ISA CAP Advanced Techniques & Methods 4

Question 1

Which advanced process control (APC) technique is most appropriate when the process has explicit operating constraints that must not be violated?

Accepted Answer

Model Predictive Control (MPC)

Answer

MPC inherently handles hard and soft constraints on inputs, outputs, and rate-of-change through its constrained optimization formulation.

Question 2

A process with a Right Half Plane (RHP) zero in its transfer function will initially respond in which direction when a step change is applied to its input?

Accepted Answer

In the opposite direction to the final steady-state change (inverse response)

Answer

An RHP zero causes inverse response: the process output first moves opposite to its eventual steady-state direction, severely limiting achievable closed-loop bandwidth.

Question 3

The LMTD (Log Mean Temperature Difference) correction factor F in a shell-and-tube heat exchanger design accounts for:

Accepted Answer

Deviation from pure countercurrent flow due to multiple passes

Answer

The F factor corrects the LMTD calculated assuming pure countercurrent flow to account for the mixed flow patterns in multi-pass exchangers.

Question 4

In process hazard analysis, what does LOPA (Layer of Protection Analysis) quantify?

Accepted Answer

Whether existing independent protection layers are sufficient to reduce risk to a tolerable level

Answer

LOPA computes the frequency of a hazardous event after accounting for the probability of failure on demand (PFD) of each independent protection layer.

Question 5

ISA-5.1 specifies that a valve positioner should be symbolized on a P&ID as:

Accepted Answer

A separate instrument bubble connected to the valve actuator

Answer

Per ISA-5.1, accessory devices such as positioners are represented as separate instrument bubbles tagged accordingly and connected to the primary final control element symbol.

(ISA CAP) ISA Certified Automation Professional Practice Test

(ISA CAP) ISA Certified Automation Professional Practice Test

ISA CAP Advanced Techniques & Methods 4