Alarms and Events Not in the Alarm List but active on Grphic elements
When there is an active alarm then the element shall fill itself with grey color and shall flash 'W' in priority color on it. But at the moment it is only filling itself with grey color not the flashing 'W' and also no triangle on the right top of faceplate and no alarms in the alarm list also.
This happened earlier(few months ago) and I restarted OPCDA/AE for the control and safety networks, the alarms came up.
but it has happened again now. Any suggestions/Thoughts on why this is happening and how to avoid it?
Alarm indication varies depending on PLC kind and graphic library
- Which brand of PLC?
- Which choice of application library?
From the description it sounds like the alarm condition is received over OPC DA, but not OPC AE.
The sooner (OPC DA) does not necessarily mean alarm, e.g. a trigger signal (true/false) can be set to true to trigger the alarm in the PLC, but the alarm block configuration may be set to inactive or made incorrect (AC 800M alarm blocks have strict rules for unique names, length of strings, illegal characters, etc.).
With AC 800M, verify the alarm's Condition State using the Alarm Conditions function in Control Builder M when online with the application. Condition State 0 means "alarm not configured, or illegal alarm parameters" - such alarms may "show grey" but not with any color, etc. depending on the design in the graphic library.
If there is an alarm raised, e.g. from an alarm block in AC 800M it might still not be picked up by the OPC Server for AC 800M (a dedicated configuration is required to collect alarms). There are also some Product Alerts published on failures in the alarm propagation from AC 800M up to the OPC server. Please download & study these if you are using this PLC brand.
The OPC AE server might have flooded and lost an alarm.
The Alarm Manager of 800xA also has a limited FIFO buffer of known alarms. "Old" lingering alarms will eventually be flushed out of the FIFO queue, when this happen all OPC AE driven indications (alarm list, alarm band, alarm sequence bar, alarm global properties, etc.) will return to normal as if there were no alarm.
To reduce the risk for overflow, the Alarm Manager storage settings might need adjustments. In short:
a) Do NOT use "Make new alarm each time a condition gets active"
b) Declare separate and smaller (e.g. 500) "storage bins" for system related alarms while keeping process alarms in the 10.000 global storage.
Alarms can be deleted from the Alarm Manager by users having the "Administrate" privilege.
Finally, alarms can be hidden, shelved or grouped which may cause them to "vanish" from locations where you expect them. Alarm Global Properties on the object will tell if the are hidden, shelved, etc. alarms.