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Instrumentation Questions For You

Process Control Loop Testing

S Bharadwaj Reddy
A very useful technique for testing process control loop response is to subject it to a “step-change” in controller output. In other words, the process is perturbed (the highly technical...

Identify Level Control Loop Tuning Problems

S Bharadwaj Reddy
A level control loop is supposed to maintain a constant level of liquid at the bottom of the stripping tower where considerable amount of vibration exists, but it seems to have...

PLC Permissive for Motor Control

S Bharadwaj Reddy
A engineer needs to write a PLC program to control a water pump driven by an electric motor. This water pump will be manually started and stopped by pushbutton switches,...

Process Control High Level Alarm Fault Analysis

S Bharadwaj Reddy
An operator reports a high level alarm (LAH-12) displayed at the control room for the last 13 hours of operation, in this sour water stripping tower unit (where sulfide-laden water...

Compressor Emergency Shutdown Root Cause Analysis

S Bharadwaj Reddy
The compressor emergency shutdown system (ESD) has tripped the natural gas compressor off-line three times in the past 24 hours. Each time the operator goes to reset the compressor interlock,...

Solenoid Valves Practical Problems

S Bharadwaj Reddy
Suppose this valve control system has a problem. The control valve (LV-104) does not move to the full-open position as it should when the solenoid is de-energized, although it will...

Troubleshoot Allen Bradley PLC Logic

S Bharadwaj Reddy
A engineer needs to write a program for an Allen-Bradley CompactLogix PLC to control a pressure relieving solenoid valve in a gas processing system. A pair of high-pressure control switches...

Liquid Flow Control Loop Controller Action

S Bharadwaj Reddy
A liquid flow control loop consisting of a flow transmitter (FT) to sense liquid flow rate through the pipe and output an electronic signal corresponding to the flow. A flow...

Motor Trip Logic using PLC Programming

S Bharadwaj Reddy
Programmable Logic Controller (PLC) Questions and Answers This PLC is being used to start and stop an electric motor, and also to shut it down automatically if any of three...

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