The Demand Driven Distribution (DDD) concept has wide-ranging implications for pumping systems. In The Netherlands, for example, it has helped drive down energy consumption and maintenance costs for the Dunea water company.
Demand Driven Distribution – Always the Best Option
Marcel van Veen from Grundfos Netherlands has no doubt, “I find that the Demand Driven Distribution concept is absolutely the way to build a pumping system, especially, where the capacity ranges are very wide. This is true even when water leakage is not a major issue, which it isn’t really in The Netherlands – for a DDD system drives down energy consumption and maintenance, which will always be important.” The DDD principles were brought into action when the Dunea water company needed a new booster station – “Booster Hillegom”. Dunea is one of the ten drinking water companies in Holland. The company’s main source of water is surface water, but they also buy drinking water from Waternet. This is where the new booster system comes in, for the water intake from Waternet was to be carried out via Booster Hillegom. The capacity range required by the station is quite unusual: Normal operation consists of between 80 – 300 m3/h, heads from 22 mwc up to 36 mwc. The average capacity requirement for the station is 140 m3/h at 23 mwc; in case of emergencies the booster station should be able to supply 700 m3/h at 36 mwc. When Dunea asked Grundfos to suggest a solution for this project, they had no specific pumps in mind – they simply described the application and its capacity and head ranges and presented Grundfos with the challenge of coming up with the best possible solution. Dunea invited five pump suppliers to meet the challenge stating that the three companies to offer the proposals would receive an official inquiry in January 2010.
Energy-Efficient, Low-Maintenance Solution
Grundfos proposed a three-pump system consisting of NB 100-315/334 with a rated motor power of 30 kW each. All pumps were to be equipped with VFD and controlled by means of MPC controls. That solution was not the only one being considered; the Grundfos team also looked into the possibility of installing a four-pump NB system or a Hydro MPC-E solution. Overall, four different possibilities were considered by the Grundfos team:
3 x NB 125-315/336 with 37 kW 3 x NB 100-315/334 with 30 kW 4 x NB 80-160/177 with 30 kW Hydro MPC-E 5 CRNE 150-2 with 22 kW. Eventually, the team’s analyses showed that the three-pump NB system was the best alternative in terms of both energy consumption and maintenance requirements.
Careful Studies of All Alternatives
For a while, the 4 x NB 80 alternative looked promising: it showed the highest capacities overall. But then an extra pump would be required and the pit would need to be larger. Furthermore, an extra VFD and extra maintenance would be needed. This would have a negative effect on the total cost of ownership for the client. Therefore, Grundfos decided to go ahead with a three-pump solution and see if that could achieve what the client wanted.
The 3 x NB 125-315/336 covered the complete range, even the emergency point, without going above 50 Hz. However, efficiency could be better, so the Grundfos team came up with the option of using 3 x NB 100-315/334 or a four-pump solution, both 30 kW. These solutions would ensure better efficiency at approximately the same power consumption. However, a three-pump solution requires a smaller pit and, obviously, lower expenditure, which prompted Grundfos to make this final recommendation. As an added bonus, the NB pumps are easy to maintain and allow for a better piping layout in the pit than an in-line system does.
When they called for design ideas, Dunea had certain plans in mind, but did not show them to potential suppliers – they did not want to restrict creativity in the solutions offered. It later transpired they their own initial design planned to have suction and pressure headers on the left and right side and in between multi-stage pumps. After talks with Grundfos, however, Dunea were convinced that NB pumps were the most efficient choice for then – and that the headers could be positioned above each other, close by the wall. The system allows for a more open pump configuration, making access much easier for staff.
Dunea were favourably impressed by the design proposal and were intrigued to learn that Grundfos could offer to supply the complete booster station, including the concrete pit and electrical work. Tentative plans were drawn up by a team comprising members from Dunea, Grundfos, a constructor (Visser & Smit Hanab), and an electrical engineering group (Cegelec).
Final Design Matched Initial Grundfos Suggestion
Eventually, the design was finalised and building on the new booster system began in June of 2010. The final design incorporated the three-pump NB system with CUE VFD’s and MPC controls exactly as they had been presented in the original plans from November 2009. The system supplied consists of:
Pumps: 3 x NB 100-315/334, 3 x 400 V – 50 Hz, 30 kW EFF1 with insulated bearing NDE, bronze impeller Pump control: 1 x Control MPC-E 3 – 30 Frequency converters:
3 x CUE 30 kW
The system – and overall building project – was completed in February 2011, and the system is now working to achieve the ambitious goals set by Dunea.
Client: “fits our policies on responsible energy consumption”
