Note: Descriptions are shown in the official language in which they were submitted.
1 326600
"Method and apparatus :Eor pipe replacemen-t"
THIS INVENTION relates to a method and apparatus for
replacing an existing old pipe, such as a water service pipe,
gas pipe or the like with a new pipe and, in particwlar, to a
method and apparatus for replacing an old pipe ~ith a new one
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without digging up the ground.
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When an old buried pipe, in particular a cast iron pipe,
has deteriorated with age or when it is necessary to replace
the old pipe with a new one due to new requirements, it is
desirable to be able to replace the old pipe with a new one
without digging up the ground, because great labour and cost
is involved in excavating the old pipe and because such -
digging work unavoidably obstructs traffic or affects means
of transport and communication.
According to a known method of pipe replacement called
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"pipe-in-pipe", a new pipe is simply inserted into the old -
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one under the ground. However, this ineYitably means that
the internal diameter of the new pipe must be smaller than
~ 20 that of the old pipe, resulting in a reduction in the
; capacity for transporting gas or water.
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~ 326600
An attempt has already been made to overcome -the above
discussed drawback of the "pipe-in-pipe" method, aæ disclosed
in U.K. Patent GB2152624B "Pipe Replacement Sys~em", GB ~-
2124325B and GB 2092701B "Mains Insertion". ~:
The aforesaid prior art discloses a method and an
apparatus for pi.pe replacement in which a new pipe is
attached to the rear end of a bursting mole having a
cylindrical body with an external diameter which ix larger -
than that of the old pipe to be replaced. The bursting mole
1~ and the new pipe move forward together, and a front end or
head of the bursting mole intrudes into the old pipe and
progressively bursts the old pipe to form an enlarged space
to receive the new pipe, so that the old pipe is replaced
with the new one.
In the aforementioned convent1onal method, however, a
: large working space is required in a rear portion of the
starting pit. The pipe line is usually laid under a road,
; and it i~ an obstacle to traffic to secure such ~ large :~
working ~pace. Moreover, in the prior art it is necessary to
~ move~:a compressor following each forward movement of the
bursting mole. In order to continue the work without moving
the~compreasor;, it would be necessary to connect a longer air
hose;~extending at least 1.5 times the length from the
startlng plt to the destlnation p1tF whlch results~in a
2;5:~ ~ lowerlng of the air supply efficiency.
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1 326600
It is indeed possible to reduce the working space by
forming a pipe line by joining specific lengths of new pipe
together sequentially according to the forward
movement of the mole. However, in such an arrangeMent,
the air supply to the mole during the replacement work is
frequently interrupted as new pipe sections are added and
the air hoses are extended (detached and rejoined). This
is a lengthy process and considerably lowers the efficiency
of the process. Moreover, as the air hose inserted through
the new pipe has many couplings, the air supply efficiency
is also lowered and there is a possibility of damage to the ~:~
internal sur~ace of the new pipe and the cost of
replacing the pipe is high due to the use of many expensive
couplings.
The present invention aiims to overcome or~ at least,
mitigate the above di~cussed pro~lems and to provide a
method of replacing an old buried pipe with a new pipe in
which the required working space is reduced and the
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replacement is carried out without interruption.
Accordingly, in one aspect, the invention provides a -;.
method of replacing an old buried pipe with a new pipe
:~ comprising a: plurality of pipe sections, which method ::;
comprise3 attaching successive new pipe sections to a
: bursting mole having a oylindrical body whose external
25~: diameter is larger than the existing old pipe, and moving --
the bursting mole forward so that a head of the bur~ting
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1 326600
mole intrudes into the old pipe and bursts it -to provide an
enlarged space for the new pipe following the bursting
mole, which method further includes supplying power to a
driving means carried by the bursting ~ole through a power
line from a power source and temporarily detaching a
longitudinal portion of each successive pipe section in
order to introduce the power line into the pipe sections
without disconnecting the line from the bursting mole.
In another aspect, the invention provides an apparatus
for replacing an old buried pip~ with ~ new pipe compri~ing
a plurality of pipe section~, which apparatus comprises a
bur~ting mole having a cylindrical body with an external
diameter which is larger than the existing old pipe, means
for attaching ~ucce~sive pipe sections to the bursting ~ :
mole, a power ~ource for ~upplying power through a power
line to a driving means carried by the bur~ting mole to
mo~e the bursting mole forward ~o that a head of the mole
intrude~ into the old pipe and .burst~ it, and means for
attaching succe~æive pipe section~ behind the bur~ting mole
wherein each pipe ~ection is adapted to be coupled to a
preceding pipe section aæ the mole advances and is pro~ided
with a detaFhable section defining a longitudinal
~- detachable portion extending the length of the pipe section ~-
: which can be temporarily detached from the pipe section in
25 order to introduce the power line into the pipe section . .
without di~connecting the power line from the bursting
: mole.
