Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
PIPELINE INSPECTION APPARATUS
This invention relates to pipeline inspection
apparatus and more particularly to apparatus movable within
a pipe for detecting potentially damaging and dangerous
flaws in the pipe with a high degree of effectiveness and
reliability. The apparatus produces a photographic record
which can be accurately interpreted and which facilitates
repair of the pipe and, at the same time, the apparatus is
relatively simple and easy to operate.
Background of the Prior Art
Various techniques have heretofore been proposed
for pipe inspection, including magnetic inspection by leakage
field and/or eddy current techniques, gamma or X-ray tech-
niques, ultrasonic techniques, television techniques and
photographic techniques. Each of such techniques may be
used to advantage in certain applications. However, each
technique, as heretofore employed, has serious limitations
in other applications, such as, for example, in the inspec-
tion of pipeline used for transport of natural gas from
o~fshore stations. Natural gas cannot be safely treated
offshore and in a raw state it may include the combination
of carbon dioxide and free water which produces carbonic
acid and causes corrosion of steel, especially when the
temperature is relatively high as is often the case. The
corrosion is augmented by an erosion effect where the rate
of flow is high and at bends and over weld beadis or the
like where the flow is turbulent.
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If locali~ed damage to the pipe could be detected
before it presents a serious problem, it would be possible
to effect repair or to otherwise take corrective measures.
For example, it is possible to move devices known as ~Ipigs~
through a pipe and by moving a series of such pigs through a
pipe, it can be cleaned, etched, washed, dehydrated and then
coated with a protective coating such as an epoxy. Such a
procedure is, of course, relatively expensive especially in
that the pipeline cannot be used for an extended period of
time, and it is not desirable to utilize the procedure
unless and until the necessity therefor can be established
by a suitable inspection. Also, even after a protective
coating is applied, there is the possibility of breaks in
the coating and further periodic inspection is desirable to
make certain that the coating is properly protecting the
pipe. Accordingly, a reliable and accurate way of inspecting
such pipeline for defects would be highly desirable.
As above indicated, prior art techniques are not
satisfactory. Magnetic inspection, if properly performed,
has many advantages including a high degree of sensitivity
to flaws of types which may cause problems and the ability
to cover large distances with suitable magnetic recording
or other information storage equipment. ~owever, there
are disadvantages including the necessity of having
operators with a high degree of skill in order to obtain
an accurate interpretation of the information obtained.
Ultrasonic techniques have a serious disadvantage in that
it is difficult to couple the ultrasonic energy into the
wall of a pipe and television techniques have a serious
disadvantage, at least in the present state of development,
in that a high sensitivity and high resolution is difficult
to obtain especially if a substantial length of pipe is to
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be inspected and the information is to be recorded. If the
information is to be transmitted through a cable, there is
a problem as to loss of sensitivity at great distances and
the difficulty in moving a cable having a large mass through
a pipeline. Photographic techniques as heretofore proposed
have had limitations not recognized in the prior art parti-
cularly with respect to obtaining records which can be
easily and accurately interpreted and also with respect to
reliability.
With regard to specific prior art disclosures,
the Nettles et al. United States Patent No. 2,892,150
discloses a device movable through a pipe and including seal
or cup members for sealing engagement with the inside of the
pipe to permit drive of the device by fluid pressure. A
magnetic testing device is provided for detecting variations
in the thickness of the wall of the pipe and indications
obtained are recorded on a recording tapeO To correlate the
recorded indications with the position of the device while
permitting variations in speed, the recording tape is driven
from a wheel engaged with the inside surface of the pipe.
The Green et al. United States Patent No. 3,064,127
discloses a pipeline survey instrument in which a survey
capsule or "pig" carries cups or sealing flanges engageable
with the inside of a pipe so that the capsule may be moved
through the pipe by fluid pressure. The capsule carries
various instruments for making tests including a radiation
analysis assembly for detecting cavities in the pipe wall, a
caliper assembly for measuring the inside diameter of the
pipe, a water detector and an electric current sensing
assembly. In addition, a recording assembly is provided for
recording the results of the various measurements. Since
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the pig may move at various speeds, the recording assembly
is driven from a wheel engaged with the inside of the pipe
and the measurements are thereby correlated with the distance
along the pipe regardless of the speed of movement of the
pig.
No camera is carried by the pig of the Green et al.
patent. However, the use of a camera for the internal
inspection o~ pipe has been proposed in other prior art
references. For example, the Pulfer United States Patent
No. 3,244,085 discloses a capsule movable along the inside
of a pipe or tube and including a camera and illumination
means. Film exposures are taken at spaced locations along
the length of the pipe or tube, the direction of each
exposure being controlled by a shutter or by control of the
duration of the operation of the illumination means.
