A new level of thinking
Owners and operators are already asking for more functionality as well as flexibility, lower costs and better performance. To meet such demands, new thinking and new engineering must be used to create technologies that might be initially more costly, yet that will prove to be the more economical solution over time while also delivering better performance.
An answer to these challenges is the creation of integrated intelligence in wastewater pumping. This is made possible by original thinking and adaptation of components in a submersible wastewater pump. By integrating power electronics, a processor, software, sensors, a synchronous electric motor and state-of-the-art self-cleaning hydraulics inside a submersible shell, wastewater pumping with integrated intelligence has been made possible.
Part 1 of this white paper describes the technological advances and shows the significant benefits that owners and operators of wastewater pumping systems will experience. Part 2, which will feature in an issue of World Pumps later in the year, will look at the intelligent functions, communication and monitoring and control features possible with intelligent wastewater pumping.
Figure 2. From a complex selection...
Figure 3. ...to one flexible solution.
The word ‘intelligent’ in wastewater pumping is a result of factors that together contribute to a new level of operational autonomy and efficiency, a pumping system designed to automatically deliver the desired performance at minimum energy consumption while reducing the total cost of ownership.
Intelligence refers to a pump system that can sense the environment it is working in as well as the load it is subjected to and adjust its behavior to meet the end-user optimization targets. By collecting and analyzing relevant data, the pump system can make smart decisions about how it operates and what feedback it will provide the user, resulting in precise process control, a reduced risk of clogging, clean and odour free pump sumps, substantial reductions in energy consumption, reduced asset management, comprehensive data reporting and lots more. In short, it delivers peace of mind to the end user.
Lean asset management
An integrated intelligent wastewater pump system consists of fewer individual components than a typical pump system. This simplification means that only a few different components such as pump volutes with different discharge sizes, an impeller per volute and a couple of motor sizes are needed to cover a large performance field.
As an example, one intelligent wastewater pump can cover the hydraulic performance of multiple different conventional pumps where different impellers, volutes and motors would have been required. This means that customers who keep their own stock of spare parts or spare pumps can benefit greatly as their inventory cost will be drastically cut. This flexibility also makes it possible to do a final pump configuration close to where the pump is needed, by just assembling a few key components.
The benefit of having just a few spare pumps in stock and being able to use them for many different operating conditions at multiple pump stations can result in considerable capital savings for the pump system’s operator or owner.
Integration of electronics
While the pump system’s upfront cost is still a major consideration, the fact is that the operational costs over the life of the pump station will vastly overshadow any price difference between competing pump system designs at the time of purchase. Increases in pump system efficiency alone may not always convince a buyer to switch to a better performing system, but a single unscheduled call to clean a clogged pump will easily tip the scales in favour of a system that has proven to be consistently clog-free.
When power electronics and a processor with control software are integrated into a submersible pump, costs are driven down and new functionality added. The challenge however, is the packaging and integration of new components, i.e. the size, shape and performance within the submersible envelope.
In order to achieve efficient component integration some elements need to be re-designed to fit the environment of a submersible pump and adapted to function as a system. The power and control electronics, which in a conventional pump control panel are mounted on a back plate, must be adapted and fitted into the head of a wastewater pump.
Furthermore, placing power electronics inside a submerged wastewater pump is beneficial since they are protected from exposure to heat, dust, dirt and extreme temperature variations. The cooling is reliable, compact and stable and not dependent on fans or A/C units. The motor leads are as short as they can be, thereby removing any issues with wave reflections and voltage spikes.
Lastly, the entire system is pre-engineered and the equipment start-up and commissioning time is drastically reduced as there is an absolute minimum of configuration via simple set-up wizards. When power electronics are placed between the grid and the motor, the system becomes frequency independent and voltage tolerant. Typically a single unit can operate with input frequencies anywhere from 50 to 60 Hz in, for example, a voltage range 380V to 480V.
How the intelligence works
The in-pump processor controls the power electronics to achieve variable pump performance, always meeting the demand at hand. A single impeller size per volute size minimizes the need for multiple spare impellers and yields maximum hydraulic efficiency as the impeller is optimized for the volute. Instead of having to remove the pump to trim or change an impeller, a different duty point can simply be met by the touch of a button.
Figure 4. Concentrated synchronous motor.
Instead of discrete pump performance curves, the new system offers an unlimited choice of performance curves within a large field. The specified duty point can always be met, yet easily changed to actual site conditions, if needed.
The intelligent wastewater pump system uses very few unique parts which drastically reduces the need to stock spare parts or spare pumps either at the end user level or at a supplier’s warehouse.
