ISA CAP Risk Management & Mitigation 3

Question 1

In fault tree analysis (FTA), what does an AND gate signify?

Accepted Answer

The top event occurs only when all input events occur simultaneously

Answer

An AND gate in a fault tree means all input events must occur simultaneously for the output (top) event to occur.

Question 2

What is the key distinction between a 'hazard' and a 'risk' in process safety terminology?

Accepted Answer

Hazard is the potential source of harm; risk combines likelihood and consequence

Answer

A hazard is an inherent property that can cause harm, while risk is defined as the combination of the probability of harm and the severity of that harm.

Question 3

Which layer of protection in a LOPA analysis is NOT typically credited as an Independent Protection Layer (IPL)?

Accepted Answer

Basic Process Control System (BPCS) control loop

Answer

The BPCS initiating cause cannot simultaneously serve as an IPL because it shares common hardware and software with the initiating event, violating the independence requirement.

Question 4

What is 'common cause failure' (CCF) and why is it important in redundant safety systems?

Accepted Answer

A single failure that defeats multiple independent channels simultaneously, undermining redundancy

Answer

Common cause failure is a single event or root cause that causes multiple redundant components to fail simultaneously, potentially defeating the benefit of redundancy.

Question 5

In LOPA, what is the typical PFD credit assigned to a well-designed and maintained passive dike/bund as an IPL?

Accepted Answer

0.01

Answer

A properly designed and maintained dike or bund is typically assigned a PFD of 0.01 (1 in 100 chance of failure) in LOPA.

(ISA CAP) ISA Certified Automation Professional Practice Test

(ISA CAP) ISA Certified Automation Professional Practice Test

ISA CAP Risk Management & Mitigation 3