Instrumentation

Control Narrative

What is the control narrative?

A system control philosophy is a document that contains a description of the operating philosophies prepared by process engineers.

The control narrative describes the control philosophy as well as the variables in the control program. Field instrument parameters, pumps, valves, and other process equipment status signals are examples of variables.

Detailed Explanation of Control Narrative

A statement of the main operating principles is found in a document called a system control philosophy. The Control Narrative describes the control philosophy and identifies the control program’s variables. Alarm set points and shutdown values are typically described in control narratives.

The control narrative specifies the conditions for the system’s programming. The Control Narrative explains the plant operation philosophy and variables to be involved in the control program. Variables include field instrument parameters, pump, valve, and other equipment status signals, and field instrument, equipment, and smart safety relay information. A control philosophy improves definitions, concepts, and procedures during design and implementation.

What is the purpose of a control narrative?

Most of the time control narratives are used for three reasons. Control narratives provide:

  • Process engineers have the chance to set out and record operational procedures on the plant floor.
  •  Documentation for operator training and comprehension of the process’s equipments, variables, For all processes, the control narrative should always be included in the skill block handbook and new operator training materials.
  • A starting point for control system programmers to write configuration code for the control system that will control the process, even if they have little experience with that particular process.

Overall, the purpose of a control narrative is to provide a comprehensive understanding of the process and its performance, which in turn can be used as a base to develop control logics for DCS/PLC systems by automation engineers.

What is included in Control Narrative?

A Control Narrative includes:

  • Process Overview: Basic description of the overall system process, including its purpose, process timeline by functional unit, major functional unit descriptions, basic description of the subsystem process, and how it works with utilities.
  • Equipment List: A complete list of all the physical equipment used in the process. Some of these are motors, valves, transmitters, and so on.
  • Software Components: Non-physical devices that are involved in the process. Control loops, totalizers, calculations, and parameters are examples of these.
  • Alarms: All non-default alarms linked with the process are defined here. These alarms will be shown in a number of places on the user interface.
  • Process Functionality Description (Interlock and sequence): Sequence descriptions are step-by-step procedures that explain how the unit works.

A. Sequence Area

1. Sequence Set Points

a. Sequence Steps

Interlocks are any corrective actions that are meant to protect the product, people, or equipment.

Concurrent Tasks: A definition of all normal process control functions that work independently of the sequences.

The chart below is an example of a control narrative chart.

control narrative chart 1
control narrative chart 2

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