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The challenge: Pump control made easy
The process of automating feed pumps in waterworks places significant demands on measuring and control technology. Today, system manufacturers usually implement complex automation concepts based on PLCs. This requires extensive expert knowledge and a proficient understanding of complex, PLC-specific programming languages. The most important goals are the cost-effective creation of an appropriate facility, its smooth and failure-free operation, long-term service and the ability to gradually expand and retrofit the facility. However, the current trend being observed is that both system manufacturers and operators are increasingly delegating the maintenance of implemented facilities to local electrical companies. This shortens response times and frees up capacities for system manufacturers. However, the highly complex PLC-based automation concepts are a potential obstacle at this point: The control expertise required to maintain them limits the choice of suitable local electrical companies.
Flexible, decentralized automation concept
An alternative to automating pump control using PLCs is the use of control relays such as the easyE4 from Eaton. Such an automation concept meets the essential requirements for pump control: The continuous availability of the facility and its installations over a long period of time. And on top of that the flexible, decentralized concept can also be implemented or maintained by a local electrical company.
Model application with three feed pumps
To illustrate the feasibility of such a control concept, the automation of a model-based application using the easyE4 has been developed.
Furthermore, the facility should be optimized in terms of its power management. To this end, the pumps should primarily be switched on only during periods of low energy tariffs; at the same time, a power limit for the consumption of electrical energy should not be exceeded when in pumping mode. Lastly, the elevated reservoirs must be sufficiently filled at all times.
On the basis of these competing requirements, special user function blocks were developed for the model application. Since these represent the knowledge of a company's experts in real-life scenarios, they are password-protected to prevent third-party access to the stored parameters. The ability to develop the user function blocks using the powerful “structured text” programming language in the case of the easyE4 means that implementing even more complex functions is simple.
In the model application, however, the capabilities of modern automation components are completely used: Numerous parameters from the Eaton DG1 variable frequency drive and the easyE4 control relay can be carried over, evaluated and "logged" via the Modbus TCP network. Start-up problems, an electrical increase in power at the same pumping capacity of the pumps or asymmetrical variables such as voltage, current, cosine φ, etc. are detected at a very early stage. In turn, this provides indications of future maintenance or service requirements. As a result, predictive maintenance is possible.
Quick programming of custom function blocks
Ladder diagram, function block diagrams and structured text were applied in parallel for programming purposes in the project. The ability to create custom subroutines in these languages supports the overall "modularity" of the concept. Structured text provides these self-written user function blocks with possibilities similar to those of the "manufacturer blocks" of easySoft 7. This allows the user to create a control system for the water sector directly from the easyE4 with custom, protected function blocks for pump management, run-time monitoring and special modules for the linearsiation of measured values and much more. In the model application, the entire concept can be implemented by means of appropriate modules, including pump control, pump management and slider control with the corresponding monitoring functions.
Slider state detection
The sliders that enable the inlet of water and prevent unwanted back flow are another important feature in the elevated reservoirs. These sliders must function reliably, and the status "open" or "closed" must be recorded correctly and transmitted to the pump control system. This is done by recording the run-time, which is based on the time taken for opening or closing, and monitoring the correct signaling sequence. In addition, the change in states is detected even if the electric drive is not in operation. This means the "slider" block also detects when the slider has been changed manually. Signaling is connected such that a possible wire break, cross circuit or short circuit in a sensor connection is detected. The measurement of current consumption and the run-time of the slider drive also provides indications of mechanical problems in the facility or of faults that are developing in the calibration of the sensor system.
Pump management with a multitude of parameters
To ensure a high level of availability, utilities are usually equipped with several feed pumps that together exceed the delivery rate required. This allows one or more pumps to be kept in reserve at all times in case a pump requires maintenance or needs to be replaced. In the past, pump management served only to record the run-time of each individual pump and to actuate the pump with the lowest run-time whenever an elevated reservoir had to be filled. The pump was serviced as soon as a specific, preset pump run-time had been reached.
Networks connect and enable decentralization. Up to 8 clients can be connected with easyNet
Comprehensive network with many possibilities
The new control concept developed for the model application is based on the Eaton easyE4 control relay. Thanks to the powerful Modbus TCP and easyNet communication networks and the extensive ability to expand the input/output level, the easyE4 control relay can also be used in projects for which a PLC would otherwise have been required. The advantage is that, despite the extensive application possibilities, commissioning can be carried out without the need for software specialists. Thanks to scalable visualization concepts, it is also possible to adapt the facility's operating level to current requirements. The options range from a cost-effective touch panel to a high-performance multi-touch display and control unit.
Expandable number of inputs/outputs
The pump control system, and the necessary parameter configurations and settings for the analog inputs/outputs, can be set up using the ladder diagram or function block diagram graphical programming languages. Even when setting up larger facilities, the easyE4 rarely reaches its limits -- up to 11 local extensions can be connected, each of which can have digital or analog inputs/outputs. At the same time, up to eight easyE4 control systems that have been expanded in this way can exchange data transparently via easyNet. This feature in particular allowed the sensors and actuators to be connected locally in the control concept for the model application, so that sufficient inputs/outputs are available everywhere.
Information via data logging for upcoming maintenance work
Recording the measurement, operating and running data of a controlled device can provide early indications of upcoming service or maintenance requirements. One of the critical elements of a fresh or waste water system comprises the feed pumps in conjunction with the associated sliders and valves. In addition to the operating hours, the current measurement data of the pumps, the time taken for opening and closing the sliders and their changes can provide indications of upcoming maintenance work. Operator interventions and changes to parameter settings can also be recorded in the data logger. Data logging can be performed in any easyE4. To this end, a manufacturer function block (DL01) is available that only needs to be parameterized. The "logged" data can be read out via the "easySoft 7" software and analyzed in Excel or transferred to a control system.
Visualization also decentralized
Visualization within a water supply system is implemented not only by the control system, but also within a system -- "on-site" directly at the pumps, frequency converters, monitoring devices, actuators and sensors. The possibilities are varied and scalable, ranging from a simple LED display and easyE4 integrated display, right through to the cost-effective touch panel of the easyE4 device family. Multi-touch displays can also be easily integrated for larger facilities. At the push of a button, the data of the corresponding variable frequency drive can therefore be displayed at a pump, together with the recorded rated flow of the meters and the status or fill level of the connected elevated reservoirs. This can be done in digital form, in color and using graphic elements such as bar graphs, pointer-type instruments or line graphs, depending on the device.
The result:
Benefits for all project participants
The concept developed for the model application based on the easyE4 offers advantages for all parties involved in the planning and operation of a water supply system: Modularization gives engineering firms a good basis for calls for tender, installation companies can reduce wiring costs thanks to the decentralized concept, and implementation times are reduced by simultaneous modular installation and commissioning. Due to the simple setup and the easy programming and parameterization of the easyE4 control relays, local electrical companies can carry out maintenance and subsequent expansions without any problems. Lastly, the long-term flexibility and availability of the facility is ensured for the investor and operator.
Background:
The model application was developed for Eaton by Ulrich Kanngießer. Ulrich Kanngießer is a freelance technical author and seminar provider. His work has focused on the world of automation for more than 30 years. He has extensive experience in consulting work, programming and commissioning, has published specialist articles (including on the topic of water supply and disposal) and has held workshops for various control systems at different manufacturers.
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