Note: Descriptions are shown in the official language in which they were submitted.
~ 2~15306
This invention relates to apparatus for inspecting the
interior wall of a pipe or bore. Such apparatus is
frequently referred to as " a borescope " and will be
referred to as such herein.
Borescopes are used for inspection of the interior
surface of all types of bore such as bore holes for wells or
for mining or the interior bores of pipes. They generally
utilize the principle of directing light towards an inner
reflecting surface of a bore to be inspected, and monitoring
reflected light therefrom. Examples of borescopes utilizing
this principle are disclosed in U.S. Patent No. 4,732,474 to
Chikama issued March 22, 1988 and in U.S. Patent No.
5,088,819 to Storz issued February 18, 1992, U.S. Patent No.
4,967,092 to Fraignier et al issued October 30, 1990 and in
U.S. Patent No. 4,657,387 to Heising et al issued April 14,
1987. The general principle is also utilized in apparatus
for inspecting any reflecting surface. Thus endoscopes for
surgically inspecting interior parts of the body cavity of
humans and animals may utilize this principle as, for
instance, in the endoscopes of U.S. Patents Nos. 4,241,729
and 3,294,085.
Known borescopes may comprise an optical probe located
at the distal end region of an elongate rod or sleeve which
is capable of being projected into the bore to be inspected.
The probe may be connected to a monitor at the proximal end
of the rod or sleeve outside the bore. Light from the probe
is directed towards the wall of the bore and reflected light
signals are transmitted to the monitor. The longitudinal
position of the probe within the bore may be adjustable.
Borescopes of the type just described vary in their
efficiency dependent on the radius of the bore whose wall is
to be inspected. If the bore is of small radius the path
travelled from the optical source to the bore wall and back
2~15306
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to the receptor is small and loss of brightness and effect
of optical aberrations may be minimal. On the other hand,
if the radius of the bore is large the path travelled from
the optical source, to the bore wall and back to the
receptor is large and appreciable distortions may occur.
Moreover, lack of definition may also become a problem.
Considerable effort has been put into the design of
optical probes small enough to be used in narrow bores
(Heising), or for all round viewing (Fraignier), or for the
provision of flexible shafts to extend round pipe or bore
bends (Storz).
Optical technology for the inspection of a surface
within a pipe or bore and at a considerable distance away
from the monitor has become very sophisticated as may be
seen from Heising et al and Fraignier et al in respective
U.S. Patents Numbers 4,657,387 and 4,967,092 referred to
above. The sophisticated apparatus which is now available
may allow for detailed inspection of sectors of inner pipe
wall. If, due to the geometry of the pipe and a probe which
is rotatable coaxially therein is such that close inspection
of the pipe wall is not possible, much of the advantage of
the modern technology may be lost. The present inventor has
addressed this problem.
According to the invention there is provided apparatus
for inspecting an interior surface of a straight bore, for
example, the bore of a drill pipe, comprising: mounting
means to attach the apparatus to a mouth of the bore; a
rigid shaft locatable in the bore parallel to the bore axis
and offset therefrom to project a first shaft end out of the
bore; light means attached to a second end of the shaft and
comprising an emitter to emit an incident light beam and a
receiver to receive a reflected light beam; the light means
~- 2 ~ 1530~
-- 3
being arranged to respectively direct incident light towards
a sector of the interior surface of the bore and receive
reflected light therefrom; a monitor; a light source;
incident light transmission means extending along the length
of the shaft to transmit light from the light source to the
emitter; reflected light transmission means extending along
the length of the shaft to transmit reflected light from the
receiver to the monitor; and means to move the shaft
eccentrically about the bore axis.
In most cases, the bore which may be either a pipe bore
or a mine shaft bore such as a well bore, will be
cylindrical. Moreover, the bore will usually be oriented in
a horizontal orientation, although it may be vertical.
Generally the apparatus will be used for inspecting the
inside straight pipes such as drill pipes in the regions
such as welds, joins between pipe sections, or regions where
damage is suspected.
The apparatus may allow incident light to be projected
towards the pipe wall over a distance appreciably less than
the radius of the pipe. Similarly reflected light travels
from the pipe wall to the receptor over a distance less than
the radius of the pipe. As the shaft moves eccentrically
about the axis of the pipe the distance travelled by
incident and reflected light remains constant.
The shaft may be a sleeve and the incident light
transmission means and the reflected light transmission
means are located inside the sleeve. Conveniently the light
source may be a source of ultraviolet light and the incident
light transmission means and the reflected light
transmission means are optical fibres.
~ 2115306
Due to the fact that the light means is located near
the pipe wall it may be possible to inspect sectors of the
pipe wall with a greater degree of accuracy than if it were
located at the axis of the pipe.
