Improve plant safety by updating alarm annunciators to SIL standards

Gary Bradshaw  explains the importance of keeping alarm annunciators up to date and the considerations plant managers must make in doing this

Updating the alarm systems of an industrial facility in line with technological advances and increasing regulations seems like a common-sense approach to safety. 

However, this isn’t always the case and physical alarm annunciators are often neglected and are out of date. 

From fuel refinery explosions to the loss of containment at a nuclear site, disasters like these are only averted if operators can quickly identify, and act upon, imminent danger. 

Often, the simplest solution is the most effective one and that is why the humble alarm annunciator remains a key part of mission-critical safety systems to this day.

Alarm annunciators are panel-based alarms that are hard-wired directly into relevant processes by a series of cables. In the event of system failure, the relevant window on the panel lights up and the alarm emits a sound, immediately giving operators the necessary information to act quickly. 

Many alarm annunciators in use today were installed decades ago and do not meet the current IEC 61508 safety integrity levels (SIL).

Many sites rely on control systems teeming with complex visualisations to warn operators of imminent danger. This can be overwhelming for operators and sometimes counterproductive. In the event of imminent danger, it is vital that the safety systems alert operators quickly and efficiently so they can respond appropriately.

Operator response times are an important part of the SIL-rating, making it vital that alarms maximise, rather than impede, the operator’s ability to respond and act quickly. 

Physical alarm annunciators must be kept up to date and must only display the safety, health and environmental alarms that plant operators must respond to.

Updating your alarms

Plant managers looking to update their alarm annunciators should bear in mind two key considerations. 

Firstly, you must ensure that they are directly hardwired into the process. The importance of this cannot be overstated.

Virtual alarms that are displayed in lists on the control system screen are susceptible to outages. If the network goes down, so do all the alarms.

Whereas if they are directly hardwired, and you lose one wire, then you only lose one alarm.

The second point to consider is that the annunciators must have a panel of windows permanently dedicated to specific processes. This enhances operator familiarity and increases their awareness when the panel sounds an alarm.

Industry approved

Arguably, there is no industry as highly regulated as the nuclear sector and none where mission-critical safety systems matter more.

In a nuclear plant, acting decisively in the moments following an emergency can mean the difference between averting danger and a major catastrophe.

When Sellafield Ltd. needed to upgrade its on-site alarm annunciators to SIL standards, in accordance with the requirements of the Nuclear Installations Inspectorate, it turned to Omniflex for help. 

The Omni 8/16 range of alarm annunciators is the world’s first range of alarm annunciators substantiated by EMPHASIS for use in SIL applications in the nuclear industry.

Gary Bradshaw is director of remote monitoring specialist Omniflex.