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1 3~6600
In order that the invention may be more readily
understood, embodiments thereof, and the prior ar-t, wi~l now
be described by way of example with reference to the
accompanying drawings, in which: : :
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Figure lA is a diagrammatic side view of a pipe section
having a detachable portion for use in a method embodying the
' present invention;
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Figure lB is a diagrammatic end view of the pipe section
of Figure 1 with the detachable portion disconnected; .
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Figure lC is an enlarged fragmentary view of the
connection between the detachable portion o the pipe ~ection
of Figure 1:
i.
Figure 2 is an enlarged view of the pipe section and
detachable portion shown in Figure lC, with a resilient ;:
lS sealing member inserted between the plpe section and the
: detachable portion;
Figure 3A~is a diagrammatic sectional view illustrating :.-
a method embodylng the present inventlon;
Figurè~3B~:(a), ~b), (c) and ~d~ are sectional views of
20 ~ :sequentlal steps aarried out in the method~of Figure 3A;
1 326600
Figure 3C is a further diagramma-tic sectional view
illustrating the me-thod embodying the present invention; ~.
Figures 4-6 are diagrammatic sectional views
illustrating apparatus used in a prior art pipe replacing
method;
Figure 7 is a diagrammatic sectional view illustrating a
prior art pipe replacement method embodying the apparatus of
Figures 4 to 6; and
Figure 8 is a diagrammatic sectional view illustrating a
further prior ark pipe replacement method.
The prior art is illustrated in F'igures 4 to 8. Figures
4 to 6 show prior art apparatus and Figure 7 illustrates a
manner of actual use of this prior apparatusi, which is taken
: from:a catalogue explaining the practical use of the
apparatus on a commercial basis, and Figure 8 illustrates a
method based on an improvement of the method of Figure 7. :. :
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~ An embodiment of prior art apparatus will now be :-:
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: sipecifically described with reference to Figures 4 to 6. .~ . - - -
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The bursting mole 8a comprises a front section which .~
20~ ~intrudes into the oId pipe ll~a and ~ursts the wall thereof, . ~.
an~ a rear section which is connected to the new pipe la to
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~ tow the new pipe behind the bursting mole O
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1 326600
The front section of the mole has a head 14a wi-th
cutting blades 13a thereon, and a front end of the head is
drawn forward by a winch (not illustrated) by way of a .
traction cable lOa which is passed through the old pipe~
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Cutting edge~ 15a are proYided on the blades 13a, and
at least one blade can be pivoted outwardly from the
bur~ting mole in order to cut the wall of the old pipe.
.
.
~ ~n Figure 5, a ~luid prei~isure hose 12a extendiny
-. forwardly through the old pipe delivers a pressure fluid to
actuate a piston 16a provided in the head of the bursting
mole. The pi~ton, in turn, act~i on blade 13a to pivot it
outwardly thereby to Cllt the wall to form an enlarged space
for the new pipe following behind the mole 8a.
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Forward movement of the bursting mole together with ~-
the attached new pipe is perfor~ed by an air hammer 17a
,
di~posed in a hollow siection of the cylindrical bocly of the
: bursting mole as illustrated in Figure 6. The piston in the
air hammer ~lides back and forth in response to pressurized -::
air clelivered through an air hose attached to the rear end, ..
~0 and additlonally by winching through the cable attachecl to
the front end of the burstin~ mole. Additionally, a
hydraulic jacking device may ~e provided to apply further
pre~sure to the rear end of the new pipe a~i disclosed by
; the Appllcant ln Japanese Patent Application No. 61-1591B4
whiah was published as unexamined application 63-139B7.
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1 326600
In practice, an air hoæe 9a for supplying air to the
hammer 17a and incorporated .inside the head of the mole, is
joined to the rear of the mole by suitahle means. An oil -
feed pipe for supplying oil under pressure to the head for
f 5 rotatin~ th~ blades 13a may also be joined to the rear of
. the mole 8a.
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When a new pipe section is joined to the pipe sections
behind the bur~.ting mole, the hoses have to be inserted
through the pipe section as typically illustrated in Figure
10 7.
Turning to the invention and ref Prring first to Figure
f' 3A, in order to replace an old bwried pipe 11 with a new
pipe 1, a bursting mole 8 iæ positioned at one end of the
old pipe line. To thi~ end~ a ~tartin~ pit 4 i~ dug in the
15 ground over a length suf~icient to expose one end of the
old pipe line to be replaced and to accommodate related
equipment and tools.
