July/August 2013
Channel Chat

DCS migration connects wastewater treatment locations

By G. Duane Grob and Robert F. Stocker

The Narragansett Bay, located on the north side of Rhode Island Sound, is New England's largest estuary. The Narragansett Bay Commission (NBC) has two wastewater treatment plants, one located at Field's Point, near Providence, R.I., and one approximately 5 miles across the bay at Bucklin Point, R.I. Each plant had a different control system technology and vastly different human-machine interfaces (HMIs).

NBC wanted to change the existing HMI at both plants to a new HMI. NBC first selected the Wonderware application server and the InTouch HMI to be the new standard for the HMI at both plants. Next it publicly requested qualifications and proposals from experienced integrators to implement the conversion.

Optimation, an engineering, design, and fabrication company headquartered in Rochester, N.Y., gathered information regarding the existing system's size, magnitude of reusability for objects and graphics, and similarity in treatment plant processes and screens. The company quoted the project and pursued what it believes is a growing industry sector: distributed control system (DCS) HMI migration.

The challenge was to design a system to replace one manufacturer's HMI product, but be flexible enough to accommodate another product by a different manufacturer as part of the overall scope. During the qualification phase of the selection process, NBC selected the system integrator based on experience with these products.

Additional programmable logic controllers (PLCs) were introduced into the overall system in addition to the existing DCS controllers. The operator only views the system as a singular entity, without the complications of which type of controller is connected to which device. The concept of conversion of screens was the easy part, while the conversion of the different control blocks into a single database for use in the development of input/output (I/O) structures and tag names became the larger task.

For this project, NBC wanted to preserve the plants' existing look and feel but upgrade the graphics, functionality, and accessibility. The original VMS consoles could then be removed as the project progressed. By completion, only the new HMI terminals would remain.

In late 2012, NBC upgraded successfully using an industry-standard HMI software. At that time, all servers were upgraded to run on a 64-bit operating system to use the full potential of installed random access memory. Terminal services were employed via two fault-tolerant servers to provide 20 HMI stations to the operators in the form of thin clients managed by thin-client software. The client selected single- and dual-monitor thin clients.

DCS1

Blower overview shows information from all controllers.


Because the two physical locations are separated by at least 5 miles of open water, a microwave link using a gigabit Ethernet was used to network the two locations. The system platform architecture includes the following:

  • Eight object servers (four per location), each configured with two redundant pairs
  • Four I/O servers (two per location), each configured as a redundant pair
  • Two terminal servers
  • Historian
  • Galaxy repository
  • 20 thin clients

The system platform communicates with a variety of PLCs and data sources, including Bailey Infi90 via the Rovisys OPC90 OPC server, the Siemens PCS7 CPUs via the Wonderware S7 I/O driver, GE Powermeters via Modbus TCP DAS servers, Allen-Bradley Compact Logix PLCs via Wonderware ABCIP DAS servers, and the Goldwind Wind Turbine Farm, via an OPC client installed directly on the Goldwind I/O servers. Optimation wrote custom failover code for the Siemens PCS7 PLCs, which tracks the master PLC rack and points all other objects to this rack within 5 seconds of failure.

There were two master HMI templates developed, one for Field's Point and the other for Bucklin Point. Between the two HMI applications, about 100 screens replaced more than 600 configured in the Bailey VMS and PCS7 systems. This reduction in screens, along with a dynamic navigation system, makes any screen accessible in a maximum of two clicks and allows the client to configure additional navigation on the fly.

The Galaxy is host to more than 1,000,000 I/O points distributed over 10,000 objects. Each object is capable of individual configuration via an Excel spreadsheet link that updates in bulk, eliminating the need to configure objects manually. This saves NBC time and money. The plant now operates solely via the new HMIs and benefits from the added functionality and serviceability of a modern HMI.

NBC now has a single database for connectivity to Bailey and Siemens controllers, as well as a similar look and feel of operations between the two plants. NBC also benefits from advanced graphics and technology for expansion, regardless of the control platform used.

ABOUT THE AUTHORS

G. Duane Grob is the engineering manager of Optimation's Philadelphia office.

Robert F. Stocker is a senior automation engineer at Optimation, a certified member of the Control System Integrators Association. Visit www.optimation.us and www.controlsys.org for more information.