Another similar disclosure is contained in the Watts et al.
United States Patent No. 3,667,359 in which the camera and
illumination means are supported by a pig which carries cups
or sealing flanges engageable with the inside of the pipe so
as to be movable by fluid pressure, as in the Green et al.
patent. The Watts et al. assembly also includes a wheel
engageable with the inside of the pipe and connected to the
camera so as to correlate the pictures with the distance
along the pipe.
In both the Pulfer and the Watts et al. devices,
the pictures are taken from one end of the capsule or pig,
the viewing axis of the camera being coincident with the
axis of the pipe and the illumination means being posi-
tioned radially outside the axis of the camera.
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The Watts et al. Patent No. 3,667,359 also dis-
closes an arrangement for directing a gas spray across the
surface of a lens assembly for preventing fogging thereof.
Summarv of the Invention
This invention was evolved with the general object
of overcoming the disadvantages of prior art pipeline inspec-
tion systems and of providing apparatus which can move within
a pipeline and which will detect potentially dangerous flaws
with a high degree of reliability and effectiveness and which
produces records which ~an be easily and accurately interpreted.
Important facets of the invention relate to the
recognition of problems with arrangements such as proposed
in the prior art~ One problem relates to the production
of photographic records which can be accurately interpreted
in a manner such that standards can be established for
determining whether a pipe is satisfactory or whether steps
should be taken to repair the pipe or otherwise take a cor-
rective measure.
In accordance with this invention, an orientation
of the viewing axis is used which has been found to produce
highly advantageous results. In particular, a viewing axis
is provided which is transverse to the axis of the pipe and
a generally rectangular image is produced which corresponds
to a generally rectangular surface area of the pipe with
length and width dimensions, respectively, corresponding to
the axial length and arcuate width dimensions of the internal
surface area of the pipe.
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It is found that the orientation in which the
viewing axis is normal to the axis of the pipe is highly
advantageous in that the relationship between the size of
defects and the size of the corresponding portions of the
images produced on the developed film is substantially
uniform. This is particularly true when the illumination
means projects a beam toward the internal surface area of
the pipe at a generally uniform acute angle to the axis of
the pipe. Thus, the dimensions of shadows produced are
generally uniformly proportional to the size of recesses in
the internal surface area of the pipeO It is found that
such relationships cannot be readily obtained with the
second orientation in which the viewing axis is substan-
tially coincident with the pipe axis. It is also difficult
to obtain uniform illumination such that the size of recorded
indications bear a readily determinable relationship to the
sizes of the actual recesses in the surface of the pipe.
For these reasons, the first orientation is highly advanta-
geous and is much to be preferred over the second orientation.
Further problems which have not been recognized
and dealt with relate to those wh~ch arise when extremely
long lengths of pipe must be inspected. When many miles of
pipe are to be inspected, it is not possible to carry
enough film and to otherwise make it possible to photograph
all portions of the pipe. In order to make the most effec-
tive use of time, equipment, and materials, it i5 found to
be highly desirable to restrict the pictures to only those
portions of the pipe in which defects are most likely to
occur. One portion of the pipe of primary interest is the
lower part of the pipe in which water may collect to combine
with carbon dioxide and cause corrosion. To restrict the
taking of the pictures to the lower portion of the pipe, the
camera support is rotatable relative to the axis of the
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pipe, so that it may be weighted to be positioned at a
predetermined angular position and thus the camera may be
positioned so that the viewing axis is directed straight
downwardly or at any desired angular position relative to
the pipe. In one type of construction, a support is pro-
vided including wheels engaged with the inside of the pipe,
and the camera support is journalled through suitable
bearings. In another arrangement, an entire pig is so
weighted as to assume a predetermined angular position, the
camera support being adjustably positionable at a certain
angular position relative to the weighted pig.
It is also desirable to record images where there
are magnetic discontinuities and magnetic leakage field
detector units are provided for use in detecting magnetic
discontinuities, such being usable to trigger the operation
of the camera.
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In accordance with a specific feature of the
invention, circuitry including a delay circuit is provided
for responding to signals produced from the magnetic leakage
field detector units to activate the camera and illumination
means in a manner such that a picture is produced of the
area producing such signals.
; In addition to producing pictures where there are
magnetic discontinuities including pipe welds, pictures may
be taken at predetermined positions along the pipe suffi-
cient in number to insure a high degree likelihood of
detecting any problems which might exist while conserving on
the amount of film used.
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~03 Additional features of the invention relate to
04 construction of the apparatus in a manner such that it is very
05 rugged and relia~le and capable of being moved through long
06 lengths of pipeline without damage to the camera and other
07 instrumentation carried by the apparatus and while also avoiding
08 any damage to the pipeline.
