GB2358601A - Housing for abrasive blasting - Google Patents

Abstract

A housing comprises two parts 1 and 2 connected by a hinge 3 and are pivotable between an open position (fig. 4 and 5) where an elongate workpiece such as a pipe may be moved laterally into and out of the housing and a closed position (figs. 1-3 and 6) where a part of an elongate workpiece may be surrounded by the housing by means of openings 5 and 6 formed by cut out regions in each of the two parts 1 and 2. The edge of each opening 5 and 6 is fitted with a seal 6a and the two parts 1 and 2 each supports a part of a latch (4, fig. 1). The housing also comprises observation windows 7, lamps 8, one or more directable blast nozzles 12, one or more gauntlets and two extraction apertures 14 and 15, disposed in upper and lower positions respectively. The housing is rotatably mounted on support means 19-21 which include an arm 21 pivotally mounted on a support.

Description

2358601 AppARATUS FOR ABRASIVE BLASTING The present invention relates to

apparatus for abrasive blasting suitable for the abrasive blasting of pipes. The invention is particularly, but not exclusively, concerned with such apparatus for use in blast cleaning

field join areas of oil, gas and other pipelines.

Oil and gas pipelines are formed from separate lengths of externally coated steel pipe which are welded together to form a pipeline before they are laid. A short section at either end of each pipe is left uncoated to facilitate welding of the lengths together. After welding the uncoated region is coated, to prevent corrosion, before the pipeline is laid.

Before welding and/or coating the uncoated sections must be cleaned. This is achieved by abrasive blasting. Conventionally this is done manually by operatives using abrasive blasting guns.

A problem with this is that the abrasive material used and any dust or dirt, for example corrosion, removed from the pipe being cleaned is discharged into the atmosphere and region surrounding the pipe. This is undesirable, especially where a pipe is cleaned in a confined space or a sensitive environment, for example on a lay barge where lengths of pipe are joined to form a pipeline being laid offshore.

Another problem is that because conventional blasting of pipe field joints is performed on a total loss or open loop basis abrasive material employed can only be used once. Large quantities of such material are -2 therefore required.

It is an object of the present invention to overcome the above, and other, problems associated with conventional abrasive blasting techniques.

According to a first aspect of the present invention there is provided apparatus for abrasive blasting comprising a housing having a first operative position in which it defines two openings arranged so that an elongate workpiece may extend through the housing, the housing defining an enclosed region between the two openings, and a second operative position in which an elongate workpiece may be moved laterally into and out of the housing.

The elongate workpiece may be a pipe. The housing may thus be used to. enclose a part of a length of pipe without having to pass the entire length of pipe through the housing. It can therefore easily be used in the blast cleaning of the field join areas of a pipeline to contain blast materials and other debris during blasting, overcoming the problems with conventional field blasting techniques.

In one embodiment the housing comprises two parts which together define an enclosure and which may be pivotally connected. The housing may be rotatably mounted on a support means. This would enable the housing to be rotated relative to a workpiece extending therethrough. The support means may enable the housing to move laterally relative to a fixed elongate workpiece. The support means may be an arm. The arm may be pivotally mounted on another support. The arm may support a ring which supports the housing via a bearing means. The housing preferably includes one or more directable blast nozzles and may also include one or more gauntlets which extend into the housing to enable an operative to manually direct the one or more blast nozzles. The housing may include at least two apertures for connection to extraction apparatus, the apertures being disposed at upper and lower positions respectively. The bottom of the housing may be shaped so as to direct material towards the lower aperture for connection to extraction apparatus. The apparatus may be arranged to enclose a part of an upright pipe.

Apparatus having the preferred features discussed above may be quickly deployed and removed from a pipe. By being rotatably mounted only a small number of nozzles, for example two, are required to blast the entire circumference of a pipe. Manually directed blast nozzles allow non repetitive work to be performed.

In order that the invention may be more clearly understood an embodiment thereof will now be described, by way of example, with reference to the accompanying drawings of which:

Figure 1 is a plan view of apparatus according to the invention; Figure 2 is a cross-sectional view taken along the line A-A of Figure 1; Figure 3 is a similar view to Figure 2 with the housing shown separated from the support ring; Figure 4 is a plan view of the apparatus of Figure 1, with the apparatus in the open position, displaced from a pipe; Figure 5 is a view similar to Figure 4, but with the housing moved laterally towards the pipe; and Figure 6 is a view similar to Figure 5 with the housing in the closed position, enclosing a portion of the surface of the pipe.

