SAFETY at oil refineries and chemicals plants is being compromised by the
very alarm systems that are meant to warn of danger.
So many alarms are installed around these plants that they are often ignored.
Worse, when an accident does happen, a confusing cacophony of alarms can mean
that operators often don鈥檛 take the right action.
鈥淎n alarm should tell you that you have to do something, and you should have
enough time to do it,鈥� says Ian Gibson, principal technical specialist for
process and control systems at Fluor Australia in Melbourne. But the sheer
number of alarms in a modern plant can make this impossible.
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Tens of thousands of alarms鈥攎ost of which signal changes in the plant鈥檚
efficiency鈥攁re often monitored by just three or four operators. Even when
things are running smoothly, 30 to 60 alarms per hour is common. 鈥淚t鈥檚 hell,鈥�
says Gibson. 鈥淭he first thing someone does is crawl under the desk and pull the
wires off the alarm horns.鈥� During an emergency such as a fire or spill more
than 30 alarms may sound per minute.
Some plants use the same tone for emergency and processing alarms, says Peter
Andow, an alarm system expert at Honeywell Hi-Spec Solutions in Southampton,
which builds computers that control chemicals plants. This makes it harder for
operators to decide when urgent action is needed. Others use different tones for
different types of warning, but allow the first alarms to continue as the more
serious alarms are tripped. This 鈥渁larm flood鈥� is compromising safety and
productivity, he told the conference.
The 1994 explosion at Texaco鈥檚 Milford Haven refinery in south Wales is a
case in point. During the preceding 11 minutes, two operators had the impossible
task of dealing with 275 alarms. The explosion injured 26 people and caused
damage worth around 拢48 million.
鈥淚t鈥檚 not the principle of alarm systems that鈥檚 wrong,鈥� says Andow, 鈥淚t鈥檚 the
number of alarms, and their configuration that needs improving.鈥�
