Intelligent control of the booster system optimises energy efficiency and ensures reliable water supply

Overview_TEXT

Overview

The Zweckverband Wasserversorgung Rottal (ZWR) [Rottal Water SupplyAssociation] in Pfarrkirchen, Lower Bavaria, Germany, supplies drinkingwater to approximately 6000 properties in 713 districts, covering over 271 km2.

When the water distribution system was established 25 years ago, boostersystems were installed in various districts to optimise water pressure.These systems ensure that the minimum required water pressure ispresent at critical points in the water network, and the solution met theformidable challenge facing ZWR to ensure a safe and reliable supply ofdrinking water for the residents over a considerable area.

However, in addition to ensuring water supply security, energy efficiencyplays an increasingly important role today. Furthermore, the old pumptechnology was also prone to failure, so ZWR made the decision tocompletely refurbish all pumping stations with new, high-efficiencybooster systems.

Increasing focus on energy requires a change in thinking

Energy optimisation is increasingly in focus, not least because of the risingcost of energy, and stricter efficiency standards. This is a trend that is setto continue. Energy is the single greatest expense for pumps and pumpingsystems, measured over the product lifetime. The cost breakdown for apump as a single unit or as part of a system is as follows:

If the total cost, including the initial investment and operation, adds up to 100 %, then energy costs account for approximately 80-85 %. Repairs andservicing account for 5-10 %. The ‘actual’ investment is therefore only 5-10%. This shows that the energy cost factor takes on special significance, andit is therefore important to ensure that all pump units work in the sameperformance range, enabling optimal energy yield.

To ensure a system that is up-and-running from commissioning requires afull-line supplier that can offer the entire range, from system analytics to control technology and optimal pumping systems. Grundfos can do this.

Efficient pump technology provides security of supply and energyefficiency

The objective was to reach a gentle constant pressure control of 8 barusing highly flexible industrial process measurement and control.

To meet this challenge, a Hydro MPC-E 5 CRIE 10-9 booster system (DEA)was set up at the main station (GPW) in Wolkertsham. The downstreamOpping pumping station (DPW) is currently equipped with a Hydro MPC 4x CRIE AKC 10-6 system.

All CRIE pumps boast sophisticated technology, high-quality materials andlow-wear bearings. Another key feature is the unique cartridge mechanicalseal. It is made of highly wear-resistant materials. Thanks to the cartridgedesign, the sealing elements can never be improperly assembled. Thedelicate sliding surfaces never are in contact with greasy fingers or dirt.This significantly reduces the chance of failure due to improper gasketinstallation.

Significant changes were made to increase pump efficiency. Tests hadshown that a gap of just 0.1 mm between the chamber and the impellerresulted in a 5 % loss of efficiency. By using a floating gasket ring, internallosses due to leaks are reduced to a minimum. All pumps used in both DEAsfeature a frequency controller (PID controller), which has proved especiallyimportant.

The Hydro MPC boasts soft pressure build-up and reduction withoutpressure surges. Only the pressure that is required is generated at any giventime. The individual pumps each work at their optimal duty point.

Demand Driven Distribution ensures constant mains pressure at thecritical point

Compared to intermittent operation, operating a water supply system at aconstant supply pressure reduces the risk of pipe breaks and water loss by10 to 20 times. Using Grundfos Demand Driven Distribution (DDD), outputpressure in the waterworks is controlled by continuously measuring thepressure at the mains end.This solves four immediate problems:

  • Increases operating comfort due to constant mains pressure, especiallyat the critical point

  • Energy savings thanks to strategic pressure reduction

  • Minimises the risk of pipe breaks and expensive repairs

  • Reduces adjustment and programming work

A data logger at the critical point (1 to 10 data loggers can be used persystem) measures all the relevant values and creates a pressure profile.These profiles are saved and sent to the pumping station daily via SMS. AProfibus type CIM 150 and CIM 040 serve as communication modules. TheGrundfos CU 354 controller is the heart of the operation and builds on thehighly versatile multi-pump controller CU 352. The intelligent controllerindependently optimises the control curve based on the data collected.Depending on the demand, the controller switches the pumps on or off,without causing pressure surges. In the case of the Opping booster system,a system analysis showed a reduced energy consumption:

Specific power consumption (old) 0.3841 kW/h

Specific power consumption (new) 0.233 kW/h

This represents a savings of approximately 39 % - a considerable amountin any water supply system.

 


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Topic:

Optimize energy efficiency and ensure reliable water supply

Location:

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farrkirchen, Lower Bavaria, Germany

Company:

The Zweckverband Wasserversorgung Rottal (ZWR) [Rottal Water Supply Association]

The Zweckverband Wasserversorgung Rottal
The Zweckverband Wasserversorgung Rottal supplies 713 districts and approximately 6000 properties with fresh drinking water
The old booster pumps
The old booster pumps in GPW Wolktersham and DPW Opping are removed.
The pump technology at GPW Wolkertsham is then replaced.
The pump technology at GPW Wolkertsham is then replaced. A Hydro MPC-E 5 CRIE 10-9 takes care of the task. Control unit CU354: all relevant data are displayed.
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