GB2293072A

GB2293072A - A method of examining an inaccessible surface

Info

Publication number: GB2293072A
Application number: GB9417231A
Authority: GB
Inventors: Daniel Alexander Constantinis
Original assignee: E M & I
Current assignee: E M & I
Priority date: 1994-08-26
Filing date: 1994-08-26
Publication date: 1996-03-13
Also published as: AU3187995A; WO1996007093A1; GB9417231D0

Abstract

A method of examining the condition of the bottom wall surface in VLCC tanks in which bell-mouth shaped lower ends (12) of oil outlet pipes (11) are disposed closely adjacent the bottom wall (10) of the vessel, and comprising a camera (14) mounted on an articulated arm system (15) so that it may be introduced through the narrow gap beneath the bell mouth pipe end and raised to an elevated position. The camera (14), preferably video, is remotely connected to a monitor whereby the tank wall beneath the bell mouth may be inspected preferably with the aid of illumination from an array of lights (17) disposed around the camera lens (16). A pair of graduated scales (18) enable accurate location of the inspected site, and an ultrasonic probe (19) may be introduced also through the narrow gap beneath the bell mouth pipe end to provide a measurement of wall thickness. This method and apparatus enable accurate and ready inspection of the wall surface without the need for removal of a lower part of the outlet pipe. The array of lights can produce radiation in the IR range. <IMAGE>

Description

A METHOD OF AND APPARATUS FOR EXAMINING A WALL SURFACE THIS INVENTION concerns a method of and apparatus for examining the condition of a wall surface and particularly, though not exclusively, a concealed area of a wall surface disposed beneath a bell mouth-shaped input end of an outlet pipe in an oil tank.

In VLCC's (very large crude carriers) for transporting crude oil by sea the oil is fed into and discharged from each tank section via one or more fixed upright pipes within the tank, each pipe having a bell mouth-shaped lower end disposed closely adjacent the bottom wall of the vessel, and the narrow gap through which the oil must flow from and into the pipe creates an increased flow velocity in the immediate vicinity which can cause deterioration of the wall surface sometimes to the extent that the thickness of the wall is reduced to a dangerous level. Regular inspection of the concealed area of the tank wall is prevented by the fixed outlet pipe and, hitherto, this has required removal of the lower region of the pipe so that the condition of the wall could be inspected.Such removal is often time consuming in view of the potentially explosive environment within such vessels and associated pipework, and so the removal is arduous and costly.

It is therefore an object of the present invention to provide a method of and apparatus for examining the condition of the wall surface beneath the input end of an outlet pipe in a vessel of this kind without the necessity for removal of any part of the pipe.

According to the present invention there is provided a method of examining the condition of a wall surface beneath the input end of an outlet pipe in a vessel for transporting liquid, where the said pipe input end is fixed closely adjacent the wall surface, comprising the steps of introducing a camera through a narrow gap between the pipe input end and the wall surface, illuminating at least a part of the wall surface beneath said pipe input end, and transmitting to a remote location signals representing a visual image of the wall surface beneath the pipe.

Preferably, the camera is manoeuvred over the wall surface and a graduated scale is introduced whereby the instantaneous position of the camera may be determined and recorded.

The method preferably includes the further step of introducing through said narrow gap an ultrasonic probe and manoeuvring same to measure the thickness of the vessel wall at any selected location beneath the pipe input end.

Further according to the present invention there is provided apparatus for examining the condition of a wall surface beneath the input end of an outlet pipe in a vessel for transporting liquid, where said pipe input end is fixed closely adjacent the wall surface, comprising a camera mounted on a support system such that the camera may be introduced through a narrow gap between the pipe input end of the wall surface, means on said camera for illuminating a part of the wall surface beneath said pipe input end, said camera being electrically connected to means for receiving signals therefrom representing a visual image of the wall surface beneath the pipe, and a graduated scale adapted to be positioned across the pipe input ends.

Preferably, said illuminating means comprises an array of light sources disposed on the camera and extending around the camera lens.

Furthermore, said array of light sources preferably produce light in the infra-red frequency range.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which: Fig. 1 illustrates a part of the bottom wall of an oil tank of a VLCC, and a lower region of an outlet pipe fixed therewithin; and Fig. 2 is an enlarged schematic view of a camera being part of the apparatus illustrated in Fig. 1 for inspecting the bottom wall of the tank.

Referring now to Fig. 1 there is fixed above the vessel bottom wall 10 an upright pipe 11 having an outwardly diverging bell mouth 12 whose lower open end 13 is located typically 25mm above the surface of the bottom wall 10.

