Another Company—A Different Emphasis on Safety Critical Instrument Systems

Another Company—A Different Emphasis on Safety Critical Instrument Systems 

Gregory McMillan, formerly an engineering fellow in process control for the Monsanto Chemical Company, approached the subject differently. His very entertaining presentation entitled, Can You Say Process Interlocks at an AIChE Loss Prevention Symposium was written as a parody of a popular youngster s TV show. [27] 

Monsanto felt there were some real benefits to separate the economic issues from the safety issues and focus on the interlocks that really require special attention. Prior to this separation, human life was grouped with major property protection and formed a large class for which it was difficult to enforce stringent design and test requirements. [27] 

In earlier times, costs associated with business interruption (which can exceed property losses) after an interlock failure were largely ignored and those interlocks were often placed with the so-called operational interlocks. McMillan s approach was a system that grouped the protection instrument loops into four classes. These are the classes and a rough idea of the number of affected loops  

McMillan reveals alarms and interlocks can proliferate to the point where they detract from the most critical loops. To be effective, a logical cause-and-effect approach to interlock classification is required. It must be determined which events are the direct and distinct causes of hazardous events. 

---

Another company - a different emphasis on safety critical instrument systems... 

---