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SEP-OCT 2017

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INTECH SEPTEMBER/OCTOBER 2017 17 PROCESS AUTOMATION as those offered by ISA, or utilize expe- rienced consultants and system integra- tors, who can assist with alarm manage- ment programs, providing guidance and assisting with implementations as the situation requires. Developing and main- taining in-house personnel is a long- term investment decision that needs to be consciously made. Using experienced consultants and system integrators to help create and maintain alarm manage- ment programs, providing guidance and assisting with implementations as the situation requires, is another investment option to consider. n ABOUT THE AUTHOR Richard Slaugenhaupt (richard.slaugen- haupt@mavtechglobal.com) is a consul- tant for MAVERICK Technologies. View the online version at www.isa.org/intech/20171002. suppressing unnecessary and ir relevant alarms. Dynamic suppression is the most challenging, because it requires creat- ing the rules the system uses to deter- mine what is important and what is not. And like a safety system, it must have the correct sensors to detect the conditions upon which those rules are based. In some respects, it can be even more complex than a safety function, because hundreds of alarms may be af- fected and many factors can enter into the decision-making process. Very complex undertaking Like safety systems, alarm manage- ment requires knowledgeable special- ists, particularly when moving into areas as complex as dynamic alarm suppression. New tools have emerged on the market to help with the design, implementation, and maintenance of such systems. The waters can be muddied further by the subjective nature of the evalua- tion. Overwhelming an operator with too many alarms at one time is clearly detrimental, but the threshold for what constitutes "too many" depends on the urgency, importance, and complexity of the required response to the event. The skill level and experience of individual operators must also be considered. Companies can either invest in devel- oping in-house alarm management per- sonnel through training programs, such Each of those air-dependent devices verifies that the air supply is adequate, and will trip if the pipe is clogged or someone inadvertently closes a valve. Now assume that the compressor mo - tor fails. It has its own alarm to warn operators and maintenance personnel that the air supply has been lost. The operators may need to open a valve to borrow air from another part of the facility while maintenance trouble - shoots the compressor. Now with the root cause already ad- dressed, does the control room need a dozen or more alarms from all those air-dependent devices, each reporting some sort of failure? Followed by yet an- other round of alarms from the systems using those devices? Clearly not. Once the common cause is announced to the operators, subsequent related alarms should be suppressed, so as not to dis- tract the operator from the real problem. Types of suppression ANSI/ISA-18.2 defines three forms of alarm suppression: 1. Shelving, where an operator manu- ally suppresses an alarm temporarily. 2. Designed suppression, where the process automation system sup- presses an alarm based on a specific set of conditions. 3. Out of service, where an alarm has been suppressed because a portion of the equipment is shut down for maintenance or some other reason. Designed suppression is the most in- teresting and challenging, and it is typi- cally divided into two categories: static and dynamic suppression. Static sup- pression is based on the state of the pro- cess and equipment. Specific alarms are enabled or suppressed during defined procedures or conditions. For example, some alarms may only be enabled dur- ing a unit startup. This simple technique is the most commonly implemented of the two suppression types. Dynamic suppression is designed to avoid alarm floods during upsets and other more complicated scenarios. It gives the system enough "intelligence" to determine the most important alarms under the circumstances, mak- ing sure they get to the operators, while Figure 3. A single event can become a common cause, launching a flood of individual alarms as the results ripple through various systems. RESOURCES "A standard grows up: The evolution of ISA's standard on alarm manage - ment (ISA-18.2)" www.isa.org/a-standard-grows-up "ISA alarm management standard packs a punch" www.isa.org/isa-alarm-management-stan- dard-packs-a-punch "Diagnosing your alarm system" www.isa.org/intech/20150805

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