There are modern controllers which will detect this situation:
"When Open Loop Detection is enabled L.dE, the controller will look for the power output to be at 100%. Once there, the control will then begin to monitor the Open Loop Detect Deviation L.dd as it relates to the value entered for the Open Loop Detect Time L.dt. If the specified time period expires and the deviation does not occur, an Open Loop Error will be triggered. Once the Open Loop Error condition exists the control mode will go off and an Open Loop message will be display. If the process value goes in the opposite direction, a Reversed Loop message is display. The sensor is likely wired in reverse polarity."
If this crew was replacing an old cast iron gas main, it probably predated such controllers. That's not necessarily a bad thing. A mechanical controller can work for many decades. It's hard to get that level of uptime from microprocessors.
The real problem here is "maintenance induced failure". Especially on a system which is not fully shut down.
"When Open Loop Detection is enabled L.dE, the controller will look for the power output to be at 100%. Once there, the control will then begin to monitor the Open Loop Detect Deviation L.dd as it relates to the value entered for the Open Loop Detect Time L.dt. If the specified time period expires and the deviation does not occur, an Open Loop Error will be triggered. Once the Open Loop Error condition exists the control mode will go off and an Open Loop message will be display. If the process value goes in the opposite direction, a Reversed Loop message is display. The sensor is likely wired in reverse polarity."
If this crew was replacing an old cast iron gas main, it probably predated such controllers. That's not necessarily a bad thing. A mechanical controller can work for many decades. It's hard to get that level of uptime from microprocessors.
The real problem here is "maintenance induced failure". Especially on a system which is not fully shut down.
[1] https://www.watlow.com/-/media/documents/user-manuals/pm-pid...