At a time when many urban infrastructures have deteriorated from age and use, we've become accustomed to seeing the familiar orange-and-white barricades and pylons signaling repair or replacement work on highways, bridges, and utilities in our cities. And when pipelines need to be replaced or expanded — especially in high-traffic urban areas — the commonly used open-cut installation method can result in a disruption and rerouting of traffic, often disturbing the flow of customers to businesses within an area. Digging up entrances, parking lots, and rearranging the landscape is not well received by business owners or residents in these areas, even when the environment is restored properly. Some innovative "trenchless" pipe installation technologies are now offering a better alternative to the disruption that generally occurs with traditional open-cut installation. These trenchless methods include: microtunneling; pipe jacking; horizontal directional drilling (HDD); slip lining; and pipe bursting. Of these methods, slip lining and pipe bursting are most often used for in situ pipe replacement work, and the pipe bursting method is the most common. Within the past few years, AMERICAN has introduced two new products — MT (Micro-Tunneling) Push Pipe and GS (Gravity Sewer) Push Pipe — that offer excellent results when used in trenchless installation, particularly with the pipe bursting method. First, I'd like to review the three different pipe bursting methods used in trenchless installation. Next, I'll tell you about the high performance attributes of AMERICAN's Push Pipe to give you an idea of the advantages it provides when used in these methods. The pipe bursting method of trenchless installation uses the old pipeline as a guide and pilot hole of sorts for installation of the new pipeline. The three different methods of pipe bursting are generically described as: (1) "push-me," (2) "pull-me," (3) and a combination "push-pull" system. All three systems involve the use of a conical-shaped bursting head sized slightly larger than the new pipe. This bursting head is then used to create a pathway for the new pipe by breaking or bursting the existing deteriorated pipe; fragments of the old pipe are then dispersed radially into the surrounding soil. Each of these methods offers installation advantages, and they may be the only methods available when buildings or surface structures prevent open-cut installation. In the "push-me" system, a joint of the new pipe is placed immediately behind the bursting head; then, the bursting head is advanced through the existing pipe by the application of direct jacking pressure to the back of the pipe joint. Once the pipe is advanced into the deteriorated pipe the equivalent of one joint length, a new joint is placed in sequence and then is advanced by the jacking frame. This process is repeated until the existing line is completely replaced. The "pull-me" bursting system utilizes either a pneumatic or hydraulic bursting head that breaks up the existing deteriorated pipe with the impact of a reciprocating hammer located within the head itself. A chain or cable is attached to the bursting head, which is then attached directly to the new pipeline material. The "pull-me" system requires that pipeline materials be fused together or that they utilize restrained joints. The "push-pull" bursting system is unique in that it uses a rigid pulling rod extending from a secured machine pit running through the existing deteriorated pipe directly to a bursting head assembled within the insertion pit. A smaller "tow" rod, made up of four-foot sections, is attached to the backside of the bursting head and extends through each section of new pipe. An adapter plate, used to attach the "tow" rod to the trailing end of the new pipe, transmits the pulling force from the bursting head to the face of the trailing pipe end. For all practical purposes, the replacement pipe is under the same load as if it were being pushed into place; thus the name "push-pull" is given to the process. Once the pipe is advanced one joint length, the adapter plate is removed and a new joint of pipe is added; the "tow" pipe is then extended by adding the appropriate length to it, and the adapter plate is again connected to the "tow" pipe at the trailing end of the new pipe section. This process is repeated until the existing deteriorated line is completely replaced. AMERICAN's MT Push Pipe and GS Push Pipe offer excellent performance characteristics when used in the type of pipe bursting installation systems I've described. Let me first review the unique design characteristics of both products and then review the results that have been achieved with their use. Specifically, AMERICAN's MT Push Pipe is available in diameters of 4 to 24 inches with a pressure rating up to 350 psi. The MT Push Pipe is a bell-less ductile iron pipe consisting of two counter-bored pipe ends joined with the use of an internal stainless steel coupling that has two O-ring seals per end. AMERICAN's GS Push Pipe is offered in diameters ranging from 4 to 16 inches with a pressure rating of 43 psi (100 feet of hydrostatic head). The GS Push Pipe is a bell-less joint that consists of one counter-bored end and a mating machined end that together form a tongue-in-groove joint sealed with two O-rings. The joint designs for both MT and GS Push Pipe are bell-less in that the joint is constructed within the existing thickness of the pipe wall, resulting in a pipe with constant outside diameter over its entire length. When used in straight alignment, these joints have column load carrying capabilities of several hundred thousand pounds. Both the MT Push Pipe and GS Push Pipe are available in lengths up to 20 feet, but can be used in sections as short as four feet for small pit sizes that are sometimes dictated by job-specific site conditions. AMERICAN's MT Push Pipe and GS Push Pipe have achieved excellent results in a variety of pipe bursting methods; both categories of pipe have been installed successfully using the Trenchless Replacement Services (TRS)/ "push-pull" method, the Tenbush Insertion Method (TIM)/ "push me" method, as well as with other "push me" methods. The use of MT and GS Push Pipe with these techniques has resulted in successful installations with distances of up to 500 feet between pits. Overall, the superior design and performance characteristics of AMERICAN's MT Push Pipe and GS Push Pipe make these products a natural choice for use in trenchless installation — a method likely to be used with even greater frequency in today's high-traffic urban areas.

Gene Oliver, Technical Director, American Cast Iron Pipe Company Workers install a section of GS Push Pipe within a secured jacking pit. This pipe will replace the existing line trenchlessly, that is, without the normal disruption associated with open-cut installation.