GB1599386A - Liquid layer thickness measuring apparatus and method - Google Patents

Description

(54) LIQUID LAYER THICKNESS MEASURING APPARATUS AND METHOD (71) We, SO "VODEN TRANS PORT", of 17, Panagurishte Street, Varna, Bulgaria, an Economic Corporation organised under the Laws of Bulgaria, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method and apparatus for measuring the thickness of a layer of a first liquid lying on a second liquid and is more particularly though not exclusively concerned with the measurement of the thickness of layers of petroleum derivatives on water resulting both from small-scale accidental spillage and from pollution of territorial waters by ships.

A method of measuring the thickness of a petroleum layer on water based on optical diffraction is known. According to this method, the thickness of the petroleum layer is determined by taking into account the colour of the water surface.

A disadvantage of this method is the fact that determination of layer thickness depends on the operator's subjective colour sensitivity and adaptation to prevailing light conditions, as well as the actual hydrometereological conditions during examination of the petroleum layer. Another disadvantage of the method is that it becomes rather inaccurate when layer thickness exceeds about 2 microns. No speciallised apparatus has been developed for use in making these measurements.

According to one aspect of the present invention, there is provided a method of measuring the thickness of a layer of a first liquid lying on a second liquid, wherein a sample of predetermined surface area of said layer on said second liquid is enclosed in a first chamber of an open bottomed measuring vessel by submerging the lower portion of said vessel in the first liquid at least to the interface between the first and second liquids, said first chamber communicating directly with a second chamber of said vessel which second chamber undergoes a reduction in transverse cross-section from its position of communication with said first chamber to an opposite end region thereof and possesses a greater height than said first chamber, the measuring vessel is submerged further so that the sample of the first liquid rises into the second chamber until the free liquid surface reaches a predetermined height, the thickness of the sample being increased by the reduction in cross-section, and then the height of the liquid interface in said second chamber is determined and said first-mentioned thickness is determined in accordance with a mathematical relationship between the difference between said heights and geometry of the chambers of the vessel.

According to another aspect of the present invention there is provided apparatus for carrying out the method defined hereinabove, comprising a vessel formed with a first chamber completely open at opposite ends having wall means parallel to its longitudinal axis and communicating at one said end with a second chamber having walls which define a decreasing cross-section away from the first chamber to a distal end of smaller surface area than said one end, the apparatus including means for determining, when the apparatus is in use, when the free liquid surface reaches a predetermined height at or near the distal end and for determining the position within the second chamber of the interface between said liquids.

The means for determining when the free liquid surface reaches the predetermined height may comprise a sensor positioned in the second chamber at said predetermined height.

The means for determining the position of the interface between said liquids may comprise a sensor located in the second chamber.

The chambers in the measuring vessel may have various configurations. For example, the first chamber may be cylindrical and the second chamber have the shape of a trtmc ted cone.

Alternatively the first chamber may have a rectilinear cross-section and the second chamber have the shape of a truncated pyramid.

It is desirable for the inner surfaces of the first and second chambers to be coated with an oleophobic substance before the vessel is used.

When using apparatus according to the invention, the value obtained for the thickness of the layer of liquid should be reasonably accurate since the thickness of a predetermined surface (rather than a particular point) is being measured. Also, owing to the generally tapering cross-section of the second chamber, the measured thickness of the layer is much greater than the actual thickness and hence the effect of error in measurement on the final result should be minimised. Further, the result obtained should be independent of the nature of the liquids.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing, which shows a vertical section through one form of apparatus according to the present invention.

The apparatus comprises a measuring vessel formed with a first chamber 1 open at the bottom and connected to a second chamber 2.

A sensor 3 for detecting the presence of free liquid surface and a sensor 4 for determining the position of the interface between the first and second liquids are fixed in the chamber 2.

The apparatus is used as follows: A predetermined surface area of liquid is enclosed by the chamber 1, and then the measuring vessel is introduced further into the second liquid so the liquid rises into the chamber 2 until the free liquid surface reaches the sensor 3. Then the sensor 4 is used to determine the position of the interface between first and second liquids. Hence the instantaneous thickness of the layer of first liquid is determined. From this, the original layer thickness may be determined in accordance with a mathematical relationship between instantaneous thickness and original thickness determined by the geometry of the first and second chambers of the vessel.

WHAT WE CLAIM IS:- 1. A method of measuring the thickness of a layer of a first liquid lying on a second liquid, wherein a sample of predetermined surface area of said layer on said second liquid is enclosed in a first chamber of an open bottomed measuring vessel by submerging the lower portion of said vessel in the first liquid at least to the interface between the first and second liquids, said first chamber communicating directly with a second chamber of said vessel which second chamber undergoes a reduction in transverse cross-section from its position of communication with said first chamber to an opposite end region thereof, and possesses a greater height than said first chamber, the measuring vessel is submerged further so that the sample of the first liquid rises into the second chamber until the free liquid surface reaches a predetermined height, the thickness of the sample being increased by the reduction in cross-section, and then the height of the liquid interface in said second chamber is determined and said first-mentioned thickness is determined in accordance with a mathematical relationship between the difference between said heights and geometry of the chambers of the vessel.

2. A method as claimed in claim 1, wherein rise of the free liquid surface to said predetermined height is detected by a sensor positioned in the second chamber at said predetermined height.

3. A method as claimed in claim 2, wherein the sensor is positioned in the second chamber at said opposite end region thereof.

4. A method as claimed in any preceding claim, wherein the position of said liquid interface is detected by a further sensor positioned in the second chamber.

