Recently that we have reviewed the key criteria for selection of a PLC or DCS, you may be thinking that your application needs capabilities from both a PLC and a DCS. If this is TRUE, then you may need a process control system for hybrid applications.
What is a "hybrid?"
• The discrete functions marriage, which PLCs handled so simply and economically, with the sophisticated analog continuous control capabilities of the DCSs
• Defined based on the industries in which the systems serve and work, like fine chemicals, pharmaceutical, food and beverage, and others"
• The PLC architectural marriage simplicity and cost with the sophisticated alarm management, operator displays, and easy but sophisticated configuration capabilities of the DCS.
This article has described the key attributes and differentiators between classic PLC and DCS systems. This same information can be used to identify the key requirements for a process control system that would be ideally suited for hybrid applications, such as those in the fine chemicals, pharmaceutical, and food & beverage industries.
• Controller – Can execute fast scan logic (10- 20 msec), such as that required for motor control, and slow scan logic (100 - 500 msec
• Engineering Configuration Languages – Provides function block diagram, ladder logic, and a powerful programming language for creation of custom logic from scratch
• Flexible Modular Redundancy – Offers the tailoring option of the level of system redundancy to deliver the required system availability by balancing up-front cost versus the cost of unplanned downtime
• Modular Batch from Simple to Complex – Provides modular batch capability to cost-effectively address the simple continuum to complex batch applications
• Alarm Management – Offers power alarm management tools to help operators effectively respond to plant upset conditions
• Asset Management and System Diagnostics – Provides both a rich set of built-in system diagnostics, as well as asset management of all critical assets in the plant (valve positioners, transmitters, heat exchangers, motors, drives, MCCs, etc.)
• Scalable Platform – software, hardware, and licensing supports smooth and economical scale up from small all-in-one systems (10's of I/O) up to large client/server systems (10,000's of I/O)