Standardized Integrated Alarm Management
Alarm management is a delicate matter, show too many alarms to an operator and alarming becomes in-effective, show too few alarms and again alarming becomes in-effective. As pictures tell a thousand words, below two pictures involving in-effective alarm management.
Milford Haven refinery UK 1997 BP Oil Refinery Texas City 2005
(Too many alarms shown) (Too few alarms shown)
The following article in Control Engineering Magazine describes the value of alarm management.
The article aims to create awareness that alarm acknowledgement is a paradigm, how it is universally considered as a necessity and that a certain level of operator involvement is always required. PLC-Easy does not use/need alarm acknowledgement due to the active automated alarm management and due to the innately higher level of automation. This makes it more suitable for a "lights out" situation as it requires significantly less operator interaction.
PLC-Easy has standardized abnormal situation alarm management incorporated in its' library modules that follows the "Effective Alarm Management Practices" guidelines by the ASM Consortium and the ISA 18.2 standard.
In contrary to conventional PLC-SCADA and DCS solutions, in the PLC-Easy solution, alarms, alarm management and status notifications are PLC based and do not reside in the SCADA system. Alarm messages etc., are automatically grouped, ordered, masked out and structured according to the S88 physical model of the application per the "Effective Alarm Management Practices" guidelines and ISA 18.2 standard. As PLC-Easy is a DCS solution in a PLC-SCADA environment, existing conventional alarms or customized non PLC-Easy based alarms can be configured in the SCADA system and combined with PLC-Easy alarms as per current industry standards and the client's alarm management philosophy.
Every alarm, warning, hardware diagnostic message etc. automatically contains the condition that caused the event (a device or process state), the consequence, the affected device(s) including the S88 path, the state of the affected device(s) and an accurate time stamp. The time stamp originates from the PLC and not the SCADA system and is accurate. This allows an operator to accurately determine a sequence of events and subsequently identify the root cause of an issue almost instantaneously.
This makes an operator more effective in identifying and resolving the underlaying issue that has caused the event.
Example: Low level switch 1401 has turned off creating a protection interlock to the Pasteurizer2 control valve 1401 causing it to trip.
Code generators are often used for the development of control software as these reduce the development time considerably. Despite that code generators reduce the development time, they don’t reduce complexity in control software but in fact do often the contrary. Most generator tools are rigid, require a high level of expertise and often need “work around's” once a control system is commissioned.
The unprecedented high level of standard software modules in a PLC-Easy application and the integrated standardized alarm management, makes PLC-Easy very suitable for code generation (N.B. PLC-Easy is not a code generator). Because of the high level of standard software modules in a PLC-Easy application (at least 80%), a code generator will not add complexity to the application nor will it cause a dependency on the code generator as code generators for conventional PLC and DCS application architectures often do. In fact, the code of a generated PLC-Easy application can barely be distinguished from an application that was created by a programmer.
Most importantly, a code generator in combination with PLC-Easy will not lead to "vendor locking" and leaves the end user with the empowerment that characterizes the PLC-Easy solution.