Maintaining a steady flow of water in China

One issue facing China is that there is usually too much rain in the south and not enough in the north. The south-to-north water transfer project was designed to help alleviate this problem. Carrying nearly 45 billion cubic metres of water annually through a 2400 km network of canals, the entire project requires a high level of automation in order to guarantee smooth and continuous flow, and the efficient transfer of water to hundreds of millions of people.

When installing automated monitoring systems on water gate stations located along the main canal, partnering with the right equipment supplier was a priority for Hefei Sanli Automation Engineering Co., one of the main systems integrators on the project. For this reason, the firm teamed up with Siemens — a decision that would prove critical to the overall project success.

In addition to ensuring continuous and efficient transmission of water, the engineering safety, water quality, flood warnings and operational management were all highly important to be considered during the development of the main canal’s monitoring system. On the Diaohe River to the Chuanhuang South section of the project, Hefei Sanli sought to meet these objectives by installing 82 Simatic S7-400 controllers, which are responsible for accurate automated control of on-site sluices to keep the flow of water steady. Siemens also provided 12 large-diameter electromagnetic flow meters ranging from DN800 to DN1600 for the main canal between Shijiazhuang and Beijing to help ensure stable and safe measurement of the water flow.

“Such a large and important water transfer project required an automation solution with high reliability and precision,” said Wang Hao, an engineer at Hefei Sanli. “Siemens equipment met our technical requirements and the expertise of the staff played an integral role in building a high-performance control system for the main canal.”

After water from the south reaches Beijing Tuancheng Lake, some of the water is used to supply the population in the surrounding area, and the surplus is transferred by the Jingmi feeder canal over 100 km to the Miyun reservoir for storage. Due to the elevation of the ­reservoir, the surplus water from the south must be pumped several metres upward through a set of nine pump stations.

Compared with the sluice gate control on the main canal, monitoring the pump stations for the Miyun reservoir storage regulation project is more complicated. “Water quality information must be quickly collected at critical control points for water transfer and transmitted in real time,” explained Hao. “This is required to carry out engineering safety monitoring of osmotic pressure, earth pressure, joint metering and the underground water level.”

To enable this monitoring, Hefei Sanli implemented 60 Simatic PCS 7 AS 410 controllers. Profibus and Profinet were also integrated for communication, which is necessary for monitoring various process variables. The PCS 7 AS 410 controllers allow the status point data to be collected in less than one second and transferred to the remote database in less than two seconds. Additionally, the CPU module has a mean time between failure (MTBF) of over 100,000 hours, guaranteeing availability of more than 99%.

For monitoring critical facilities such as gate stations, redundancy is a major challenge. The Simatic PCS 7 AS 410 helps ensure reliable data transmission with its paralleled hot standby function and redundant Profibus structure in which racks, power supply modules, CPU modules, and synchronous modules all have the same configuration. If one segment of the network is down, the communication can be rerouted through the remaining functional network sections.

All too often in automation engineering projects, failure is a result of communication problems between products or systems supplied by different vendors. Hao believes partnering with Siemens on the middle line of the south-to-north water transfer project helped avoid that problem. “Communication between equipment and instruments at the newly built pump stations and existing gates was integral to the overall project success,” he said. “The strong compatibility of Siemens equipment enabled seamless integration with our network, which was vital for such a critical project.”