May/June 2011

ISA Certified Automation Professional (CAP) program

Certified Automation Professionals (CAPs) are responsible for the direction, design, and deployment of systems and equipment for manufacturing and control systems.

CAP question

In the ISA-84 standard, the concept of Multiple Independent Protection Layers refers to:

A. Multiple layers in a control system architecture, which provide redundant data pathways from sensors and plant-floor level devices to servers, historians, and business networks, in order to ensure reliable data capture.

B. Independent layers of protection for which each layer helps to reduce the overall level of risk of the process. The inner layers help to prevent a hazardous event (explosion, fire, etc.) from ever occurring, and the outer layers are designed to help lessen the consequences of an event once it has occurred.

C. Independent software modules where each successive layer monitors each layer below to ensure the integrity of the sensor signals processed and the transfer of data to the next-higher software module.

D. Independent layers of project management decision-making, which help ensure project execution is performed to meet schedule and budget constraints.

CAP answer

The correct answer is B, "Independent layers of protection for which each layer helps to reduce the overall level of risk". ISA-84 addresses Functional Safety and Safety Instrumented Systems. A consequence of the concept of multiple independent protection suggests minimization of risk occurs when safety instrumented systems are completely independent from process control systems.

Answer A is not correct since ISA-84 does not directly address data flow on the plant floor. The stated concepts in this answer choice are covered in other standards, such as ISA-95.

Answer C is not correct. This answer choice describes supervisory process control functionality, which is not covered in ISA-84.

Answer D is not correct.  ISA-84 is not a standard that addresses project management or project execution techniques.

Reference: ANSI/ISA-84.00.01-2004 Part 1, Functional Safety-Safety Instrumented Systems for the Process Industry Sector - Part 1: Framework, Definitions, System, Hardware and Software Requirements, 2004, ISA.