This organization ensures businesses take all necessary measures to prevent major accidents involving dangerous substances such as ammonium nitrate and is enforced by the UK Health & Safety Executive (HSE).
However, during a review of the emergency shutdown system under IEC61508 Functional Safety Standard, officials found they needed an urgent upgrade of electrical, control and instrumentation to satisfy SIL2 System designation.
That end, the fertilizer company and HSE selected Moore Industries STZ and STA to provide a hardwired shutdown system meeting the requirements for SIL2 system capability.
The STZ temperature transmitter features sensor backup and failover capability along with a flexible configuration to accept a range of existing thermocouples. The STA trip alarm, which is the company’s plant standard for SIL hardwired trip alarms, features highly reliable relays and configuration software that is easy-to-use yet robust.
The STZ accurately measures redundant temperature sensors and provides measurement and sensor diagnostics. Should the primary sensor fail, the backup/failover sensor will be transmitted to the STA, Safety Trip Alarm.
The STA relays trip when conditions exceed the temperature high and low limits for process safety, triggering an alarm and emergency shutdown. The STA also retransmits its temperature input back to the DCS, via its 4-20mA analog output.
One of the main areas needing attention was the critical temperature monitoring of the reactor process and the requirement for hardwired alarms on selected safety loops.
Source: Moore Industries