GB2258285A - Die for use in lining pipe - Google Patents

Abstract

A die for use in lining an existing pipe with a polymer liner pipe comprises two die halves 2, 3 and two bolts 29 for securing the halves together to form the assembled die. At the abutment faces 11a, 11b and 12a, 12b dowels 17, which are fixed to die half 3, engage in channels 14 so as to locate the die halves in proper alignment preparatory to securing them together. When the dowels are non-parallel the two halves only fit together properly one way round. Holes 26 in the die half 2 are clearance holes with respect to the bolts 29 and the clearance reduces the likelihood of the bolts binding on the walls of the holes 26 when the die halves are separated in the presence of forces urging them apart. <IMAGE>

Description

A DIE The invention relates to dies and, more particularly, to dies for use in pipe lining.

Known methods of lining an existing buried pipe, such as a gas, water or sewage pipe, comprise pulling a plastics pipe, such as a polyethylene pipe, through a die to reduce the diameter of the plastics pipe and then through the existing pipe. After removal of the pulling force the plastics pipe is either allowed to or caused to expand into engagement with the internal wall of the existing pipe.

Such methods are described, for example, in British Gas UK patent application publication Nos. 2218485 and 2218491.

In one known method a one-piece die is mounted on a rig which is anchored to the ground at a position generally opposite but spaced from and above the near end of the buried existing pipe which is to be lined. In this case once the plastics pipe has been pulled through the existing pipe it may be cut at a location downstream of the die, that is at a location whereat the pipe is of reduced diameter form. Since the portion of the plastics pipe of reduced diameter shrinks in length as it expands to engage the internal wall of the existing pipe the location at which the pipe is cut prior to expansion has to be a sufficient distance from the near end of the existing pipe to leave the end of the plastics pipe protruding from it after complete shrinkage has occurred. The protruding spigot end enables a connection to be made to an adjacent length of plastics pipe.

Although this method employing the ground-anchored rig and onepiece die works satisfactorily, applicants sought a method which utilised equipment which was more compact, easier to mount and anchor to withstand winch loads during the pulling operation, and facilitated quicker carrying out of the method. This led to the applicants developing equipment comprising a frame which could be clamped directly on the end of the buried existing pipe and a split die which was securable to the frame. The split die comprised two half segments made of mild steel which were held together by two hardened machine dowel bolts which were on diametrically opposite sides of the assembled die. These bolts also served to guide the segments into correct alignment before being secured together and to maintain such alignment once secured together.

In order that the segments were in the correct relative positions the shanks of the dowel bolts were close or machine sliding fits through holes in one of the segments and close screw fits in threaded holes in the other one of the segments. After pulling polyethylene pipe through the existing pipe using this form of equipment the polyethylene pipe can be cut at a suitable location upstream of the die where the pipe material is not under tension.

However, the polyethylene pipe remains trapped in the die with the die under load. The length of pipe downstream of the die remains under tension until the die is split.

When the die is split i.e. disassembled into its component segments, the die and frame can be dismantled and removed from the existing pipe without the plastics pipe having to be cut downstream of the die i.e. on the side of the die where the pipe in under tension.

Although the intention was for the die to be used, split and reassembled repeatedly for further operations, applicants have found that the die cannot readily be repeatedly reassembled with accuracy in the field. The die half having the holes through which the shanks of the bolts are close or machine sliding fits tends to bind on the bolts as the die is split due to the forces associated with the polyethylene pipe being held in tension acting on the die segments. As a result of this binding it is relatively difficult to remove the hardened machine bolts and damage can be caused since wear occurs on the mild steel inner surfaces of the bolt holes of the segments. This wear can cause the bolt hole to become somewhat oval shape in cross-section with the result that the bolts are no longer close or machine fits in the respective holes and thus the segments no longer fit together accurately.In some instances, the binding may result in a bolt breaking while an attempt is being made to remove it from the segments.

Hardening the die half prone to damage would mean using higher quality material, such as higher quality steel, in order to avoid distortion and this would increase the cost of the materials.

An object of the present invention is to provide a die composed of die segments which can more readily be repeatedly reassembled accurately.

