Halifax water uses advanced pressure management pilot to reduce leakages



Aging water systems face a number of challenges, including a growing and urbanizing population, water scarcity and more extreme weather events, an aging workforce, and increasing expectations from customers.

For reasons such as these, water utilities worldwide are moving to more advanced operational management solutions using the Internet of Things (IoT). These IoT devices can provide valuable insight into the operational efficiency of a water system and give utility operators the analysis and intelligence necessary to help make informed decisions for performance improvement.

After hitting a static level of breaks and non-revenue water (NRW) loss, for Halifax Water (HW) the challenge is increasing leak awareness to reduce run time.

As part of its 2021-22 annual business plan, Halifax Water is developing recommendations to reduce NRW loss.

To help support these plans, HW partnered with Mueller for a performance trial of an advanced pressure management and control platform. Kevin Healy, operations engineer with HW said: “We’ve worked with Mueller in the past, so we were eager to start the trial. Additionally, from a deployment perspective, our system already had district metered areas (DMAs) with pressure reducing valves, and access to an enabled LTE-M cellular network.”

While subdivision of the network into DMAs enables closer management of pressure and leakage, pressure monitoring and control solutions can also be effective in open networks. The pilot program included three phases of implementation.

Sentryx Intelligent Network web interface - site location map view
Figure 1. Pressure surging and transients detected at one of the Halifax Water air release valve locations.

Pressure Monitoring and Analytics

Phase one of the pilot program served to evaluate the communication and reporting functionality of the pressure loggers, as well as the data analytics, notification alarms, and data visualization of the Sentryx™ Intelligent Network cloud-based software service. A total of three pressure loggers were installed. Two are single-port pressure recorders within existing air release valve chambers, and one is a triple-port pressure logger to record inlet, outlet, and control chamber pressure of an existing pressure reducing valve (PRV) station.

The Sentryx Intelligent Network is a highly available, highly secure software service that stores data and maximizes the value available from it by applying machine learning algorithms and visualizes it in the most actionable formats. This includes maps, graphs and tables.

During phase one of the pilot program, HW was able to derive valuable insights about its network that it did not have before and see these using the software service’s maps and graphs.

Some of the most interesting insights included the detection of pressure surges and transients at one of its air valve installations as seen in Figure 1. It is a standard feature of the loggers that they collect statistical data that enables transients to be detected. In addition, a routine fire flow test could easily be identified, as seen in Figure 2.

Figure 2. Fire flow testing pressure drop recorded at two seperate pressure recorders.

While HW previously had pressure sensors reporting to SCADA, the Mueller data loggers enabled the utility to monitor pressure and flow at air release valves (ARVs) and other locations without existing power and communications, without the expense of adding power or communications in an existing chamber.

Remote Controlled PRV

The “Zinck PRV station” seen in Figure 3 has a 100 mm PRV main supply and a 250 mm PRV fire flow backup. It is the only primary feed into the Mowatt intermediate DMA, as seen in Figure 4. The PRV was retrofitted with the advanced pilot valve (APV) with the existing PRV pilot system still installed, but valved-off to allow for backup control during routine maintenance. A control logger was also connected to the PRV. Utilizing the APV and control logger, the PRV can now be controlled remotely with the new advanced pressure management system.

Figure 3. APV and controller installed on a 100 mm Singer 106-PR pressure reducing valve.
Figure 4. Mowatt intermediate district metered area.

The Mowatt intermediate DMA in Halifax has 479 connections, 37 fire hydrants and 52 mainline valves and 6.4 km of watermains. As the first proof of concept to HW, the APV pilot was locally set and programmed to operate as a normal fixed outlet PRV. The current PRV pilot system on the 100 mm PRV was set to a constant 71 PSI, and the APV was programmed to regulate the PRV output to the same 71 PSI outlet pressure.

“I was impressed with how well the PRV outlet pressure was maintained – particularly in low-flow scenarios. The Sentryx software allowed us to change the PRV setpoint remotely and even adjust the opening/closing speeds of the PRV to offer an even smoother outlet pressure,” said Healy.

Once the new pilot proved its ability to regulate and keep a constant outlet pressure, HW moved on to test control using “flow modulation”. In flow modulation, the PRV outlet pressure is varied based on the actual demand in the DMA.

This allows a lower pressure set point at night when demand is low and system head loss is at its minimum. During peak demands, pressure is increased to overcome system head loss and ensure sufficient pressure within the DMA.

Flow modulation is ideal for lowering pressure in off-peak demands to reduce leakage flows and the occurrence of watermain breaks. It also responds quickly to increase pressure at peak demands or for fire flow requirements.

Automatically-Optimized PRV

Rather than setting fixed or timed outlet pressure from the PRV, in automatic optimization mode, the system takes in data from the PRV and from a logger placed deeper in the network where the water utility wants to deliver fixed pressure levels. That position is called the “control point”.

All the user needs to do is set the target pressure levels required at the control point by time of day and day of the week. The Sentryx Intelligent Network software service does the rest. It receives data from the PRV control logger and the control point logger and calculates the optimal control curve to achieve the target pressure. It then makes adjustments to the PRV outlet pressure continuously. The profile is created in the software service, then sent down to the control logger. It takes just seven days to be confident in its first curve. The curve is automatically re-calculated regularly to account for changes in demand. These may be seasonal or may result from changes in customer usage in that area of the network over time (e.g., the building of new housing). The system ensures that pressures are maintained at the minimum viable level at all times. This in turn reduces leakage and the likelihood of pipe bursts. This method of optimized pressure management gives HW the highest level of security of supply.

Although the DMA flow profile and “night flow” for the Mowatt intermediate zone shows that there is very little leakage in this zone, HW was still able to obtain savings from the optimized PRV control mode. Under fixed outlet control, the average daily DMA demand was 210 m3/day (55 kGal/day).

In optimized PRV control mode, the daily DMA demand was 204 m3/day, a savings of 6 m3/day or 2.8% of the average daily demand. In a pressure zone or DMA where leakage levels are 10%, 20%, or even 30%, the savings would be significantly higher.

Click here to read the article in Environmental Science & Engineering.