Jack Chopper wrote a good article ("Turn Off That Alarm!" September '11, www.ControlDesign.com/alarmoff), but he missed the real point of designing an alarm and monitoring system or an operating system, and they are in no way the same thing.
I agree with the principle of three levels of alarms. A flashing yellow should not be an audible alarm, but rather to let the control room know something is out of tolerance. The next should be visual and audible with an attention alert, and should be used only for something that is not getting better or that can cause major problems if action is not taken.
The last resort is the red flashing and audible alarm that tells the control room that an emergency or backup pump has started. This is where the danger is high. The other thing to think about is the audible level of the alarm. Never make it so loud as to wake the dead—so loud that the crew wants nothing more than to make the noise stop—so they can think or take action.
Don't assume, but rather ask, as the list of failsafe actions might take place automatically, even when it might drain a tank or shut down a critical piece of machinery. Never think you can just automate something and save on good, trained, qualified people. Lastly, and most importantly, be sure the key people are a part of the design and testing as well as commissioning, and be sure that what is in the system is correct and set properly.
Phantom alarms or incorrect alarms are what cause major shutdowns, system failures and costly shutdowns. Don't turn off the alarm, but rather make the right alarm.
Clark Dodge, President,
CED Consulting, www.cedconsulting.com