One of our PET resin plant is in a shut down mode and some of its instruments such as pressure transducers, flowrate measuring devices and temperature sensors are giving reading that doesn't make a whole lot of sense. For example the flow rate for Ethylene glycol is showing to be 200 Kg/hr but its not even possible since the plant doesn't have any material left inside it at all. Similary, one flow rate is showing -300 Kg/hr. Similar problems are being faced some temperature and pressure sensors.
Heres my question for Electrical engineers (Since, I am not one) are those false reading common for instruments? or we need to pull them out and re-calibrate them? so the flow rates show No flow at all i.e., 0 kg/hr or is there something about these instrument that they are only designed to work when something is actually flowing through them or else they will show strange readings?
I apologize if my question looks stupid :p but some input from y'all would be awesome ^^