Each day, 850 main breaks occur in North America. A study by Utah State University reported that the average break rate per 100 miles of pipe can be as high as 24.4 breaks per 100 miles of pipe. If your utility is on the higher side of that number then it is highly probable that you could benefit significantly by controlling the pipe network better through a focused valve asset management program. These types of programs are geared toward reducing the footprint of emergency isolations and reducing the amount of time required to isolate those main breaks (duration). Based on criticality, a systematic reduction of the footprint and duration of main break events can have a dramatic impact on how much water is lost through the breach and how much damage that water does to other infrastructure. How would you describe your preparedness to isolate critical mains?
What Percentage of Valves in Your Pipe Network Can be used for Isolations?
There are three questions that must be answered about each valve: If the answer to any of these questions is no then the valve is not usable.
- First can you find it? Just because it can be found on the map does not mean you can find it in the field because maps are not always spatially accurate. Sometimes maps do not show all the valves and sometimes they do not are not up to date enough to show when valves were abandoned or removed from the network all together. Mapping errors are the number one reason utilities have trouble finding valves.
- Next, can you gain access to it? Sometimes you must find the valve using a metal detector because it is buried and other times you can just walk right up to it but need to jackhammer the lid off and still other times you can get the lid off but there is hard material that must be jetted and vacuumed out. Accessibility can change every time a road is paved and it can change in an instant on private property where fences and temporary structures can be erected on valves making them inaccessible. The second most common reason valves are unusable is because they are inaccessible.
- Finally, does it mechanically operate? Does the valve have an operating nut, is it missing gears, is it frozen in one position, does the operator turn without moving the gate? These are common situations when valves are not touched at a high enough interval. However, mechanical problems are the most infrequent. This means that we can make significant headway toward improving usability by addressing accessibility and mapping issues.
Key Performance Indicator: Usability
A simple way of predicting how much impact improving usability would have is to express it as a percentage of all valves. For example, a usability of 80% means that 80% of all valves are usable. I.e. they can be found, they are accessible and they mechanically operate. This is means that if your average isolation is designed to be four valves then 80% usability means that 3.2 valves will work (80% x 4 = 3.2) valves. Stated differently, three valves will work and 0.2 (20%) of the time a fourth will work. To further simplify, at 80% usability a four-valve isolation will not require backup 20% of the time.
Small changes in usability have big impacts on this probability. For example, consider moving from 80% of all the valves being usable to 90%. The difference is: (90% x 4 = 3.6) compared to (80% x 4 = 3.2) a 40% improvement in how frequently all four valves would be usable in an isolation. But more interestingly if we assumed there were 100 main breaks at 80% usability 20% of the isolations do not get backed up which means 80 do get backed up. Compared to 90% usability where 60% of the isolations do not get backed up which means that only 40 do get backed up. This means a 10% improvement in usability can make a 50% change in how many isolations are backed up. Small changes can make big differences.