09 In one type of construction, the camera may be moved by
means of wheels engaged with the inside surface of the pipe and
11 driven by drive means including an electric motor or other power
12 source. In another type of construction, the camera may be
~13 supported on a pig which is moved through the pipe by a fluid
14 pressure differential on opposite sides thereof. In the
~`15 construction in which wheels are used, the assembly may be
16 connected to a cable and reversing means are provided for
17 automatically reversing the drive when the device is moved a
18 certain distance in the pipe. The drive means may preferably be
~19 operated to a release condition to permit withdrawal of the
device through a tether.
21 According to one embodiment of the invention, in pipe
22 inspection apparatus, a device is arranged to be inserted into a
23 pipe for longitudinal movement therewithin. Photographic camera
24 apparatus is carried by the device including film storage and
transport apparatus arranged for feeding film through an image
` 26 area and optical apparatus for projecting to the image area an
, 27 image from an internal surface area of the pipe. Illumination
28 apparatus illuminates the internal surface area of the pipe, and
~29 operating apparatus operates the film storage and transport
~30 apparatus and the illumination apparatus during movement of the
31 device along the pipe for recording on the film a sequence of
32 images of the internal surface of the pipe. Drive apparatus
33 including drive wheel apparatus engages the inside surface of the
34 pipe and motive power apparatus rotates the drive wheel apparatus
to move the device along the pipe. Connection apparatus is
36 adapted for connecting a tether to the device for withdrawal of
37 the device from the pipe independently of the drive apparatus.
38 The drive apparatus is operable between a drive condition wherein
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-~03 the drive wheel apparatus are in pressure engagement with the
~04 inside surface and are coupled to the motive power apparatus to
05 develop a relatively high frictional force opposing movement of
06 the device by the tether and a release condition in which the
~07 frictional force is reduced to a relatively low value, and
08 apparatus interconnecting the connection apparatus with the drive
09 apparatus for operating the drive apparatus to the release
condition in response to application of a predetermined force by
~11 the tether.
12 According to a further embodiment, reversing apparatus
13 is operable upon movement of the device through substantially a
14 predetermined distance along the pipe for reversing the drive
apparatus to effect movement of the pipe in a reverse direction.
16 The reversing apparatus is comprised of apparatus for developing
~17 an electrical pulse in response to movement of the device through
~18 a certain distance. Counter apparatus counts a predetermined
`;~19 number of the pulses to develop a reversing signal, and apparatus
responsive to the reversing signal reverses the drive apparatus.
21 According to a further embodiment, in pipe inspection
22 apparatus, a device is arranged to be moved downward through a
23 vertically extending pipe section and thence into a horizontal
-24 pipe section for longitudinal horizontal movement therein. The
~25 device is comprised of photographic camera apparatus including
~26 apparatus defining a rectangular image area, film storage and
27 transport apparatus arranged for feeding film through the image
28 area and optical apparatus for projecting an image to the image
29 area. The optical apparatus is arranged to project the image
~30 along a viewing axis from an internal surface area of the pipe
31 with the viewing axis being normal to the axis of the pipe and
32 with the generally rectangular image being produced in the image
- 33 area which corresponds to a generally rectangular internal
` 34 surface area of the pipe and which has length and width
dimensions respectively corresponding to the axial length and
36 arcuate width dimensions of the internal surface area.
37 Illumination apparatus illuminates the internal surface area of
38 the pipe. Operating apparatus operates the film storage and
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03 transport apparatus and illumination apparatus during movement of
04 the device along the pipe for recording on the film a plurality
05 of images corresponding to axially spaced generally rectangularly
" 06 surface areas of the pipe. The illumination apparatus is spaced
`~ 07 axially from the viewing axis and is arranged to project light
; 08 toward the internal surface area of the pipe in a direction at a
09 substantially uniform acute angle to the axis of the pipe and
with substantially uniform intensity, the relationship between
11 the direction of the light and the surface of the pipe being
12 substantially uniform throughout all of the internal surface of
13 the pipe such that shadows are produced across recesses in the
14 internal surface area of the pipe and such that there is a
substantially uniform relationship between the size of the images
~- 16 of the shadows and the size of corresponding recesses in the
~17 internal surface area. Engagement apparatus including at least
18 two axially spaced cup members defining resilient annular flanges
19 are in engagment with axially spaced portions of the inside
surface of the pipe. A central housing section supports the
~21 camera and illumination apparatus therewithin. A pair of cup
~22 member support structures is secured to opposite ends of the
23 central housing section for support of the central housing
; 24 section from the cup members. The viewing axis is approximately
mid-way between the cup member support structures. Weight
26 apparatus operative under the force of gravity urges the device
27 toward a certain angular position when moving longitudinally
28 through a horizontal pipe section and places the viewing axis at
2~ a predetermined angular position relative to the pipe.
