GB2360362A

GB2360362A - Moisture measuring apparatus

Info

Publication number: GB2360362A
Application number: GB0006347A
Authority: GB
Inventors: Peter Samuel Hancock; Maurice Edward Twentyman
Original assignee: Ceram Research Ltd
Current assignee: Ceram Research Ltd
Priority date: 2000-03-17
Filing date: 2000-03-17
Publication date: 2001-09-19
Also published as: GB0006347D0

Abstract

A method and apparatus for measuring the quantity of water in a porous solid member. The apparatus 10 comprises an enclosure member 14 locatable against the solid member. Inlet and outlet pipes 20,22 extend through walls of the member 14. Air can be blown from a pump 30 through an air desiccant tube 28 and flow gauge 26 into the enclosure member 14. Air exhausts through the outlet pipe 22 and passes into a moisture measuring cell 24 which permits the quantity of water in the solid member to be calculated.

Description

2360362 Measuring Apparatus This invention concerns apparatus for

measuring the quantity of fluid in a solid member, and particularly but not exclusively apparatus for measuring the water content in a solid member, and especially the water content of plaster of Paris moulds or articles of clayware. The invention also provides a method of using such apparatus.

Numerous industrial instruments are available for the measurement of the relative humidity of air, or the moisture content of powders. When used to measure the moisture content of powders the instrumental probe is inserted into the powder. This is not however possible with a porous solid member. other methods of measurement, which include monitoring the moisture content by weighing or by inserting conductivity probes, are often not feasible. For instance, soluble salts can limit the use of electrical conductivity probes.

An example of the type of porous solid that has been difficult to assess by conventional means is the plaster of Paris moulds used in the manufacture of ceramic products. The moulds for sanitaryware items are large, heavy and frequently attached to machinery, making weighing impractical as a control measurement. Smaller moulds for tableware are easier to handle, but weighing is not a technique which lends itself to automated control. Clayware products also pose difficulties as they have to be fully dried before firing, they do not dry evenly, and so spot measurements are of much greater value than overall average values.

According to the present invention there is provided apparatus for measuring the quantity of fluid in a porous solid member, the apparatus comprising means for causing a gas flow over a surface of the member, and means for measuring the quantity of fluid in the gas flow from said surface.

Also according to the present invention there is provided apparatus for measuring the quantity of fluid in a porous solid member, the apparatus 2 comprising means for defining a substantially sealed enclosed volume against a surface of the member, means for causing a gas flow through said enclosed volume and hence over said surface, and means for measuring the quantity of fluid in the gas flow from the said volume.

The apparatus preferably also comprises means for measuring the flow rate of gas through said volume and/or over said surface.

The apparatus may be arranged such that the gas is air, which air may be taken from and/or vented to atmosphere.

Means may be provided for substantially removing any of said fluid from the gas prior to the gas passing into the enclosed volume or onto said surface.

The volume defining means preferably comprises an enclosure member engagable against the surface of the solid member to define the enclosed volume. An inlet and outlet are preferably provided extending through the enclosure member, and through which the gas flow passes.

The fluid removing means may be connected to the inlet.

The enclosure member may be shaped to define an enclosed volume adjacent a generally flat surface of the solid member, and the enclosure member may be shaped to define a substantially hemispherical volume adjacent the solid member.

Alternatively, the enclosure member may be shaped to close an opening in the solid member, with the enclosed volume being defined by the opening and the enclosure member.

A seal may be provided around an edge of the enclosure member. The seal is preferably flexible so as to be sealingly engagable against a non-flat surface, and may comprise an 0-ring or bellows seal.

3 Pump means may be provided for causing the gas flow through said enclosed volume. The pump means may blow gas through the enclosed volume, or alternatively may suck gas therethrough.

The apparatus may measure water content, and the fluid removing means may be in the form of an air desiccant tube.

Alternatively, the apparatus may measure solvent content, and may measure the content of a gas.

The apparatus is preferably portable.

The invention also provides a method for measuring the quantity of fluid in a porous solid member, the method comprising causing a gas flow over a surface of the member and measuring the quantity of fluid in the gas flow from said surface.

