Distributed Control Systems: Definition, Use Cases and Benefits Within CMMS

You’ve probably heard the phrase, “Don’t put all your eggs in one basket.” Managing physical industrial facilities, however, usually has very little to do with eggs – unless you recognize that the same timeless warning applies to both henhouses and physical plants.

Distributed Control Systems (DCS) were first introduced in the mid-1970s in response to the limitations and risks associated with centralized control systems. The design emerged from the vulnerabilities of control systems powered by a single digital computer. Control systems reliant on single computers managed numerous facility functions but posed significant risks of extensive damage and downtime in the event of a malfunction. 

Distributed systems, on the other hand, utilize multiple control computers, each overseeing a limited set of functions. This design significantly reduces the risk of widespread failures if one system experiences an issue.

In this article, we’ll explore control systems, including their functionality, benefits, and practical use cases across industries. We’ll also introduce the benefits of LLumin’s Computerized Maintenance Management System (CMMS+) in supporting DCS maintenance.

What Are Distributed Control Systems (DCS)?

A Distributed Control System (DCS) employs multiple control computers (or controllers) to manage and monitor specific processes or areas within a facility on a continuous basis. It is designed to distribute monitoring and control functions across multiple systems, which increases safety and efficiency.

These controllers communicate with a main control room where employees can monitor and view the real-time conditions of entire facilities and groups of equipment. DCS systems are frequently used in industrial plants and manufacturing facilities.

Types of DCS

Supervisory Control and Data Acquisition (SCADA) Systems

SCADA is a type of control system comprised of multiple computers, networks, and user interfaces that provide users with a high-level supervisory view of real-time machines and processes. It enables an organization to control and monitor multiple processes in a facility and remotely control facility infrastructure with human-machine interface (HMI) software. This type of system is critical for organizations that manage large-scale industrial facilities and plants, and it is the most commonly used, as it provides multiple means of interfacing with and remotely controlling these locations.

Programmable Logic Controller (PLC) Systems

A PLC is a type of industrial computer used to automate, monitor, and control individual devices. It is small and modular and designed to operate in harsh conditions and environments with dust, humidity, and vibration. PLCs can be programmed to perform tasks such as regulating temperature, controlling conveyor belts, and operating other types of machinery. For comparison, PLCs are designed to control individual devices, while a DCS can control multiple facilities, machines, and processes.

Process Automation System (PAS)

PAS systems collect information from measurement devices and monitor and control motors and valves in chemical plants, oil refineries, and paper and pulp factories. These systems are networked to sensors, controllers, operator terminals, and actuators. They share similarities in design to DCS and SCADA systems.

How a DCS Works: Components and Architecture

DCS maintenance requires an understanding of system components and architecture. In this section, we will provide a general overview of the key elements of a DCS system and explain how they work together to support continuous monitoring and control of facilities and processes.

DCS systems contain the following components:

Central Control Room

The control room integrates data from all control stations and manages the entire DCS system. It is equipped with computers running specialized software capable of providing a comprehensive overview of facility operations and KPIs (key performance indicators), documenting actions and historical events, and deploying new functions. 

Controllers

Controllers are responsible for monitoring and controlling processes throughout a facility. These devices collect data, communicate with other controllers, and process data using control algorithms. 

Human-machine interface (HMI)

HMIs provide a user interface that enables operators to monitor and control industrial processes in real time. They visualize process data and enable users to adjust parameters, troubleshoot issues, and access historical data. 

Data Networks

DCS systems rely on communication between all system components and the central control room. This is facilitated by network infrastructure that supports continuous data transfer. These networks can be wireless or wired but must ensure seamless, reliable, and real-time data transfer and updates. 

Smart Devices or Input/Output (I/O modules)

I/O modules are designed to connect controllers and other devices, such as sensors, actuators, and other equipment. These devices can convert digital signals into formats that can be processed by controllers. They come in various types that support various communication protocols. 

DCS System Architecture

A Distributed Control System has a distributed architecture comprised of multiple controllers and networked connections that facilitate reliable data transfer between components. This type of architecture differs from centralized control systems with main components in a single location. DCS system architecture is important for DCS maintenance and for a better overall understanding of how this system works. 

Devices used by DCS systems are divided into five levels, ranging from level zero that is comprised of field devices, upwards to level four which controls production scheduling.  These five levels include: Level Zero: This level is comprised of field devices, such as sensors Level One: This level consists of I/O devices, smart devices, and processors Level Two: This level includes supervisory computers that collect data from processor nodes.  Level Three: This level consists of coordinating computers responsible for production control Level Four: Is the computer center that is responsible for production scheduling

DCS hierarchical architecture consists of field sensors that gather and process information at level zero. This information is then sent to “level one” smart devices or I/O modules. These devices are responsible for managing process variables and supporting specific processes. 

From here, at level two, the data is moved to supervisory computers, where data is analyzed to produce specific outputs. Outputs are based on the control logic of whatever program or software is controlling operations. 

At the top level sits the main control room, responsible for overseeing ongoing processes and implementations. Here, main operators can gain a comprehensive view of the entire system, intervene when necessary, and send control actions to specific stations. 