This invention contemplates other objects, features and
` 31 advantages which will become more fully apparent from the
32 following description taken in conjunction with the accompany
~33 drawings.
34 Brief Description o~ the Drawings
FIGURE 1 is a side ele~Jational view, partly in section,
36 illustrating pipe inspection apparatus constructed in accordance
~37 with the invention;
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FIGURE 2 illustrates diagrammatically in side
elevation the positioning of camera and strobe light units
of the apparatus in relation to the pipe;
FIGURE 3 is another diagrammatic view looking from
a position as indicated by line III-III of Figure 2;
FIGURE 4 is a sectional view taken substantially
. along line IV-IV of Figure l;
` FIGURE 5 is a top plan view of another form of
ii^~! apparatus constructed in accordance with the invention;
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~, 10 FIGURE 6 is a side elevational view of the apparatus
, of Figure 5;
FIGURE 7 is a side elevational view of another
form of apparatus according to the invention;
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FIGURE 8 is a sectional view taken substantially
along line VIII-VIII of Figure 7;
- FIGURF 9 is a schematic electrical diagram for
the apparatus of Figures 7 and 8;
~ FIGURE 10 is a view illustrating a modified apparatus
;: constructed in accordance with the invention, shown moving
~ 20 through a bend portion of a pipeline;
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FIGURE 11 is a side elvational view of a drive
unit of the apparatus of Figure 10; and
FIGURE 12 is a schematic electrical diagram of the
apparatus of Figures 10 and 11.
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;`` ~escription of Preferred Embodiments
Reference numeral 10 generally designates a pipe
inspection apparatus constructed in accordance with the
principles of this invention. The illustrated apparatus 10
is in the form of a "pig" device similar to those used for
, cleaning, washing and coating pipes and it includes two rear-
; ward cups 11 and 12 and two forward cups 13 and 14 which are
respectively disposed behind and in front of a central
housing section 15 in which a camera assembly 16 is sup-
ported. The cups 11-14 are of a resilient elastomeric
material and define flanges for resilient sealing engagement
with the inside surface 17 of a pipe 18, permitting the
apparatus to be driven by the pressure of gas pumped through
the pipe 18 or by the pressure of compressed air or the like
pumped into the pipe 18. The pipe 18 may, for example, be
used to carry raw natural gas from an off-shore location to
an on-shore processing station and the apparatus 10 is
designed to produce high resolution photographs which will
reveal erosion and corrosion at pipe bends, pitting at
~ 20 circumferential welds and heat-affected areas and corrosion
;~ such as caused by puddles at low pipe line areas.
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The camera assembly 16 includes a lens disposed
above a protective glass plate 2~ held by a support 21 on
a horizontal wall portion 22 of the section 15. To illu-
minate the surface of the pipe, a pair of strobe lights are
provided behind a pair of ports 23 and 24 which are disposed
on inclined wall portions 25 and 26 of the central housing
section 17, the ports 23 and 24 having ylass windows for
transmission of light therethrough.
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As diagrammatically shown in Figures 2 and 3, the
camera assembly 18 includes a camera 28 having a lens 29
which projects an image to a film plane at which a film 30
is moved from a supply reel 31 to a take-up reel 32, suitable
electrically operated drive means being provided for driving
the take-up reel 32 to advance the film 30 for taking each
picture. With this arrangement, and with the viewing axis
of the camera, indicated by broken line 34, being normal to
~` the axis of the pipe, a generally rectangular image is
projected to an image area of the film 30 which corresponds
`~ to a generally rectangular internal surface area of the
` pipe. The image has length and width dimensions which
respectively correspond to the axial length and arcuate
width dimensions of the internal surface area. Thus, as
indicated diagrammatically by lines 35 and 36 in Figure 2,
the forward and rearward limits of the rectangular image
area on the film may correspond to rearward and forward
` limits of a generally rectangular surface area of the
~ internal surface 17 of the pipe 18. As indicated by lines
; 20 37 and 38 in Figure 3, the side limits of the rectangular
image area of the film 30 may correspond to arcuately spaced
limits of a generally rectangular surface area of the internal
surface 17 of the pipe 18.
As also shown diagrammatically in Figure 2,
strobe lights 39 and 40 are mounted behind the ports 23
and 24 to project beams of light along axes as indicated by -
broken lines 41 and 42. Each strobe light is spaced axially
from the viewing axis and each projects a beam of light
toward the internal surface area of the pipe which is to be
photographed, along an illumination direction at an acute
angle to the axis of the pipe.
