily performing the required safety instrumented functions under all the stated conditions within a stated period of time ?safety integrity level (sil) ?discrete level (one out of four) for specifying the safety integrity requirements of the safety instrumented functions to be allocated to the safety instrumented systems. safety integrity level 4 has the highest level of safety integrity; safety integrity level 1 has the lowest abb - page 9 functional safety safety function the likelihood of the safety function being achieved determined from the risk assessment abb - page 10 functional safety safety function safety function: in order to prevent the rupture of pressure vessel “x”, valve “y” should open in 2 seconds when the pressure in the vessel rises to 2.6 bar. safety integrity: the safety integrity of the safety function shall be sil 2 safety integrity level abb - page 11 functional safety the essence of functional safety functional safety requirements spec functional safety requirements specification safety integrity requirements specification safety functions requirements specification determined from the risk assessment determined from the hazard analysis abb - page 12 functional safety bpcs vs. sis ?both composed of sensors, controllers and final element ?control loop maintain a process variable within prescribed limits ?sis monitors a process variable and take action when required ?differences in dynamics ?bpcs - signals moves often, failure can be detected by plant personnel ?sis signals may be motionless for years (normally static), failures difficult to detect abb - page 13 functional safety sis engineering requirement ?design to fail-safe ?design diagnostics to automatically detect fail-danger ?design manual test procedures to detect fail-danger ?design to meet international and local standards ?also ?satisfy the functional requirement ?satisfy performance requirement abb - page 14 functional safetysis - sif ?1 sis can have 1 or more sif(s) ?multiple sifs can include common equipment ?if an equipment is in more than 1 sif it need to be designed for the highest sil requirement. abb - page 15 functional safetysif safety instrumented function temperature transmitter temperature transmitter logic solver solenoid shut-off valve ?safety instrumented function (sif) (from iec 61511 1) ?safety function with a specified safety integrity level which is necessary to achieve functional safety and which can be either a safety instrumented protection function or a safety instrumented control function ?related to a specific hazardous event abb - page 16 functional safetysif safety instrumented function ?sif is an action a sis takes to bring the process or the equipment under control to a safe state. ?this function is a single set of actions that protects against a single specific hazard. ?a sis is a collection of sensors, logic solvers and actuators that execute one or more safety instrumented functions (sifs) that are implemented for a common purpose. ?sif often refers to the equipment that carries out the single set of actions in response to the single hazard, as well to the particular set of actions itself abb - page 17 functional safetysif examples ?sif 1: open sprinkler valve when a flame is detected in order to reduce the size of fire ?sif 2: close valve to stop material flow into tank to prevent spillage of high level is detected, which may result in environmental damage ?sif 3:cut of fuel in an industrial burner when fuel pressure is to low to sustain combustion, which may result in flameout and possible explosion due to fuel buildup in the combustion chamber abb - page 18 functional safety equipments for sif ?need to clearly identify what type of equipment is included in the sif vs. auxiliary equipment not actually needed to provide protection against the hazard. ?is this piece of equipment needed to protect against the specific hazardous event. abb - page 19 functional safety personnel as part of sif ?operator normally respond to alarms ?can be considered as level of protection, not the sis ?not sil determination on operator action ?the availability and reliability of the operator action must be considered. abb - page 20 functional safetysis safety instrumented system temperature transmitter temperature transmitter level switch logic solver solenoid shut-off valve pump safety instrumented system with multiple sifs flow transmittersolenoid sif 1 sif 2 sif 3 sif 4 globe valve abb - page 21 functional safety safety integrity level sil 4 sil 3 sil 2 sil 1 probability of failure on demand (low demand mode of operation) risk reduction factor =10-5 to =10-4 to =10-3 to =10-2 to = 0.01 to =10-5 to =10-4 to =10-3 to =10-2 to = 0.01 to 0.1 abb - page 25 functional safety safety integrity level ?to establish engineering procedures to prevent systematic design errors ?the equipment used to implement any safety instrumented function must be designed using procedures intended to prevent systematic design errors. the rigor of the requirement is a function of safety integrity level ?more rigid procedures for higher sil safety integrity level sil 4 sil 3 sil 2 sil 1 abb - page 26 functional safety safety program safety systemsafety culture things & activitiesthoughts & actions increase knowledge & skillencourage “value abb - page 27 functional safety safety system the safety system acts like the framework or skeleton abb - page 28 functional safety safety culture around the safety system, wraps the muscle and fiber of the safety culture abb - page 29 functional safety safety culture if you take away the muscle/safety culture, all you have is a pile of bones if you take away the safety system/skeleton, all you have is a pile of mush abb - page 30 functional safety definitions and acronyms ?ansi: american national standards institute ?availability: percentage of time that a system is able to perform a defined function under stated conditions. ?bpcs: basic process control system (dcs system) ?bqms : basic quality management system ?fail-safe: a failure that causes a “false or spurious” trip of a safety function unless that trip is prevented by the architecture of the safety instrumented function ?dcs: distributed control system. ?diagnostic coverage (dc): the fractional decrease in the probability of dangerous hardware failure resulting from the operation of the automatic tests ?dmr: dual modular redundant ?e/ e/ pe: electrical/ electronic/ programmable electronic safety- related systems ?esd: emergency shutdown system. ?euc: equipment under control. refers to the plant equipment. abb - page 31 functional safety definitions and acronyms ?fault tolerance: describes the number of faults on a subsystem that the components can withstand before causing the loss of the safety function. ?fmea: failure mode and effect analysis ?fmeca: failure mode and effect and consequence analysis ?fmeda: failure mode and effect and diagnostic analysis ?fsa: functional safety assessment ?fsm: functional safety management ?functional safety: part of the overall safety relating to the euc and the euc control system which depends on the correct functioning of the e/e/pe safety-related systems, other technology safety-related systems and external risk reduction facilities ?hazop: hazard & operability ?hse: health, safety and environmental agency. uk health and safety agency. ?iec: international electrotechnical commission. ?isa: instrumentation, systems, and automation society (note this is a new definition for this acronym) abb - page 32 functional safety definitions and acronyms ?moc: management of change ?mtbf: mean time between failures ?mttr: mean time to repair ?operational safety: the ability of a system to support plant operation so that the demand rate on safety functions can be kept to a minimum. ?osha: occupational safety & health administration. us health and safety agency. ?pes: programmable electronic system. refers to the safety system controller. ?probability of failure on demand (pfd): the probability of a system failing to respond to a demand. (pfd= 1-availability) ?psm: process safety management ?redundancy: a defense against random hardware failures, but not systematic failures. redundancy options include dual, triple, quad. ?reliability: probability that a system can perform a defined function under stated conditions for a given period of time. abb - page 33 functional safety definitions and acronyms ?risk assessment: process of making risk estimates and using the results to make decisions. ?risk: the probable rate of occurrence of a hazard causing harm and the degree of severity of the harm ?fail dangerous: a failure that prevent a safety instrumented function from performing its automatic protection function. ?safe failure fraction (sff): the ratio of the average rate of safe failures plus dangerous detected failures ?safety instrumented function (sif): functions that have to be performed to reduce risk to an acceptable level. ?safety instrumented system (sis): system composed of sensors, logic solvers, and final control elements for the purpose of taking the process to a safe state when predetermined conditions are violated. ?safety integrity level (sil): a measurement of the overall performance of a