According to the invention a die for use in pipe lining comprises two or more segments having abutment surfaces and means for releasably securing the segments together in abutting relationship to form the assembled die, each segment having at least one formation which is engageable with a complementary formation of an adjacent segment so as to locate adjacent segments in proper alignment with respect to each other, when the opposing abutment surfaces are in abutment, preparatory to securing the segments together to form the assembled die.

The formations and complementary formations may be so designed that they are in engagement with each other to locate the segments in proper alignment only when the abutment surfaces of adjacent segments are in abutment with each other.

Preferably, the securing means comprises two or more screw fastening members, such as bolts, with each fastening member having a shank which passes with clearance through a hole in one of two abutting segments and which has a threaded portion which screws into a threaded hole in the other of the abutting segments. The provision of clearance for the shank through the hole reduces the likelihood of binding between the segment and the shank as a result of forces tending to urge the segments apart during initial stages of disassembling the die.

It will be appreciated that the clearance provided should be made sufficient to eliminate substantially completely the undesired binding under the conditions to which it is known that the die will normally be exposed. Conveniently, the die is formed from two segments comprising two die halves, in which case, when the die is in the assembled condition the shanks of the fastening members, and thus the respective holes in the halves, may be disposed substantially parallel to each other with the shank of each fastening member passing with clearance through a respective hole in the same one die half and the threaded portion screwing into a respective threaded hole in the same other die half.

Furthermore, each die half segment may have two co-planar abutment surfaces for abutting respective ones of the two coplanar abutment surfaces of the other die half segment such that when the die halves are in proper abutment the shank of each fastening member extends through respective abutting surfaces.

Conveniently, when the die is in the assembled condition, the shanks of the fastening members and the associated holes in the two die halves extend substantially perpendicularly to the coplanar surfaces.

Preferably, each formation or complementary formation is a projection, and each associated complementary formation or formation is a recess.

The projection may have opposite side portions which slope towards the associated segment in a direction away from the projection. Such sloping side portions can facilitate guiding the segments into proper relative alignment. Each sloping side portion may be of convex form and may be provided, for example, by a projection of semi-circular cross-section, such as a projection of substantially semi-cylindrical form. In a preferred embodiment, the projection is formed by a protruding half of a cylindrical element, such as a rod or dowel, which is fixed in a groove or channel extending through the abutting surface of the associated segment. Conveniently, the cylindrical element may be fixed in the groove or channel by means of one or more welds.Such an arrangement facilitates replacement of a damaged or distorted projection since the cylindrical element may readily be machined out of the recess and a fresh one located and then fixed into the reamed out recess. Preferably, where the die is composed of two halves and where each die half has two coplanar abutment surfaces, a said projection of semi-cylindrical form projects from each of the co-planar surfaces associated with a single one of the two die halves. Within the common plane the two projections may be in either parallel or non-parallel relationship with respect to each other. The non-parallel relationship is preferred where it is advantageous that the two halves fit together properly only one way round with respect to each other.Moreover, the non-parallel relationship can prevent the two die halves moving both laterally and longitudinally with respect to each other when in abutment.

In order that the present invention may be more readily understood, reference will now be made, by way of example only, to the accompanying drawings, in which : Figure 1 is an exploded perspective view of one embodiment of die according to the invention, Figure 2 is an end view of the die with a part shown in section, Figure 3 is a plan view from above of the lower half of the die as viewed with respect to Figure 2, Figure 4 is a side view of the die as seen in the direction of arrow A in Figure 2, and Figure 5 is a somewhat schematic vertical sectional view through the ground showing a die according to the invention in the assembled condition and mounted on a frame which is clamped to an existing buried pipe.

With reference to the drawings, a die 1 for use in pipe lining comprises two half segments 2,3. Together the inner surfaces 4,5 of the two segments define the die orifice 6 which is of circular cross-section and which generally tapers lengthwise of the die at an angle#from one end 7 to the other end 8. Thus, the half segments 2,3 are semi-circular in cross-section and define equal portions of the orifice. The outer peripheral surfaces 9,10 of the die segments are generally semi-cylindrical so that the assembled die has a generally straight cylindrical outside surface.

The die half 2 has two co-planar abutment surfaces lla and 12a for abutting the corresponding co-planar abutment surfaces llb and 12b, respectively, of the die half 3. The plane containing the abutment surfaces lla,llb,12a and 12b in the assembled die also contains the longitudinal axis 13 of the die. Thus the two segments may be regarded as being separable across a longitudinal, diametrical plane.