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The arrangement with the viewing axis of the
camera at right angles to the axis of the pipe, thereby
producing a generally rectangular image corresponding to
a generally rectangular internal surface area of the pipe,
is highly advantageous in that the relationship between the
size of defects and the size of the corresponding indica-
tion on the film is substantially uniform. As a result,
standards can be established for determining whether a pipe
can be passed as being satisfactory or whether remedial
action should be taken to repair or service the pipe. The
necessity ~or requiring an inspector of the film to exercise
critical judgment is minimized.
The illumination of the surface area of the pipe
as disclosed is also advantageous for similar reasons, it
being noted that the relationship between the direction of
the light and the surface of the pipe is substantially
uniform throughout the entire internal surface area of
the pipe which corresponds to the image produced.
Since the internal surface area of the pipe which
is photographed is of limited angular extent, it is important
that the portion photographed be selectable and identifiable.
It is also found to be important that the pictures be taken
in an angular direction which has the greatest likelihood of
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producing indications of any critical defects which may exist.
In inspecting horizontal runs of pipelines such as used for
, conveying raw natural gas, it is found that the lower portion
of the internal surface of the pipe is generally of primary
/- interest because liquids can accumulate to cause corrosion
.' of the pipe under certain conditions. In accordance with
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the invention, the apparatus 10 is weighted in a manner such
that the viewing axis 34 of the camera may be in a vertical
plane through the axis of the device or at any desired angle
relative to such a vertical plane.
In Figure 1, a rearward cup assembly including the
rearward cups 11 and 12 and associated elements is shown in
section. As illustrated, a spacer structure 44 is sandwiched
between the cups 11 and 12 and a holding ring 45 is disposed
against the rear side of the rear cup 11 while a plate 46 is
disposed against the forward face of the cup 12. The forward
face of the plate 46 is recessed to receive the rearward end
of the central housing section 15, a radially inwardly
facing annular shoulder 47 being provided which engages a
rear end of an annular flange portion 48 of the central
housing section 15. Four bolts 49 are provided having head
portions engaging the plate 46 and having shank portions
extending through the cup 12, spacer structure 44, cup 11,
plate 45 and washers 50 with nuts 51 being threaded on the
rearward terminal ends of the shank portions of the bolts 49.
The forward cup assembly which includes cups 13
and 14 is similar to the rearward cup assembly and includes
a spacer structure 52 similar to the spacer structure 44, a
ring 53 similar to the ring 45 and four bolts 55.
To hold the rearward and forward cup assemblies
against the rearward and forward ends of the central housing
section, four elongated bolts 58 are provided which have
shank portions extending through the forward cup assembly,
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thence through sleeves 59 positioned between the rearward
end of the forward cup assembly and the plate 46 at the
forward end of the rearward cup assembly, thence through
the rearward cup assembly and through washers 60 with nuts
61 being threaded on the rearward terminal ends of the
elongated bolts 58.
The spacer structure 44 is formed from a pair of
rings ~3 and 64 and a plurality of spacer sleeves 62 through
which the shank portions of the connecting bolts 49 and 58
extend. To weight the apparatus so as to cause it to
assume a predetermined angular position, a weight member 66
of semi-cylindrical shape is located between the rings 63
and 64. The weight member 66 is of a heavy material, prefer-
ably lead, and a similar weight member is preferably included
in the forward cup assembly.
For most applications, the viewing axis of the
camera is preferably at a six o'clock position so as to be
in a vertical plane through the axis of the apparatus and so
as to produce photographs of the bottom of the pipe where
corrosion may be produced as the result of the accumulation
of liquid, particularly in low pipeline areas. However, the
viewing axis may be positioned at any desired angular posi-
tion. To adjust the viewing axis of the camera, the nuts 61
may be loosened and the central housing section 15 may then
be rotated to the desired angular position relative to the
weights of the cup assemblies a~ter which the nuts 61 may be
tightened to securely lock the housing section 15 in the
desired angular position.
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The illustrated apparatus may be propelled by the
pressure of a gaseous medium in the pipeline, either the
natural gas or other product normally carried by the pipe-
line or compressed air or the like introduced into the
pipeline. The illustrated apparatus may thus be self-pro-
pelled or it may, in the alternative, be propelled by a
towing pig in which case cups of the apparatus may be
provided with openings or grooves for passage of the gaseous
medium past the apparatus to the towing pig.
In the apparatus 10 of Figures 1-4, the entire
apparatus is rotated to a predetermined angular position
whereby the force of gravity acts on the weights which are
positioned to place the center of gravity of apparatus to
the offset of the angular position. It is also possible
to support the camera for rotation by the pipe axis to a
predetermined angular position while supporting the camera
from support means non-rotatably engaged with the inside
surface of the pipe. Referring to Figures 5 and 6, refer-
ence numeral 6~ generally designates an apparatus in which
the camera is supported for rotation about the pipe axis
from the support structure non-rotatably engaged with the
pipe.
