What Are Industrial Control Systems?

Control systems are computer-based systems that are used by many infrastructures and industries to monitor and control sensitive processes and physical functions. Typically, control systems collect sensor measurements and operational data from the field, process and display this information, and relay control commands to local or remote equipment. In the electric power industry they can manage and control the transmission and delivery of electric power, for example, by opening and closing circuit breakers and setting thresholds for preventive shutdowns. Employing integrated control systems, the oil and gas industry can control the refining operations on a plant site as well as remotely monitor the pressure and flow of gas pipelines and control the flow and pathways of gas transmission. In water utilities, they can remotely monitor well levels and control the wells’ pumps; monitor flows, tank levels, or pressure in storage tanks; monitor water quality characteristics, such as pH, turbidity, and chlorine residual; and control the addition of chemicals. Control system functions vary from simple to complex; they can be used to simply monitor processes—for example, the environmental conditions in a small office building—or manage most activities in a municipal water system or even a nuclear power plant.

In certain industries such as chemical and power generation, safety systems are typically implemented to mitigate a disastrous event if control and other systems fail. In addition, to guard against both physical attack and system failure, organizations may establish back-up control centers that include uninterruptible power supplies and backup generators.

There are two primary types of control systems. Distributed Control Systems (DCS) typically are used within a single processing or generating plant or over a small geographic area. Supervisory Control and Data Acquisition (SCADA) systems typically are used for large, geographically dispersed distribution operations. A utility company may use a DCS to generate power and a SCADA system to distribute it.

A control system typically consists of a “master” or central supervisory control and monitoring station consisting of one or more human-machine interfaces where an operator can view status information about the remote sites and issue commands directly to the system. Typically, this station is located at a main site along with application servers and an engineering workstation that is used to configure and troubleshoot the other control system components. The supervisory control and monitoring station is typically connected to local controller stations through a hard-wired network or to remote controller stations through a communications network—which could be the Internet, a public switched telephone network, or a cable or wireless (e.g. radio, microwave, or Wi-Fi) network. Each controller station has a Remote Terminal Unit (RTU), a Programmable Logic Controller (PLC), DCS controller, or other controller that communicates with the supervisory control and monitoring station. The controller stations also include sensors and control equipment that connect directly with the working components of the infrastructure—for example, pipelines, water towers, and power lines. The sensor takes readings from the infrastructure equipment—such as water or pressure levels, electrical voltage or current—and sends a message to the controller. The controller may be programmed to determine a course of action and send a message to the control equipment instructing it what to do—for example, to turn off a valve or dispense a chemical. If the controller is not programmed to determine a course of action, the controller communicates with the supervisory control and monitoring station before sending a command back to the control equipment. The control system also can be programmed to issue alarms back to the operator when certain conditions are detected. Handheld devices, such as personal digital assistants, can be used to locally monitor controller stations. Experts report that technologies in controller stations are becoming more intelligent and automated and communicate with the supervisory central monitoring and control station less frequently, requiring less human intervention.

Checklists for Industrial Wireless Systems Deployments

Checklists for Industrial Wireless Systems
The document "Guide to Industrial Wireless Checklists", developed by the National Institute for Standards and Technology, is intended to be a practical guide used by engineers and managers facilitating them to go through the process of defining the objectives of their wireless systems and examining the environments where the wireless systems are to be deployed, then helping them in selecting, designing, deploying, and monitoring the wireless systems using existing technology in a factory.

Checklists from the above referenced document have been culled and available here for download.



Network Backbone Basics: Hubs, Bridges, Switches, and Gateways

Network Backbone Basics
As the process industry steadily moves to wireless networking components, its important to understand the basics. This post and the video below describe four key backbone components for data networking.

Signal flow and data transfer are assisted within a network by various devices known as backbones. The four different backbone devices are hubs, bridges, switches, and gateways. Each device transports data in a specific way.

A hub is a centralized connecting device. Often located at a center of a star network that automatically rebroadcasts any signal or data that it receives from one device to all other devices on the network. Because all the devices connected to a hub are competing for media usage, it's possible for collisions to occur when two devices send transmissions simultaneously. For this reason, it's important to avoid using a hub for messaging that requires immediate response.

Another network backbone device is called a bridge. Network bridges are smart devices that process and record information about signal traffic between devices in the networks. The bridge then uses this information to determine the most efficient path for data transfer, between a transmitting and a receiving device, without having to send it to every device in the network.

A switch is a multi-port network bridge that uses packet switching to forward data to one or multiple specific devices. Because more than one transmission can occur at a time, switch operating speeds are very fast. Switches are also full duplex devices that allow data signals to flow simultaneously in both directions. This eliminates the risk of data collisions that may occur in other network backbone devices.

When two segments of the same network have different communication formats a gateway is needed to connect them. A gateway performs a conversion function so that a computer on an Ethernet network using a TCP/IP protocol may communicate with a PLC on a subnet using the ControlNet protocol. Even though these two protocols are incompatible, the gateway can connect them on the same network and allow them to function together. Hubs, bridges, switches, and gateways - the backbones of networking - perform individual and important functions in keeping networks performing at their highest level.

https://analynk.com
(614) 755-5091