Seeing the Heat

Infrared sewer inspection technology now includes display of temperature in full color, opening up new applications for investigating issues

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Long established as pipe inspection tools, sewer cameras continue to be refined. In 2001, Aries Industries introduced the ThermaView camera, the first to use infrared heat-sensing technology in addition to visible light to examine pipelines.

 

In other industries, heat-sensing infrared cameras have been used where visible light was obscured. One example includes firefighters working in heavily smoke-filled burning buildings. George Rada, Aries senior product manager, says the technology was initially adapted for sewer cameras mainly to serve the growing cured-in-place pipe (CIPP) lining market.

 

During CIPP lining, the pipe liner covers lateral openings, which then must be located and reinstated. Because there’s usually a temperature difference between the pipe being lined and the air or water in the lateral behind the liner, infrared cameras can detect the lateral where visible-light cameras might not.

 

The original ThermaView camera enables operators to switch back and forth between a visible-light mode and an infrared imaging mode, which displays in black-and-white. The latest version, ThermaView II, includes both imaging modes, but the infrared camera can produce color as well as black-and-white images in either of the two modes. It is also smaller and lighter.

 

Besides helping to locate laterals on lining projects, the newer technology can offer clues to the sources of leaks into a line based on the temperature of the incoming water. Ambient groundwater temperature in a storm sewer is usually about 45 degrees F, so a variation from that temperature might indicate an unusual situation.

 

In one instance, a ThermaView II prototype camera was used in a storm sewer where there was a strong inflow from an undetermined source. The infrared camera showed that the inflowing water was hot. A nearby pizzeria was determined to be the likely culprit, and investigation established that its sewer discharge was improperly connected to the storm line.

 

On May 13, 2010, Rada demonstrated the ThermaView II technology for the Engineering Division in the City of Madison, Wis. Wally Dyer, a street and sewer maintenance worker, operated the unit, assisted by laborer Ben Hodas. David Bogie, owner of Envirotech Equipment Co. in Pewaukee, Wis., an Aries distributor, also took part.

 

Walk-around

The ThermaView II camera looks similar to other Aries sewer cameras. About 14 inches long, it has a cylindrical rear body and a rectangular camera head. Two arms at the front hold a cube-shaped pan-and-tilt camera and light head.

 

The chief difference with other cameras is in the camera head. Whereas visible-light cameras have a lens on one end only, the ThermaView has lenses on opposite ends, one for visible light and the other for infrared. Using a remote-control panel, the operator can switch from one mode to the other.

 

A pan function allows the operator to continuously pan 360 degrees left to right. The head also rotates clockwise or counterclockwise in either viewing mode. Because of the extra space needed in the camera head for the infrared optics, there is no room for zoom components for the visible-light camera. The infrared lens has electronic optical zoom to 2x and 4x.

 

The visible-light lens is surrounded by 12 warm-white LEDs. The infrared camera needs no lighting. The camera is fully compatible with existing Aries tractors, camera controllers, and monitoring and control equipment. In the visible-light mode, it displays a distance readout. In the infrared mode, the monitor display includes three additional features:

• A blue dot in the center pinpoints the temperature target and is used to aim the device.

• At the bottom left corner of the screen, a digital readout displays the temperature of the blue dot’s target — the reading is accurate to plus-or-minus one-half a degree.

• On the left edge of the screen, a bar icon displays the temperature on a vertical scale from 0 to 300 degrees F. Readings can be switched to Celsius or turned off.

 

In the black-and-white infrared mode, the camera can be set to show the highest temperature as dark and the lowest white, or the reverse. In color, “the lighter the color, the hotter it is,” Rada says. The camera can be set to show temperature variations in regular color or in more intense color. Color differences show relative — not absolute — temperatures. For example, a stream of water at 40 degrees F might be one color if it is the warmest water in view and another color if it is the coolest.

 

The system is designed to be controlled by the standard Aries camera controller. Certain control switches are repurposed. The Starlight button on the control panel is used to change the camera from the visible-light to the infrared mode and back again. The zoom-in control in the infrared mode is used instead to choose which color mode to display. To activate the digital zoom feature in infrared mode, the operator uses the zoom-out control.

 

Operation

Dyer mounted the camera to an Aries TR3200 Steerable Badger crawler unit owned by the city, then drove the city’s camera truck to Advance Road, in a light industrial neighborhood on Madison’s southeast side. There, Hodas opened a manhole and lowered the camera unit attached to the crawler into the sewer.

