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Instrumentation Technician Course - Process Control Loops -Lesson 1

Updated: Dec 7, 2020

My name Is Chris and welcome to the site! I'm here to teach you all, about the skills and knowledge it takes to be an Instrument technician in industry today.

Firstly, If you don't already know, I'm going to explain what an Instrument Technician Is and what it is we do. I've been an Instrument & Control technician for over a decade now, working in the Oil & Gas industry for the last 7 years.

An Instrument technician generally works on automation and safety equipment within Industry.

Process Variables

Industry has various types of process variables it wishes to control, here are the main ones you will find:

  • Pressure – This could be the pressure of gas within pipework.

  • Temperature – The temperature of a reactor for example.

  • Flow – The flow of chemical dosing in a process plant.

  • Level – The height of liquid in a vessel

  • PH – The PH of waste water.

Process Control Loops

Instrument technicians interact with all the equipment that measures and controls these process variables.

These all form part of a "process control loop" that aims at controlling a process variable at a desired set-point. A process control loop is made up of the following parts:

  • Process variable

  • Set-point

  • Sensor

  • Logic solvers

  • Actuators.

Example Process Control loop - Home Heating

Let’s explain the components of the process control loop with an example we are all familiar with - A home heating system - This isn't exactly how all heating systems work but it will help us understand a process control loop in terms we are all familiar with.

In our example of home heating system, we have all the components of a process control loop.

Set-point - This is the temperature we decide we want our rooms to be so we are nice and comfortable.

Process variable - This is the actual temperature of the room at this very moment.

The sensor - In this example the thermostat of the heating system is the sensor. It sends a signal of the current temperature of the room to the boiler.

Sensor - In this example the thermostat of the heating system is the sensor. It sends a signal of the current temperature of the room to the boiler.

The logic solver - Our boiler electronics is acting as the logic solver. Comparing the set-point, the temperature we want our room to be, the Process Variable, the actual temperature of the room and deciding when to turn the boiler on.

The actuator - Actuators act to control the process variable. Our radiators in the room are the actuators. When the boiler ignites and pumps hot water to the radiator the room starts to warm.

These separate parts all work to keep the room at the perfect temperature.

This is the same in industry – Although sometimes things are a lot more complicated!

What Instrument Technicians do with process control loops

Calibration of sensors – This is comparing the sensors against a constant in order to ensure accuracy of the equipment.

Planned maintenance - As well as calibration this can also include function testing of equipment to make sure it behaves as expected and prevent future breakdowns.

Repair – When planned maintenance fails to prevent equipment going wrong, Instrument technicians will be tasked with the repair of failed Instruments. This involves skilled fault finding.

Safety Systems

As well as working on process control, Instrument techs also work with plant safety systems. This involves working on emergency shutdown systems that automatically put the plant in a safe condition if there is an emergency.

On petrochemical sites there is also equipment that detects fire and gas releases. Instrument technicians will be responsible for maintaining this equipment.

Hopefully This has given you a good introduction into what it is Instrument Technicians do. We will explore these topics in depth in future articles.

Check out my YouTube Video below on the same subject if you like the visual format!

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