To examine the condition of the wall surface beneath the bell mouth 12 for any deterioration, a camera 14 mounted on an articulated arm system 15 is introduced through the 25mm gap beneath the bell mouth 12 and may then be manoeuvred as illustrated to an elevated position thus to scan the otherwise concealed area of the wall surface 10.

Preferably, the camera 14 is of the type to produce video signals which are transmitted to a monitor and recorder (not shown) at a remote location.

To illuminate the wall surface sufficiently to produce a visible image, there is provided as shown in Fig. 2, around the camera lens 16 a preferably circular array of infra-red light sources 17 to provide uniform distribution of the light cast onto the bottom wall surface 10.

Before or after introduction of the camera 14, there is preferably placed across the open end of the bell mouth 12 a pair of graduated scales 18 at right-angles to one another. In this way the camera 14 may record an image according to its exact location on the surface. By manoeuvring the camera both vertically and horizontally on the articulated arm system both overhead and planar views may be taken of the wall surface.

In practice, the articulated arm system 15 of the camera will be manoeuvred by a first operator who introduces the camera beneath the bell mouth 12 and who will manoeuvre the camera as required by a second operator stationed at the video monitor. Thus, the two operators will combine to produce and record images of the entire concealed area of the wall surface beneath the bell mouth 12.

After such information is received and recorded, perhaps also on a computer, an ultra-sonic probe 19 may be introduced by the first operator, again beneath the bell mouth 12 and, with the aid of the camera, be position as required to measure the thickness of the wall 10 in any desired location thereon. Thus, any deterioration or voiding of the wall 10 beneath the surface may be measured by this means.

Inspection of the wall surface using this technique and the apparatus described, may be carried out on a regular basis and in the event of deterioration, the bell mouth may be removed to permit restorative work on the wall. However, if no deterioration has occurred removal of the bell mouth is avoided.

It will be seen therefore that the method and apparatus of the invention will substantially reduce the need for regular removal of the bell mouth ends of outlet pipes in VLCC tanks whilst ensuring that any deterioration in the condition of the tank walls may be detected early and prevented from progressing to a dangerous extent.

Claims

1. A method of examining the condition of a wall surface beneath the input end of an outlet pipe in a vessel for transporting liquid, where the said pipe input end is fixed closely adjacent the wall surface, comprising the steps of introducing a camera through a narrow gap between the pipe input end and the wall surface, illuminating at least a part of the wall surface beneath said pipe input end, and transmitting to a remote location signals representing a visual image of the wall surface beneath the pipe.

2. A method according to Claim 1, wherein the camera is manoeuvred over the wall surface and a graduated scale is introduced whereby the instantaneous position of the camera may be determined and recorded.

3. A method according to Claim 1 or Claim 2, including the further step of introducing through said narrow gap an ultrasonic probe and manoeuvring same to measure the thickness of the vessel wall at a selected location beneath the pipe input end.

4. A method according to any preceding claim, wherein the camera, once introduced through the narrow gap between the pipe input end and the wall surface, is manoeuvred to a position spaced from the wall surface thus to scan the area of the wall surface obscured by the pipe.

5. Apparatus for examining the condition of a wall surface beneath the input end of an outlet pipe in a vessel, where said pipe input end is fixed closely adjacent the wall surface, comprising a camera mounted on a support system such that the camera may be introduced through a narrow gap between the pipe input end and the wall surface, and means for illuminating a part of the wall surface beneath said pipe input end, said camera being electrically connected to means for receiving signals therefrom representing a visual image of the wall surface beneath the pipe

6. Apparatus according to Claim 5, further including a graduated scale adapted to be positioned across the wall surface beneath the pipe input end.

7. Apparatus according to Claim 5, wherein said illuminating means comprises an array of light sources disposed on or adjacent the camera and extending around the camera lens.

8. Apparatus according to Claim 7, wherein the array of light sources produce light in the infra-red frequency range.

9. Apparatus according to Claim 5, wherein the support system comprises an articulated arm system which may be introduced through said narrow gap and then manoeuvred so that the camera may be disposed at a position spaced from the wall surface.

10. Apparatus according to Claim 5, including an ultrasonic probe adapted to be introduced through said narrow gap to a position beneath the pipe input end.

11. Apparatus for examining the condition of a wall surface, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

12. A method of examining the condition of a wall surface beneath the input end of an outlet pipe in a vessel for transporting liquid, substantially as hereinbefore described.