The method preferably uses apparatus according to any of the preceding fifteen paragraphs.

Initially the apparatus may be swept with gas free of said fluid, and this may be accomplished by defining the enclosed volume against a non- porous member substantially free of said fluid.

In the case of measuring water content, the enclosed volume is preferably defined against a dry plate, which plate may be metallic.

The fluid measurement is preferably compared against calibrated measurements previously made against solid members with a known fluid content.

Examples of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:- 4 Fig. 1 is a diagrammatic view of a first apparatus according to the invention; Fig. 2 is a similar view to Fig. 1 of a second apparatus according to the invention; and Fig. 3 is a table showing measurements obtained from apparatus similar to that shown in Figs. 1 and 2.

Fig. 1 shows apparatus 10 suitable for measuring moisture content in an article such as a plaster of Paris mould 12 used in the ceramics industry. The apparatus 10 comprises an enclosure member 14 in the shape of a hollow hemispherical member. A rubber seal 16 is provided around the edge of the member 14. The member 14 can be located on the mould 12 as shown to define a smaller hemispherical enclosed volume 18 against a circular area of the mould surface 17.

Inlet and outlet pipes 20, 22 extend through the walls of the member 14. The outlet pipe 22 connects via pipework to a moisture measuring cell 24 which exhausts via further pipe work to atmosphere. The inlet pipe 20 connects to a flow gauge 26 which leads via pipework from an air desicant tube 28 and an air pump 30. Instead of the pump 30 a pressurised gas cylinder could be provided which connects via pipework to the upstream end of the tube 28.

In use, the apparatus 10 is initially purged of moisture by operating the pump 30 and locating the closure member 14 against a dry metal plate (not shown) such that any moisture in the apparatus 10 is swept out as air is blown through the apparatus 10. The enclosure member 14 is subsequently located against the mould 12 and once equilibrium has been reached after a suitable time such as a minute, the moisture content is measured using the cell 24.

The measurement from the cell 24 can be plotted on a calibration table as shown in Fig. 3 to determine the moisture content. Fig. 3 shows on the vertical axis air moisture content in gkg-1 against mould moisture content in percent. This measurement has previously been made for moulds of known moisture content, with the diamond shapes showing the undried working face of the mould, whilst the squares show the measurements given for the dry back face of the mould. The flow gauge 26 is used to ensure that a substantially constant flow is kept for all readings.

Fig. 2 shows a modified apparatus 32. The apparatus 32 is similar to the apparatus 10 except as follows, and thus equivalent components similar reference numerals have been used. For the apparatus 32 a suction pump 34 is provided downstream of the measuring cell 24, with the upstream end of the desiccant tube 28 being open to atmosphere. Accordingly, in this instance air is sucked through the apparatus 32 rather than being blown.

There is thus described apparatus suitable for measuring the moisture content of plaster of Paris moulds, or other articles such as items of clayware. The apparatus is of relatively simple construction and can thus be inexpensively and robustly manufactured to be usable in a portable manner in a wide range of environments.

Various modifications may be made without departing from the scope of the invention. For instance, the enclosure member could take a different form. In some instances the enclosure member may be in the form of a bung or similar which locates in an opening in a solid member to close same and measure the moisture content of air caused to flow through the opening. In some instance it may be possible to dispense with an enclosure member, and simply to measure moisture content or the like in a gas which is deflected against a surface. Different means could be used for pumping air or removing moisture from the air prior to entering the enclosure member. The flow meter may be dispensed with when using pumps capable of delivering a constant flow rate.

It is to be realised that the invention is usable for measuring fluids other 6 than water. For instance, the invention could be used to measure solvents or gases such as formaldehyde coming off chipboard. The apparatus need not operate with air, and it could be possible for a different gas to be pumped through the enclosure member. Utilising thermally resistant materials the apparatus could be used to measure vapours evolved above room temperature.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

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Claims

1. Apparatus for measuring the quantity of fluid in a porous solid member, the apparatus comprising means for causing a gas flow over a surface of the member, and means for measuring the quantity of fluid in the gas flow from said surface.

