Note: Descriptions are shown in the official language in which they were submitted.
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1 FIELD OF THE INVENTION
2 The present invention relates to an apparatus and
3 process for removing a long section of buried old pipe and
4 replacing it with new pipe, without excavating the section
along its full length.
6 BACKGROUND OF THE INVENTION
-
7 It is known to remove and replace a section of
8 buried old pipe, such as a cast iron water main, using a
9 "trenchless~ procedure involving:
10 - Digging pits at each end of the pipe section,
11 to expose the pipe at those points;
12 - Breaking up and removing the exposed segments
13 of old pipe, to thereby clear the pits;
14 - Installing a skid-mounted, rod string-tripping
machine in the first pit, which machine is
16 adapted to feed and withdraw a string of rods
horizontally. The machine typically has one
18 or more double-acting cylinders mounted in a
19 frame for extension and contraction in a
horizontal plane, together with means for
21 releasably clamping onto the rod string, so
22 that the cylinder rods and rod string may move
23 longitudinally as a unit in the course of a
24 cylinder stroke;
25 _ Forming a string of rods (which have threaded
26 pin and box couplings at their ends) having a
27 radially expandable toothed dog assembly at
20~3~8
1 its end and feeding it part way through the
2 pipe section;
3 - Expanding the dog assembly to engage it with
4 the old pipe;
- Actuating the rod string-tripping machine to
6 advance the engaged portion of the old pipe
7 section into the first pit in short lengths.
8 Each such length of old pipe extending into
g the pit is then severed radially. The severed
lo length of old pipe is removed. This process,
11 of tripping the rod string with dog assembly
12 in and out, to engage and remove sequential,
13 discrete parts of the old pipe section, is
continued until the entire pipe section has
been removed;
16 - Threading the rod string back through the now
17 pipe-free passageway, from the first pit to
18 the second pit;
19 - Attaching an expander (that is, a cylindrical
plug) to the second end of the rod string and
21 pulling it back through the passageway, to
22 increase its diameter;
23 ~ Removing the expander at the first pit and
24 again threading the rod string back through
the expanded passageway to the second pit; and
26 - Pulling the section of new pipe into the
27 expanded passageway from the second pit using
28 the rod string, to complete the replacement.
2013~
l Such a system is disclosed in U.S. patent
2 4,626,134, issued to Coumont.
3 The described system has some shortcomings. It
4 involves repeated trips with the rod string through the old
pipe bore and the passageway formed by the pipe in the soil.
6 And it further involves fracturing the old pipe, that has
7 been advanced into the first pit, along a vertical plane
8 using a guillotine-type means, to yield a discrete short
g length of pipe, and then presumably manually breaking up and
removing this length. This latter operation interrupts the
ll continuity of the process and unites with the multiplicity of
l2 trips to stretch out the time needed to complete the
l3 replacement.
l4 It is the objective of the present invention to
provide an improved trenchless system whereby old pipe is
l6 replaced with new pipe in a single trip of the rod string.
SUMMARY OF THE INVENTION
l8 The present invention is a variation of the
l9 previously described conventional system in which:
- first and second pits are dug at each end of a
2l buried section of old pipe which is to be
22 replaced;
23 - a cylinder-type rod string-tripping machine is
24 emplaced in the first pit; and
- the machine is used to extend and withdraw a
26 string of rods horizontally, as required, to
27 accomplish the steps of pulling the old pipe
28 into the first pit for break-up and removal,
2~3~8
1 expanding the old passageway and pulling new
2 pipe into the expanded passageway from the
3 second pit.
4 For purposes of definition, the word ~trip~ is
intended to encompass either of forming and extending or
6 withdrawing and disassembling a string of rods. The phrase
7 ~round trip" covers the sum of forming, extending,
8 withdrawing and disassembling a string of rods.
9 In one aspect, the invention is directed toward a
pipe replacement process that involves using only a single
11 round trip of the rod string and preferably incorporates
12 simultaneously splitting the old pipe longitudinally, using
13 mechanical means, in the course of advancing the old pipe
14 into the pit. In another aspect, the invention comprises the
assembly of components used to carry out the process
16 described.
