HMI Clients Extend the Reach of SCADA Systems

As water and wastewater plants add increasingly sophisticated controls, the automated acquisition and analysis of data from ongoing processes become an essential part of operations. The days when operators wandered through the plant, jotting down readings from meters and manually making adjustments to keep conditions near optimum may be numbered. Today, operators no longer need to be in a central control station to monitor operations. Instead, they can tap into vital information from anywhere, at any time.

Automation efforts increase efficiency and eliminate time-consuming manual logging of data. Supervisory Control and Data Acquisition (SCADA) systems provide instantaneous and simultaneous control of plant operations and allow operators to check the status of equipment and make on-the-fly adjustments. As plants face tighter and tighter regulations, access to this information is critical to both day-to-day operations and overall management.

The human-machine interface (HMI) provides an intuitive, graphical interface to allow operators to monitor and control processes. In many ways, the HMI hides the complexity of the underlying monitoring and control system, even as it provides greater insight into control of operations. The payoff is reduced operating costs, improved processes, easier maintenance, better documentation for meeting regulatory requirements, and the ability to respond quickly to changing conditions.

Flexible Access

The HMI typically resides on one or more PCs, which communicate with control devices such as PLCs and RTUs, collecting data and issuing commands. Most of todays most powerful HMIs, such as the Cimplicity? HMI from GE Fanuc, are built on the Windows™ operating system. Windows allows robust HMI applications to be developed using industry-standard tools. In addition, it offers flexibility in providing access for supervisors and operators.

Flexible Access

HMIs bring flexibility to SCADA applications in water/wastewater systems. The Village of Hazelcrest, Ill., found that the move to automated HMI-based monitoring and control improved productivity dramatically. Reports and charts are generated automatically in about 15 minutes, eliminating about a half day of paperwork. Overtime is cut in half and the staff is freed to pursue other projects, like a new chlorination system and upgraded water and flowmeters.

Client/Server Architecture

The Cimplicity HMI is built on a client server architecture. A central server collects data from control devices and manages the data in a runtime database. This server attaches to clients, or viewers, which contain the graphical interface allowing operators to interact with the system. In the simplest system, the server also acts as the sole client. Beyond the database, the HMI provides a sophisticated set of alarms that can alert operators to potential or real problems.

For example, water levels can be monitored to provide an informational alarm when they reach certain high or low levels and a reactive alarm if levels reach critically high or low levels that demand immediate attention.

The city of Virginia Beach monitors more than 20,000 points in its SCADA system, with all data being collected on redundant HMI servers. Data and alarming pass directly into an SQL server database, which supports both dispatch and work order operations. The effect is a streamlined operation in which all needs are serviced from a single point.

The ability to access the HMI server in a flexible, convenient manner can ease headaches. Today?s technology offers several ways to extend the reach of the HMI in cost-effective ways by allowing flexible access to the system, from the plant floor or the other side of the world. A central server does not limit access, and can actually increase it.

Client PCs can be connected to the server over a standard Ethernet network. The system can be extended with all the flexibility associated with networks, including both local-area and wide-area access using Microsoft Remote Access Server software. The need to provide a licensed copy of the client HMI software makes prudent planning a wise step when determining the number of clients. In the case of Virginia Beach, 15 client PCs give full-time access to a variety of personnel, from the superintendent to the process engineer to the laboratory technicians.

An HMI can also make the system accessible with standard browsers, such as Microsoft? Internet Explorer™ or Netscape? Navigator™. Operators can view many of the same screens as a standard HMI client, with access to most alarms and controls. This option is particularly attractive for systems with a large number of potential users who will access the system intermittently. The server is licensed to support a small to medium number of simultaneous users through the Internet/Intranet connection.

The gateway extends the simpler Web viewer by allowing a user to access the runtime server directly. By creating dedicated HTML pages with live data links, users can monitor points and perform limited setpoints. The benefits are similar to those for WebView, but with increased ability to control as well as monitor.

Internet-based access also helps in obtaining expert support from vendors without the costs of a service visit. Remote monitoring allows vendors to view conditions and even troubleshoot problems immediately and productively, without the time and expense required for a site visit.

The HMI can fit into the palm of a user?s hand. A Microsoft Windows? CE palmtop computer can become an HMI client. Communicating over a wireless Ethernet connection, the palm top allows the operator to view on-line status, receive alarm updates, and do setpoints. An operator can be anywhere in the plant, maintaining and troubleshooting equipment, while having the same view into the process as the dispatcher in the central control location.

The same text alarms available at client stations can be selectively routed to an alphanumeric pager. This option integrates smoothly into the system and does not require any changes to the alarm information beyond selecting which alarms are sent to the pager.

Conclusion

Since timely, accurate information is one key to successful management of water and wastewater plants, access to that information is critical.

Conclusion

The ability to collect data automatically, make use of it in numerous ways, and access it quickly and easily from wherever is most convenient is the key to using the information efficiently and productively.