The Operations and Maintenance Department of Rogue Valley Sewer Services, a sanitary authority in Central Point, Ore., used to summon the vacuum truck crew to flush obstructions — at substantial expense — when an inspection team located them.

 

Plastic mechanical test plugs caused the major problem, either dangling or falling into the line as their wing nuts eroded. Lengths of broken PVC pipe, rocks, rags, and other debris also brought immediate action. The authority’s goal is to inspect all 400 miles of the sewer system every five years and clean it every three years.

 

“It was frustrating to stare at a blockage right in front of the camera and be unable to reach out and grab it,” says inspection crew leader Larry Rogers. Operations manager Terry Sackett agreed. They envisioned a grasping device but had no idea how to make it.

 

Then inspection technician Kevan Kerby joined the team. Based on his co-workers’ idea and a lifetime of building moving objects with Lego blocks, he fab-ricated a tool mostly from scrap materials that retrieves items smaller than 8 inches and weighing less than 15 pounds. Since the Pipeline Piranha went on the prowl, the flusher crew is free to focus on its pipe-cleaning schedule.

 

Building blocks

Sackett set a $3,000 limit, including man-hours, on the project and gave Kerby a week to make a working prototype. “I spent many hours doodling as different mechanical ideas went through my mind,” Kerby says. “The hardest part was keeping the design small enough to fit in an 8-inch pipe. We also wanted to build cheap in case it didn’t work, so I looked for suitable materials in the shop.”

 

Kerby cut the base and jaws from 1/8-inch plate steel and used door hinges to make the jaws open and close. He made the jaws’ operating linkage from rods welded together and some nuts and bolts. He bought two automotive choke cables to transfer power from the low-end electric actuators in the base to the jaws. The actuators and 400 feet of electrical cable were the only other purchased items. The materials cost $1,500.

 

“I scrapped the first attempt because the linkage was too short,” says Kerby. “As I assembled the rods, I could see that the proportion of power to travel of the jaws was incorrect.” He jury-rigged the wires of the second prototype to some batteries to test the device. It worked, and Kerby met the budget.

 

The 9.5-inch-long jaws open to 8 inches, close completely, exert 15 psi, and have carbide chips glued on the ends to increase their grip. Four screws mount the jaws to an OmniEYE III pan-tilt-zoom camera from RS Technical Services Inc. Another four screws mount the base to the TransSTAR tractor transporter, also from RS Technical Services.

“We plug the electrical cable into a socket in the inspection truck, then plug the other end into the cable reel,” says Kerby. “It takes 10 minutes to set up the unit because it’s basically plug and play.” The electrical cable with reel weighs 80 pounds and feeds parallel to the transporter’s single-conductor cable. The tractor can pull the combined weight 400 feet, the distance between most sewer access points.

 

Looking ahead

The Catch 22 in the project was the length of the jaws. The longer they are, the more leverage it takes to give them strength. “Our problem is that when the jaws are open, the camera shows us only their last two inches,” says Rogers. “If they were any shorter, we couldn’t see what we were doing. Because we used low-end actuators, they don’t have much power, but it is enough to retrieve 5- to 10-pound mechanical plugs.”

 

Inspection technician Quintyn Zilembo named and custom-painted the invention. Since the team deployed the Pipeline Piranha in March 2009, it has retrieved 10 fallen mechanical plugs and two dangling ones. “Occasionally, we lose a wheel off the transporter,” says Rogers. “Now, instead of calling out the flusher crew or ordering a replacement, we’ll bring it back with the Piranha. That also saves us a lot of money.”

 

Zilembo is designing a new set of jaws he calls the Hammerhead. The lower jaw is contoured to the invert of the pipe to scoop up rocks and similar larger items more easily. The team also has ideas on how to streamline the Piranha’s design and increase the strength of the jaws. The tool is patented.