Sizing of Pumping Systems for irrigation needs careful consideration in order to achieve optimum performance, efficiency and long-term reliability. So, what are the main factors and requirements to take into account? We’ve put together this handy guide to help you understand how to choose the right irrigation booster pumps for your specific needs and environment.
Irrigation Booster Pump Sizing: Head and Flow
Head and flow are the main requirements for any system, however there is a lot of information required to get the best efficiency and reliability.
Head is seen as the highest point of discharge from the pumps, but we need to understand the total amount of static head and other head losses in the system to define the Total Head. Pipework costs may push installers towards using less costly small-bore mains to the discharge points, only to undermine the long-term energy cost and system performance.
Unfortunately, the friction loss within a small-bore irrigation system will demand more energy, escalating the running costs for energy. With this in mind, the more flow, the larger the bore pipework required, especially for the main distribution pipework. Other losses are found in any pipework system and should be accounted for when calculating the total head. Sprinklers, irrigators, fittings, valves will have an identified head loss valve and by careful selection and design some of these losses can be reduced.
Once the total head and flow has been determined, the process of selecting the pumping system can begin. Most facilities such as golf clubs, sports grounds, parks and large gardens will require a system using 2 or more pumps with a ‘jockey’ pump to cope with small fluctuations in pressure demands.
Pump Control Systems
The control of these pumps is via an electrical control system which will monitor the pressure with the discharge water main and will start the pumps as demand increases. One pump may be required initially, but as demand increases an additional pump will be deployed to maintain pressure.
In some cases, the control systems may be as simple as using mechanical pressure switches to activate the motors via crude ‘direct online’ starting methods, but more commonly variable speed drives are being used to match performance with demand, giving better overall performance and economy.
A reliable and efficient control system will have a myriad of additional built in protection features supplementary to the expected motor overload protection; dry running protection is essential to avoid damaging the pumps due lack of incoming water. Equally, under pressure protection may be provided to shut the system down if there is a delivery main burst, or unplanned discharge beyond normal planned flows occurs.
Power supply is a very important consideration, ensuring that there is sufficient supply to meet the demand of a new system, while location of system is important trying balance the best location of the pump set to optimise the irrigation obligations but not too far from a main power supply to avoid escalating costs of larger power cabling to avoid voltage drop which will undermine the system.
Examples: Booster Pumps for Irrigation
Recent examples of diverse booster pumps installations for irrigation show how different applications can be applied successfully.
As part of a wider water management scheme on a Hertfordshire golf course, this project required a booster set meeting very high industry standards in order to improve the distribution of water around the expansive course where the water was extracted from the lake.
A Dual Booster Set was sized and selected, complete with 2 x 5.5kW vertical multistage pumps, motor mounted variable speed drives and bespoke control panel to Irritech specification, including back up fail-safe system via Digital Pressure Controllers. The pump set in a duty / assist configuration will achieve a performance of 20m³/hr at 8.8 bar pressure.
Large Irrigation Schemes
A large-scale system recently commissioned indicates the scale and sophistication that can be employed, which included Dual 132kW Multistage Pumps with a 45kW jockey pump all on VSD control, a triple 30kW set with 5.5kW jockey pump, and 2 no. Single 55kW boosters each with an 11kW feeder pump, operating on a dual redundancy basis with mirrored PLC and software.
The booster set is used daily to water the main pitch at the bet365 stadium.
The home of Stoke City FC, the bet365 stadium, as with all major sporting grounds, requires watering daily to keep their pitch in a premium condition. Searching for an efficient and economic product that could provide reliable irrigation with automatic control. The system, which comprised of fixed and variable speed clean water multistage pumps, was designed and manufactured to provide both the flow and water pressure required for the football ground.
Selection of Booster Pumps for Irrigation
For expert help on irrigation booster pump sizing and the selection of the right pumping systems for your specific requirements and environment, get in touch with the expert team at T-T Pumps on +44 (0)1630 647200.