The apparatus 68 is in the form of a camera unit
and it includes a camera 70 which includes electrically
operated film storage and -transport means whereby photo-
graphic film is moved from a supply reel within one end
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portion 71 of a housing 72 to a take-up reel within an
opposite end portion 73 of the housing 72. The camera
70 further includes a lens assembly 74 which operates to
project an image of the inside surface of the pipe onto a
section of the film positioned at an image area interme-
diate the supply and take-up reels.
To illuminate the inside surface of the pipe, an
electrically operated strobe flash unit 76 is provided
arranged to project a beam of light along an axis 77 which
intersects the central axis of the lens 74, indicated by
reference numeral 78, at a point on the inside surface of
the pipe.
The orientation of the illumination and lens axes
77 and 78 are of substantial importance. Preferably, the
lens axis is generally normal to the inside surface of the
pipe, i.e., at substan~ially a right angle to the pipe axis
and the illumination axis is at an acute angle, preferably
on the order of 45 degrees or less. Corrosion pits or the
like cast shadows such that from inspection of a developed
picture, an accurate estimate can be made with xespect to
the depth of a pit or the like and as to whether it neces-
sitates a repair opera~ion on the pipe.
A counter 80 is energized from pulses generated
in response to movemen~ of the apparatus within the pipe
and registers the distance traveled, being disposed within
the field of ~iew of the lens 74 so as to record the posi-
tion in each film frame.
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The camera 70 is secured to a frame 81 which
carries caster wheel assemblies 82, 83 and 84 at one end
thereof. At the opposite end thereof, the camera support
frame 51 is hingedly connected through a hinge pin 85 to
a plate 86 which is hingedly connected through a pin 87
to a second plate 88 which, in turn, is connected through
a third pin ~9 to a support plate 90, the axes of the pins
85 and 87 being in spaced parallel relation and the axis
of the pin 89 being at risht angles ~o the axes of the pins
85 and 87. A coiled tension spring 91 is secured between
an outer end of the camera support frame 81 and the support
plate 90 to normally hold the end o~ the camera frame 81
and the plates 86, 88 and 90 against one another as shown.
In moving through ~urns or bends in the pipe, the camera
frame 81 may, if necessary, pivot relative to plate 86
about the axis of pin 85 or the camera frame and the plate
86 may together pivot relative to the plate 88 and the axis
of the pin 87 or the camera frame 81 and plates 86 and B8
may pivot relative to the plate 90 about the axis of the
pin 89.
The support plate 90 carries the strobe unit 76
and the counter 80 and is supported through a pair of posts
92 and 93 from a frame 94 which is journalled within a
cylindrical housing 95 for movement about the axis of the
cylindrical housing 95, preferably with one ball-bearing
assembly 96 being provided at one end of the housing 95
and another similar assembly being provided at the other
end. Suitable slip rings are pro~ided within the cylin-
drical shell or housing 95 for transmission of electrical
control signals to the camera 70, strobe unit 76 and
counter 80.
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To support the housing 95 for movement within
the pipe, it carries three wheel assemblies 98 spaced
equi-angularly, 120 degrees from each other, each including
a frame 100 extending longitudinally in generally parallel
relation to the axis of the housing 95 and carrying a pair
of wheels 101 and 102 at the opposite ends thereof, the
frame 100 being supported from the housing 95 through
compression sprinas 103, 104 and ].05, operative to urge
the wheels 101 and 102 into engagement with the inside
surface of the pipe.
The apparatus 68 may be propelled by means of a
motor-driven drive unit as disclosed in our prior copending
application or it may be propelled by a suitable towing pig.
For such purposes, a bar 106 is connected through a U-joint
107 to one end of the housing 95.
Figure 7 shows a modified form of apparatus which
is in the form of a camera unit 110 similar to the camera
unit 68 of Pigur~s 5 and 6 and having a camera 111 on a
frame 112 which is supported ~hrough a hinge assembly from
a support plate 114 which is supported through posts 115
and 116 from a frame journalled in a housing 117. Housing
117 is supported for movement wi~hin a pipe 113 through
three wheel assemblies 119, each including a frame 120
which carries wheels 121 and 122 and which is connected to
the housing 117 through compression springs 123, 124 and
125. A flash unit 126, corresponding to flash unit 76, s
mounted on the support plate 114.
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Magnetic detection means are provided for sensing
inhomogeneities in the pipe. In the illustrated arrangement~
three units 127, 128 and 129 are provided, each of which
extends arcuately, the three units being offset axially and
being in overlapping relation to cover an arcuate distance
corresponding ~o the arcua~e dimension of the effective field
of view of the camera. The units 127-129 may have the same
construction and may be resiliently supported in substantially
the same way. Unit 127 may, for example, include an arcuate
core 131 of permanently magnetized material and of generally
U-shaped cross-sectional form with a coil 132 wound thereon.
