This project had everything, difficult soil, a large diameter casing and an extremely long bore length. This was easily one of the longest pipe rams of this diameter ever accomplished.
Permalok steel casings were chosen for the Medford project. Often during a ramming or a jack and bore project, welding casing segments can take many hours of production time. Permalok casings employ a mechanical press fit design that provides a strong, quick connection between casings as an alternative to welding. Don Gonzales, President of Northwest Boring said “The physical impact from pipe ramming, especially large diameter ramming, on a casing is immense. I have never had a Permalok joint fail. We chose Permalok for two reasons. One was the production time saved from not having to weld. And two was the success rate. If we’re going to put the world’s biggest and most powerful pipe rammer, the Taurus, on pipe, I want Permalok.”
In order to connect the 24-inch diameter Taurus ramming tool with the 80-inch Permalok casing, a series of tapered cones were used. The configuration for the Medford ram included two tapered ram cones.
A special push ring was used with the Permalok casing so that the actual ramming force was transferred to the casing itself rather than the pipe’s connection joints. The first 80-inch ram cone reduced the overall diameter from 80 inches to approximately 36 inches. The next cone further reduced the overall diameter to the point where the tool is connected, friction fit, to the cone thereby completing the assembly.
After the final tool assembly, ramming began at a furious pace with the first 20-foot section taking approximately 30 minutes to ram in place. Ramming times ranged between 30 to 40 minutes up to 140 feet.