GB2096021A

GB2096021A - High pressure liquid jetting guns

Info

Publication number: GB2096021A
Application number: GB8109188A
Authority: GB
Original assignee: British Hydromechanics Research Association
Current assignee: British Hydromechanics Research Association
Priority date: 1981-03-24
Filing date: 1981-03-24
Publication date: 1982-10-13
Also published as: GB2096021B

Abstract

In order to increase the area cleaned when a narrow jet of high pressure cleaning liquid is directed along a path extending across a surface (2) to be cleaned, the cleaning jet nozzle (7) is oscillated, for example by piston- cylinder assemblies (8 and 9), so that the jet 12 follows a zig-zag path across the surface (2). The piston-cylinder assemblies (Band 9) may be driven by hydrostatic pressure derived from a pressure intensifier (13) used to supply high pressure cleaning liquid to the gun (1). Alternatively the nozzle (7) may be eccentrically mounted on a rotating member (11). <IMAGE>

Description

SPECIFICATION High pressure liquid jetting guns Technical field of the invention This invention applies high pressure liquid jetting guns for producing high pressure liquid jets for cleaning purposes and is particularly related to the subsea use of such equipment.

Background art It is known to provide high pressure liquid jetting guns, for use in cleaning surfaces, comprising a high pressure liquid conduit having an inlet and a discharge outlet, with a cleaning jet nozzle attached to the discharge outlet of the high pressure liquid conduit.

It is also known that, in the use of liquid cleaning jets, higher pressure operation, at pressures of up to and exceeding 4,000 bars, is beneficial in certain cases even at a given fluid power level. This means that a higher pressure coupled with a lower flow is better than lower pressure at larger flow for removing certain surface features such as corrosion from welded steel structures underwater.

If a fixed amount of power is available, then the jet diameter at high pressure, say 2000 - 3000 bar, is typically much smaller than that a jet at 200 to 300 bar pressure. Although the high pressure jet is much more effective, its small size makes its application by a diver, or even by a surface operator, difficult because it is not possible for him to sweep quickly and accurately so that the fine lines of the sweep lie closely alongside each other.

Disclosure of invention It is an objection of the present invention to provide a high pressure liquid jetting gun in which less precision is required of the operator in directing a jet of high pressure liquid at a target surface to be cleaned.

This objective is achieved by providing oscillating means for swinging the discharge axis of the cleaning jet nozzle laterally about a mean position so as to cause a jet of liquid emerging from the nozzle and directed onto a surface to sweep across the surface, relative to the intersection between the surface and the discharged axis of the nozzle, when the discharge axis of the nozzle is in its mean position.

Two embodiments of the invention are hereinafter described, by way of example, with reference to the accompanying drawings.

Brief description of drawings Figure 1 is a schematic view of a surface to be cleaned, showing the paths traced out by a stable jet of high pressure cleaning liquid; Figure 2 is a schematic view of a surface to be cleaned, showing the path traced out by an oscillating jet by means of apparatus in accordance with the present invention; Figure 3 is a schematic view of high pressure liquid jet cleaning apparatus in accordance with the invention; and Figure 4 is a schematic sectional end view of a modified form of part of the apparatus shown in Figure 3.

Best modes for carrying out the invention As shown in Figure 1, in order to clean a band 21 on a surface 2, by means of a high pressure liquid jetting gun, it is necessary to move the gun so that the jet of cleaning liquid traces out a series of parallel paths 22. Clearly, this requires great steadiness on the part of the operator and this involves great difficulty, particularly when cleaning submerged surfaces. This difficulty is overcome by means of the present invention by causing the jet to oscillate from side to side as it is directed along a path extending downwards, in the direction of arrow 23, across the surface 2, as shown in Figure 2. In this case a band 21 is cleaned as a result of the zig-zag path 24 traced out by the jet.

As shown in Figure 3, a high pressure liquid jetting gun 1, accoding to the invention, for use in cleaning a submerged surface 2 is supplied with sea water at high pressures of up to and exceeding 4,000 bars.

This sea water is drawn into pressure intensifier 13 through a filter 25 connected to an inlet tube 26 and discharged through a supply conduit 27 connected to a radial inlet 5 of a passageway 3 inside the gun 1.

The pressure intensifier 13 is driven by working fluid passing through supply lines 14 and 15 extending through the surface 28 of the sea water 29.