17 More particularly, in the equipment aspect there is
18 provided a novel combination of components, assembled and
19 ready for use to simultaneously expel the old pipe, split it
longitudinally, expand the passageway and emplace new pipe in
21 the expanded passageway. The assembly of components
22 preferably includes:
23 - A string-tripping machine positioned in the
24 first pit, with at least part of the exposed
old pipe having been broken out beforehand so
26 that the machine has access to the bore of the
27 buried section of pipe, so as to extend its
28 rod string thereinto;
;~()136~
1 - A string of rods extending from the string-
2 tripping machine through the bore of the old
3 pipe to a second pit whera at least part of
4 the old pipe exposed at that pit has also been
broken out;
6 - Means for mechanically breaking up the old
7 pipe as the latter is expelled. Said means
8 are located in the pit into which the old pipe
g is being advanced. Nore preferably, the means
comprises a stationary, hollow, conical member
11 having its small end positioned adjacent the
12 outlet from the old pipe passageway, so that
13 old pipe being advanced will move over the
14 small end of the conical member and the pipe
will be split longitudinally and broken up as
16 it continues to pass along the length of the
17 conical member, said conical member forming a
18 central passage therethrough for accommodating
19 the rod string;
~ A tool assembly attached to the second end of
21 the rod string at the second pit. The tool
22 assembly comprises a unit of sequentially
23 connected components. More particularly, it
24 comprises: means for centralizing the axis of
the terminal end of the rod string in the bore
26 of the old pipe; means for bearing against
27 the annular second end face of the old pipe,
28 so as to drive the old pipe ahead of it when
29 pulled on; means for expanding the passageway
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1 which originally contained the old pipe; and
2 means for engaging the new pipe to pull it
3 into the expanded passageway behind the old
4 pipe as the latter is expelled. More
preferably, the centralizing means comprises a
6 guide member adapted to fit snugly in the old
7 pipe and the second means comprises a circular
8 pull plate attached thereto. The guide member
g functions to centralize the pull plate so that
it will bear evenly against the full extent of
11 the annular second end face of the old pipe.
12 Attached to the pull plate is the third means,
for expanding the passageway as it passes
14 therethrough. More preferably, the third
means comprises a short cylinder or plug
16 having an outside diameter that is slightly
17 larger than that of the passageway through
18 which the old pipe extends. The fourth means,
19 for engaging the new pipe, may preferably
comprise means for attaching to the front end
21 of the new pipe or a rod and pull plate
22 assembly that extends through the bore of the
23 new pipe and bears against the annular surface
24 of its rear end; and
- as a final integer, the string of new pipe to
26 be emplaced in the expanded passageway.
2~13~8
1 In the process aspect, the invention comprises:
2 - excavating first and second pits at the first
3 and second ends of the section of old pipe to
4 be removed and replaced, to thereby expose the
pipe at those points;
6 - breaking up the two segments of exposed pipe,
7 to clear the pits;
8 - inserting, in the first pit, first means for
g horizontally tripping a rod string;
- inserting, in the first pit, means for
11 longitudinally splitting old pipe being
12 advanced thereover, said second means being
adapted to enable a rod string to extend
therethrough;
- tripping a string of rods through the bore of
16 the old pipe section;
17 - attaching, to the second end of the rod
18 string, a tool assembly comprising, in
19 sequence, second means for bearing against the
annular second end face of the old pipe
21 section, third means, secured to the second
22 means, for expanding the diameter of the
23 passageway as said third means passes
therethrough, and fourth means, secured to the
third means, for engaging new pipe to pull it
26 into the expanded passageway, said fourth
27 means having a section of new pipe associated
28 therewith; and
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1 - pulling on the first end of the rod string
2 with the first means and progressively
3 disassembling the rods as they become
4 available in the first pit, thereby advancing
the old pipe into the first pit and over the
6 splitter means, whereby the pipe is split
7 longitudinally, while simultaneously pulling
8 the tool assembly through the old passageway
9 to expand it and bring the new pipe into the
expanded passageway until the section of old
11 pipe has been replaced with new pipe.
