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Challenge: Pump control made easy
The process of automating the feed pumps in a waterworks places significant demands on the measuring and control technology. Today, system manufacturers usually use PLCs to implement complex automation systems. This requires extensive specialist knowledge and mastery of complex, PLC-specific programming languages. The most important objectives include the cost-effective design of a suitable facility, its smooth, fault-free and long-term operation, and the ability to gradually expand and retrofit the facility. Recently, however, system manufacturers as well as operators are increasingly delegating the maintenance of the facilities they implement to local electrical contractors. This shortens response times and frees up capacities for system manufacturers. However, highly complex PLC-based automation systems are a potential obstacle in this regard: The expertise required to maintain them limits the choice of qualified local electrical contractors.
Flexible, decentralised automation systems
One alternative to PLC-based pump control automation is the use of control relays such as the easyE4 from Eaton. Such an automation system meets the essential requirements of pump control: the continuous availability of the facility and its installations over a long period of time. What's more, this type of flexible, decentralised system can also be implemented and maintained by a local electrical contractor.
Model application with three feed pumps
To illustrate the feasibility of such a control system, we commissioned a model application for pump automation based on the easyE4.
In addition, the facility’s energy management system should be optimised. To this end, the pumps should primarily be switched on during periods of low energy tariffs; at the same time, the operation of the pumps should not exceed the predefined power consumption limit. And finally, the elevated tanks must be sufficiently full at all times.
Based on these competing requirements, Ulrich Kanngießer developed specific user function blocks for the model application. As these function blocks contain the real-life expertise of the company in question, they are password-protected in order to prevent third parties from accessing the stored parameters. Thanks to the option of creating user function blocks using the powerful structured text programming language, the easyE4 also simplifies the implementation of more complex functions.
The model application fully exploits the possibilities of modern automation components: Numerous parameters of the Eaton DG1 variable frequency drive and the easyE4 control relay can be transmitted, evaluated and logged via the Modbus TCP network. Problems during start-up, an increase in electrical power while the pumping capacity of the pumps remains unchanged, or asymmetrical variables such as the voltage, current, power factor, etc., can thus be detected at a very early stage. This in turn provides indications of future service requirements, and thus also enables predictive maintenance.
Quick programming of custom function blocks
In this project, the ladder diagram, function block diagram and structured text were used in parallel for programming. The ability to create custom subroutines in these languages supports the overall modularity of the design. Structured text provides these user-developed function blocks with similar options as the manufacturer function blocks in easySoft 7. This allows users to create control systems for the water sector directly based on the easyE4, including their own protected function blocks for pump management, run-time monitoring and special modules for the linearisation of measured values and much more. The entire automation design of the model application can be implemented using the relevant modules, including pump control, pump management, gate-valve control and the corresponding monitoring functions.
Valve state detection
Another important feature of the elevated tanks are the gate valves that allow for the inflow of water and prevent unwanted backflow. These gate valves must function reliably, and their "open" or "closed" state must be correctly detected and transmitted to the pump control system. This is done by recording the run time, which is based on the time required for opening and closing, and by monitoring the correct signalling sequence. Moreover, the state change can also be detected when the electric drive is not in operation. This means that the function block also recognises when the state of the gate valve has been changed manually. Sensors are connected in such a way that a potential wire break, cross-circuit or short-circuit can be detected. Measuring the current consumption and the run time of the gate-valve drive also provides indications of mechanical issues or emerging faults in the calibration of the sensor system.
Pump management involving a wide range of parameters
To ensure a high level of availability, water utilities are usually equipped with several delivery pumps that together exceed the required flow rate. This means that one or more pumps can be kept in reserve at all times in case one of them needs to be serviced or replaced. In the past, the only purpose of pump management was to record the running time of each pump and then to activate the pump with the lowest running time when an elevated tank needed to be filled. The pump was serviced as soon as a specific, preset pump run time had been reached.
Networks connect and enable decentralised systems. Up to eight clients can be connected via easyNet
A comprehensive network with many possibilities
The new control system that has been developed for the model application is based on the easyE4 control relay from Eaton. Thanks to the powerful Modbus TCP and easyNet communication networks and the extensive expansion options at the input/output level, the easyE4 control relay can also be used in projects that would otherwise require a PLC. This has the advantage that no software experts are required for commissioning, despite the extensive application options. Thanks to scalable visualisation solutions, it is also possible to adapt the operating level of the system to the latest 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 parameter configurations of the analogue inputs and outputs can be set up using the graphical programming languages ladder diagram or function block diagram. Even when setting up larger systems, the easyE4 rarely reaches its limits – up to 11 local extensions can be connected, each of which can have digital or analogue inputs/outputs. At the same time, up to eight expanded easyE4 control relays can exchange data transparently via easyNet. In the control system for the model application, this feature in particular made it possible to connect the sensors and actuators in a decentralised manner, thereby ensuring that sufficient inputs and outputs are available.
Predictive maintenance information via data logging
Recording the measurement, operating and running data of a controlled device can provide early indications of pending service or maintenance needs. A critical element in any freshwater or wastewater system are the feed pumps and the associated gates and valves. In addition to the operating hours, the real-time pump data, the time required to open and close the gates and any changes in these times can also indicate that maintenance work may be required. Operator interventions and any changes to the parameters can also be recorded in the data logger. Data logging can be performed on any easyE4. A manufacturer function block (DL01) is available for this purpose, which only needs to be configured. The logged data can then be read out via the easySoft 7 software and analysed in Excel or transferred to a control system.
Decentralised visualisation
Within the waterworks, visualisation is not only implemented via the controller, but also within the system itself – directly on site at the pumps, variable frequency drives, monitoring devices, actuators and sensors. The available options are varied and scalable, ranging from a simple LED display to an easyE4 with integrated display and the cost-effective touch panels of the easyE4 family. For larger facilities, multi-touch displays can also be easily integrated. At the push of a button, the data of a variable frequency drive can thus be displayed at the corresponding pump, together with the nominal flow rate recorded by the meters and the status or fill level of the connected elevated tanks. This information can be provided in digital form, in colour and, depending on the device, with graphic elements such as bar charts, pointer instruments or line graphs.
Result:
Benefits for everyone involved in the project
The easyE4-based system developed for the model application offers advantages for all parties involved in the planning and operation of the water supply system: Modularisation provides engineering firms with a sound basis for tenders, while the decentralised system design reduces the wiring costs for installers, and implementation times are shortened thanks to simultaneous modular installation and commissioning. Due to the simple design and the easy programming and configuration of the easyE4 control relays, local electrical contractors can easily carry out maintenance work and subsequent expansions. And finally, the automation system ensures long-term flexibility and availability for investors and operators.
Background:
The model application was developed on behalf of Eaton by Ulrich Kanngießer. Ulrich Kanngießer is a freelance technical writer and seminar leader. He has been involved in the world of automation for more than 30 years. He has extensive experience in consulting, programming and commissioning, has published technical articles (including on the subject of water supply and disposal) and has conducted workshops on various control systems for different manufacturers.
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