Process Control Loop Testing
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...
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Identify Level Control Loop Tuning Problems
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...
Process Control High Level Alarm Fault Analysis
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
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,...
Liquid Flow Control Loop Controller Action
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...
Practical Process Control System Questions & Answers – 16
Inspecting the trends of PV and SP on a process chart recorder, you notice the poor quality of control: The “wandering” of the process variable (PV) around setpoint may be...
Practical Process Control System Questions & Answers – 14
In this process, maple syrup is heated as it passes through a steam heat exchanger, then enters an evaporator where the water boils off. The purpose of this is to...
Practical Process Control System Questions & Answers – 13
In this process, maple syrup is heated as it passes through a steam heat exchanger, then enters an evaporator where the water boils off. The purpose of this is to...
Practical Process Control System Questions & Answers – 12
In this process, two chemical streams are mixed together in a reactor vessel. The ensuing chemical reaction is exothermic (heat-producing) and must be cooled by a water cooling system to...
Practical Process Control System Questions & Answers – 11
Examine this P&ID for a level control system in a vessel where two different fluids (Feed A and Feed B) are mixed together: Determine the effect on the control system’s...