12 DESCRIPTION OF THE DRAWINGS
13 Figure 1 is a partly sectional, simplified side
14 view of the rod-tripping machine positioned in the first pit;
Figure 2 is a partly broken away side view showing
16 the tool assembly simultaneously expelling old pipe,
17 expanding the passageway, and pulling in new pipe to replace
18 the old pipe;
19 Figure 3 is a sectional side view at an
20 intermediate third pit with the splitter functioning to
21 longitudinally split old pipe being advanced into the pit;
22 Figures 4a - 4g are side views showing the steps
23 involved in replacing pipe in accordance with a three pit
24 version of the present invention; and
Figure 5 is a sectional side view showing the
26 expander, its connection with the second rod string, and the
27 second rod string extending through the new pipe section to
28 the second pull plate.
2~3136~
1DESCRIPTION OF THE PREFERRED EMBODIMENT
2A specific embodiment of the invention will now be
3 described in conjunction with using first and second end pits
4 1,2 and a third intermediate pit 3 for the replacement
process. Typically the pipe being replaced has a diameter of
64 to 12 inches and the pits are spaced apart about 40 to 500
7 feet.
8The pits are dug to expose the end segments 4 of an
9old pipe section 5 that is to be replaced.
10The exposed pipe segments 4 are broken up,
11typically with sledgehammers or the like, and the pieces are
12removed to clear the pits.
13A rod-tripping machine 6 is inserted into the first
14pit 1. The machine 6 comprises a frame 7 having a pair of
15parallel, spaced apart I-beams 8. A pair of parallel,
16horizontally extending, hydraulically actuated, double-acting
17cylinders 9 are mounted in the I-beams 8. A block 10 extends
18transversely between the I-beams 8 and is attached to the
19outer ends of the cylinder rods 11. The I-beams 8 function
20to guide the block 10 in the course of reciprocating, sliding
21travel. The block 10 carries a pivotally mounted clamp
22member 12. The clamp member 12 is operative to releasably
23lock the last rod 13 of the rod string 14 to the block 10.
24 The frame 7 of the machine abuts vertically extending piles
15, so that it cannot shift forwardly when pulling on the rod
26 string 14.
27The rod string 14 is formed of short steel rods 13
28 having threaded pin and box ends.
"21D~ 3~
1 In the course of tripping the rod string 14 into
2 the bore 16 of the old pipe section 5 or into the passageway
3 17, a rod 13 is manually screwed into the first end of the
4 string 14. The clamp member 12 is tightened to secure the
end rod 13 to the block lO. The cylinders 9 may then be
6 extended to advance the rod string 14 one stroke length into
7 the bore 16 or passageway 17, as the case may be. Similarly,
8 in tripping the rod string 14 out of the bore 16 or
9 passageway 17, the clamp member 12 is clamped onto the last
10 rod 13 of the string 14 with the cylinders 9 in the extended
11position. The cylinders 9 are then contracted to pull on the
12rod string 14 and withdraw it through a travel of one stroke
13length. The last rod 13 may then be unscrewed manually and
14removed. In this conventional fashion, the rod string 14 can
15be made up rod by rod and tripped in or it can be
16disassembled rod by rod and tripped out. In conjunction with
17tripping, the power of the cylinders 9 is available to apply
18a powerful pushing or pulling force to the rod string 14, as
19required.
20A splitter 18 is positioned in the intermediate pit
21 3. The splitter 18 is mounted on vertical piles l9 and is
22 aligned axially with the passageway 17. As shown, the
23 splitter 18 is conical in form and has its small end directed
24toward the outlet 20 of that portion 21 of the passageway 17
25which extends between the third and second pits 3,2. The
26splitter 18 forms a central axial opening 22 for the passage
27therethrough of the rod string 14.
28In operation, as the old pipe 5a is advanced out of
29 the passageway portion 2l into the pit 3, it passes over the
~2~ 3~8
splitter 18, as shown in Figure 3, and is split
2 longitudinally and broken up.
