Pipe protector

The present invention relates to protectors used to prevent piping or tubing from touching the surface of a bore hole, and in particular is related to discrete pipe coating protectors for in situ mounting on a product carrying pipe line or tubing to be received within an underground bore or within another pipe.

DESCRIPTION 
1. Technical Field 
The present invention relates to protectors used to prevent pipes or tubing 
from touching the surface of a bore hole, and in particular is related to 
discrete pipe coating protectors for in situ mounting on a product 
carrying pipe or tubing line to be received within an underground bore or 
within another pipe. 
2. Background Art 
There are known methods and apparatus for simultaneously drilling a bore 
hole along an underground arcuate or straight path between two surface 
locations to by-pass an obstacle thereinbetween and embedding a product 
pipe or tubing line in the bore hole. First, a drill string having a drill 
bit at the driving or frontal end of the string is used to create a pilot 
bore and a reamer is used to enlarge the pilot bore; the reamer can either 
be arranged on the drill string a distance behind the drill bit or mounted 
onto the drill string after the pilot bore has been completely drilled; 
the terminal front end of the product pipe is either secured directly 
behind the reamer or at a terminal end of the drill string by means of, 
i.e., a pull-back swivel carrying a pull head; the pipe line is then moved 
and embedded into the bore hole created by the drill bit and reamer, 
either during or at the end of the drilling operation by pulling out the 
drill string at the opposite end of the bore hole. Such a method is the 
subject of U.S. Pat. No. 4,679,637 granted to Cherrington et al. 
While other methods are also practicised, the above method has the 
advantage of allowing drilling of a bore and placing of a product pipe or 
tubing line in one same operation. 
The pipe lines embedded in such horizontal and arcuate bores, which provide 
surface to surface conduits under obstacles such as rivers, lakes, 
mountains and the like, are either directly used for transporting or 
conveying fluids including water, gas, oil production and the like, or to 
accommodate cables for electricity supply, telephone and other purposes. 
The embedded pipeline is subjected to environmental conditions which may 
eventually degrade the pipe and render them useless. Thus, many pipes used 
nowadays for such purposes are made of materials which are resistant to 
environmental agents, i.e. PVC-pipes, and/or, in the case of metallic 
pipes, are coated on the outside surface with a protective coating 
material, such as polyurethane (PU), polyethylene (PE) and the like. 
Accordingly, it is important that the outer surface and/or coating of the 
product carrying pipe be not damaged when pulled into and through the bore 
hole during the embedding procedure. Such damage will occur more readily 
within rough bore holes surfaces where sediment materials are hard and 
non-homogenous and thus provide a rugged surface along which the product 
pipe is dragged during the emplacement operation. This same considerations 
apply where a smaller diameter pipe line is to be embedded into a larger 
diameter pipe line when the latter is no longer useable due to possible 
damage it may have sustained. The large diameter pipe may also be a casing 
which has been installed in the bore hole for receiving the actual pipe 
line. 
One approach taken to prevent pipe coating damage has been to provide a 
second coating or protection layer on the outer pipe surface over the 
coating. The second coating layer is made of a material such as cement or 
Epoxy, and has a thickness sufficient to ensure that no damage will be 
sustained by the pipe coating located underneath the protective coating. 
One disadvantage has to be seen in that the protection layer, which is 
uniformly applied over the entire length of the pipe tubing greatly 
increases tubing weight and costs and, thus, the power required to pull 
the drill string through the bore hole; this increases the tubing and 
installation costs by a substantial factor. 
Another approach has been to cast cement into the bore hole receiving the 
pipeline so as to fill the annular gap between pipe and bore hole during 
the embedding operation; the drill string dragging the pipeline is moved 
through the bore hole while the cement is being filled in. This method is 
also known as slip forming or continuous protective layer casting. While 
the cement fills the annular gap between bore and pipe surfaces, thus, it 
does not prevent the pipe coating coming into contact with the bore 
surface; furthermore, considerable expenditure is required, both as to 
material costs and process technology to embed the pipe in the bore hole. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an alternative to the 
known methods and devices for protecting the outer coating of a product 
pipe or tubing line during emplacement in a bore hole, and in particular 
in bore holes along an underground arcuate path between two surface 
locations. 
