Using ABB's WaterMaster electromagnetic flowmeter to measure water abstraction
Improving water resource management through accurate measurement in water abstraction applications
Measurement made easy
The need to manage water supplies more carefully has led to the introduction of water abstraction controls in many parts of the world. These controls can apply to applications where water is being drawn for purposes such as drinking water, industrial usage or irrigation.
Abstraction controls offer two main benefits. Firstly, restricting the amount of water that can be drawn from any one source helps to prevent any associated environmental damage, such as depletion or, where water is drawn from a watercourse, harm to aquatic life. Secondly, quantifying the amount of water that is extracted enables existing stocks to be better managed and conserved.
Water can be abstracted from various sources, including streams, rivers, reservoirs and underground aquifers. Where abstraction controls apply, users will normally be licensed to draw a specific quantity of water from a specified location over a set period of time for a specific purpose. It is therefore necessary to measure the amount of water abstracted in some way and for the figures to be recorded to ensure that consumption remains within the prescribed limit.
Purposes of abstraction controls:
- Improved management of water resources, including efforts of abstraction on the environment
- To check that the abstractor is complying with the terms of their abstraction license
- To enable accurate calculation of annual charges
- To gain a clear overview of how much water is available for other uses after the licensed abstraction amount
- To help create an informed assessment of overall demands, which can then be passed to government or some other supervisory authority for action
Various types of flowmeters can be used to measure water abstraction, including mechanical, ultrasonic and electromagnetic technologies.
Selecting the appropriate flow meter for the application depends on a number of factors, including the desired accuracy and repeatability and also the characteristics of the installation. For example, where water is being abstracted from a river or a stream, pebbles and sediment may be present which could quickly damage and even destroy a mechanical meter. Where sea water is being abstracted, the salinity of the water can also quickly wear out a stainless steel flow meter, requiring consideration of the materials of construction.
As the metered values may be used to bill the abstractor and to access the overall quantity of water available, it is important that any flow-meter used can offer the required levels of accuracy and repeatability. Not only that, but it must also be able to withstand the various rigors of the application, especially where high levels of sediment or other non-ideal conditions may be present.
With moving parts subject to wear and tear, mechanical meters can quickly suffer reduced accuracy, leading to either under or over-registration of flows. Furthermore, the need for mechanical meters to be periodically tested, re calibrated and repaired means that they have to be removed, requiring users either to replace the meter with a temporary device or cease abstraction until the meter is refitted back into the line.
Ultrasonic flowmeters also suffer various drawbacks which can make them unsuitable for water abstraction applications. Transmit time meters in particular can struggle to handle flows with high levels of particulate matter, requiring a strainer to be fitted. Both transmit time and Doppler meters can also be affected by velocity profile distortions, requiring from 10 to 40 upstream diameters, depending on the severity of the disturbance. The turn down of ultrasonic meters is also limited within an ideal range of 20:1 to 40:1. Ultrasonic meters can also be difficult to install and set up, especially where high accuracy is required.
Electromagnetic flowmeters overcome these problems. Compared to other flow meter types, electromagnetic flowmeters offer greatly enhanced accuracy and repeatability throughout their operational life, with uncertainty of ±1 % reading or better. With no moving parts, they do not suffer from problems with wear and tear, minimizing maintenance and require no upstream strainers to filter sediment. A choice of flow primary linings affords further protection against high sediment flows, with users able to choose from a variety of materials, including ceramic linings for particularly abrasive flows.
The ability of electromagnetic flowmeters to better handle distorted velocity profiles also means that the amount of piping upstream and downstream of the meter is reduced.
What can ABB offer?
ABB's WaterMaster and AquaMaster electromagnetic flowmeters offer the ideal solution for water abstraction applications. Both flow meter ranges bring a host of advanced features and functionality for water measurement.
A key feature of the WaterMaster is its revolutionary octagonal sensor design. By improving the flow profile, the octagonal design minimizes the upstream and downstream pipe lengths required from the point of installation, substantially lowering the cost of fitting the meters into new or existing pipelines.
The WaterMaster also features onboard verification capability. Called VeriMaster, it assures operators of the performance of the meter through constant self-checking. When coupled with ABB's VeriMaster software tool, it enables operators to produce a printed verification certificate for regulatory compliance.
Available in sizes from 10 to 2400 mm (3/8 to 96 in), all WaterMaster sensors have a rugged, robust construction to ensure a long, maintenance-free life even under the most difficult conditions experienced in water and wastewater applications. The sensors are inherently submersible (IP68, NEMA 6P) as standard, ensuring suitability for installation in chambers and metering pits which are liable to flooding. All sizes of the WaterMaster are buriable and are straightforward to install.
WaterMaster is proven to be robust and reliable, with unmatched diagnostic capabilities providing the right information to keep the process up and running. Alarms and warnings are classified in accordance with NAMUR NE107.
Available in sizes from 10 to 600 mm (3/8 to 24 in) the AquaMaster can be installed anywhere, making it the true anyplace, anytime, flowmeter for abstraction, distribution and network management applications. The meter sensor can be buried, fully submerged or mounted in a chamber. The transmitter can be installed with it or separately at ground level up to 200 meters away, ideal when the sensor is required to be buried under a road or highway.