800xA time adjustment
A customer wants to adjust the system time on his 800xA system without causing any ill effects. How can this be done safely?
Here is the details from the customer:
Our DCS is 7 minutes behind local time. Can I change it, by ~30 seconds at a time, to see if it can handle it? Then do it over the course of a day or so? Our timers are all hour order of magnitudes, so I am not too worried about them; but I am concerned about PID’s. Do you have any experience with this? Seems like going forward would not matter, plus there are rate of change limits on the valve output…
- First of all, going ahead of time is much safer as compared to going back due to existing of History and Alarm and Event of previous time stamp.
- Yes it is possible to change the time. Before doing it, you need to check the time scheme of the system and it is healthy.
If Controller is the time master for CS and CS is time master for PPA and non PPA nodes (through NTP), then change can be initiated from the controller. Keep a check on Time Differences Tab in Service Structure- Time Service. Increment the time in smaller iterations of the order of 1 Minute. Wait and verify and go on with next..
- I really dont think so PID will be affected by time.
- THe things that will be affected are the Basic History and Alarm n Events. OPerator will this when plotting the trends.
If you can elaborate on your time scheme in detail, we can give you more detailed plan.