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One end of a traction cable 10 is passed through the ~-
old pipe 1 and i~ attached to a front end of the bursting ..
mole 8 0 The cable 10 is attached at its other end to a
winch ~not shown) which pulls the bursting mole into the -~-
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: : oId:pipe to burst it and replace it with the new pipe 1
: fvllowing behind the mole 8. Since the external diameter
of ~he cyllndrical section of the burstin~ mole is larger -.;
25 than that of the old pipe, a space lincluding ~ragmentis of :
8~
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1 326600
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the old pipe~ larger than the old pipe is formed by the
s bursting mole to accommodate the new pipe attached to the
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I rear end of the mole 8.
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In the method illustrated in Figure 3A, the new pipe 1
is in the form of short pipe sections. As shown in Figures
1 tA3, ~B) and (C), each pipe section 1 is provided with a
lonyitudinal detachable portion 6 constituting a removable
part of the periphery o the pipe in parallel to the axial
direction thereof~ In the example illustrated~ stepped
portions 7 are provided on the edges of the longitudinal
'~ detachable portion 6 which engage with correspondingly
stepped portions 7 provided in the periphery of the pipe lo
,'
, Each of the stepped portions 7 of the pipe ~ection 1 and
the detachable portion 6 are pxovided with aligned bores
7a. The bores are provided with an internal ~crew thread
7b. The ~tepped portion~ 7 of the pipe ~ection 1 and the
detachable portion 6 are secured together by a ~crew 5 (or
, ~ other faætening member such as a bolt) having a shaf~
provlded with a ~crew thread corresponding to that provided -
in the bore~ 7a. A re~ilient sealing member 18 (as shown
in Flgure 2~ in the form of a rubber ætrip i~ interposed
between the stepped portionx 7 to provide a satisfactory
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~ eal between the pipe section 1 and the detachable portion
,~
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3 ~ 25 ~ Fi~ures 3A-C Illuætrate~the proce~ of formin~ a new ~ ~
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1 326600
pipe line by joining together individual pipe seckions 1.
Each pipe section includes, as shown in Figu~e lA, a recess
lb at one end and a collar lc at the other end. This
design allows easy joining of successive sections.
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, 5 The steps involved in the illustrated pipe
,, .
~ replacement method a.re as follo~J~: -
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: 1. A power line (in the form of an air hose~ 9 ex-tending : -
from a power source 19 (in the form of a ~ompressor) for
driving the mole is joined to the ret~r thereof and a cable
, 6l
i; lO 10 extending from a winch ~not shown) is joined to the
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~ front of ~ole 8. The mole 8 is then mo~ed forward with the
. 1l
~ tip end o~ the mole intruding .into the old pipe 11 and the
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old pipe is burit by the ~ole 8. The air hose g supplies
compresil3ed air to a driviny mean~ (in the form of an air :-
hammer) incorporated in the head of the mole, thereby
advancing the mole ~ into the space vacated by the old pipe
. 110 ~'~
. ~ 2. Ais illustrated in Figure~ 3B la) to ~d)~ the
longitudinal detachable portion 6 is removed from a pipe
sect~on l to be joined to the rear of the mole 8. The air
hoae 9 is then inserted into the new pipe and the
longltudinal de~aahable portion ~ is secured in place in
the periphery of the pipe 1 by the screw 5. The mole and
the new pipe section ~ are integrally se~ured to each other
: 25 by suita~le mean~, ~uch~a wire, to form a sealed
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~ connection. Furthermore, as shown in ~igure 3C, the mole 8
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f and the new pipe section 1 are moved forward together into
Z the space formed by the burst old pipe 11. The air hose 9
is alternately let out and rewound fro~ a hose reel 20 when
a pipe section 1 is to be fi-tted to the new pipe line.
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The air hose 9 is then inserted into a new pipe
ection 1 which is then joined in the same manner as
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above to the rear end of the preceding pipe section whereby
the extension from the ~tarting pit to the destination pit
10 i~ easily and neatly achieved.
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By the abo~e procesæ, pipe ~ection~ can be added to
the new pipeline without interrupting the air supply to the
f bursting mole~ -
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A method according to the present invention allow~
15 replacement work to be efficierltly carried out even when
the starting pit is narrow and has a relatively small
working area.
3~
i~ A method according to the pre~ent invention results
in, among other things, the reduction of working ~pace,
20 shortening of working t]me, omission of certain working
in truments, protection of the internal surfaces of the new
pipes and an improvement in the efficiency of air supply to
j~ the ~ursting mole.
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The new pipe may be either a replacemen-t pipe for the
old pipe or a ~heath for the replacement pipe.
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