 

Dyer explained that a leak on this line had stumped maintenance crews for some time. He hoped the ThermaView II camera might offer fresh insights. Using the control panel, Dyer sent the camera in the visible-light mode down the sewer, stopping occasionally to survey lateral junctions with the pan-and-tilt feature. At 386 feet in, he stopped. A few feet ahead, water from a leaking joint poured into the line in two streams at the 8 o’clock and 4 o’clock positions.

 

Previous water samples were positive for chlorine, suggesting a municipal source rather than groundwater or stormwater, but the water department had not been able to pinpoint its origin. After watching the leak in the visible-light mode, Dyer used the camera controller to switch the camera to the infrared lens.

 

Now the water streaming in displayed as green while the rest of the line was reddish-orange. Dyer aimed the blue dot in the center of the infrared image straight at the leak. The temperature indicator read 35 degrees F — probably too cold for groundwater or stormwater, which more likely would be between 45 and 50 degrees.

 

Dyer tilted the camera head down, targeting the blue dot on the sewer flow. The temperature indicator rose, fluctuating between 42 and 45 degrees. Continued inspection of first the sewer water and then the leak stream showed fluctuating temperatures. The sewer line temperature had dropped slightly, to between 39 and 41 degrees. The leak temperature went as low as 23 to 25 degrees (the sub-freezing temperature of liquid water was made possible by the rapid flow), then warmed up again to the low 30s and then 35.

 

Rada pointed out that water flowing in from any source can change temperature based on its specific source. For instance, flow from a residential lateral after a toilet flush is likely to be room temperature or possibly a little cooler. Flow from a shower is likely to be much higher.

 

Dyer noted there was an ice-making plant in the neighborhood with a lateral 60 feet further downstream from the leak. He sent the camera down to the lateral, at 449 feet, and got a reading of 39 degrees for its discharge.

 

Meanwhile, the main sewer flow’s temperature had fallen to 32 degrees, probably from the blending of the cold water from the leak upstream, Rada said. “A lot of water coming through can have a significant effect on the temperature of the flow,” he said.

 

As observation continued, discharge from the ice plant lateral warmed to about 40 degrees, and its color on the monitor shifted to red. It dropped again to 32 degrees and turned blue. Rada suggested that different phases of a process might be responsible for the fluctuating temperature there.

 

Dyer briefly switched to the two black-and-white infrared modes, then back to color. For a further comparison, he switched the camera to visible-light mode and reversed the crawler to return up-stream to the leak. Switching back to infrared mode revealed that the leak water was now warmer, coming in at 44 degrees. Then it warmed further to as high as 48 degrees.

 

Dyer concluded the inspection by slowly bringing the crawler back to the zero point, running the infrared mode and observing the temperature along the line, which mostly stayed at 44 to 46 degrees.

The investigation offered a clue as to the leak source that would not have been otherwise available. Rada reported that a follow-up visit to the ice plant later on the day of inspection revealed an extensive, boggy area around the plant. City crews concluded that a lateral there might not have been properly attached to the sanitary sewer and earmarked the area for follow-up inquiry.

 

Observer comments

Dyer was impressed by the ThermaView II and its visuals and readouts, which he found easy to read and understand. The machine overall carried very much the look and feel of the Aries product line: “That’s the nice thing about it,” he said. “It’s so compatible with everything else. It’s just like running another piece of their equipment.”

 

The images that the visible-light camera sent back were clear, sharp and well lit. The infrared images offered dramatic contrasts in color to show differences in water temperature.

 

At one point, when water washed directly over the infrared camera lens, the temperature reading dropped to near zero. In that instance, Rada explained, the water likely confounded the infrared reading. Once clear of the water, the reading’s accuracy was restored.

 

The ThermaView II appears to offer a useful new technology in underground visual inspection. A well-designed training program and materials might help operators make the most of the camera’s features and learn how to interpret its images appropriately.

 

Manufacturer comments

The recording of liquid water at temperatures down to 23 degrees F may seem anomalous, but Rada noted that it is common for flowing water to exist at sub-freezing temperatures.

 

Additionally, he said, in the case of the Madison leak, the water may have contained salt from a softener or from a cleaning process. He has suggested that the city investigate that possibility, as well.

Rada noted that the compatibility of the ThermaView II with existing Aries systems and Aries TR3000 and 3200 series tractors should make it easy for operators to learn to use it. “All you need to do is change the camera,” he said. He noted that Aries holds a patent on use of infrared technology in pipeline inspection and is the only manufacturer now offering it.



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