UDT Expression Tag Alarm With Active and Clear Delay Prevents Pipeline From Triggering

Ignition
1

Hi

I'm working on a Heat Stress system that uses tag alarms and pipelines to notify users when the conditions of their work area requires additional relief from work.

Inside a UDT, I have it setup where, given a temperature memory tag (will be an OPC tag in Production), an expression tag will take the value and translate it into a state integer (ex temp > 31.5 state = 5). I have 4 alarms setup for the expression tag, when the state (value) is 2, 3, 4, and 5. Each of the 4 alarms has an active and clear pipeline notification that is used for contacting users. Everything is working properly up to this point.

However, I want to prevent notification from occuring when the state is constantly switching between 2 because of the temperature reading being on the cusp of the state thresholds. I attempted to use the Active Delay and Clear Delay with a delay of 30 seconds for each to accomplish this. It appears though that when I implement these delays that it prevents the alarm pipelines from triggering altogether.

Is this the correct path I should be taking to implement the delays?

2

No, you should be using deadband on the temperature value, not time delays.

It is somewhat difficult to do with your architecture, where you are turning off lower-priority alarms when higher levels are hit. Consider not using an expression to yield a state. Instead, place the four alarms on the temperature tag with the levels as the alarm setpoint, and include a small deadband on each alarm. Let the lower priority alarms stay active when the higher priority engages.

3

The reasoning for the expression tags was because we have a different set of relief states for workers who are acclimatized vs non-acclimatized to the conditions of the work area. I guess I could still manage to have that work out as alarms directly on the temperature tag. In my mind it just seemed simpler the way I initially set it up.