2. Apparatus for measuring the quantity of fluid in a porous solid member, the apparatus comprising means for defining a substantially sealed enclosed volume against a surface of the member, means for causing a gas flow through said enclosed volume and hence over said surface, and means for measuring the quantity of fluid in the gas flow from the said volume.

3. Apparatus according to claim 2, in which the volume defining means comprises an enclosure member engagable against the surface of the solid member to define the enclosed volume.

4. Apparatus according to claim 3, in which an inlet and outlet are provided extending through the enclosure member, and through which the gas flow p, a c' s e s.

5. Apparatus according to claims 3 or 4, in which the enclosure member is shaped to define an enclosed volume adjacent a generally flat surface of the solid member.

6. Apparatus according to claim 5, in which the enclosure member is shaped to define a substantially hemispherical volume adjacent the solid member.

7. Apparatus according to claims 3 or 4, in which the enclosure member is shaped to close an opening in the solid member, with the enclosed volume being defined by the opening and the enclosure member.

8 8. Apparatus according to any of claims 3 to 7, in which a seal is provided around an edge of the enclosure member.

9. Apparatus according to claim 8, in which the seal is flexible so as to be sealingly engagable against a non-flat surface.

10. Apparatus according to claims 8 or 9, in which the seal comprises an 0ring.

11. Apparatus according to claims 8 or 9, in which the seal comprises a bellows seal.

12. Apparatus according to any of claims 2 to 11, in which pump means are provided for causing the gas flow through said enclosed volume.

13. Apparatus according to claim 12, in which the pump means blow gas through the enclosed volume.

14. Apparatus according to claim 12, in which the pump means suck gas t h r o u g h. t, -1 - P- e- n. c- l o -Q e- d x 7 o l 11 M - e.

IS. Apparatus according to any of the preceding claims, in which means are provided for substantially removing any of said fluid from the gas prior to the gas passing into the enclosed volume or onto said surface.

16. Apparatus according to claim 15 when dependent on any of claims 2 to 14, in which the fluid removing means is connected to the inlet.

17. Apparatus according to any of the preceding claims, in which the apparatus measures water content.

18. Apparatus according to claim 17 when dependent on claims 15 or 16, in which the fluid removing means is in the form of an air desiccant tube.

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19. Apparatus according to any of claims 1 to 16, in which the apparatus measures solvent content.

20. Apparatus according to claim 19, in which the apparatus measures the content of a gas.

21. Apparatus according to any of the preceding claims, in which the apparatus comprises means for measuring the flow rate of gas through said volume and/or over said surface.

22. Apparatus according to any of the preceding claims, in which the apparatus is arranged such that the gas is air.

23. Apparatus according to claim 22, in which the air is taken from and/or vented to atmosphere.

24. Apparatus according to any of the preceding claims, in which the apparatus is portable.

25. A r.n. i C t h c) d f n_ r r ne an s 11 r. i n cT the quantity of fillir' ill n inn-rniie colirl MúiMIa 11 r M. --- --- - 1,mM-0 0. U, the method comprising causing a gas flow over a surface of the member and measuring the quantity of fluid in the gas flow from said surface.

26. A method according to claim 25, in which apparatus according to any of claims 1 to 24 is used.

27. A method according to claims 25 or 26, in which initially the apparatus is swept with gas free of said fluid.

28. A method according to claim 27, in which the sweeping is accomplished by defining the enclosed volume against a non-porous member substantially free of said fluid.

29. A method according to claim 28, in which in the case of measuring water content, the enclosed volume is defined against a dry plate.

30. A method according to claim 29, in which the plate is metallic.

31. A method according to any of claims 25 to 30, in which the fluid measurement is compared against calibrated measurements previously made against solid members with a known fluid content.

32. Apparatus for measuring the quantity of fluid in a porous solid member, the apparatus being substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawings.

33. Apparatus for measuring the quantity of fluid in a porous solid member, the apparatus being substantially as hereinbefore described with reference to Fig. 2 of the accompanying drawings.

34. A method for measuring the quantity of fluid in a porous solid member, the method being substantially as hereinbefore described with reference to the

35. Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.