SACA Safety Systems and Functional Safety 2

Question 1

In safety system voting logic, what does a '1oo2' (one-out-of-two) architecture mean?

Accepted Answer

Either one of two sensors detecting the hazard is sufficient to initiate a safety action

Answer

A 1oo2 architecture initiates the safety function if either one of two sensors detects an abnormal condition, improving availability at the cost of potentially more spurious trips.

Question 2

Which IEC standard specifically addresses Safety Instrumented Systems (SIS) for the process industry sector?

Accepted Answer

IEC 61511

Answer

IEC 61511 is the process-industry sector application of IEC 61508, covering engineering and operation of SIS in oil, gas, and chemical plants.

Question 3

Probability of Failure on Demand (PFD) is used to measure:

Accepted Answer

The likelihood a safety system fails to act when a safety demand occurs

Answer

PFD quantifies the probability that a safety function will fail to perform its intended action when a demand occurs, and is used to verify that the required SIL target is met.

Question 4

The safety lifecycle concept in IEC 61508 requires that safety activities be performed:

Accepted Answer

Throughout all phases from concept through decommissioning

Answer

The IEC 61508 safety lifecycle is a cradle-to-grave approach encompassing concept, design, implementation, operation, maintenance, and decommissioning to ensure functional safety is maintained throughout.

Question 5

Per IEC 60204-1, Stop Category 0 on a machine is defined as:

Accepted Answer

An immediate removal of power to the machine actuators

Answer

Stop Category 0 is an uncontrolled stop achieved by immediately removing power (or interrupting energy) to the machine actuators, which is the default safe state for E-stop functions.

SACA - Smart Automation Certification Alliance Practice Test

SACA - Smart Automation Certification Alliance Practice Test

SACA Safety Systems and Functional Safety 2