Alarm Management 02
Alarm Management 02 : Alarm Problem History: From their conception, large chemical, refining, power generation, and other processing plants required the use of a control system to keep the process operating successfully and producing products. Due to the fragility of the components as compared to the process, these control systems often required a control room to protect them from the elements and process conditions. In the early days of control rooms, they utilized what were referred to as "panel boards" which were loaded with control instruments and indicators. These were tied to sensors located in the process streams and on the outside of process equipment. The sensors relayed their information to the control instruments via 4-20 mA current loop in the form of twisted pair wiring. At first these systems merely yielded information, and a well-trained operator was required to make adjustments either by changing flow rates, or altering energy inputs to keep the process within its designed limits. Alarms were added to alert the operator to a condition that was about to exceed a design limit, or had already exceeded a design limit. Additionally, Emergency Shut Down (ESD) systems were employed to halt a process that was in danger of exceeding either safety, environmental or monetarily acceptable process limits. Alarm were indicated to the operator by annunciator horns, and lights of different colors. (For instance, green lights meant OK, Yellow meant not OK, and Red meant BAD). Panel boards were usually laid out in a manner that replicated the process flow in the plant. So instrumentation indicating operating units with the plant was grouped together for recognition sake and ease of problem solution
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