Of course it is desirable that the light means is
longitudinally adjustable within the bore. This involves
providing means to longitudinally adjust the position of the
shaft within the pipe. Preferably the shaft is
longitudinally adjustable in indexed increments.
In one embodiment, the mounting means comprises a
platform attachable to a mouth of the bore either by
internal threading or by external threading to align the
shaft parallel with axis of the bore and the means to
eccentrically move the shaft about the bore axis is an
eccentric mounted on the platform to be rotatable about an
axis coaxial with the bore axis and having an eccentric
bearing therethrough, the shaft extending through the
bearing for movement therewith on rotation of the eccentric.
The eccentric may comprise a disc arranged parallel and
concentric with the platform and rotatable about its axis,
the eccentric bearing for the shaft being offset from said
axis, and a circular strap geared to gearing around the rim
of the disc to rotate the disc. The circular strap may be
driven manually or through a motor. When it is driven
manually it may be provided with a handle.
A spacer may be provided to space the platform axially
from the mouth of the bore, and the platform is attached to
the mouth of the bore through the space. The spacer may
comprise a screw threaded bore to engage a complementary
externally screw threaded spigot of the mouth of the bore.
2115306
An embodiment of the invention will now be described
by way of example with reference to the drawings in which:
Figure 1 is a view of one embodiment of apparatus
according to the invention having mounting means for
mounting it on a drill pipe having external threading;
Figure 2 is a perspective view of apparatus similar to
that of Figure 1 but having means for mounting on a drill
pipe having internal threading;
Figure 3 is a central longitudinal section of the
apparatus of Figure 1;
Figure 4 is a view of the apparatus of Figure 2 as
viewed from the top; and
Figure 5 is a view of the apparatus of Figure 2 as
viewed from the under side.
The drawings show an embodiment of apparatus according
to the invention for inspecting the inner wall of a vertical
drill pipe 10.
It should, of course, to be understood that the
apparatus may be used to inspect the interior of any bore
provided that means are provided at the mouth of the bore
for secure mounting of the apparatus.
The drill pipe 10 may have any orientation, i.e it may
be vertical or horizontal or angled. In fact in practice it
is quite likely that it will be horizontal. Any orientation
shown in the drawings id for ease of illustration. In the
embodiment shown in Figure 1 the drill pipe 10 is provided
211531~6
-- 6
with an externally screw threaded spigot 12 which is
engageable with a screw threaded socket 14 of an annular
plate 16 of mount 18. In the embodiment shown in Figure 2
the drill pipe 10 is provided with an internally threaded
socket 13 which is engageable with a screw threaded spigot
15 of platform 20 of mount 18.
When the apparatus is to be mounted on an externally
threaded drill pipe, the mount 18 comprises a platform 20
spaced above plate 16 by four spacing pedestals 22 of which
only three can be seen. Thus, it is possible to screw plate
16 onto the upper end 12 of the drill pipe so that the
spigot 12 of the drill pipe extends into the space between
plate 16 and annular platform 20 and thus does not foul
operating parts above it. On the other hand, when the
apparatus is to be mounted on an internally threaded pipe,
the mount 18 comprises only annular platform 20.
A shaft 24 extends into the drill pipe 10 through the
spigot 12, the plate 16 and platform 20 of mounting 18. The
shaft 24 comprises a sleeve carrying light transmission
connectors 26 between an optical eye 28 at a lower end 30 of
the shaft 24, and on the one hand, and a light source 32
and, on the other hand a monitor 34. The optical eye 28 is
attached to the end 30 of shaft 24 to direct a beam incident
light towards a sector of the interior surface of drill pipe
10 generally normal to the surface. Suitably the light is
ultraviolet light, although white light can be used, which
when directed at the internal surface of a pipe which has
been treated with a fluorescent dye or particles, causes
fluorescence when the dye concentrates e.g. in flaws or
defects. This may provide a very clear visual image. It
is, however, important that the optical eye is a set
distance from the surface to be inspected. The eye is
located to receive reflected light from the interior wall of
'~ 211~31~6
drill pipe 10. The connections 26, which may be a liquid
optic system or optical fibres, carry incident light from
the optical source 32 to the optical eye and carry reflected
light from the optical eye to the monitor 34, which may be
an eye piece or camera.
The shaft 24 is located within the drill pipe 10 to
project from it as end portion 36 and is located parallel
but not coaxial with the longitudinal axis of the drill pipe
10 by means of an eccentric 38.
