EP0164914A1

EP0164914A1 - Jet cleaning operation

Info

Publication number: EP0164914A1
Application number: EP85303395A
Authority: EP
Inventors: William Allison
Original assignee: Nis Engineering Ltd
Current assignee: N.I.S. ENGINEERING LIMITED
Priority date: 1984-05-15
Filing date: 1985-05-14
Publication date: 1985-12-18
Also published as: GB2160130B; GB8412382D0; GB2160130A

Abstract

A method of performing a jet cleaning operation comprising using a jet which incorporates particulate material which will dissolve or change phase in the medium sur_- rounding the jet.

Description

The present invention relates to jet cleaning operations.
It is well known to effect cleaning of substrates by directing at the substrate a high velocity jet. Frequently an abrasive material e.g. sand, is incorporated in the jet to assist the cleaning operation. One example of such a technique is the nuclear industry in which a submerged water jet with entrained sand is used for removing scale from radioactive substrates. It is however a disadvantage of such a process that the sand becomes radioactively contaminated which gives rise to problems both in recycling the sand for subsequent cleaning operations and in ultimately disposing of the radioactive sand.
It is an object of the invention to obviate or mitigate the abovementioned disadvantages.
According to the present invention there is provided a method of performing a jet cleaning operation -comprising using a jet which incorporates particulate material which will dissolve or change phase in the medium surrounding the jet.
Preferably the jet is a liquid jet and preferably the particulate material is a frozen material i.e. the solid phase of a material which would normally be in a different phase (e.g. liquid) at the temperature of the jet cleaning operation. The liquid jet is most preferably a water jet and the frozen material incorporated therein is preferably ice. Alternatively, the particulate material may be one which is soluble in the medium surrounding the jet. Thus, where the jet is one which is submerged in water the particulate material may be for example, salt or sugar alternatively, the particulate material may be a frozen gas, e.g. cardice.
Preferably, the liquid jet is one which is submerged in a bath of the same liquid as the jet (preferably water) and is most preferably a cavitating jet, for example produced by the apparatus sold by N.I.S. Engineering Limited under the trade mark CAVALANCHE.
In the-method of the invention the particulate material acts as an abrasive to ass t the cleaning operation. The material may then simply be allowed to change phase and may be disposed of as a liquid.
The invention will be further described by way of example only with reference to the accompanying diagrammatic illustrations.
As illustrated in the drawing, a jet head 1 for producing a cavitating jet is submerged in a bath of water 2. A high velocity water stream is passed along a line 3 to the head 1 from which (due to the interior construction of the head) issues a cavitating jet 4. A radioactive plate 5 to be descaled is located in the path of the jet 4.
Supported around the jet head 1 by individual struts 6 is a cylindrical cowl 7 communicating with a supply of particulate ice 8.
The hydrodynamic depression produced by the cavitating jet 4 causes particulate ice 8 to be drawn from the supply into the cowl 7 and become entrained in the jet 4. Ice is thus incorporated in the jet 4 directed against substrate 5 and assists in the cleaning operation. After striking plate 5, the ice 8 will simply melt into the water 2.
It will be appreciated that the water may become radioactively contaminated during the course of the cleaning operation. This is not a serious problem as there are well established techniques for the disposal of radioactive liquids.
The melting of the ice in the bath 2 will cause the level thereof to rise. Though this will cause no problem in most instances, it is possible to obviate the volume increase. This can be achieved by using particulate material of a dissimilar nature to the tank liquor, e.g. a frozen gas, or a solid which will dissolve in the bath 2. For example, a frozen gas will turn to gas which in turn will rise through the host liquor and escape from the surface of that liquor. Typically, carbon dioxide ice (cardice) particules could be used in this instance, resulting in a fairly stable tank level.
It will be appreciated that the abovedescribed specific embodiment of the invention overcomes the problems associated with the use of conventional abrasive material (e.g. sand) for cleaning radioactive substrate, i.e. problems associated with recycling radioactive abrasive and disposal of the radioactive abrasive.

Claims

1. A method of performing a jet cleaning operation comprising using a jet which incorporates particulate material which will dissolve or change phase in the medium surrounding the jet.

2. A method as claimed in claim 1 wherein the jet is a liquid jet.

3. A method as claimed in claim 2 wherein the jet is a water jet.

4. A method as claimed in claim 2 or 3 wherein the liquid jet is a submerged jet.

5. A method as claimed in claim 4 wherein the jet is submerged in water.

6. A method as claimed in claim 4 wherein the liquid jet is a cavitating jet.

7. A method as claimed in any one of claims 1 to 6 wherein the particulate material is a frozen material.

8. A method as claimed in claim 7 wherein the frozen material is ice.

9. A method of performing a jet cleaning operation substantially as hereinbefore described with reference to the accompanying drawing.