Hi everybody, good morning!
It is very important and well known that an alarm system is well maintained and that all alarms are configured following best practices to avoid overloading the operators. For process alarms, we have many parameters available that are vital to guarantee this, such as:
- Delay (ON and OFF);
- Hysteresis;
- Dynamic suppression according to other processes or equipment conditions;
- etc.
However, how do you guys deal with PVBAD and MODULE ALARMS? For example, sometimes it would be interesting to configure a delay off for an instrument failure or communication failure alarm, avoiding chattering behavior, but I don't think that Delta V inherently has this function. Is that right? So, how do you handle these kind of alarms in your sites? Any suggestions?
One option is to allow the Operator Supervisor (or any Operator, depending on your site standards/regulation) to shelve alarms that are in some conditions (for example, chattering), but it is more like an mitigating action and not preventive. Also, if the Supervisor takes too long to shelve it, there is a chance that a more important alarm occurs in the meantime and the operator may miss it because he was overloaded (safety issue). If we could configure parameters like delay off or dynamic suppression easily it would be a more elegant solution in my opinion, that should be used together with the shelving and/or other mitigating actions.
It is good to say also that each situation shall be evaluated carefully so you don't jeopardize the process safety. Do not configure hysteresis, delays and dynamic suppression without assessing the risks associated, and preferably involve a multi-disciplinary team for this task (Production, Automation and Process Engineers, and also senior Operators).
Best regards,
Rafael Araujo
I typically use a condition function block that we use to evaluate ^/BAD_ACTIVE.CV and then assign the module alarm to the OUT_D of the condition block. This gives you the ability to set a delay with "Time_Duration" parameter of the condition block. For an upgrade project this functionality would be incorporated into the PCSD or your site template modules.
In reply to gxmontes:
In reply to Michael Moody:
If you haven't already submitted this (good) suggestion to UDEP, best to get it in there so it makes it into version 15 . . .
The other nice feature would be for the SAM utility to capture all the settings from user-configured alarms.