Electricity and Control April 2023

SAFETY OF PLANT, EQUIPMENT + PEOPLE : PRODUCTS + SERVICES

Upgrading safety-critical alarm annunciators

Businesses in the nuclear, petrochemical and oil and gas sectors generally follow best practice guidelines, like the EEMUA 191 standard, with respect to safety-critical alarm systems. However, as regulations increasingly re quire data acquisition and sequence-of-events capabili ties for critical alarm systems, it can be difficult for plant managers to find a cost-effective way of keeping up. Gary Bradshaw, Director of remote monitoring specialist Omniflex, says installing a distributed alarm annunciator system can provide the solution. In high-consequence risk environments like the nuclear, petrochemical and oil and gas industries, the use of safety, health and environmental (SHE) alarms is a key part of best practice guidelines like the EEMUA (Engineering Equipment and Materials Users Association) 191 standard. One of the key requirements of the EEMUA 191 standard is that critical alarms must be easy to understand, promoting quick and effective operator responses. This is where traditional hardwired alarm annunciators play a role as they promote ease of use and rapid responses. Alarm annunciators are panel-based alarms that are hardwired directly into relevant safety-critical processes, where each window relates to a fixed alarm point from the sensor. If an abnormal event is detected, the rele vant window on the panel lights up and the alarm emits a sound, immediately giving operators the necessary in formation to act. Bradshaw says it is common to still see in use alarm annunciators that were first installed in the 1980s and 1990s. Some of these are no longer manufactured or supported and most do not meet the current safety re quirements. As a result, many sites face obsolescence and support issues and now need to upgrade critical alarm systems. Updating alarm systems He says there are three key considerations that plant managers need to take into account when updating alarm annunciators in their facilities. Firstly, it is crucial that they determine which alarms are classified as SHE alarms and ensure that these are directly hardwired into the processes. This is essential because networked alarms can be susceptible to outages, which means, if the network goes down, the plant loses all the alarms on that network. If alarms are individually hardwired and one wire is lost, only one alarm is lost, and if this alarm is detected from a normally closed alarm contact, then a wire break would still be seen as an alarm on the annun ciator window. The second consideration is the importance of having each of the alarm windows on the annunciator panel per manently dedicated to a specific process. This facilitates pattern recognition and familiarity for the operators and improves operator response times, an important aspect of safety standards.

Distributed alarm annunciator systems, like the Maxiflex system, can help safety-critical facilities meet strict safety standards. Thirdly, all alarms should be appropriately prioritised using an easy-to-understand system, such as colour coding each window to match the severity of the alarm it represents. This gives operators a clear order of priority in situations where multiple alarms go off and further sup ports them to respond quickly and effectively. Maximum flexibility Omniflex’s Maxilarm alarm annunciator system offers a complete distributed modular alarm management sys tem for safety-critical plants. It incorporates features such as sub-millisecond time stamping at source, inte grated analogue logging and remote Omni X LED alarm fascias, to meet EEMUA 191 guidelines. The Maxilarm system provides a dependable layer of plant protection and early diagnostics of faults in real time. The system can be configured using standard 24 Vdc and 48 Vdc input modules and has specialist sequence of-event digital input modules. These ensure all the digi tal inputs are time stamped in real time to a resolution of less than one millisecond. It is ideal in facilities where the potential for multiple simultaneous alarms is high and it is important for operators to know the chronological order of alarm alerts. It also improves data auditing and event analysis capabilities.

For more information contact Omniflex. Email: gary@omniflex.com Visit: www.omniflex.com

28 Electricity + Control APRIL 2023