The co-planar surfaces lla,12a and llb,12b are each provided with a recess in the form of a channel 14 or 15, respectfully, of semi-circular cross-section. Each channel extends lengthwise from one end of the associated die segment to the other end at the same angle ~ to the longitudinal axis 13 of the die as the general angle of taper of the inner surface of the die.

In each of the channels 15 in the surfaces of the lower segment 3 as viewed in Figure 2 there is a cylindrical element or dowel 17 which is fixed in position, for example by spot welds as at 18. As can be appreciated from Figure 2, the fixed dowels 17 provide semi-cylindrical projections 19 which engage closely in the matching channels 14 in the surfaces of the upper die half segment 2 (as viewed in the drawings) to locate the segments in proper alignment when the opposing abutment surfaces lla and llb, and 12a and 12b are in abutment.

The die half segment 3 has screw threaded holes 22 which extend perpendicular from the co-planar surfaces llb,12b through the segment. The die half segment 2 has two part cylindrical recessed portions 23 providing planar end-walls 24 which are parallel to the co-planar surfaces lla,12a . Cylindrical plain holes 26 of larger diameter than holes 22 extend perpendicularly from the co-planar surfaces lla,12a to the end walls 24.

The diameters of the holes 26 are greater than the diameters of the threaded holes 22.

When the two die halves 2,3 are matched up with the projections 19 engaged in the respective channel 14 in the die half 2 and the surfaces lla,llb and 12a,12b abutting, the two halves are in proper alignment preparatory to being secured together. In this position the plain holes 26 are co-axial with respective ones of the threaded holes 22. It will also be appreciated from Figures 1 to 4 that since the dowels 17 are non-parallel with respect to each other there is only one relative position of the two halves in which the abutment surfaces lla, 12a and llb, 12b can abut in a matching fashion, i.e. when the projections 19 are both engaged in the channels 14, such that the two segments are properly aligned preparatory to securing them together.It will be understood that one or the other of the longitudinal edges 14a of the channels 14 can slide down the respective convex sloping surfaces of the semi-cylindrical projections so that the projections 17 and channels 14 are in engagement.

To secure the die halves 2,3 together the threaded shanks 30-of bolts 29 are passed through the larger diameter plain holes 26, which serve as clearance holes, and are screwed into matching threaded holes 22. The bolts 29 are screwed in until the bolt heads 31 are tightened against the portions of the end walls 24 surrounding the clearance holes 26. As can be seen from Figure 2, when the bolts 29 are fully tightened the heads 31 are completely within the recessed portions 23, and so do not protrude beyond the outer peripheral surface 9, and the two shanks 30 extend parallel to each other.As can also be seen from Figure 2, when the die is in the assembled condition, with regard to the common plane containing the co-planar surfaces lla,llb,l2a and 12b, on each diametrically opposite side of the die, the tightened bolt 29 is located between the outer cylindrical surface 9,10 and the dowel 17 whilst the dowel 17 is located between the bolt 29 and the inner surface 4,5 of the die.

In use, preparatory to lining a buried pipe, 35, made for example of cast iron or steel, with a plastics pipe 36, the assembled die 1 is bolted, via the provision of holes 37 in the die halves 2,3 extending parallel to the longitudinal axis 13 through the die, to the end of a die frame 38 which is secured by clamps 39 onto the end of the existing buried pipe.

After the plastics pipe 36 has been drawn or winched through the buried existing pipe 35, with the frame 38 and die 1 still in position on the buried pipe, the plastics pipe is cut upstream of the die, such as at position 41, i.e. in a non-stressed region of the plastics pipe.

The die halves 2,3 may then be unbolted from the frame 38 followed by the unscrewing of the bolts 29 which clamp the die halves together.

As the bolts 29 are loosened, stress or forces associated with the plastics pipe in the region of reduced diameter urging recovery or reversion of the pipe towards its original unstressed larger diameter state can cause the die halves to move apart from each other in a non-aligned manner. Consequently, the two bolts are carefully unscrewed at the same time in an incremental manner until the stress has been relieved which is when the die halves have moved sufficiently far apart. It will be appreciated that the threaded portions of the bolt shanks should be of sufficient length so as not to disengage from the threaded holes 22 before the stress has been relieved.

