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

One sensor is active while the second serves only as a backup

Answer

Both sensors must agree before a safety action is taken

Answer

One sensor votes while the second is placed in standby mode

Question 2

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

Accepted Answer

IEC 61511

Answer

IEC 61508

Answer

ISO 13849

Answer

IEC 62061

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

The frequency of spurious trips per year in normal operation

Answer

The probability that normal production will be interrupted by a control fault

Answer

The chance that a sensor reading will drift during steady-state operation

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

Only during initial design and commissioning

Answer

Only when the system undergoes a major modification

Answer

During production operation and scheduled maintenance only

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

A controlled deceleration to stop before removing power

Answer

A stop triggered only by a safety PLC command

Answer

A stop that requires manual reset before restarting

Question 6

What is a 'safe state' in the context of a Safety Instrumented Function (SIF)?

Accepted Answer

A predefined condition where risk to personnel and equipment is reduced to an acceptable level

Answer

A state where production throughput is maximized

Answer

A state where all process alarms have been cleared

Answer

A state where the control system has been switched to manual mode

Question 7

What is the key difference between a Safety Instrumented System (SIS) and a Basic Process Control System (BPCS)?

Accepted Answer

A SIS is an independent protection layer that acts when the BPCS cannot keep the process safe

Answer

A SIS controls the process continuously while a BPCS activates only on safety alarms

Answer

A BPCS must meet higher SIL requirements than the SIS it supports

Answer

There is no functional difference; they serve the same control purpose