Accordingly, in a first aspect, the present invention provides a pipe 
protector for product pipes to be embedded in a bore hole, the protector 
comprising an integral, sleeve like body moulded in situ onto and 
preferably entirely surrounding the circumferential outer surface of a 
discrete length of the pipe, the body being made of an abrasion resistant, 
castable material which in a cured state provides a substantially rigid, 
noncompressible casing of predetermined thickness which is firmly bonded 
to the outer surface of the discrete length of pipe. 
As used herein, the expression "product pipe" should be understood to 
encompass pipelines and tubing lines, which are either assembled from a 
plurality of discrete pipe or tube element or from continuous material, 
and pipe or tube element or from continuous material, and which are used 
as a tubular casing for lines or to convey fluids between two points. The 
bore hole can extend between two surface points, between a surface and an 
underground location, or between sub-surface locations. The product pipe 
may be a metallic one, made of plastics or other materials. The product 
pipes for which the pipe protector is primarily intended have no retention 
means integrally formed therewith, such as flanges or annular grooves on 
their outer surface, which could provide axial retention means to prevent 
slippage of the protector; thus, it is understood that the adhesion and a 
keying effect provided by irregularities and surface roughness of the 
otherwise plane surface of the product pipe or its protective coating with 
the material of the protector ensures that the latter is maintained in an 
axially and rotationally fixed manner on the pipe and withstands shearing 
forces exerted during the process of emplacing the pipe or tubing line 
within the bore. It is to be understood that when emplacing a pipeline, a 
plurality of pipe protectors are to be arranged (moulded) with 
predetermined distance from one another along the length of such pipeline. 
While the protectors are principally intended for pipes which are to be 
embedded in horizontal or inclined bores, they can also be used for pipes 
that are to be emplaced in substantially vertical bores where it is 
necessary to prevent surface contact between bore or bore casing pipe and 
pipe. 
A material for the protector which currently is understood to be suitable 
to co-act with a polyethylenecoated metal pipe used to convey fluid, i.e. 
liquid gas, and ensure proper "coupling" between the protector and the 
pipe coating is an acrylic modified resilient polyester resin blended with 
graded silica to form a pourable paste which is catalysed by the addition 
of a benzoyl peroxide dispersion. Such a resin is offered under the trade 
name Scotec GS 140995A. The protector material can also be reinforced with 
suitable abrasion resistant fillers. 
Preferably, the sleeve-like body is cylindrical in cross-section and is 
provided with a plurality of axially extending grooves on the outer 
circumferential surface of the body, the flutes being angularly spaced 
from one another around the periphery of the body. 
Alternatively, the sleeve-like body comprises a hollow-cylindrical base 
section and a plurality of axially extending ribs integrally formed with 
and radially protruding from the outer surface of the hollow-cylindrical 
base section, the ribs being arranged with angular distance from one 
another around the periphery of the body. The flutes formed between the 
ribs are designed so as to allow fluid passage along the outer surface of 
the product pipe when received in the bore. This is important for 
applications in which the bore drilling and product pipe embedding 
operations are carried out simultaneously and fluids used to 
cool/lubricate the drill bit and reamer have to be removed through the 
anular gap formed between the product pipe (or tubing) and bore surface 
past the pipe protectors. 
The integral ribs may advantageously be shaped as regular trapeziae in 
cross-section, that is be prismatic protrusions, with an arc-shaped base 
and outer peripheral surface, and if desired have on the outer peripheral 
surface a plurality of small, axially extending grooves. It is to be noted 
that by reducing the actual surface of the protector which will come into 
contact with the bore surface, frictional resistance will be minimised 
during the emplacement procedure in which substantial drag forces are 
exerted on the pipe or tubing line. 
In order to facilitate the tubing or pipeline emplacement procedure, it is 
also advantageous for the sleeve-like body to have a chamfered terminal 
frontal end face, that is the annular front end surface and/or the front 
end surfaces of the ribs are inclined in backward direction, as the case 
may be. 
