Practical Instrumentation Questions - Instrumentation Tools

pH Monitoring System Triggers an Alarm

This pH monitoring system triggers an alarm if the pH value of the process water in the neutralization tank drifts past trip values.

Solenoid-controlled valve refuses to move when the operator pushes the switch. The control valve remains in fully-closed position.

Two pressure-actuated lifts are used to raise a heavy weight off the ground. One lift uses oil under pressure while the other uses air.

Explain what these symbols represent, and how they are to be interpreted. Also, comment on the construction of a spool valve.

Describe in detail the effect this calibration error will have on the performance of the analytical process control system.

Sketch arrows next to each of the two solenoid valves showing the directions of air flow in the energized (E) and de-energized (D) states.

Determine the necessary PLC switch actuation status (i.e. low versus high process stimulus) to turn the yellow lamp on.

Inspecting the trends of PV and SP on a process chart recorder, you notice the poor quality of control loop.

A potable water storage tank requires a high level alarm to warn operations personnel. Design a simple indicator circuit.

Describe in detail the effect this heat exchanger problem will have on the performance of the analytical control system.