Pipe Extraction Assisted By Pre-Stressed Strand

1 . A method comprising:

disposing a wire strand through an existing pipe, the existing pipe having first and second ends and an underground section disposed between the first and second ends;

securing the wire strand to a pipe puller at the second end of the existing pipe;

gripping the wire strand with a first wire clamp at the first end of the existing pipe;

while the first wire clamp is gripping the wire strand, moving the first wire clamp away from the first end of the existing pipe;

after the step of moving the first wire clamp away from the first end of the existing pipe, securing the wire strand with a second wire clamp;

thereafter, releasing the grip of the first wire clamp and moving the first wire clamp toward the first end of the existing pipe;

thereafter, gripping the wire strand with the first wire clamp; and

thereafter, moving the carriage away from the first end of the existing pipe with the wire strand gripped by the first wire clamp.

2 . The method of claim 1 , further comprising:

subsequently, while continuing to grip the wire strand with the first wire clamp gripping the existing pipe with a pipe clamp; and

pulling the pipe with the pipe clamp and the first wire clamp.

3 . The method of claim 2 wherein the first wire clamp and pipe clamp are supported on a carriage, and wherein:

the step of pulling the pipe comprises extending a cylinder to translate the carriage.

4 . The method of claim 2 wherein the first wire clamp comprises three jaws having a central passage disposed between the three jaws, and wherein:

the step of gripping the wire strand with the first wire clamp comprises reducing a space between the jaws.

5 . A method comprising:

disposing a wire through an existing pipe, the existing pipe having first and second ends and an underground section disposed between the first and second ends, wherein a first direction is defined as being from the second end toward the first end;

anchoring the wire to the existing pipe at the second end;

thereafter, pulling the wire in the first direction from the first end without moving the pipe, thereby stretching the wire; and

thereafter, while maintaining the wire in tension, pulling the existing pipe and the wire in the first direction from the first end.

6 . The method of claim 5 in which the step of pulling the wire from the first end comprises:

with a first wire clamp, pulling the wire in the first direction;

thereafter, with a second wire clamp, gripping the wire and holding it in place; and

thereafter, releasing the wire with the first wire clamp.

7 . The method of claim 6 further comprising:

after releasing the wire with the first clamp, moving the first wire clamp in a direction opposite the first direction; and

thereafter, pulling the wire in the first direction prior to the step of pulling the pipe and the wire in the first direction from the first end.

8 . The method of claim 5 in which the step of pulling the existing pipe and the wire in the first direction from the first end comprises:

gripping the wire with a first wire clamp;

gripping the pipe with a pipe vise; and

thereafter, while the wire and the pipe are gripped, extending an actuator to move the first wire clamp and the pipe vise in the first direction.

9 . The method of claim 8 , wherein the pipe vise and first wire clamp are supported on a carriage.

10 . The method of claim 8 in which the step of pulling the wire in the first direction from the first end without pulling the pipe comprises:

with a first wire clamp, pulling the wire in the first direction;

with a second wire clamp, gripping the wire and holding it in place; and

thereafter, releasing the wire with the first wire clamp.

11 . The method of claim 10 in which the pipe vise and first wire clamp are supported on a carriage, and the carriage is supported on a stationary support structure.

12 . The method of claim 11 in which at least a portion of the support structure is interposed between the carriage and the second wire clamp.

13 . The method of claim 5 further comprising:

securing a replacement pipe to the second end of the existing pipe; and

thereafter, extracting the existing pipe and thereby installing the replacement pipe along substantially the same path previously defined by the existing pipe prior to its extraction.

14 . A method of tensioning a wire prior to extraction of a pipe, comprising:

placing a wire within a pipe, the pipe having a first end and a second end;

at the second end, securing the wire to the pipe;

at the first end, pulling the wire without moving the pipe until the wire is at a desired tension, wherein the desired tension is less than the force required to overcome an adhering bond between the pipe and an underground environment.

15 . The method of claim 14 in which the step of pulling the wire comprises:

gripping the wire with a first wire clamp;

while gripping the wire, pulling the first wire clamp without moving the pipe;

thereafter, gripping the wire with a second wire clamp; and

thereafter, releasing the wire with the first wire clamp.

16 . The method of claim 15 further comprising:

thereafter, moving the first wire clamp toward the first end of the pipe;

thereafter, gripping the wire with the first wire clamp; and

thereafter, pulling the first wire clamp without moving the pipe.

17 . The method of claim 15 wherein the step of gripping the wire comprises:

moving a plurality of jaws toward the wire rope such that a space between the plurality of jaws is smaller than the diameter of the wire rope.

18 . The method of claim 15 further comprising:

providing a pipe pulling apparatus, the pipe pulling apparatus comprising:

a stationary frame;

a carriage movable relative to the stationary frame;

a first wire clamp supported on the carriage; and

a second wire clamp configured for support on the stationary frame;

wherein the step of pulling the wire is performed by the pipe pulling apparatus.

19 . The method of claim 18 , further comprising:

gripping the wire with the first wire clamp;

with the carriage, pulling the first wire clamp away from the pipe;

supporting the second wire clamp on the stationary frame such that the second wire clamp is not permitted to move toward the pipe;

gripping the wire with the second wire clamp; and

thereafter, releasing the wire with the first wire clamp.

20 . The method of claim 19 in which the second wire is permitted to move away from the pipe when supported on the stationary frame.