Norfolk County is a city in Ontario, Canada. It was merged into one city in 2001 with a population of more than 60,000. Norfolk is located 56 kilometers (35 miles) southwest of Hamilton and 97 kilometers (60 miles) southeast of London.
The county recently encountered a major breakthrough in its 12-inch ductile iron water mains. This is the only supply from the Port Rondon community to the St. Williams community, which means that the impact on residents is huge. The team suspected that the leak on this line was caused by pitting, which is a common cause of failure of ductile iron pipes. During the maintenance period, the water staff pointed out that the bottom of the ductile iron water main was obviously deteriorated and corroded.
There are other communities in Norfolk, which are obtained from well sites through these mains transmission lines. These sites are also vulnerable to attacks due to a single feed and lack of redundancy. “Said Jeff Demeulemeester, a Norfolk certified engineering expert and project manager.
Norfolk’s 10-year capital plan is an integral part of its long-term financial sustainability plan and emphasizes the importance of ensuring priority, proven and affordable projects. The current status of its water pipes must be understood to ensure effective preventive maintenance.
The county submitted a request for proposals to evaluate the condition of its water pipes. After multiple rounds of testing and deliberation, the Echologics ePulse non-invasive condition assessment technology provided by Mueller was selected to determine the existing structural condition and find any existing leaks and abnormalities.
For this project, Echologics tested approximately 6.9 kilometers (4.3 miles) of ductile iron gearbox headers that travel mainly along the front road. Norfolk chose this part of the pipeline because of its lack of redundancy and previous interruption history. Since the failure of this line may also have a significant impact on the residents of Norfolk, a condition assessment survey was conducted to determine whether any areas along the line have experienced severe degradation. Based on the survey results, AECOM Engineering Company recommends the next pipeline renewal plan as needed.
Figure 3. Describes a customized decision tree to select the update method (repair and replacement) for 54 pipe sections based on ePulse Inspection Results..jpeg
ePulse technology is achieved by connecting two acoustic sensors to each existing contact point (such as a fire hydrant, valve or direct contact with the pipe wall). Sound waves are induced in the pipeline, and the propagation speed of the sound waves is measured between the two sound wave sensors.
The speed of sound wave propagation depends on the condition of the pipe wall. After the on-site work is completed, the speed of the sound is combined with other information collected on-site (including distance and water temperature), and then a proprietary advanced algorithm is used to determine the remaining average wall thickness of each segment.
These results are interpreted in the form of three categories of “good”, “medium” and “poor”. A wall damage rate of less than 10% is indicated as good; a wall damage percentage from 10% to 30% is indicated as medium; a percentage greater than 30% is classified as “bad”.
AECOM project manager Khalid Kaddoura said: “Each ePulse result represents the average condition within a period of time between the two sensor connection points.” The replaced pipes are ranked. For this purpose, the ePulse results are very good.”
Figure 2: The sensor is magnetically connected to the valve and the cable is connected to the transmitter for acoustic condition assessment.
The second part of the project requires the investigation of leaks and abnormal conditions to be completed at the same time as the status assessment. This is the advantage of deploying ePulse because the same acoustic correlator can be used to perform assessment and leak detection at the same time.
After a 12-day evaluation period, ePulse results showed that 12 of the 54 network segments were in poor condition, with an average wall thickness loss of more than 30%. In addition, there are 30 sectors in an intermediate state, and the original wall thickness has lost 10% to 30%. Another 11 network segments are in good condition, the original wall thickness loss is less than 10%, and the remaining one network segment cannot distribute the results.
No leaks were found during the investigation. However, a point of interest (POI) was identified. The POI logo indicates that some (but not all) of the criteria for a positive leak test result have been met. The second investigation later confirmed that the leakage noise originated from the normal working pressure relief valve in the meter well.
Demeulemeester said: “We are very pleased that the project provided us with the data we need to prioritize and set an educated replacement schedule based on the remaining wall thickness of the water pipe.” “Furthermore, the cost of the evaluation is considered insignificant because it Provided Norfolk County with the necessary data to prioritize the replacement of our transmission main network with priority over the 10-year capital plan. Based on the “worst priority” replacement schedule, we were able to maintain the timing with the required financial plan Consistent.”
Based on the results collected by the Echologics field team, AECOM has developed a customized renewal decision tree and some budget cost estimates for renewal programs. Combined with the ePulse inspection results, the decision tree is based on the following three condition categories: good, medium and poor.
For the first two categories of good and medium, it is recommended to evaluate the hydraulic performance of the water mains. If it falls within an acceptable range, an additional evaluation will be performed to check the characteristics of the water. If the water quality does not meet local standards, rehabilitation interventions are recommended.
On the other hand, if the hydraulic performance of the water pipe is unacceptable or is determined to be in poor condition, it is recommended to replace the hydraulic power, if more hydraulic power is required. If the hydraulic capacity is sufficient, consider updating the technology case by case based on the analysis of cost and floor space of the building.
After the project is completed, Norfolk County plans to replace the pipe sections that are in poor condition and determines to replace more pipe sections in its 10-year capital plan.
PE, Alain Lalonde is the regional manager of Echologics in Mueller, Canada. You can contact Lalonde via [Email Protection].
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Post time: Mar-08-2021