While the sleeve-like body of the protector need not have a uniform wall 
thickness in circumferential direction, the sleeve-like body is preferably 
symmetrical in cross-section, such that the pipe can be emplaced 
substantially centralised within the bore hole and a pipeline section 
extending between two spaced apart protectors, which section is subject to 
bending between two support locations, maintains sufficient distance to 
the bore hole surface. The wall thickness of the cylindrical base section 
is determined such as to prevent cracking thereof under the loads applied 
during the insertion and emplacement procedure. 
In a further aspect, there is provided a method for emplacing a pipe or 
tubing line in a bore hole or bore hole casing along an underground path 
between two surface or sub-surface locations, wherein a plurality of 
discrete pipe protectors as hereinbefore described are moulded in situ and 
with predetermined distance from one another onto and surrounding the 
circumferential outer surface of the pipe at predetermined locations of 
the pipeline, each protector being cast from an abrasion resistant curable 
material using a mould adapted to releasably and sealingly encase a volume 
corresponding to the shape of the protector over the circumferential 
surface of the respective discrete length of pipe, and wherein the pipe is 
moved into the bore upon the protectors being cured and the moulds 
removed. 
The casting technology for moulding the protectors onto the discrete 
lengths of pipe or tubing line is conventional and may include use of a 
two-piece fibreglass mould having mould halfs hingedly connected with one 
another and adapted to be closed over the circumference of the pipe or 
tubing line at predetermined protector locations. 
In yet another aspect of the invention, there is provided a method for 
protecting the outer coating of a pipe or tubing to be emplaced in a bore 
hole or bore hole casing, which may extend along an underground arcuate 
path under an obstacle between two surface or sub-surface locations, 
wherein a plurality of discrete pipe protectors as herein before described 
are moulded with predetermined distance from one another at predetermined 
locations onto and surrounding the circumferential outer surface of the 
pipeline, each protector being cast from an abrasion resistant curable 
material using a mould adapted to releasably and sealingly encase a volume 
corresponding to the shape of the protector at said predetermined 
locations over the circumferential surface of respective discrete lengths 
of pipe where the protectors are to be moulded. 
A contact enhancement layer may be applied between the outer coating of the 
product pipe and the inner-circumferential surface of the sleeve-like body 
of the protector such as to promote bonding action between the protector 
and the coating of the product pipe. 
The present invention, in its different aspects, as well as further 
advantages thereof, will be more fully understood from the ensuing 
description of a preferred embodiment thereof which is provided with 
reference to the accompanying drawings.

PREFERRED MODE FOR CARRYING OUT THE INVENTION 
In FIG. 1 is illustrated in a highly schematic and simplified way a drill 
string 1 used to drill a bore hole along an arcuate path underneath an 
obstacle, such as a river, between two surface points. The drill string 1 
comprises at its frontal driving end a roller cone bit 2 with mud motor 3 
for drilling a pilot bore. In backward direction along the drill pipe 4 of 
the drill string 1 is located a reamer 5 used to enlarge the bore diameter 
to the final size of the bore hole 7. In further rearward extension, the 
drill string 1 passes through a cooling fluid collector manifold 9 
arranged at the terminal end of a surface casing 8 inserted into the bore 
hole opening. Such an apparatus and a method for drilling an underground 
arcuate path bore hole between two surface locations and the subsequent 
procedure for emplacing a product tube or pipeline is known for example 
from a number of US Patents granted to Cherrington et al, for example U.S. 
Pat. N0. 4,679,637, the contents of which is incorporated herein by way of 
short hand cross-reference. While said US patent discloses to first 
complete the pilot bore hole and subsequently connect the reamer t o the 
drill string to enlarge the bore diameter, this operation can also be 
accomplished in one passing of the drill string. As can be seen from the 
schematic illustration of accompanying FIG. 2, the product pipe or tubing 
line 10 to be emplaced in the enlarged bore hole 7 is not mounted directly 
behind the reamer, but is instead fixed at the rearward most of the drill 
pipes 4 of the drill string 1 by means of a pull-back swivel 11 and 
pull-head 12 mechanism. The drill string 1 pulls the product pipe 10 into 
the enlarged diameter bore hole 7 either upon completion of the enlarged 
bore hole or while the bore is still being drilled. The product pipe 10 is 
provided at predetermined length intervals with discrete, sleeve-like 
cylindrical pipe coating protector elements 20. The pipe coating 
protectors 20 are used to ensure that the relatively scratch-sensitive 
PE-coating of the stainless steel product pipe 10 does not come in touch 
with the bore hole surface during the pulling and embedding operation. 