A suitably sized gap or clearance around the shank 30 of each bolt 29 as a result of the provision of the larger diameter holes 26 in die half 2 has been found by the applicants to more readily enable separation of the die halves without the bolts 29 binding on the die half 2 since the gap permits some non-aligned movement before binding occurs. Thus, the bolts 29 are used to clamp the die halves together while the projections 19 and channels 14 are used to locate the halves accurately in the desired aligned positions to ensure that a properly assembled die is achieved.

If the dowels 17 become damaged, then because they are only held in the recesses 15 by two small welds 18 they can relatively easily be machined out of the recesses and be replaced by fresh pieces of dowel which are welded in position.

By way of example the die halves may be made of mild steel, with the dowels being made of silver steel. The bore or orifice of the die may be hard chrome plated and polished to a required size in a known manner. In applicants experiments involving the embodiment of die described with reference to the drawings, 16mm diameter bolts 29 were used while the plain clearance holes 26 in die halve 2 measured 18mm in diameter. Thus, the clearance or gap between the shank of the bolt and the wall defining the hole was substantially lmm all round.

Whilst a particular embodiment has been described above it will be understood that various modifications may be made without departing from the scope of the invention. For example, the recesses and projections need not have substantially exact matching forms, such as semi-cylindrical forms. Instead, for example, the projection may be semi-cylindrical whilst the complementary channel may be of V-shaped cross-section.

Furthermore, the projection and recess need not extend throughout the length of the die. For example, the projection and recess may be circular in plan view. Moreover, the two dowels need not be of the same size or shape provided of course that the associated recesses are each appropriately sized and shaped to accommodate the respective one of the dowels.

Claims (16)

1. A die for use in pipe lining comprising two or more segments having abutment surfaces and means for releasably securing the segments together in abutting relationship to form the assembled die, each segment having at least one formation which is engagable with a complementary formation of an adjacent segment so as to locate adjacent segments in proper alignment with respect to each other, when the opposing abutment surfaces are in abutment, preparatory to securing the segments together to form the assembled die.

2. A die as claimed in claim 1, in which the securing means comprises two or more screw fastening members, each fastening member having a shank which passes with clearance through a hole in one of two abutting segments and which has a threaded portion which screws into a threaded hole in the other of the abutting segments.

3. A die as claimed in claim 1 or 2, in which the die is formed from two segments comprising two die halves.

4. A die as claimed in claim 3, as dependent on claim 2, in which when the die is in the assembled condition the shanks of the fastening members are disposed substantially parallel to each other and in which the shank of each fastening member passes with clearance through a respective hole in the same one die half and the threaded portion screws into a respective threaded hole in the same other die half.

5. A die as claimed in claim 3 as dependent on claim 2, or claim 4, in which each die half segment has two co-planar abutment surfaces for abutting respective ones of the two coplanar surfaces of the other die half segment and in which when the two segment halves are in proper abutment the shank of each fastening member extends through respective abutting surfaces.

6. A die as claimed in claim 5, in which when the die is in the assembled condition, the shanks of the fastening members and the associated holes in the two die halves extend substantially perpendicularly to the co-planar surfaces.

7. A die as claimed in any of the preceding claims, in which each formation or the complementary formation is a projection, and each associated complementary formation or formation is a recess.

8. A die as claimed in claim 7, in which the projection has opposite side portions which slope towards the associated segment in a direction away from the projection.

9. A die as claimed in claim 8, in which each sloping side portion is of convex form.

10. A die as claimed in claim 9 in which the projection is of semi-circular cross-section.

11. A die as claimed in claim 10, in which the projection is of substantially semi-cylindrical form.

12. A die as claimed in claim 11, in which the projection is formed by a protruding half of a cylindrical element which is fixed in a groove or channel extending through the abutting surface of the associated segment.

13. A die as claimed in claim 12, in which the cylindrical element is fixed in the groove or channel by means of one or more welds.

14. A die as claimed in claim 11, 12 or 13, as dependent on claim 3 and on claim 5 or 6, in which a said projection projects from each of the co-planar surfaces associated with a single one of the two segments.

15. A die as claimed in claim 14, in which the two projections are in non-parallel relationship with respect to each other.

16. A die for use in pipe lining, substantially as hereinbefore described with reference to the drawings.