Best practices: once again into the breech
This morning's final session in the "Best Practices" track focused on alarm management. Dr. Joseph Alford, recently retired from Eli Lilly, and Mik Marvan, Matrikon's alarm management product manager, threw a life preserver to automation professionals drowning in a tsunami of alarms. Dr. Alford condensed 35 years of batch processing alarm management experience into a few key slides.
To rescue the average batch processing plant floor operator from the more than 3,000 alarms he has to account for on a given shift, do the following things, says Dr. Alford
Using the "alarm management" system on a car as an example, he demonstrated the characteristics of an ideal alarming system. In a car, the "alarms," such as a low fuel guage, represent an "abnormal" situation that requires a response. The alarm systems are accurate and reliable. Ordinarily people don't question whether the low fuel indicator really means they have to stop for gas. These alarms permit a reasonable time for response: The driver has time to get to the gas station. Most important, the alarms are few in number, in spite of the fact that cars are complex systems. Why can't the alarm systems in our batch processing operations have the same characteristics, asks Dr. Alford.
Allowing for the additional characteristics of batch operations, such as multiple process steps, multiple phases, process loads, set points that are a function of time, and few, if any steady-state operations, these are his recommendations for building such a system.
- Adhere to the basic definition of alarms"”"abnormal situations requiring a response." Just doing this will knock out about 75% of alarms, says Alford.
- Tag alarm records with sufficient information needed to use the information for displays, sorts, queries and report generation. Include lot numbers, category, priority, process step/phase, etc.
- Generate more "intelligent" alarms that make use of all available relevant information, such as those that include if-then rules incorporating redundant sensors, trend slopes, other correlated variables.
- Eliminate nuisance alarms. Do not include "notifications" on alarm displays. Make every effort to separate information messages from alarms.
- When color-coding displays, use each color only one time. If red indicates a high-priority alarm, don't use that color for anything else.
- Minimize multiple alarms for each event.
- Ensure that alarms alert, inform and guide. They should tell the operator everything he needs to know about the alarm. "Most commercial systems do a great job of alerting, a mediocre job of informing and a bad job of guiding," says Alford.
- Set up a system that allows sufficient mining of alarm data. Make records easy to access and understand. Include sufficient alarm tag information. Include "relative time" information. The fact that the alarm occurred at is less important than that it occurred 2 hours into, say, a sterilization process. Include utilities that allow the creation of pareto charts and other trending information and those that include the ability to combine discrete and continuous trends. This is all about providing the necessary context.
Mik Marvan concluded the session with showing how Matrikon's Alarm Management System can help companies implement these best practices. See www.matrikon.com for detailed information about this system.