FIG. 3 and 4 illustrate such a pipe coating protector in more detail. As 
can be seen there, the protector 20 comprises a hollow cylindrical base 
section 21, the circumferential wall of which has a relatively small 
thickness. A total of four axially extending ribs 22 are integrally formed 
with the base section 21 and arranged equi-distantly around the 
circumference of the protector body 20; the ribs 22 thereby form 
thereinbetween extending flutes 23. As best seen in FIGS. 3 and 5, the 
cross-section of the ribs 22 is that of a regular trapezium with an 
arc-shaped base 24 and arc-shaped outer peripheral surface 25 as well as 
inclined side surfaces 26. The front and rear terminal end surfaces 27 and 
28 of the ribs 22 are also chamfered with a predetermined angle, which in 
the specifically shown example is 25 with respect to the horizontal plane. 
While not illustrated, the outer peripheral surface 25 may have a 
plurality of small, axially extending grooves. By way of example only, 
when designed for use with a 10" diameter product pipe, which is to be 
located in a bore hole of about 350 mm diameter, the height of the ribs 22 
from the outer surface of the cylindrical base section 21 is about 25 mm, 
the thickness of the cylindrical base section 21 is also approximately 25 
mm. It is of course also possible to have other thickness ratios. The 
overall length of the protector body 20 is about 350 mm. It is to be 
understood that the specifically illustrated cross-section of the pipe 
protector body 20 and its dimensions are examples only which are not to be 
interpreted as limiting the protector shape to the one specifically 
illustrated. For example, the number of ribs 22 can be increased, and the 
specific cross-section altered. 
The protector body 20 is cast in situ onto a desired one of a plurality of 
locations along the length of the product pipe 10 using conventional 
casting techniques for curable materials. Herefore, a two-piece mould can 
be used, having an interior surface contoured such as to provide the outer 
shape of the pipe protector body 20 when arranged at the predetermined 
location on the product pipe and closed such as to sealingly encircle a 
volume zone over a discreet length of the surface of the product pipe. A 
typical distance between neighbouring protection is 7-10 m. 
The material used for casting the pipe coating protector bodies 20 is 
chosen such as to be compatible with the outer protective coating of the 
product pipe and ensure proper adhesion and inter-keying with the minute 
surfaces irregularities present in such product pipes. The bond between 
the inner surface of the hollow cylindrical base section 21 of the pipe 
coating protector body 20 and the pipe coating ensures that the pipe 
coating protector 20 is fixed against rotation and axial movement along 
the product pipe. That is, any type of gliding between the pipe coating 
protector 20 and the product pipe type 10 is inhibited. 
The pipe protector material has also to be chosen taking into consideration 
the type of soil/strata into which the tubing is to be emplaced. One pipe 
protector material suitable for a PE-coated pipe to be embedded in a bore 
hole in a sand stone formation is mentioned above. 
One of the main features of the pipe coating protector according to the 
present invention is that it requires no additional mechanical fasteners 
or fastening devices to be fixed onto the product pipe and that it 
provides a one-piece element which can be said to be integrated with the 
product pipe as a result of being produced by cast moulding onto the outer 
surface of the product pipe. 
While the specific shape of the pipe coating protector body 20 described 
and illustrated herein constitutes one preferred embodiment of the 
invention, as does the above described method for emplacing a product pipe 
or tubing line having a plurality of such pipe coating protectors arranged 
at spaced intervals along the length of the pipe line or tubing, it is to 
be understood that the invention is not limited to these precise forms and 
that changes may be made without departing from the scope of the invention 
as set forth in the claims.