Discussion of Prior Art

Trenchless technology for the replacement of underground pipe is not new, and the standard equipment and methods generally used are well known. This standard equipment for this technology is very large, heavy, and therefore requires additional large, heavy duty equipment for the transportation to, and the placement thereof on site, and the operation thereof on site.

There are several methods of propelling a pipe bursting, and/or cracking and expanding device, and pulling a new pipe through an existing pipe The most commonly used methods are large cable winches, and/or rod pushers or pullers that are usually hydraulically powered, and often used with a pneumatic percussive device helping to drive the pipe breaking device. Winches give continuous motion during pulling, while rod pushers/pullers generally give cycled motion in which they pull, then a rod must be either added or removed, before the return stroke, and next pull stroke. Sometimes rod pushers are converted to cable pullers, eliminating the need for rod removal.

Winches and rod pushers/pullers that can produce pulling forces of up to 75 tons can themselves weigh 2 to 5 tons and must be handled and placed in position to pull; they are powered by correspondingly heavy duty equipment, cranes, trucks, and back-hoes, etc. They also need large excavations, such that the support equipment can take up enough room so as to create traffic problems and even require street closures.

This also means that only large companies with large financial resources can afford the equipment necessary to replace underground pipes, and because the costs and maintenance on this equipment can be high, their prices are also high. Therefore the use of this prior art trenchless technology has been limited mainly to the 4 inch or above size pipe of municipal or corporate supply and sewer lines, and is used mainly by large contractors.

Most people are unfamiliar with the term 'Trenchless Pipe Replacement'. Some other names commonly used are "No-Dig", "trenchless pipe rehabilitation", "pipe breaking", "Trenchless Technology" and "trenchless pipeline replacement". No matter which name it is going by it simply means splitting an old, worn out pipe while inserting a new one ...all at the same time!

Trenchless technology includes a large family of methods utilized for installing and rehabilitating underground utility systems with minimal surface disruption. Basically it refers to a method of replacing underground pipe-work without digging long, ugly trenches that disrupt lawns, sidewalks, driveways and just about any other property feature that has the misfortune of existing above an underground line!

The trenchless method installs the new pipe by pulling it through the old pipe, even if the existing pipe is collapsed, behind a special breaking head (or cone) that expands a clear channel ahead of the new pipe as it travels underground. One small pit is all that is necessary for most jobs in order to feed the new pipe into the ground... a compact but powerful pulling machine is located at the destination point, often inside a building, to pull the pipe in from the pit.

The operation is simple, requiring relatively few steps.

The first step is to determine where the line must begin and then end. Once determined, two small pits are dug, each approximately 24" wide x 36" and as deep as required for the particular job. One pit (the entry pit) will be used to feed the line, and the other (the pulling pit) will contain the pulling unit ready to pull the pipe through the ground.

The pulling unit is then assembled in the pulling pit and butted against wooden shoring that surrounds the old pipe or newly bored pilot hole. Next the pulling cable is hand-pushed from the entry pit through to the pulling pit and threaded into the machine. In the entry pit, the cable is passed through the hollow bursting cone, through the pipe guide,
through the new pipe and attached to the pipe boot with a retaining pin. (See diagram)

Once assembled and ready to go, the Honda power pack is started up, charging the hydraulic cylinders, or on heavier jobs the backhoe is positioned and the chain attached. The pulling operation can now commence. The unit will pull the new pipe through the soil at a rate of approximately two feet per minute up to four feet per minute . (Note: Some soil conditions may cause this rate to vary). In the entry pit, as the new pipe is almost all the way in, the process will pause. The cable will be fed through the next length of pipe, the boot and pin attached, and the head of the new length will be fused to the tail of the preceding one. The pulling process can now resume and the cycle will be repeated until the job is finished. Once done, the pulling unit is disassembled, the cable is retrieved and the pulling process is complete. The diagram below illustrates the process the process overall.

*Please note that for the purposes of this brief description, "pipe" refers to the line being pulled no matter what type.