Laclede Gas Discovers Alternative Method For Cathodic Protection

Process Helps Speed Anode Installation Process
May 2009 Vol. 64 No. 5

“Greg showed us how a vacuum excavator equipped with a core saw could speed up our process,” says Dean Pieper, equipment general foreman for Laclede Gas. “Now we can install an anode in under two hours with minimal rehabilitation to the street. It has saved us precious time and money.”

The procedure is relatively simple and fast. The crew arrives on site and begins their set up process. An 8 inch round diamond tip core saw is placed at the desired spot where the anode will be installed near the main. The core saw is powered by hydraulic pump installed on a McLaughlin V500LTHD vacuum excavator. To stabilize the core saw, the vacuum suction hose is connected to the saw and the suction from the vacuum securely holds the saw down to the concrete. A water hose is attached to the core saw to help keep the blade cool during the core process.

“With the core process it only takes five to 10 minutes to complete the bore,” says Biggs. “The coupon typically measures eight inches in diameter and 8.5 inches thick. We even use the suction from the vacuum to extract the coupon out of the street.”

Once the coupon has been removed, the vacuum is used to extract the soil. The anode must be installed below the gas main, so the depth can range from four to 8 feet depending on the depth of the main.

“In the past we used air to break up and extract the soil,” says Biggs. “Now we use water and it’s much faster. The McLaughlin unit generates 3,000 psi of water pressure through the wand and turns the soil into slurry within minutes, resulting in a nice clean hole to install the anode.”

Finishing touches

The crew will lower the anode into the hole, remove the coating on the main and attach the wires using a Cadwell Welder. When the connection has been made, the coating is repaired and the hole is backfilled with crushed rock to within an inch of the bottom of the concrete pad. An epoxy is then placed on top of the crushed rock to within 2 inches of the top of the hole. The coupon is inserted back into the hole and the excess epoxy is removed.

“Sometimes we get into areas where the main or carrier pipe can be deep,” says Pieper. “In these cases, the crews use a special tool to weld the anode wires onto the pipe. It can be a difficult task when you’re only working with an eight inch diameter hole.”

Laclede’s North District currently has two crews working on this project and each can average six installations daily and has doubled their daily output.

Ron Adler explains that some installations are more difficult than others.