By fitting flowmeters inside its reservoirs, Sydney Water improved the management and utilization of its water assets without disrupting supply.

Water is a precious resource, especially when dry conditions create the combination of peak demand and reduced availability. To improve its water management and conservation, Sydney Water needed to find an accurate and effective way of measuring the inflow and outflow of water through its reservoirs.

The traditional way to install flowmeters at a reservoir is to dig up the pipe work and build new valve pits. This involves emptying the reservoir and is labor intensive and disruptive. Sydney Water found a better solution by fitting Sitrans F M electromagnetic flowmeters. The F M MAG 5100 W flowmeter is ideally suited for water applications and can be supplied with an EPDM liner specifically for drinking-water applications requiring special approvals.

The Sitrans F M MAG 5100 W sensors were adapted for this application with a customized junction box on top of the mag sensor supplied by SFI Stonehouse. This design is unique in the market and was initially developed for North Sea offshore applications. It is double sealed and is waterproof to 30 meters without potting. The inside cabling was fully potted in Australia for the application. Sydney Water installed more than 10 internal flowmeters to both inlets and outlets in its reservoirs. With the F M MAG 5100 W meters, it is possible to fit the flowmeters inside the reservoirs while they remain full of water. Moreover, by fitting the flowmeter inside the reservoir, it is possible to fit a single meter to the main outflow before it splits into multiple pipe connections.

Sitrans F M MAG 5100 W electromagnetic flowmeter

Installation dive

Each reservoir presented a variety of wall- or floor-located outlets; uneven floor areas; and obstructing walls, posts, and floor joints. Following site surveys, custom-made pipe work, adapters, and supports were constructed for each installation. The entry and exit pipes of high-density polyethylene (HDPE) were made to a length of three times the flowmeter diameter at entry and exit to ensure a laminar flow through the meter. These pipes were tapered to ensure a minimum flow rate of 0.25 meters per second through the meter for measurement accuracy.

After the first installation, when divers did much of the assembly work under water, the team decided to fabricate complete assemblies in a factory environment, even though this involved handling large assemblies on-site. For some larger units it was necessary to remove roof sheets from the reservoirs to gain access. This inconvenience was more than outweighed by shorter dive times, especially in cold winter temperatures.

Once in the water, complete units weighing up to 1,000 kilograms could be “walked” around inside the reservoir using flotation lift bags to take the weight. The first stage was to mount an HDPE adapter flange to the existing outlet and bolt and epoxy seal it in place. The flowmeter assembly was then moved into position and bolted to the inlet or outlet penetration. After supporting legs had been fixed in place, the weight could be transferred from the lift bags.

Lifetime calibration

A stainless steel guide wire was run from the control unit on the flowmeter up to the reservoir roof. Heavy-duty marine cables were then attached and connected. The Sitrans flowmeter features a Sensorprom memory unit that stores sensor calibration data and transmitter settings for the lifetime of the product. Using this feature, each flowmeter could be set up on commissioning and left to transmit flow measurements without any further supervision. All the flowmeter installations were completed successfully without disrupting water supplies or requiring major work – a success enabled not least through the commitment and excellent performance of the Australian Siemens team with Col Gassman, Allan Pogonowski, and John Kearton. Now, after 18 months’ operation, the data provided by the Sitrans flowmeters have enabled Sydney Water to achieve significant savings and efficiency improvements.

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