Loop Checking and Tuning Basics
This content is designed to introduce the user to the concepts of loop checking of instrumentation at a facility, as well as the fundamentals involved with tuning the loops to get an optimum response and ultimately better control of the facility / installation. The content is broken up into two distinct sections:
- Loop Checking
- Tuning Basics.
The two modules are intended to be a guide for an engineer or instrument technician with limited knowledge of loop checking and tuning concepts, and wishes to expand their knowledgebase.
The first section deals with the loop checking process. It doesn’t focus purely on checking the loop during start-up of a plant / facility / installation, instead it considers the loop checking to be an ongoing function of continuous improvement, as it looks at the loop tuning over time to ensure the loop performance is kept at an optimum level. It details the basics for performing a loop check, the requirements needed to perform the initial loop check at a Factory Acceptance Test (FAT), and the requirements to perform / repeat the testing during Site Acceptance Test (SAT).
It also then reviews the processes required to benchmark the tuning of the control loop (as the tuning will degrade over time). It looks at what is required to design and perform the test, and then analyse and report the test results. The final part of this section looks at sustaining the performance of the control loop through maintenance strategies and specific loop performance programs.
This section of the module looks at the tuning basics for control loops. It looks at the different control actions that can be configured for the controller and the valve (final element), and the different control functions available for tuning. It details the PID (Proportional Integral Derivative) control algorithm and the effects of adjusting each individual component of the PID control, various methods to tune the loops (Lambda tuning; Ziegler-Nichols tuning; etc.), an overview of adaptive control, and the tuning requirements for different applications (i.e. cascade loops; compressor loops; heat exchanger loops; etc.).