There can be four type of failures which can affect ESP:
1. Electrical
Motor winding burnout can happen. Insulation breakdown itself can happen, some cable damages or short circuits.
2. Mechanical
Shaft breakage happens, wear of bearing can occur, impeller damage or the coupling failure.
Keep good ...

I am not sure if I have got your query right.
Just to start with, what are he critical instrumented systems...
ESD
SIS
F&G
HIPPS - High Integrity Pressure Protection Systems
BMS
Critical alarms in DCS
Now are they maintained together with shutdown systems?
Functionally, they are connected but ...

I might have recommended you something deep; it's good you cleared us out.
Measurement & Instrumentation Principles by Alan S Morris.
Let me know if that helps.

Useful one.

Short, and precise explanation.
Keep that as reference document.

Check this. Well written.

See the motor management system is to protect the motor and benefits with the following:
1. starts only when safe
2. runs within safe electrical and mechanical limits
3. trips when necessary — for the right reason
4. reports what happened and predicts what may fail next
5. works with the control and ...

A good reference to follow.

First thing you need to look into is that a PCV that cannot move properly will NOT regulate pressure.
Possible issues here could be:
Stem seized
Actuator diaphragm/piston failure
Packing too tight
Grit, rust, debris lodged in the trim
Foreign material from upstream piping
Erosion of plug/seat ...

Thank you ww2i.