To Tag or Not to tag?
Alarming Differentiation
HMI alarming is used to notify workers and machine operators of component failures or changes in operation. For these notifications, timing is an essential factor, both in how accurately the time of the change is recorded and how quickly that message is communicated. As HMI software has improved over the years, the methods for alarming have become faster and more accessible, enabling users to more quickly respond to and resolve issues in machinery.
Server-side alarming is the traditional method of alarming for legacy controllers from Rockwell Automation® (non-Logix5000) and controllers from other manufacturers. Server-side alarm management is available through Rockwell Automation’s HMI platform, FactoryTalk View Studio. While this method is more advanced than RSView32 or legacy HMI alarms, there are still some downsides. Server-side alarming generates a considerable amount of network traffic, which can exceed the bandwidth capacity for a Local Area Network (LAN) if there are other high-speed devices connected via Ethernet and many tags and alarms set to continually scan. Additionally, server-side alarms are time stamped at the HMI, which means less-than-accurate results.
Logic-based alarms are an improvement over server-side alarms in terms of speed and accuracy. When the alarm triggers in the processor, a message is broadcast to all the HMIs that are attached to that processor, significantly reducing the load on the network’s bandwidth. Additionally, when a Logix-based alarm is triggered, the time stamp is generated from the processor and then sent to the HMI as a history that can be logged. This makes the records more consistent than in server-side alarming, where the time stamps register as they are received by the computer (meaning that if an alarm triggers when an HMI is not started up, the HMI will have no history of the alarm).
Controller-side and Logix tag-based alarms are an alarming functionality that can be managed from one central location (Studio 5000 Logix Designer), minimizing the time it takes for operators to get this data. In these methods, alarms are defined on “tags” or “structures” in the controller. These types of alarming are designed to handle applications with high alarm counts, as they require only periodic evaluation, support bulk generation of alarms via XML import/export and have a small memory footprint, creating less network traffic. Studio 5000 offers a single environment for configuring/editing alarms and simplified design workflows that require no additional programming. For example, when defining alarms, there is no need to add instructions on a rung of ladder code to indicate whether it is an analog or digital alarm, and, when triggered, alarms are automatically sent to FactoryTalk Alarms and Events.
Users can streamline their alarm management solutions by integrating Logix tag-based alarms through FactoryTalk View SE and FactoryTalk Optix. These alarms are configured directly within the Logix controller tags. When using this alarming in FactoryTalk View SE and FactoryTalk Optix, there is no need for additional alarm logic, custom scripting or tag duplication. The native communication makes for easier and shorter engineering and development processes and ensures consistency in alarm definitions across the entire system. Alarms are automatically displayed in real-time on the HMI screen and are able to be logged in a historical record, improving response times and knowledge of the state of the overall system.
Not only do FactoryTalk View SE and FactoryTalk Optix work seamlessly with Logix tag-based alarms, but they also support advanced alarm handling features such as shelving, prioritization and filtering. These functionalities provide contextual information to alarms for more advanced and faster troubleshooting. Additionally, Studio 5000 offers centralized alarm configuration (for easier maintenance and management) and FactoryTalk Optix's cloud-connected architecture enables scalable, cross-platform visualization and remote access to alarms. Logix 5000 controllers from Rockwell Automation® that support tag-based alarms include the ControlLogix 5580, GuardLogix 5580, CompactLogix 5380, Compact GuardLogix 5380, CompactLogix 5480 and FactoryTalk Logix Echo (V2 and up). Tag-based alarms are also available with firmware V31 or later. Using a fully-integrated Logix system with tag-based alarms optimizes both plant-floor and enterprise-wide operations.
Questions
Contact your McNaughton-McKay account manager or visit your local branch to learn more about alarming differentiation and which set up is right for your project.