The vital role for alarm annunciators in safety critical systems

Conventional alarm annunciators have seen a resurgence in popularity recently, displacing computer monitors for critical alarms. Omniflex is the only manufacturer of a SIL1 certified alarm annunciators approved for use in the nuclear industry.

Before the days of computerised systems, industrial plants used alarm lamps not only to notify operators of abnormal conditions, but to operate the plant. The function of these lamps developed into the alarm annunciator as we know it today, and became the standard method of indicating the presence of alarms and displaying plant status.

The introduction of computer monitor based control systems during the 1980s and 1990s saw a wholesale absorption of alarm window displays on to the computer screen, where flexibility and space saving were perceived as desirable attributes.

This created a down-turn in the sales of the conventional alarm annunciator systems and many of the companies manufacturing these alarm annunciator products were either sold off or went out of business altogether.

Over the last five years the alarm annunciator has seen a resurgence in popularity especially for use in IEC61508 SIL 1 and SHE (Safety Health and Environmental) alarm monitoring applications. There is a current trend unerway to identify critical alarms and return them from the computer screen to discrete alarm windows.

This is being done for two reasons: Firstly, alarm annunciators offer pattern recognition to the operators in the form of LED alarm fascias instead of just providing an exhaustive list of alarms and events which the operators have to scroll through, where in some instances alarms can be overlooked. Secondly, the analysis of plant failure modes is leading to the separation of critical alarm monitoring and process control systems for safety reasons.

Omniflex (originally Conlog) has been manufacturing alarm annunciator systems since the late 1960s and continues to do so today with an ever growing market share. The Omniflex Omni 16 range of alarm annunciators has been manufactured since 1983 and the latest versions have been assessed to IEC61508 SIL1 by TUV, Evaluation International, and the European Nuclear Industry.

For many years now Omniflex have been providing replacement alarm annunciator systems for many Blue Chip companies throughout the world, replacing obsolete systems such as the old Highland UC20/30 (with an exact Omni 30 replacement), System/Series 90, MPAS90 and the Rochester TADS, AN3100, AN6100, AN6150 (Displays only), X11 and X12 versions. The replacement systems, in many instances, fit into the existing panel cut-outs using retro-fit plates (in any colour) and are provided with interface terminals and wiring looms to make installation quick and very cost effective. These replacements systems restore the safety of these systems by providing modern safety certified replacements for systems that are now obsolete and becoming unreliable through their age.

A design service is also offered to provide consultancy to ensure that the existing alarm annunciators are fully compatible with the new ones. This will include any wiring diagrams and drawings to assist with any cross wiring that may be necessary.

Alarm annunciators are gaining popularity in the modern safety conscious world. Older installations that were facing obsolescence concerns are finding themselves ahead of the game in modern safety philosophy. Updating these systems to offer the latest features, capabilities and reliability is not only possible but common place.

For further information, contact Omniflex.

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