When the unit moves over a corrosion pit or other discontin-
uity in pipe 118, the magnetic linkage field of the permanent
magnet core 131 changes, inducing a corresponding electrical
signal in the coil 132. Core 131 is supported from the sup-
port plate through springs 133 and 134 for resiliently
yieldable contact with the inside of pipe 118.
The camera unit 110 also incorporates means for
sensing changes in the internal dimensions or configuration
of the pipe such as caused by indentations, bends or obstruc-
tions. Such means include three switch units 136, each
associated with ~he ~rame 120 of one of the wheel assemblies
119 to be actuated when the fra~e is moved radially inwardly
a predetermined e~tent.
Figure 9 is a schematic diagram of the electrical
connection of units of the camera unit 110 of Figures 7 and
~. The magnetic leakage field de~ector units 127~129 are
~3~53~4
- 20 -
connected through amplifiers 137-139 and through circuitry
140 to a threshold detector 141 which develops an output
signal in response to a leakage field signal having an
amplitude greater than a predetermined amplitude.
The output signal so developed is applied to a
delay circuit 142 which after a certain delay, propor~ional
to the speea of travel of the appar~tus, applies a signal
to the strobe unit 126 of the camera unit 110 so as to take
a picture of the portion of the pipe which produced the
signal de~eloped by the magnetic detection circuit. The
signal applied to the strobe is also applied through a
delay circuit 144 to a film advance control 145 of the
camera of the unit 110.
~he switch units 136 are connected through
circuitry 146 to another delay circuit 147 which after
a certain delay, proportional to the speed of travel of
the apparatus, applies a signal to the strobe unit 126
and also to the delay circuit 144. It is noted ~hat the
direction of movement of the unit 110 is assumed to be
to the right as viewed in Figure 7 so that the dimensional
and magnetic detector means is ahead of the camera unit.
The arrangement of Flgures 7~ 8 and 9 is par-
ticularly advantageous in inspection of long pipeline
runs, in which it is desirable to avoid unnecessary
consumption of film and to restrict the picture-taking
to those sections of the pipe which are of possible
interest as indicated by dimensional changes or the
presence of magnetic discontinuities.
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It may be noted that the camera in any case may
be rotated about the axis of the pipe to various positions
and/or suitable split mirrors or other optical elements may
be used to effect taking of the picture of the entire
internal surface of the pipe. In most applications, however,
the taking of pictures may be restricted to the lower part
of the inside surface of the pipe, where corrosion is apt to
occur because of the accumulation of liquid, and the apparatus
of Figures 1-4 is advantageous in this respect.
The apparatus of Figures 1-4 is also advantageous
in that the camera and the strobe lights are supported in
well-protected positions behind glass windows of the ports
in the central housing section 15. It is further noted that
with the central housing section being disposed between the
forward and rearward cup assemblies, a protected region is
provided for the taking of the pictures. The arrangement
thus serves to minimize problems with interference due to
puddles of liquid in the pipe, splashing of liquids and
liquid droplets or vapors in the air or gas in the pipe.
Z0 Reference numeral 150 generally designates a modi-
fied type pipe inspection apparatus constructed in accordance
with the principles of this invention. The apparatus 150 is
shown in a bend of a pipe 157 which may, for example, be a
bend at the lower end of a vertical pipe section which extends
down from an off-shore station.
The illustrated apparatus 150 includes a camera
unit 152 and a drive unti 153 with a coupling therebetween
including a bar 154 having opposite ends coupled to the
units 152 and 153 through U-joints 155 and 156.
The illustrated drive unit 153 includes three motor-
driven wheel assemblies 158 each including a pair of wheels 159
on a shaft 160 driven through a gear reduction unit 161 from an
electric motor 162. The housing of each motor 162 is hingedly
connected to a frame member 164 through a pin 165 and at the
opposite end, a compression spring 166 acts between a pin 167
carried by the frame member 164 and a socket member 168 which
is secured to the housing of the gear reduction unit 161, the
wheels 159 being urged radially outwardly into pressure engage-
ment with the inside surface of the pipe 151. Pin 167 may be
withdrawn for release of pressure as hereinafter described.
The three wheel assemblies 168 are preferably in equi-angularly
spaced relation, 120 degrees from each other.
At the opposite end of the drive unit, three idler
wheel assemblies 170 are provided, each including a pair of
wheels 171 urged radially outwardly by a spring 172, the
assemblies 170 being preferably spaced e~ui-angularly, 120
degrees from each other. A battery unit 174 is carried by
the frame of the drive unit 153 between the motor-driven
wheel assemblies 158 and ~he idler wheel assemblies 170 and
an electrical control unit 175 is carried on a projecting
frame member 176. A hook 177 is provided on the terminal end
of the frame member 176 for connection to a tether cable 178.
