During the design of pump stations in wastewater treatment, the top priority is to equip the pumps with sufficient output. This is the only means for reliably transporting wastewater the way that gravity would. Regardless of the advances offered by technology over the decades, nothing has altered this core task.
Yet, while the function has remained the same, the execution has changed over time. And this has led to extremely heterogeneous plant structures that can complicate servicing. Solutions that support current technology and maintenance are particularly in demand during modernization work. As a result of these demands, WAGO has developed application software for pump controls in which even the smallest details receive consideration.
In Germany, pump stations are among the oldest public infrastructure, next to streets and railway bridges. Some pumping stations that have carried out their tasks for more than 100 years have been converted into cultural centers or even museums. Advances in technology can be potentially read from a pump station: where gas motors functioned as drives a century ago, pumps are now driven by electricity and largely operated by automation technology. The development of new types of impellers and sensors have led to significantly higher outputs and efficiencies as well as improved possibilities for monitoring. However, the modernization and automation of pump stations has grown organically over the decades, and this is precisely the origin of the extremely heterogeneous automation structures that we currently find in pumping stations. It is especially common in large wastewater treatment facilities, where the operators may run 70 pump stations that include pumps or motors from three different manufacturers that are in turn regulated by three or four different control systems.
Modernization as an Opportunity
Over the course of modernization, the opportunity presents itself to standardize the hardware and software in pumping stations, because while the motor and other mechanical parts are generally retained during refurbishing, the sensors, electronics, and automation are replaced. However, because most operators convert their pumping stations in stages, and not all at once, this is often not the case. Instead, the system operators bundle up to 20 pumps into a batch for which modernization bids are tendered. Even if the operator intends to use the modernization to convert the pumps to one system, in that the tender specifies which hardware should be used during the renovations, there is still no certainty that the software installed on the devices will be programmed in a similar, standardized fashion – not least because every application engineer or programmer writes their software code differently. In the worst case scenario for operators, the maintenance expenses can be as high as those for modernization, because the service technicians have to examine the programming for each controller separately in order to search for potential errors during maintenance or servicing.
Standardized Control Due to Carefully Thought-Out Application Software
In order to reduce these expenses, WAGO developed application software for controlling pumps that combines basic functions for recurring tasks with a large degree of freedom for setting individual parameters. Project-specific variants of the software need only be configured, and not programmed. This significantly reduces software engineering costs. The hardware base for the application software is the WAGO-I/O-SYSTEM 750, which can easily link in systems that developed heterogeneously, due to its more than 500 different I/O modules and numerous interfaces. The pump control can thus be universally used and reliably ensures that the system is networked into the entire drinking water or wastewater operation. The application software is designed for pump stations with two to six pumps with different outputs. Based on the experience that WAGO has gained over numerous projects in wastewater treatment facilities, it meets the exact demands that typically occur during pump operation: load management, corrosion protection, and securing redundant operations.
Different types of pumps are generally provided in pumping stations to further ensure the availability of the station in the case of interruptions or during maintenance work. These include base-load pumps, peak-load pumps, rest drainage pumps and reserve pumps. However, the additional pumps within a facility may be used for more than peak loads or redundant operation. In addition, they should run in regular timed intervals to prevent operational interruptions. Otherwise, operational errors are inevitable, because pumps that remain motionless are subject to dirt loads, connections can be seized by corrosion, or mechanical components can clog.
The different uses for pumps can be correspondingly defined using the application software from WAGO. If a reserve function is configured for one of the pumps, the WAGO controller ensures that this assignment is changed after every operating cycle so that the affected pumps are still regularly operated. In addition, the application monitors the pump runtimes and starts them automatically after a long period of inactivity for a set time to prevent corrosion.
Load Spike Prevention
When the pumps are switched on, they should not all start up at once, if possible, but rather sequentially in order to prevent unnecessary loading on the electrical network. The WAGO controller supports this with a start-up delay. A second pump of the same type is therefore only started up after the first pump has operated for a predefined time period. The length of this time period depends on the individual application and on the effective load management on site – and can therefore be easily parameterized in the pump controller. This minimizes loads on the electrical network and likewise contributes to emergency power operation when using generators.
Flexible Level Switching
By using changing operating parameters, it is also possible to largely protect pump systems from contamination, like fat deposits, that are a serious problem for operators when they accumulate on the walls of the pump shaft. Fats from households or gastronomic companies are discharged to the sewer system and float to the top of the water surface in the pump shaft. Because the water level is held at the same level in the pump shaft by the pump, the fat floating on the water has the best conditions for settling in the pump shaft. This process is further promoted if the fats are already in a lipophilic phase. The layer faces inward, threatens to clog the sump pump, and can only be mechanically removed. To prevent this process from occurring – or at least to delay it, the switch on and off points of the pumps are configured to be flexible. The settings can be customized with the aid of the e!COCKPIT engineering tool, which is integrated in the PFC200 and PFC100 Controllers for the WAGO-I/O-SYSTEM 750. If this is implemented, then the actual switching point randomly falls slightly above or below the specified water height in the sump. This varies the water level in the pump shaft and better distributes the fat deposits.
Everything at a Glance
With a view toward ease of operations, an intuitively usable, web-based visualization is included in the new, standardized WAGO application software for pump stations. The pumps can be monitored and controlled both from the control center and also directly on site using a touch panel connected to the controller. Users can freely select how the pumps should be identified for the purpose of the assignments. The pump control, programmed using IEC 61131-3 standardized languages, merely provides general functional frameworks for controlling up to six different pumps of different types. The details of the control program are part of the individualized customer design.
This includes specific demands for system availability. More than ever, demands for system availability are prompting operators and service companies to consider new maintenance strategies and to introduce effective measures. Conventional maintenance approaches, like reactive or even preventative maintenance, are changing over time in the direction of predictive maintenance according to Industry 4.0. With this software solution, WAGO provides a foundation that is a reliable statement about what is coming. Key data like phase currents, throughflow values, pressure, temperature, and cos phi, as well as load and alarm management are the foundation for operating a more predictive maintenance. At the same time, the standardized software solution reduces operator investments in different software packages and recurring updates, as well as training for service employees.
Text: Kay Miller, WAGO
Photo: ADOBESTOCK, WAGO