3 Having reference to Figure 2, a tool assembly 23 is
4 provided for attachment to the second end o~ the rod string
14, once the string has extended into the second end pit 2.
6 More particularly, the tool assembly 23 comprises a
7 centralizer 24, adapted to screw onto the end of the rod
8 string 14. The centralizer 24 has a tapered section 25 at
9 its forward end and a cylindrical section 26 at its rear end.
The cylindrical section 26 is dimensioned to closely fit the
11 inside surface 27 of the old pipe 5a.
12 A vertically extending, circular pull plate 28 is
13 threaded onto the rear end of the centralizer 24. The pull
14 plate 28 is equal in diameter to the outside diameter of the
old pipe 5. When centered, the pull plate 28 is adapted to
16 bear evenly against the annular second end face 29 of the old
17 pipe section 5. By obtaining even distribution of pulling
18 pressure around the full extent of the end face 29, the
19 likelihood is minimized that the pipe 5a will buckle when
pulled toward the first pit 1.
21 An expander 29 is threaded onto the rear end of the
22 pull plate 28. The expander 29 has a forwardly positioned,
23 conical section 30 and a rearwardly positioned, cylindrical
24 section 31. The cylindrical section 31 has an outer diameter
slightly greater than the diameter of the original passageway
26 17. The rear end of the cylindrical section 31 is open.
27 A second rod member or string 32, having threaded
28 ends, is screwed into a coupling 33 attached to the inner end
29 34 of the expander 29. The coupling 33 is co-axial with the
-" 20i36~
1 expander 29, so that the second rod string 32 is aligned with
2 the centralized rod string 14. The rod string 32 extends
3 through the section 35 of new pipe. A second circular pull
4 plate 36 is threaded onto the rear end of the second rod
string 32 and bears against the annular end face 37 of the
6 new pipe section 34. The second pull plate 36 is threaded
7 along the second rod string 32 a sufficient distance so as to
8 bring the front opening 38 of the new pipe section 35 into
9 the open-ended cavity 39 formed by the expander cylindrical
section 31. The opening 38 is therefore protected from the
11 entry of soil.
12 Having reference now to Figures 4a - 4g inclusive,
13 the pits 1, 2, 3 are excavated to expose the pipe segments 4.
14 The pipe segments 4 are broken up and removed. The rod-
tripping machine 6 is then inserted into the first end pit 1
16 and the splitter 18 is positioned in the intermediate pit 3.
7 The rod string 14 is tripped by the machine 6 through the
18 bore 16 of the old pipe section 5 until its second end enters
19 the second end pit 2. Part of the tool assembly 23,
comprising the sequentially connected centralized first pull
21 plate 28, expander 29, and second rod string 32 are then
22 attached to the rod string 14. The new pipe section 35 is
23 threaded onto the second rod string 32. The second pull
24 plate is threaded up behind the end face 37 of the new pipe
section 35, to advance the pipe opening 38 into the shielding
26 enclosure of the expander 29. At this stage, the rod string
27 14 is ready to be tripped from the second end pit 2 to the
28 intermediate pit 3. As the rod string 14 is progressively
29 withdrawn and disassembled at the first pit 1, the old pipe
20i36~8
1 5a in passageway portion 21 is advanced into pit 3 and broken
2 up on splitter 18 while simultaneously the passageway portion
3 21 is expanded by expander 29 passing therethrough and new
4 pipe 35a is pulled into the expanded passageway 21. Once new
pipe 35a has been emplaced in passageway portion 21, the
6 splitter 18 is moved to the first pit and the procedure
7 repeated to remove the balance of the old pipe and replace it
8 with new pipe in one trip.
9 Various alternatives to the system described will
readily suggest themselves. For example, instead of using a
11 conical splitter to break up the advancing old pipe, one
12 could use a hydraulically actuated assembly acting from the
13 side to crush the old pipe. Instead of using a rod and pull
14 plate assembly to engage the new pipe, one can fuse a plastic
nose to the forward end of the new pipe and attach it to the
16 rod string 14 with means such as a clevis assembly.
The scope of the invention is defined by the claims
18 now following.
.
14
