List of top Instrumentation and Process Control Questions asked in GATE Chemical Engineering

Consider the surge drum in the figure. Initially, the system is at steady state with a hold-up \( V = 5 \) m³, which is 50% of the full tank capacity, \( V_{\text{full}} \), and volumetric flow rates \( \vec{F}_{\text{in}} = \vec{F}_{\text{out}} = 1 \) m³/h. The high hold-up alarm limit \( V_{\text{high}} = 0.8 V_{\text{full}} \) while the low hold-up alarm limit \( V_{\text{low}} = 0.2 V_{\text{full}} \). A proportional (P-only) controller manipulates the outflow to regulate the hold-up \( V \) as \( \vec{F}_{\text{out}} = K_c (V - \vec{V}) + \vec{F}_{\text{out}} \). At \( t = 0 \), \( \vec{F}_{\text{in}} \) increases as a step from 1 m³/h to 2 m³/h. Assume linear control valves and instantaneous valve dynamics. Let \( K_c^{\text{min}} \) be the minimum controller gain that ensures \( V \) never exceeds \( V_{\text{high}} \). The value of \( K_c^{\text{min}} \), in h\(^{-1}\), rounded off to 2 decimal places, is _____.

A PD controller with transfer function \( G_c \) is used to stabilize an open-loop unstable process with transfer function \( G_p \), where \( G_c = K_c \frac{(T_D s + 1)}{(\frac{T_D}{20})s + 1} \) and \( G_p = \frac{1}{(s - 1)(10s + 1)} \), and time is in minutes. From the necessary conditions for closed-loop stability, the maximum feasible value of \( T_D \), in minutes, rounded off to 1 decimal place, is _____.

For the block diagram shown in the figure, the correct expression for the transfer function \( G_d = \frac{y_1(s)}{d(s)} \) is:

Consider the block diagram in the figure with control input u, disturbance d and output y. For the feedforward controller, the ordered pair (K, a/ẞ) is

Consider the control structure for the overhead section of a distillation column shown in the figure. The composition controller (CC) controls the heavy key impurity in the distillate by adjusting the setpoint of the reflux flow controller in a cascade arrangement. The sign of the controller gain for the pressure controller (PC) and that for the composition controller (CC) are, respectively,