Eccentric 38 comprises a disc 39 rotatable on bushing
40 and having an offset bearing aperture 41 through which
shaft 24 passes. Bushing 40 holds the shaft 24 of the
borescope and is tightenable by means of compression ring
46. Thus disc 39 is able to rotate coaxially about the axis
of drill pipe 10 so that bearing aperture 42 describes a
circle about the axis of drill pipe 10. When shaft 24 of
disc 39 is located in bushing 40 of disc 39 and disc 39 is
rotated, then the shaft 24 moves eccentrically about the
axis of drill pipe 10. Thus, optical eye 28 on lower end 30
of shaft 24 will describe a circle around the axis of drill
pipe 10. Optical eye 28 is arranged to direct incident
light generally radially outwardly towards the inner wall of
drill pipe 10.
Due to the arrangement of shaft 24 in bushing 40 of
disc 39, the distance of optical eye 28 from the wall of the
pipe 10 will always be less than the radius of drill pipe
30. The actual distance of optical eye 28 from the interior
wall of drill pipe 30 will depend on the actual location of
bushing 40 in disc 39. It is quite possible that disc 39 be
provided with more than one aperture 40 so that the distance
of bushing 40 from the centre of disc 39 may be varied to
vary the distance of the optical eye from the inner wall of
21~5306
-- 8
the drill pipe may be varied. A disc having a plurality of
apertures at different distances from the axis may be useful
if the apparatus is to be used to inspect the interior walls
of drill pipes of different radii. When it is desired to
use the apparatus or drill pipes of different radii, it is
only necessary to provide different threaded socket 14 or
threaded spigot 13.
While the operation of the eccentric 38 may be by any
conventional means, it may be convenient to provide a handle
48 to turn disc 39.
It is important that optical eye 28 always be directed
towards the interior wall of the drill pipe 10. Thus, it is
important that shaft 24 should not rotate about its own axis
to allow the optical eye 28 to be directed in other
directions, for example, diametrically opposite to the
direction indicated in the drawings. For this reason, the
shaft 24 may be secured in a fixed bushing 40 of eccentric
38 but should be freely rotatable in compression ring 46.
The optical eye itself may utilize any convenient
technology but the use of ultra violet light may be
preferred.
The borescope may be adjusted longitudinally in the
drill pipe by loosening compression ring 46 and sliding the
borescope in bushing 40. A series of notches may be
provided on the shaft of the borescope. Each notch may be
spaced from the next notch by the desired distance between
the longitudinal viewings. The notches may be a visual
guide or may engage a projection to automatically stop
longitudinal movement after the desired distance has been
covered.
2L 1~3D6
g
In operation it may be desired to inspect the entire
circumference of the drill pipe in the region of a suspected
defect 52. Such suspected defect will be referred to for
ease of language as a pipe weld, since welds are a common
site of defects. It should be appreciated that any region
of the pipe may be inspected whether suspect or not. In
this instance, the longitudinal position of the shaft 24 is
adjusted so that the optical eye 28 is longitudinally
coincident with the position of the weld 52. The radial
position of the optical eye 28 is set at a starting position
by means of the handle 48. Ultra violet light is supplied
to the optical eye 28 by liquid light guide connections 26
from optical source 32. Reflected light is received from
optical eye 28 through liquid light guide connections 26 to
monitor 34 where it may be reviewed. The optical eye may be
eccentrically moved around the axis of drill pipe 10 by
means of turning handle 48 through a desired amount, in, for
example, the direction of arrow A in Figure 4. The viewing
procedure is then repeated. When handle 48 has completed a
complete revolution the whole inner periphery of the drill
pipe in the region of weld 52 will have been viewed. It is
possible to move the handle 48 continuously or each section
may be viewed independently. The increments of angle
through which handle 48, and eye 28, may be chosen as large
or as small as required.
If the weld 52 has any appreciable longitudinal
dimension, the longitudinal position of the optical eye 28
may be adjusted and the procedure may be repeated. Various
technology is available for monitoring the reflected light
from the inner wall of the drill pipe. For example, the
signals received may be compared with signals from a perfect
weld. Discrepancies will be easily observable. However,
any suitable monitor technology may be employed.
21153~6
-- 10 --
It will be appreciated that although an embodiment of
the invention has been described in connection with a drill
pipe, the apparatus may be used to inspect the interior
surface of bores of many other pipes. It is only required
that the mouth of the pipe be provided with means to engage
with engagement means of mount 18. While use of the
invention in connection with pipes is especially intended,
it may be possible to utilize the invention for inspecting
bore holes such as well shafts, mine shafts, and the like.
In this case it will be necessary to provide a fitting to
the mouth of the bore to provide the necessary engagement
means to the mouth of the bore.
The optical eye works in conjunction with a fluorescent
dye provided on the inside of the pipe. When a defect in
the pipe occurs magnetic interference patterns are set up
and consequently fluorescent particles tend to cluster at
those points. When illumination is provided the dye
fluoresces and a clear picture is obtained which may be
inspected visually or by video. Sometimes it is preferred
to make a video recording of all the regions where
inspection is required so that it may be viewed in comfort
without the necessity of using an eye piece.
