GB2159069A

GB2159069A - Blasting nozzle

Info

Publication number: GB2159069A
Application number: GB08412625A
Authority: GB
Inventors: John Link
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-05-17
Filing date: 1984-05-17
Publication date: 1985-11-27
Also published as: GB8412625D0

Abstract

A blasting nozzle has inlets 10, 11 (or 31, 30) for high pressure water and abrasive containing water to be accelerated by the high pressure water, the arrangement being such that rotation is imparted to grains of abrasive. The grains may be rotated about their own axes and/or the jet of abrasive grains may be swirled, by applying a drag to one side of the jet upstream 15 or downstream 14 of the nozzle outlet 12, by supplying the abrasive slurry between two fan shaped water jets 31, one jet being faster than the other, or by using angularly inclined water jets in, or at the outlet of, the nozzle. <IMAGE>

Description

SPECIFICATION Blasting nozzle The present invention relates to a blasting nozzle.

The nozzle of the invention is useful in cleaning apparatus employing abrasive laden jets of water.

The use of abrasive laden jets is common in cleaning such items as the legs of oil rigs, but such situations create special difficulties because the cleaning is actually performed by a diver who may be some way below the sea water surface. Problems arise in connection with the supply of abrasive from the surface to the point of operation. It is generally not practical simply to supply the abrasive laden water at high pressure down a pipe because there will be a considerable pressure drop and there will be rapid wear on the pipe.Accordingly, a common procedure is to supply a water laden abrasive at relatively low pressure down one conduit of flexible pipe and to supply water at high pressure down a second conduit or flexible pipe, these two supplies meeting at a nozzle which has an inlet connected to each supply and an outlet through which the abrasive laden jet passes. The high pressure water is dispersed within the nozzle in a diverging jet and this creates a vacuum producing action in the inside of the nozzle which entrains and accelerates the abrasive containing water which is supplied to the interior of the nozzle at low pressure. A nozzle assembly of this type is shown, for instance, in Figure 2 of US Patent 3 994097.

The aim of this invention is to improve the cleaning effect of such nozzles.

According to the present invention, there is provided a blasting nozzle having inlets for high pressure water and abrasive containing water to be accelerated by the high pressure water, the arrangement being such that rotation is imparted to grains of abrasive by the nozzle.

The rotation of the grains can be about their own axes, particularly if the grains are large.

Alternatively, instead of, or as well as rotating them individually, a swirling action can be introduced into the flow of abrasive particles.

Various ways are envisaged for imparting such rotation or swirl. Those presently contemplated include applying a drag at one side of the abrasion laden jet. This could be done by the provision of a rough surface, or perhaps the provision of any surface, beyond the nozzle outlet on one side of the jet. Alternatively, different surface conditions could be provided within the nozzle. In an alternative way, the abrasive containing slurry can be supplied and carried between two generally plain jets of high pressure water, one of which may be arranged to move faster than the other. This can easily be provided by an appropriate selection of apertures and supply passages for such high pressure water jets.In other embodiments, high pressure water jets surrounding or generally surrounding the abrasive laden water in the barrel can be introduced into the barrel in such a way as to impart rotation, for instance by being inclined to the barrel axis.

Alternatively, some or all of the high pressure water can be discharged from the nozzle to the outside in a plurality of diverging jets, each of which is inclined to planes radial to the nozzle in such a way that on encountering the high pressure which in use prevails outside the nozzle, due to its operation below sea level these jets are diverted inwardly so as to create a rotational effect.

In order that the invention may be more clearly understood, the following description is given, by way of example only, with reference to the accompanyiong drawings, in which: Figures 1 to 3 are schematic side sectional views of three embodiments according to the invention, Figure 4 is a section from the line IV--IV of Figure 3, Figures 5a and 5b are schematic side and end views showing part of a further embodiment of the invention.

As shown in Figure 1 the nozzle of the invention comprises, in known manner, an inlet 10 for high pressure water, an inlet 11 for abrasive laden water and an outlet 12. The high pressure water passes through a reduced orifice 13, where it diverges towards a converging part of the nozzle, thus providing a vacuum effect and entraining and accelerating abrasive conveyed through the inlet 11.

On leaving the outlet 12 one side of the resulting spray runs along a surface 14, which may be flat or arcuate, tapered or of constant width. This provides a drag on one side of the spray leading to a swirling action which, depending upon the size of the grains, may effect the grains about their own axes and/or lead to a general swirling of the jet.

Figure 2 is an embodiment which is similar except that in place of the part 14 the nozzle includes a roughened surface 15 just upstream from its outlet 12. This will again impart a drag on part of the outflowing jet leading to swirling and/or rotation.

In the embodiment of Figures 3 and 4, the abrasive laden supply is to the barrel of the nozzle through a central orifice 30 on either side of which are orifices 31 and 32, connected as shown to a joint supply 33 of high pressure water and adapted to provide generally flat fan shaped jets. Of course, many other shapes of jet could be used instead.

However, one jet moves faster than the other, a situation which can be brought about by a throttling action in the supply to either of the orifices 31 or 32 or by appropriate dimensioning of these two orifices. Thus, in the barrel of the nozzle a swirling or rotational effect will again be obtained.

Figures 5a and 5b show schematically a further feature of the invention. Whether or not the abrasive laden supply is otherwise accelerated by high pressure water, and whether or not some rotational swirling motion is imparted within the nozzle, it is contemplated according to this form of the invention to have multiple high pressure water outlets from the nozzle at its outlet end, each of these being directed in a manner such that it diverged away from adjacent jets and also diverges from the axis of the nozzle as suggested by the arrows in the Figures. On encountering the external high pressure, bearing in mind the operation is below sea level, these jets are bent back towards the axis and also in a sense which is rotational about the axis and in this way imparts a swirling or rotational movement.

The invention is particularly appropriate for use with my British Patent 2 057 879 which effectively provides without interruption an appropriate abrasive mixture of relatively constant abrasive content.

This invention can be combined, if desired, with one or both of the inventions of my co-pending applications or even date herewith.

Claims

1.A A blasting nozzle having inlets for high pressure water and abrasive containing water to be accelerated by the high pressure water, the arrangement being such that rotation is imparted to grains of abrasive.

2. A nozzle according to claim 1, wherein the grains rotate about their axes.

3. A nozzle according to claim 1 or 2, wherein the grains are caused to rotate about an axes from which they are remote.

4. A nozzle according to claim 1,2 or 3 including a surface extending beyond the outlet of the nozzle to provide a drag effect on the issuing jets.

5. A nozzle according to claim 1,2 or 3 including a differential surface effect within the nozzle upstream of the outlet.

6. A nozzle according to claim 1,2 or 3 wherein the abrasive is entrained between high pressure water flows of different velocity.

7. A nozzle according to claim 1,2 or 3 wherein a rotational effect is imparted to the high pressure water within the barrel of the nozzle when or prior to its encounter with the abrasive laden water supply.

8. A nozzle according to any preceding claim including high pressure water outlets adjacent the nozzle outlet, such high pressure outlets directing jets in a direction inclined to and away from the nozzle axis and diverging from each other.

10. A blasting nozzle constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.