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Data-Linc Group and Siemens help provide environmentally friendly heating for Beijing’s Temple of Heaven area

Beijing China’s Temple of Heavenly Peace
Clear skies over Beijing China’s Temple of Heavenly Peace
The Challenge
Winter was on the horizon. The heating system needed to be updated, and the system supplied heat not only to business clients, but residential ones as well. Devising a system to monitor and control 14 boiler rooms spread over a large geographical area was a formidable challenge. Because of the boiler rooms’ widely scattered locations, laying cable for data communication was not an option. Not only would it be expensive, but the time required for cable installation would mean the project could not meet the schedule to provide heat for the upcoming winter. Because of these factors, the end user and the consulting company decided to use a wireless solution to link both of the central control rooms and the remote boiler rooms.

New, clean burning gas fuel boilers in Beijing China
New, clean burning gas fuel boilers in Beijing China's Temple of Heaven area
In order to improve the winter air quality in the Temple of Heaven area of Beijing, the government of Chongwen District needed to replace the coal fuel heating with gas fuel boilers in that area.
To revamp the automation and communication system, they selected a Canadian consulting company with extensive experience and a strong reputation for heating system design.

The Solution
The system was designed around a Siemens S7-300 PLC with a WinCC HMI for each boiler room and central control room. Because all of the boilers would be monitored and controlled from the command centers, the end user and consulting company required that the wireless communication devices have the highest degree of reliability and seamless compatibility with the Siemens system. After reviewing a number of options, they decided to choose Data-Linc SRM series radio modems because they offer exceptional data reliability and integrity. After comparing Data-Linc Group’s 2.4 GHz band SRM wireless Ethernet modem with other wireless products, they found that the Ethernet SRMs have very high RF sensitivity with superior interference immunity that out-performed other wireless products. Because Data-Linc’s modems also offer an extended operating temperature range of -40 to 75 C, it made them a perfect choice for the outdoor installation— Beijing’s winter temperature can drop to –20 C.

radio antenna installation by tower The Installation
For monitoring and control, the command center consisted of two Master SRM Ethernet radio modems, four SRM wireless Repeaters connected to an Ethenet Hub and two local PCs running WinCC HMI. Each of the 14 remote boiler rooms houses a PC with WinCC HMI software, a S7-300 PLC with Profibus D and an SRM wireless Ethernet modems. By using OPC server and client services, either or both of the two local Central Control PCs could monitor and control any of the 14 remote boiler rooms (See diagram). The communication between the Central Control Master SRM wireless Ethernet and the Remote Ethernet radio modems in any of the selected boiler rooms was extremely fast— it takes approximately one second to activate the remote PC screen and gain access to the necessary information at the remote location. The twenty-two radio modems— 14 Remote station modems, two Masters and six Repeaters— operate flawlessly without interfering with each other. Robust, reliable access and control: achieved.

This installation met the demands and the schedule. It has been in operation since before the winter of 2000, and has successfully supplied clean heat to businesses and residences in Beijing’s Temple of Heaven area ever since.

License Free Radio Modem Communications With Siemens S7-200 PLC Remotes

The following application note reports on the very first installation worldwide of any license-free radio modems for data communications with the Siemens S7-200 architecture. It appeared as the front page article written by Cascade Control in the January 1996 issue of "InControl," a quarterly newsletter published by Cascade Controls & Electric Supply, the Siemens Distributor based in Seattle, Washington.

TOSCO´s refinery in Ferndale, Washington, was faced with a challenge. The pump and valve system used to direct the transport of various petroleum products throughout their tank farm was deteriorating. This control system, originally installed in the 1950s, consisted of individual push buttons and pilot lights for each of the many pumps and valves. Due to the harsh environment and heavy use over the years, many of the junction boxes and field connections to the pumps and valves had deteriorated to the point of making the system almost inoperable.

Evaluation of the existing system indicated that virtually all field wiring and related components required replacement. It sounds simple, but the fact that these tanks, pumps and valves are spread throughout a tank farm that covers many acres, made the replacement cost very high. in addition, any new control system would be required to interface directly with TOSCO´s sophisticated DCS (distributed control system) This would require all the pumps and valves to be hard wired into expensive DCS inputs and outputs. The estimated labor and material costs quickly exceeded $130,000.

TOSCO´s Project Manager contacted Cascade Controls to determine if any other solutions existed. He had heard about wireless communication to remote I/O from Cascade Controls and wanted more information.

After reviewing the application, Cascade Controls suggested controlling the system with a combination of PLCs and radio modems, thus reducing the highest cost item- field wiring. The main controller would be a Siemens Simatic TI545, utilizing the Field Interface Module, communicating to the tank farm via the Data-Linc SRM frequency hopping spread spectrum 900MHz serial radio modems (no site license required). At each tank cluster, a Remote radio modem was connected to a Simatic S7-200, the new mini-PLC from Siemens, providing direct connection to the pumps and valves in the field. Another cost savings was in the DCS connection to the system via the Simatic TI545 PLC. A Modbus server in the PLC provided the needed interface so the DCS could control and view the status of the remote I/O and thus, the field devices.

The use of Spread Spectrum Radio Technology and the Intelligent I/O capabilities of the Simatic S7-200 and TI454 resulted in a large capital savings on the project. The approximate cost of the PLC system was less than $40,000!

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