I have a boolean expression tag looking at machine line speed. If line speed drops below "50", the line is considered to be down, the indicator tag changes to "0". I have an alarm setup with an active delay of 3,600 seconds (one hour) to alert staff if the machine is down for over an hour.
- Notification pipelines are all working properly
- Indicator tag working as desired
- Alarm appears to work for nearly all downtime scenarios except as detailed below...
Occasionally, when trying to get the line back running, an operator may briefly jog the machine at production speed for a few seconds which flips my indicator tag back to "1". It appears that this is causing the active delay to also reset. This can cause a prolonged outage to not trigger the alarm. Is this expected behavior of the active delay?
Is there a simple way to ignore these incidental start-ups?
Try setting your clear delay to something other than zero, maybe 60 or 30.
Edit: Nope, this will only apply after the alarm has already turned on.
If I had to do something like this I would handle this in the PLC and ignore based on machine state. In this case, if they are jogging, I wouldn't allow a reset of the signal.
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I would agree, however, I'm using the jog term loosely here and this short 'start-up' is typically accomplished as a standard run command as opposed to a machine jog.
Well then how do you know the difference between a legitmate run command and something else? Whatever the answer to that question is what you use to reset.
This production line runs "sets". A set may require two or more hours of runtime. After a set is complete, on average, the line should be cleared and set up to start a new set within half an hour. Management would like to know if this outage duration extends beyond an hour.
As part of the reset process between sets, a splice is pulled through the machine. This is accomplished by issuing a run command to the line to progress the splice through the machine at run speed and that process is what is creating problems for my alarm as this resets the active delay. Say during the operation of pulling the splice through there were to be a mechanical issue and maintenance was called thus creating a longer outage... my alarm would not trigger for yet another hour.
Hopefully that makes sense - thank you for the discussion thus far.
You need to find something that only happens on initial startup of a new set. From the PLC/HMI perspective, if there is no difference between the two then it sounds like there isn't much you can do without creating a difference yourself.