Configuration implementation considerations for distributed control systems
There are many manufacturers that have designed and built distributed control systems (DCSs) with a large selection of features and enhancements to choose from. No matter what the control systems platform’s structure is the tag name/point name implementation methodology is basically the same. There are some things that can be done before the actual plant implementation is done onsite to make this process more efficient. Once the necessary research and proper investigation of interface circuitry for field instruments is done, the configuration process is more reliable and cost-effective for the client-especially during a plant turnaround with time restraints.
The control systems engineer is familiar with the software connections and the main DCS parts through the control system configuration. To understand what type of devices an engineer will be interfacing with, the following considerations are noted:
- Hardwired inputs. These physical wires make the connection between the DCS and the field. For example, the analog input signal by voltage, thermocouple type and resistance temperature device.
- Other field devices such as control valves. When considering the implementation of control valves, care must be given to the regulatory controller action inside the DCS whether the valves is a fail open or fail close type. The process and I&E engineers verify the information and pass it on to the control systems engineer for correct configuration of controllers.
- Digital representation. This is another signal represented by a square wave that is either high or low, on or off. They control the interactions of devices such as pumps, motor starters and solenoid valves. The I&E technician would have to know what device and circuitry to pass this information to the control systems engineer.
- Tag name/point name configuration. This configuration is the measuring boundaries that may also be known as ‘process variable engineering unit low and process variable engineering unit high.’ Based on process engineering and I&E technical information, a value should be determined and given to the control systems engineer.
- Alarming values must be determined. This will give the control system an indication that a trip valve has been reached. These valves are significant because this lets the process operator know what adjustments to make to keep the process in a safe condition and protect personnel and equipment.
These are some of the basic configuration parameters that are used no matter what DCS platform is been used. Keep in mind that a particular control system will have similar descriptions, but in principle, they convey the same information.
This post was written by Ronnie Harris. Ronnie is a senior engineer at Maverick Technologies, a leading automation solutions provider offering industrial automation, strategic manufacturing, and enterprise integration services for the process industries. Maverick delivers expertise and consulting in a wide variety of areas including industrial automation controls, distributed control systems, manufacturing execution systems, operational strategy, business process optimization, and more.
Maverick Technologies is a CSIA member as of 10/25/2016.
Honeywell Automation College
Fundamentals of Process Control Theory—–Paul W. Murrill
Safety Instrumented Systems: Design, Analysis and Justification, 2nd Edition —–Paul Gruhn & Harry L. Cheddie
Emerson/Fisher Valve Handbook —–Emerson Process Management
Purdy’s Instrument Handbook #1—–Ralph Dewy, 2008 Edition
Purdy’s Instrument Handbook#2 —–Ralph Dewy, 2015 Edition
Purdy’s Instrument Troubleshooting —–Ralph Dewy, 2001 Edition
Ugly’s Electrical References —–Jones & Bartlett Learning, 2014 Edition