Referring to the drawings an abrasive blasting enclosure comprises a housing formed from first 1 and second 2 generally similar parts which together define an enclosure. These are formed from sheet metal and their inside surfaces lined with rubber. They are connected together by a hinge 3 which enables them to be pivoted between an open position, as shown in Figures 4 and 5, and a closed position, as shown in Figures 1 to 3 and 6. The two parts 1 and 2 respectively support two engageable components of a spring loaded latch means 4 operative to retain them in the closed position.

The upper and lower surfaces of each of the parts 1 and 2 include semi-circular cut out regions. When the parts 1 and 2 are in the closed position the cut out regions of each part align so that, together, the parts define an enclosure with two aligned generally circular openings 5 and 6 formed by the cut-out regions. The edge of each cut-out region is fitted with a brush type sea[ 5a,6a which extends radially inwardly in the plane of the cut-out region. Thus when the parts 1 and 2 are in the closed position a seal 5a,6a extends around the periphery of the two aligned openings 5 and 6.

The openings 5 and 6 allow an elongate workpiece, for example a pipe, to pass through the enclosure. The size of the openings 5 and 6 is preferably only slightly larger than the cross-section of a workpiece to be enclosed, so that a suitable seal is established between the workpiece and openings. Thus, when a workpiece extends through both openings the housing defines an enclosed region surrounding the part of the workpiece which extends between the openings 5 and 6.

When the latch means 4 is released and the two parts 1 and 2 are pivoted to the open position a workpiece may be moved laterally relative to the housing. The housing may therefore be used to enclose a part of the outside surface of a pipe without having to thread the pipe longitudinally through an opening.

Each of the two parts 1 and 2 of the housing includes an observation transparency 7 and an internal lamp 8, so that an operator can see a workpiece enclosed by the housing. The two parts 1 and 2 also each define an aperture 9 into which is fitted a rubber gauntlet (not shown) which extends into the housing, and an aperture 10 into which is fitted a short, flexible blasting hose 11 which extends into the housing and has a blasting nozzle 12 fitted to the end thereof. The opposite end of each hose 11 is fitted with a connector 13 to enable it to be connected to an external supply of abrasive material and compressed air.

An operator can manipulate the blasting nozzles 12, using the gauntlets, in order to blast the surface of a workpiece extending through the housing.

During abrasive blasting of a workpiece the housing will contain the abrasive material blown through the blasting nozzles 12 as well as any dust and debris generated by the blasting process. In order to reduce the amount of such materials escaping into the environment, past the seals 5a and 6a, each part of the housing 1 and 2 defines two further apertures 14 and 15 through which material and air may be extracted.

The illustrated housing is intended for enclosing regions of pipes in an upright orientation. Pipes are, for example, oriented in this fashion when an offshore pipeline is layed using the so-called J-lay technique. Thus, in operation, openings 14 and 15 will lie one above the other. In use, relatively light material in the housing, such as dust and debris blasted from the surface of a pipe, will remain suspended in the air in the housing. This material can be extracted via a vacuum hose connected to the upper aperture 14. Relatively heavy material in the housing, principally the abrasive material, for example grit, used for blasting, will fall to the bottom of the housing. The inside surface of the housing slopes downwardly towards the lower aperture 15 which is located at the lowest point of the housing. The abrasive blasting material can therefore be extracted via a vacuum hose connected to the lower aperture 15, and subsequently re used.

The rate of extraction of air and material from the four extraction apertures 14 and 15 should exceed the rate at which air and material is introduced into the housing through the blasting nozzles 12. The net result is that air is drawn into the housing, past seals 5a and 6a, reducing or preventing the escape of dust and other debris.

The first and second parts 1 and 2 of the housing are each connected to a support framework 16 on which are rotatably mounted vertical 17 and horizontal 18 rollers. The rollers are arranged to co-operate with a support ring. The support ring is substantially annular in cross-section and formed from two pivotally connected components 19 and 20 each of which is semi annular in cross-section. The support framework 16 and parts 1 and 2 are suspended by way of the rollers 17 and 18 from the support ring 19,20 so that the support framework 16 and parts of the housing 1 and 2 may rotate relative to the support ring 19,20.

