One northwest city completed an analysis on their current pump station equipment, and decided to replace their outdated system with a SCADA system connected to smart PLCs or RTUs.
The city also needed to meet new regulatory requirements issued by the Department of Ecology. These regulations required that the current pump station network be able to quantify an overflow at any given permitted site. This was not possible with the older monitoring and data collection equipment in place at the time. When it was installed, data collection was expensive, forcing officials to limit data collection parameters to only minimal data necessary to perform the city’s previous business and permit requirements.
This was not possible with the older monitoring and data collection equipment in place at the time. When it was installed, data collection was expensive, forcing officials to limit data collection parameters to only minimal data necessary to perform the city’s previous business and permit requirements.
Designing the New System
The city decided that in order to meet the regulatory requirements, a new system was in order. Specifically, one that could provide more data from their field equipment and add intelligence to the remote sites to compute and log lift station flow rates and increase the accuracy of data during overflow events.Systems Interface Inc. and Rockwell Automation® teamed up and designed just such a system.
“The customer preferred a nationally recognized, name-brand solution with local distribution and required Modbus® protocol,” said the municipal business manager for Systems Interface. “The solution had to be PLC-compatible and the customer preferred the Allen-Bradley® hardware, yet A-B couldn’t accommodate the need for Modbus.”
ProSoft Steps In
A large number of SCADA projects in the Oil and Gas and Water and Wastewater industries have been specified with the Modbus protocol. ProSoft’s processor, developed jointly by ProSoft Technology and Allen-Bradley, is aimed specifically at these opportunities. It is an Allen-Bradley PLC that has been modified to include the Modbus Slave protocol.
Once the Modbus protocol is activated, a Modbus host can read and write data from all the common Modbus data types. In addition, support has been provided for the transfer of Floating Point data. A host can also access the processor Status File S2 to remotely monitor the health of the unit or do such things as setting the real-time clock.
“The city couldn’t compute station flow rates, including overflow events, with the past system,” said Systems Interface’s municipal business manager. “Now they can track the well level and integrate it over time to accurately compute and log well inflow, outflow, and how much overflow has occurred.”
More Control, More Information
The new telemetry system consists of a hot backup, redundant, dual processor headquarter master station talking to 72 RTUs at each of the city’s sewer pump stations. “ProSoft’s Modbus Communication Modules function independent of the PLC, sharing the task of communications and allowing the processor module to concentrate on control and data functions,” said a Systems Interface project manager.
The RTUs monitor the pump station activities and control the operation of the sewage removal equipment, which consists of either pumps or air compressors. The headquarter master polls each RTU via a modem connection, and staff at the headquarters monitor the status and alarms in order to track pertinent data and be able to respond to emergency situations. This is far different from the previous system, which couldn’t track or control any station flow rates.
The new SCADA system will change all of that.
Learn more about ProSoft Technology’s solutions for Rockwell Automation platforms here.