Leak mystery solved with tethered inline Sahara tool
What keeps a water utility manager up at night? Getting a phone call from a distraught resident about an unplanned (and unwanted!) ornamental pond developing in the cul-de-sac.
On an already soggy, wet day in early November 2016, water began filling a cul-de-sac in an affluent neighbourhood in the City of Southlake, Texas. To contain surface flooding, Southlake water authorities took immediate remedial action by sequentially shutting down each water line in the area in an attempt to isolate the leak.
In addition, the City used external listening devices to try and locate the leak – the external listening devices indicated that some kind of leak was present, but the City was unable to pinpoint the location. In the end, the City had to shut down the 42-inch Caylor bar-wrapped potable water main, a low-pressure gravity main passing through the area. This was done to confirm that the 42-inch Caylor Main was leaking.
Sure enough, once the 42-inch Caylor Main was shut down, the water stopped surfacing. When the City reopened the main, the water did not resume surfacing. Despite the inconclusive evidence, the City remained convinced that the 42-inch main was the leak source.
Soggy ground, horse pasture and and muddy conditions hamper inspection
With uncertainty remaining, the City of Southlake called in Pure Technologies to assist in identifying and locating the leak. Unfortunately, the bad luck continued, as heavy rains and muddy conditions hampered Pure and its mobilization truck from access to the pipeline right-of-way. Even crews from Southlake got stuck when they tried drive the pipeline right-of-way.
One possible additional access point was available through a private owner’s horse pasture, but low-hanging power lines created a safety hazard that would prevent crews from accessing the site by that route.
Disappointed, the crews demobilized to wait for better weather or a better access point.
Sahara® platform selected for speed, accuracy and on-the-spot results
The next day Southlake identified another access point 1,000 feet further upstream, and prepared it for the Sahara inspection.
The Sahara leak detection platform was selected for its ability to provide same day results, and to accurately locate small leaks with sub-meter accuracy. The tethered tool is propelled by a small parachute inflated by the product flow, requiring a flow velocity as little as one foot per second to progress through a water main.
Because the Sahara inline tool is tethered, an operator has complete control, and can closely examine events of interest such as leaks, gas pockets and visual anomalies in real time.
Second attempt to find the leak
For the assembled crews, pressure escalated to quickly find the leak location.
Once the Pure mobilization crew set up the installation equipment and inserted the Sahara sensor, the pressure gauge indicated only 36 PSI, not the best scenario for leak detection. Furthermore, the inspection was heading uphill toward the area of interest, and could expect even lower pressure nearer to the suspected leak location area due to loss of head pressure as the pipe ascended the slope.
Further complicating matters, the pipe wall thickness was determined to be about 4 inches, and leak paths that pass through 4 inches of concrete and mortar can often include sharp bends that can muffle leak signatures.
From the insertion point, Sahara inspected a total of 2,400 feet, passing through the cul-de-sac area at around 1,600 feet from insertion.
A slow pullback of the tethered Sahara tool to recheck areas of interest
During deployment, review of acoustic data noted a few areas of interest, but nothing definitive. The inspection continued past these areas of interest in the hopes of finding something more conclusive. When nothing was found, the Pure crew began a slow pullback of the tethered Sahara tool to recheck the areas of interest.
One of the benefits of a tethered tool is that two inspection passes can be conducted on the same section on the same day.
Of the possible leak areas, one acoustic anomaly seemed promising, and that spot was marked above ground.
Because this suspected leak did not, even in post analysis, present with all the elements of a leak signature, and because it lacked a distinctive peak location, Pure Technologies recommended that the City of Southlake check a 7-foot length of the pipe, all the way around the pipe.
Surprise, surprise, 4 leaks verified
As directed, Southlake crews excavated the indicated areas and found not one but four leaks. The presence of four leaks in close proximity to one another, all at low pressure, explained the difficulty of finding a leak peak.
The four leaks located ranged from pencil-sized to quarter-sized. The sloppy mortar job over an access plate into the 42-inch Caylor Main was just good enough to help muffle the leaks, but not good enough to protect the cylinder from corrosion and eventual leakage.
In the end, despite difficulties of inspecting small leaks in a low-pressure environment, the inspection was deemed a success, and Southlake was extremely pleased with the accurate results.
Thanks to collaboration between crews from Southlake and Pure, the mystery leak was solved. The inline tethered Sahara tool came through again.