A new, simpler and more compact high performance, synchronous motor further improves pump system efficiency allowing operation at reduced pump capacity while maintaining high motor efficiency. The concentrated winding synchronous motor does this and meets the proposed future super-premium motor efficiency (IE4) standard.
Benefits of an advanced drive unit
In an intelligent wastewater pumping system, the pump’s drive unit is an assembly consisting of monitoring and control circuitry, software, power electronics and a synchronous motor in a single package. By utilizing a new motor design, the concentrated winding design, benefits such as increased motor efficiency, controllability, dramatically improved low speed efficiency and reduced size is derived.
The stator consists of multiple identical stator lamination packages with individual coils that are placed side-by-side inside the stator housing. The concentrated winding stator can be produced efficiently and at a shorter height than an induction motor of corresponding rating.
The rotor is equipped with permanent magnets that create and maintain the rotor’s magnetic field, yielding very low rotor losses and synchronous speed operation. The low losses means that virtually no heat is generated in the rotor and thus no heat is flowing to the bearings via the shaft. This results in a cooler running rotor and a motor with longer bearing life due to less thermal stress on the bearings.
Due to the high motor efficiency the winding temperature is lower than normal. Add to this the advanced temperature protection system where motor power is reduced should circumstances warrant it, and the result of the design is a longer motor life.
The concentrated winding synchronous motor requires power electronics to start and run the motor. The power electronics offers full control of the pump shaft speed and torque; therefore the wastewater pumping system can operate within a large flow/head field. The embedded software serves to control the motor’s speed and torque as well as reading momentary load requirements.
The intelligent wastewater pump can operate on 50Hz, 60 Hz or anything in-between and at voltages from 380V to 480V. Each pump size covers an infinite range of performance curves, often substituting the coverage of six to eight standard wastewater pumps. These features along with the reduced number of pump components offers a high level of operational flexibility, especially for large municipalities and water boards, because inventories of spare pumps or parts can be drastically reduced.
By adding a gateway in the control cabinet the performance of an intelligent wastewater pump can be controlled in real time to meet the application needs. A master pump station controller or Programmable Logic Controller (PLC) will control the gateway to regulate the pump output as directed.
An optional gateway or controller enables data communication and measurement/analysis, providing communication to the world via standard communication protocols. The pumping station can easily be connected to remote station monitoring systems including Supervisory Control and Data Acquisition (SCADA) systems.
Smarter and smaller
Integrated intelligence creates opportunities for reduced costs as well as a smaller control panel footprint, both physically and environmentally. Substantial reduction of CO2 emissions will result from installations with intelligent pumps and a pump station controller. The reduced physical footprint is due to relocation of major components from the control panel to within the submersible pump as well as the compactness of new components, a result of innovation, adaptation and integration of technology.
The pump and control cabinet have a much smaller physical size and the reduced environmental footprint is due to the system’s very efficient use of energy, a result from new pump station control algorithms.
The reduction in cabinet size depends on which pump system with which the comparison is made, as well as the environment that the cabinet will be operating in.
When comparing a cabinet for a variable frequency drive (VFD) pump system in a duplex sewage pump station with two intelligent wastewater pumps which have integrated intelligence, it becomes obvious that the cabinet size has shrunk dramatically, as has the cabinet cost. The reason for this is the absence of two variable frequency drives, two motor protection devices, two pump monitoring devices and associated wiring and wire terminations. The surface area of the cabinet’s back-panel can be reduced to half or less than half of its original size.
For control panels located in outdoor environments in warm or hot climate zones, the size reduction will be even more drastic because the heat generating power electronics are placed inside the submersible pump rather than inside the cabinet. There is no need for VFD oversizing, ventilation fans or control panel air-conditioning to compensate for the high temperature environment. This advantage will drastically reduce the upfront purchase cost, increase the system reliability and lower the pump station energy usage.
The creation of an intelligent wastewater pumping platform, utilising integrated components, will significantly advance the industry by offering maximum flexibility, reliability, lean asset management and both capital and operational cost reduction.
Benefits such as reduced footprint, connectivity and significantly lower lifecycle costs are all met by combining different elements of the intelligent wastewater pump platform to meet a specific application challenge, the ultimate solution for maximum peace of mind.
Part 2 of this white paper will appear in World Pumps later this year.
Stefan. M. Abelin
Director, Marketing Project Office, Xylem
Stefan has 35 years of experience in the pump industry. He manages the marketing project office at Xylem's wastewater pumping department and has been closely involved in the launch of Xylem’s Flygt Concertor, the world’s first wastewater pumping system with integrated intelligence.