5. A method of measuring the thickness of a layer of a first liquid lying on a second liquid, substantially as hereinbefore described with reference to the accompanying drawing.

6. Apparatus for carrying out the method of claim 1, comprising a vessel formed with a first chamber completely open at opposite ends having wall means parallel to its longitudinal axis and communicating at one said end with a second chamber having walls which define a decreasing cross-section away from the first chamber to a distal end of smaller surface area than said one end, the apparatus including means for determining, when the apparatus is in use, when the free liquid surface reaches a predetermined height at or near the distal end and for determining the position within the second chamber of the interface between said liquids.

7. Apparatus as claimed in claim 6, wherein the means for determining when the free liquid surface reaches the predetermined height comprises a sensor positioned in the second chamber at said predetermined height.

8. Apparatus as claimed in claim 6 or 7, wherein the means for determining the position of the interface between said liquids comprises a sensor located in the second chamber.

9. Apparatus as claimed in any one of claims 6 to 8, wherein the first chamber is cylindrical and the second chamber has the shape of a truncated cone.

10. Apparatus as claimed in any one of claims 6 to 8, wherein the first chamber is of rectilinear transverse cross-section and the second chamber has the shape of a truncated pyramid.

11. Apparatus as claimed in any one of claims 6 to 10, wherein inner surfaces of the first and second chambers are coated with an oleophobic substance.

12. Apparatus for measuring the thickness of a layer of a first liquid lying on a second liquid, substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (12)

**WARNING** start of CLMS field may overlap end of DESC **. When using apparatus according to the invention, the value obtained for the thickness of the layer of liquid should be reasonably accurate since the thickness of a predetermined surface (rather than a particular point) is being measured. Also, owing to the generally tapering cross-section of the second chamber, the measured thickness of the layer is much greater than the actual thickness and hence the effect of error in measurement on the final result should be minimised. Further, the result obtained should be independent of the nature of the liquids. For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing, which shows a vertical section through one form of apparatus according to the present invention. The apparatus comprises a measuring vessel formed with a first chamber 1 open at the bottom and connected to a second chamber 2. A sensor 3 for detecting the presence of free liquid surface and a sensor 4 for determining the position of the interface between the first and second liquids are fixed in the chamber 2. The apparatus is used as follows: A predetermined surface area of liquid is enclosed by the chamber 1, and then the measuring vessel is introduced further into the second liquid so the liquid rises into the chamber 2 until the free liquid surface reaches the sensor 3. Then the sensor 4 is used to determine the position of the interface between first and second liquids. Hence the instantaneous thickness of the layer of first liquid is determined. From this, the original layer thickness may be determined in accordance with a mathematical relationship between instantaneous thickness and original thickness determined by the geometry of the first and second chambers of the vessel. WHAT WE CLAIM IS:-

1. A method of measuring the thickness of a layer of a first liquid lying on a second liquid, wherein a sample of predetermined surface area of said layer on said second liquid is enclosed in a first chamber of an open bottomed measuring vessel by submerging the lower portion of said vessel in the first liquid at least to the interface between the first and second liquids, said first chamber communicating directly with a second chamber of said vessel which second chamber undergoes a reduction in transverse cross-section from its position of communication with said first chamber to an opposite end region thereof, and possesses a greater height than said first chamber, the measuring vessel is submerged further so that the sample of the first liquid rises into the second chamber until the free liquid surface reaches a predetermined height, the thickness of the sample being increased by the reduction in cross-section, and then the height of the liquid interface in said second chamber is determined and said first-mentioned thickness is determined in accordance with a mathematical relationship between the difference between said heights and geometry of the chambers of the vessel.

2. A method as claimed in claim 1, wherein rise of the free liquid surface to said predetermined height is detected by a sensor positioned in the second chamber at said predetermined height.

3. A method as claimed in claim 2, wherein the sensor is positioned in the second chamber at said opposite end region thereof.

4. A method as claimed in any preceding claim, wherein the position of said liquid interface is detected by a further sensor positioned in the second chamber.

5. A method of measuring the thickness of a layer of a first liquid lying on a second liquid, substantially as hereinbefore described with reference to the accompanying drawing.

6. Apparatus for carrying out the method of claim 1, comprising a vessel formed with a first chamber completely open at opposite ends having wall means parallel to its longitudinal axis and communicating at one said end with a second chamber having walls which define a decreasing cross-section away from the first chamber to a distal end of smaller surface area than said one end, the apparatus including means for determining, when the apparatus is in use, when the free liquid surface reaches a predetermined height at or near the distal end and for determining the position within the second chamber of the interface between said liquids.

7. Apparatus as claimed in claim 6, wherein the means for determining when the free liquid surface reaches the predetermined height comprises a sensor positioned in the second chamber at said predetermined height.

8. Apparatus as claimed in claim 6 or 7, wherein the means for determining the position of the interface between said liquids comprises a sensor located in the second chamber.

9. Apparatus as claimed in any one of claims 6 to 8, wherein the first chamber is cylindrical and the second chamber has the shape of a truncated cone.

10. Apparatus as claimed in any one of claims 6 to 8, wherein the first chamber is of rectilinear transverse cross-section and the second chamber has the shape of a truncated pyramid.

11. Apparatus as claimed in any one of claims 6 to 10, wherein inner surfaces of the first and second chambers are coated with an oleophobic substance.

12. Apparatus for measuring the thickness of a layer of a first liquid lying on a second liquid, substantially as hereinbefore described with reference to the accompanying drawing.