UFC760BE41 UFC760BE42 ABB Mainboard control system control board

UFC760BE41 UFC760BE42 ABB Mainboard control system control board

UFC760BE41 UFC760BE42 ABB Mainboard control system control board

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Demand Mode of Operation

For safety-instrumented functions where the demand rate is specified to be once per

year or less, Table 3 in part 1 of IEC61511 will be used for defining the safety

integrity level.

Continuous Mode of Operation.

For safety-instrumented functions where the demand rate is specified to be more

than once per year or greater than twice the proof test frequency, Table 4 in part 1 of

IEC61511 will be used for defining the safety integrity level.

Safety Requirement Specifications

The Safety Requirement Specification is the main input for the design of the SIS.

The requirements may be collected in one single document or a collection of several

documents and drawings. The requirements should be expressed in such a way that

they are clear, precise, verifiable, maintainable and feasible with respect to all

phases of the lifecycle.

Normally the Safety Requirement Specification will cover the following items:

• A description of all the safety instrumented functions.

• Common cause failures shall be identified and taken into account.

• Safe state shall be defined for each identified SIF.

• Any individually safe states which, when occurring concurrently, create a

separate hazard shall be identified.

• Source of demand and demand rate for the SIF shall be identified.

• Proof test interval for each SIF.

• The response time for the SIS to bring the process to a safe state.

• The safety integrity level and the mode of operation for each SIF.

• A description of SIS process measurements and their trip points.

• A description of SIS process output actions and the criteria for successful

operation, for example, requirements for tight shut-off valves.