DCS architecture enables redundancy and the system to scale and various levels. It also ensures reliability, so that if one part of the system fails, other parts of the system can support lost functionality and prevent unexpected downtime. It can also be the case that one DCS system is integrated with the aforementioned DCS systems, such as SCADA or PLC systems, and other legacy control systems. 

Benefits of Implementing DCS in Industrial Settings

The most important feature of a DCS system is its reliability, which provides redundancy and support in the case that one component of the system fails. However, there are other important benefits of implementing DCS in industrial settings. We will discuss them in more depth below.

Improved Reliability

Distributed architecture and redundancies ensure reliability and fault tolerance. The failure of one controller will not compromise the entire system, reducing the risk of catastrophic downtime. Redundant components and other backup mechanisms can be deployed to ensure system reliability. 

Efficiency and Scalability

Real-time monitoring and control enable industrial facilities to optimize processes and reduce waste and energy consumption. Further, DCS systems are highly flexible. More control units can be added as needed to accommodate additional equipment and processes. These units can also be integrated into the larger network without the need to reconfigure the entire system. 

DCS Maintenance and Monitoring

Software, such as LLumin’s CMMS+, and other diagnostic tools can be easily used to monitor health and performance remotely, without the need for manual and time-consuming inspections. Developing issues can be identified before they lead to unexpected mechanical failures and downtime. 

Improved Decision-Making and Performance

With actionable data, operators can make more informed decisions and respond to potential issues. Further, DCS systems enable fast response times, local control, and reduced latency.  

Compliance and Safety

DCS systems help organizations meet regulatory requirements and maintain a safer working environment. This is because continuous monitoring of critical parameters. When thresholds are exceeded, it will trigger alerts and enable fast response to developing issues. 

Use Cases of Distributed Control Systems Across Industries

DCS systems are used across several industries and applications. To provide a broader understanding of the importance of these systems and their role in monitoring and regulating essential processes, we have listed their most common use cases below:

Distributed Control Systems Across Industries
	Chemical and Petrochemical Plants: DCS systems are essential for monitoring and controlling chemical reactions, ensuring precise measurements, and maintaining safety standards. They are deployed to monitor several processes, such as distillation and polymerization, and help ensure chemicals and petrochemical products are high-quality while improving energy efficiency and reducing waste.
	Power Generation: Power plants deploy DCS systems to regulate turbines, boilers, and other critical systems. These systems can help optimize energy production and distributed by continuously monitoring and regulating process variables such as flow rates, temperature, and pressure. This enables operators to make necessary adjustments to minimize fuel consumption and increase overall performance levels.
	Food and Beverage: In this industry, DCS ensures production consistency and compliance with food safety regulations. It can manage several processes, including batch processing, cooking, cooling, and packaging.
	Oil and Gas: DCS plays an important role in managing pipelines, refineries, and offshore platforms, supporting processes such as production and refinining. By controlling and monitoring several processes, including drilling, pumping, and processing, it can help reduce the risks of leaks, hazards, and environmental risks, while helping to ensure reliable, undisrupted operations.
	Pharmaceuticals: DCS systems are crucial for maintaining compliance with regulatory standards, ensuring strict process control, as well as the accuracy of drug formulations. DCS systems can be used to monitor and control processes such as mixing, granulation, drying, and compression, and parameters such as temperature, pressure, and flow rates.

DCS Maintenance

Like other types of complex systems comprised of multiple components and equipment, proactive maintenance will play a critical role in ensuring your DCS system is up-to-date and serviced before unexpected breakdowns and downtime occur. 

Regular maintenance can improve the efficiency and reliability of your control system. Neglecting timely maintenance can increase risks of equipment failure, downtime, data loss, and potential safety hazards. In addition to performing regular maintenance, it will be essential to ensure your safety and cybersecurity protocols are updated and well-distributed. 

LLumin’s CMMS+ system can integrate with your DCS system and provide several benefits, such as real-time advanced analytics, predictive maintenance capabilities, and comprehensive maintenance planning, scheduling, and reporting tools. 

When you choose LLumin’s CMMS+, you can:

• Reduce Maintenance Costs: Leverage predictive insights to address potential issues before they escalate into costly downtime, emergency repairs, and last-minute inventory orders. 
• Optimize Asset Performance: Gain detailed insights into equipment health and performance, helping you make more informed decisions to improve asset performance and reliability. 
• Ensure Compliance: Easily meet regulatory requirements with advanced reporting and documentation tools that can help encourage team participation and accountability. 
• Inventory Control: Ensure you always have needed spare parts on hand. Reduce excessive inventory levels and stockouts.

How predictive maintenance strategies can enhance your distributed systems

Partner With LLumin

LLumin’s CMMS+ is an advanced maintenance and asset management solution capable of supporting multiple facilities and equipment types across industries. It has the tools and features organizations need to deploy and support proactive maintenance, monitor KPIs, encourage team accountability, and drive improvement. 

LLumin also provides a fully honed implementation process, ongoing training, and customer support, which will ensure your teams have the knowledge and hands-on experience needed to start seeing the results of proactive maintenance. If you have further questions about DCS maintenance, contact us today!