.
The camera unit 152 includes a camera 180 (Figure
12) which includes electrically operated film storage and
transport means whereby photographi~ film i5 moved from a
supply reel 181 within one end portion of a housing 182 to
a take-up reel 183 within an opposite end portion of the
housing 182. The camera 180 further includes a lens assembly
184 which operates to project an image of the inside surface
of the pipe onto a section of the film positioned at an image
area intermediate the supply and take-up reels.
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To illuminate the inside surface of the pipe, an
electrically operated strobe flash unit 186 is provided
arranged to project a beam of light along an axis 187 which
intersects the central axis of the lens 184, indicated by
reference numeral 188, at a point on the inside surface of
the pipe.
The orientation of the illumination and lens axes
187 and 188 are of substantial importance. Preferably, the
lens axis is generally normal to the inside surface of the
pipe, i.e., at substantially a right angle to the pipe axis
and the illumination axis is at an acute angle, preferably
on the order of 45 degrees or less. Corrosion pits or the
like cast shadows such that from inspection of a developed
picture, an accurate estimate can be made with respect to
the depth of a pit or the like and as to whether it necessi-
tates a repair operation on the pipe.
A counter 190 is energized from pulses generated
in response to movement of the apparatus within the pipe and
registers the distance travelled, being disposed ~ithin the
field of view of the lens 184 so as to record the position
in each film frame.
The camera 180 is secured to a fra~e 191 which may
carry suitable caster wheel assemblies at one end thereof,
using a construction such as shown in Figures 5 and 6, for
example.
Figure 12 is a schematic diagram of electrical cir-
cuitry for the apparatus 150. Control circuitry 196 is
connected through lines 198l 199 and 200 to the camera 180,
strobe unit 186 and counter 190 and is also connected to a
switch device 202 which is operated from one of the wheels
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- 24 -
engaged with the inside surface of the pipe, such as one of
the idler wheels 171 and which generates a pulse in response
to rotation of the wheel through a certain angle and thereby
in response to movement of the apparatus a certain distance.
Electronic counter means are provided in the control circuitry
l99 to apply a triggering signal to the strobe unit 186 after
a certain number of such pulses. After a certain delay,
indexing pulses are applied to the counter l90 and also to
film drive means of the camera 180.
Motor control circuitry 204 is provided which is
connected to the battery unit 174 and to the drive motors
162 and also to the control circuitry 196 and a start switch
206. With the apparatus disposed in one end of a pipeline or
in a launching pipe section which feeds into a pipeline, the
start switch 206 is depressed to cause energization of the
drive motors 162 and to initiate movement of the apparatus
along the pipeline. The apparatus may continue movement
until it reaches the other end of a pipeline. Alternatively,
counter means within the motor control circuitry 204 may
respond to signals from the control circuitry 196 to operate
after a certain number of pulses are applied and thereby
after the--apparatus travels a certain distance, to reverse
the polarity of the voltages applied to the motors 162 and
to cause the apparatus to move in the reverse direction and
return to its initial position. This automatic reversing
feature is highly advantageous in that the portion of a
pipeline extending only a relatively short distance such as
from 1,000 to 2,000 feet away from an offshore station may
be inspected. Many of the problems which can be detected
by the apparatus are found within such a relatively short
distance frorn offshore stations and the use of the apparatus
in this way is thus highly productive. Also, it does not
require that the apparatus be capable of travelllng very
large distances.
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A very high degree of reliability can be obtained
with drive means such as illustrated but it is nevertheless
desirable to provide a back-up in the event of failure of
the drive means, and it is for this reason that the hook 177
is provided for connection to the tether cable 178, so that
the apparatus can be withdrawn by means of the cable 178.
It is noted that the motor-driven wheel assemblies 158
desirably include the gear reduction units 161 which allow
the motors to be operated at relatively high speeds so as to
be of relatively small si~e. With such gear reduction units,
however, it is found that in case of deenergization of the
motors, the high degree of friction is encountered when
attempting to move the apparatus by means of the tether
cable 178. In accordance with a specific feature, a spring
210 is provided in the connection between the cable 178 and
the hook 177 and three lines 211 are provided between the
cable 178 and the pins 167 of the drive wheel assemblies.
When the tension in the cable 178 reaches a predetermined
level, the spring 210 is stretched to an extent such that
the cable 178 acts through the lines 211 to retract the
pins 167 and to allow the inner ends of the springs to move
inwardly and thus release the pressure applied by the wheels
159. Accordingly, the apparatus can be readily withdrawn,
friction being minimized.
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