The vertical rollers 17 bear on a horizontal surface of the support ring 19,20 and the horizontal rollers bear on an outside surface of the support ring 19,20. When the pivot between the components 19 and 20 forming the support ring and the hinge 3 joining the two parts of the housing 1 and 2 are aligned the parts may be moved between the open and closed positions, whereupon the support ring components 19 and 20 will also move between open and closed positions.

One of the support ring components 19 is fastened to a horizontal support arm 21 which is in turn pivotally mounted on an upright support tube 22.

The support arm 21 allows the enclosure to be swung in an arc 23, so that it may be moved laterally relative to an upright pipe.

The illustrated apparatus would typically be used for abrasive blast cleaning the join areas between lengths of pipeline 24 being assembled in an upright orientation. Such a pipeline is illustrated in Figures 1 and 2 in dashed lines, and in Figures 4 to 6 in a solid line.

When a pipeline is being assembled from separate lengths of pipe many operations must be conducted at each join, for example cleaning, heating, welding and coating. It is usually desirable that as many operations as possible are carried out at join site without needing to move the pipe, particularly when the pipeline is upright. The rate at which a pipe can be laid depends upon the rate at which these operations can be carried out.

There is considerable commercial pressure for the operations to be performed as quickly as possible.

The illustrated apparatus enables blasting of the join area of a pipeline to be performed quickly, safely and economically in a confined space.

Typically, a blasting operation would start with the apparatus as shown in Figure 4 with the housing in the open position and laterally displaced from a pipeline 4.

The housing is then swung, by pivoting arm 21, towards the pipeline 24, sO'that the pipeline is received into the cut-out regions in the top and bottom of one of the parts 1 forming the housing. The other part 2 is then pivoted relative to the first to bring the two parts to the closed position so that the two components of the latch 4 hold them together in the closed position. This forms a suitable seal between the edges of the housing and the pipeline 24, enclosing a region of the pipeline.

Air is now extracted from apertures 14 and 15 of the housing whilst operatives blast the enclosed region of the pipe by manipulating the blast nozzles 12 using the gauntlets. Access to the entire circumference of the pipe is achieved by rotating the housing about the support ring. During blasting, abrasive material recovered through the lower extraction points 15 may be re-used.

When blasting is completed, the housing is returned to its original position relative to the support ring, the latch 14 is released, the housing opened and the whole assembly moved away from the pipe by pivoting arm 21 so that another operation can be performed on the pipeline.

In another embodiment a housing could be used to enclose part of a horizontally oriented elongate workpiece.

The above embodiment is described by way of example only, many variations are possible without departing from the invention.

Claims (14)

1 Apparatus for abrasive blasting comprising a housing having a first operative position in which it defines two openings arranged so that an elongate workpiece may extend through the housing, the housing defining an enclosed region between the two openings, and a second operative position in which an elongate workpiece may be moved laterally into and out of the housing.

2. Apparatus as claimed in claim 1, wherein the housing comprises two parts which together define an enclosure.

3. Apparatus as claimed in claim 2, wherein the two parts are pivotally connected.

4. Apparatus as claimed in any preceding claim, wherein the housing is rotatably mounted on a support means to enable the housing to be rotated relative to a workpiece extending therethrough.

5. Apparatus as claimed in claim 4, wherein the support means enables the housing to be moved laterally relative to a fixed elongate workpiece.

6. Apparatus as claimed in either claim 4 or 5, wherein the support means is an arm.

7. Apparatus as claimed in claim 6, wherein the arm is pivotally mounted on another support.

8. Apparatus as claimed in either claim 6 or 7, wherein the arm supports a ring which supports the housing via a bearing means.

9. Apparatus as claimed in any preceding claim, wherein the housing includes one or more directable blast nozzles.

10. Apparatus as claimed in claim 9, wherein the housing includes one or more gauntlets which extend into the housing to enable an operative to manually direct the one or more blast nozzles.

11. Apparatus as claimed in any preceding claim including at least two apertures for connection to extraction apparatus, the apertures being disposed at upper and lower positions respectively.

12. Apparatus as claimed in claim 11, wherein the bottom of the housing is shaped so as to direct material towards the lower aperture.

13. Apparatus as claimed in any preceding claim arranged to enclose a part of an upright tube.

14. Apparatus for blasting substantially as herein described with reference to the accompanying drawings.