A flexible hose 4 extends between one end of the passage way 3 and a cleaning jet nozzle 7 mounted in a support member 10, within a tubular casing 30, to provide a cleaning jet 12. A balancing nozzle 31 is fitted to the other end of passageway 3 so as to provide a retro jet 32 which balances the cleaning jet 12 issuing from the nozzle 7 for cleaning the surface 2. The retro jet 32 passes through the rear end of the tubular casing 30 which is formed with apertures 33 so as to allow sea water 29 to pass in a rearward direction through the rear end of the tubular casing 30.

Low pressure working liquid such as oil, typically at about 300 bar, is supplied from the pressure intensifier 13 to two cylinders 9 mounted on diametrically opposite sides of the tubular casing 30 and containing reciprocable pistons 8. Thus, response to variations in the hydrostatic pressure of working within the pipelines 16 and 17, the pistons 8 cause the support member 10 to oscillate, thereby swinging the axis of the jet 12 about an axis extending perpendicular to the axis of the jet 12 when the axis of the jet 12 is in its mean position. As an alternative mode of construction, the flexible hose 4 can be replaced by a jointed metallic tube.

As shown, the gun 1 is provided with a handle 34 and a trigger mechanism 18 which may be mounted on the handle 34. The trigger mechanism 18 is mounted in a control circuit 19 connected to control means 20 which are effective to by-pass working liquid from the lines 14 and 15, unless the trigger mechanism 18 is actuated. This provides a fail-safe way of ensuring that no sea water is pressurised unless required by the operator of the gun 1.

The use of low pressure working liquid in the lines 16 and 17 and the control circuit 19, instead of high pressure liquid, results in the efficient utilization of energy and in the simplification of the oscillating means 8 and 9 and the trigger mechanism 18.

In a modification of the invention, the pistoncylinder assemblies 8 and 9 are replaced by rotary means 11 for rotating a circular support member 10 and the discharge nozzle 7 is mounted eccentrically in the support member 10. Thus, on rotation of the support member 10, the discharge jet 12 is caused to sweep laterally of the discharge axis. Moreover, because this sweeping action follows a path which is circular relative to the mean position of the discharge axis, the gun 1 can be used to clean bands 21 when moved along any axis across the surface 2 instead of along an axis in the direction of arrow 23, in Figure 2, which is perpendicular to the lateral oscillation carried out by the jet 12.

Claims

1. A high pressure liquid jetting gun (1), for use in cleaning surfaces (2), comprising: a high pressure liquid conduit (3 and 4) having an inlet (5) and a discharge outlet (6); and a cleaning jet nozzle (7) attached to the discharge outlet (6) of the high pressure liquid conduit (3 and 4); characterised in that: oscillating means (8 and 9, or 10 and 11) are provided for swinging the discharge axis of the cleaning jet nozzle laterally about a mean position so as to cause a cleaning jet (12) emerging from the nozzle and directed onto a surface (2) to sweep across the surface (2) relative to the intersection between the surface (2) and the discharged axis of the nozzle (7) when the discharged axis of the nozzle (7) is in its mean position.

2. A gun, according to Claim 1, characterised in that the oscillating means comprise piston-cylinder means (8 and 9) which are operable to rock the nozzle (7) back-and-forth about an axis which normal to the discharge axis of the nozzle (7) when the discharge axis of the nozzle (7) is in its mean position.

3. A gun, according to Claim 1, characterised in that: the oscillating means comprise a support member (10) and drive means (11) for rotating the support member (10) about the discharge axis of the nozzle (7) when the discharge axis of the nozzle (7) is in its mean position; and the nozzle (7) is mounted in the support member (10) eccentrically of the rotational axis of the nozzle (7).

4. High pressure liquid jet cleaning apparatus comprising a gun (1), according to any preceding claim, characterised in that: a pressure intensifier (13) is provided for supplying the gun (1) with high pressure liquid; supply means (14 and 15) are provided for supplying the pressure intensifier (13) with working liquid at a lower pressure than the high pressure liquid; and supply lines (16 and 17) extends from the pressure intensifier (13) to the oscillating means (8 and 9, or 10 and 11)forthe provision of working liquid for effecting operation of the oscillating means-(8 and 9, or 10 and 11).

5. Apparatus, according to Claim 4, comprising a trigger mechanism (18) for controlling the gun (1), characterised in that: a control circuit (19) for working liquid extends between the pressure intensifier (13) and the trigger mechanism (18); and control means (20) are effective to by-pass working liquid through the pressure intensifier (13) without pressurising liquid supplied to the gun (1).

6. A high pressure liquid jetting gun substantially as hereinbefore described with reference to an iliustrated in Figure 3 or Figure 4.

7. High pressure liquid jet cleaning apparatus substantially as hereinbefore described with reference to and as illustrated in Figure 3 or Figure 4.