The questions that are important while preparing for interviews are
1. How to use a differential pressure transmitter for level measurement?
A differential pressure transmitter yields a linear output for the differential pressure measured across its chambers, HP and LP.
So you have to connect transmitter’s HP leg to the bottom of the tank and its LP leg to the top of the tank.
2.Why a gap controller used in controlling a level in a high pressure vessel?
Gap controller’s yield changes from minimum to maximum and vice versa when the process measurement diverges the set point by the set gap. Thus, the final control element i.e. control valve acts like an on-off valve.