GB2259366A - Water-finding probe - Google Patents

Abstract

A probe suitable for determining the depth of water in an oil storage tank comprises a number of elongated transparent members (8) separated by conducting members (7) and supported by means of a conducting cross-piece (2). On one face of the probe the elongate members constitute a smooth face and on the other side the transparent members (6) are recessed to define grooves into which water-finding paste may be placed. The transparent members may be made of polymethyl methacrylate and the conducting members of brass. The support frame (2) is provided with a hole (5) for connecting a line for suspending the probe in a tank. <IMAGE>

Description

WATER-FINDING PROBE The present invention relates to a water-finding probe, in particular to a probe to determine the level of water collected at the bottom of oil storage tanks.

GB 2 082 326 discloses a water-finding probe which is intended to be used with a water-finding paste. A water-finding paste is a material which changes colour when it comes into contact with water. Such materials are commercially available. GB 2 082 326 discloses a water-finding probe comprising a transparent glass bar which is provided with brass channeling along its edges. The transparent glass bar has a matt finish receptive to water-finding paste on one side and a smooth finish on the other side.

A problem with the use of glass is that there is a risk of breakage. Furthermore with any non-conducting material there is the risk of generating static charges. In environments which can contain flammable vapours, such as oil storage tanks, this is a serious problem.

According to the present invention a probe suitable for determining the depth of water in an oil storage tank and having a back surface for receiving a water-finding paste and a front surface through which the water-finding paste can be viewed is characterised in comprising a plurality of elongated transparent members, a plurality of elongated conducting members, each transparent member being adjacent to a conducting member, the conducting members being in electrical contact with one another, the transparent and conducting members being so arranged as to constitute a smooth face on the front side of the probe and wherein on the back side of the probe the outer surface of the elongated transparent members lies below the outer surfaces of the adjacent conducting members so as to define grooves in which water-finding paste may be placed, and a support connecting means for connecting a line to support the probe and to allow electrical contact to the conducting members of the probe.

The elongated transparent members are most conveniently in the form of strips of polymethyl methacrylate or similar transparent polymer of generally rectangular cross-section.

The conducting members are conveniently made of brass. The conducting members may all have the same cross-section. However it is preferred that the two outer conducting members are of increased width to provide a supporting and strengthening frame for the probe.

The conducting members must be in electrical contact with one another. This is most easily achieved by having a conducting cross piece extending across the top of the device. This cross-piece may have a hole by which the probe may be suspended from a line and lowered into a tank. The suspending hole being in the conducting cross-piece allows for electrical contact to be made to the probe so that it can be earthed.

Where there are outer frame members and a cross-piece these may be formed from separate blocks of conducting metal or may be formed together from a single block.

To minimize the dangers from static change accumulation the exposed surface area of any individual transparent member is most desirably less than 2.8 x 10-3 m2. In practice the exposed surface area will be considerably less than this as a result of the practical limitations on the size of the water finding gauge imposed by the need to be able to fit through openings in tanks and to be raised and lowered manually by persons using the gauge.

The exposed surface area is the area which is not in contact with conducting material.

The total width of the gauge may, for example, be 40 to 80 mm and the length may be in the range 200 to 400 mm.

The width may be between 1 and 5 mm, more preferably 2 to 4 mm.

It is convenient for the conducting members, other than any outer frame members which may be present, to be approximately the same width as the transparent members.

The width length and the number of transparent area conducting members will generally be selected to give a width and length of transparent members which satisfies the exposed surface area criteria mentioned above.

The transparent and conducting members are so arranged that the front side of the probe has a smooth surface which can be easily wiped clean from any oil. Such a surface is most conveniently provided as a flat surface in which the outer surfaces of the conducting and transparent members provide for such a flat surface.

The rear surface is arranged so as to provide elongated depressions defined in the transparent members for receiving and holding water-finding paste. The recessed surfaces may be provided by starting with transparent and conducting members of the same thickness and having flat outer surfaces, with the transparent surface being machined away subsequently to provide elongated grooves. Alternatively the transparent members can be of lesser depth than the conducting members so that if they are at the same level on the front side then the transparent members will be recessed on the back side.

The number of transparent members provided will depend on the desired total width. Thus there may be for example between 4 and 10 transparent members.

The transparent and conducting members may conveniently be held together by means of screws which are passed through holes bored laterally through the members.

A graduated scale may be provided along the length of the probe. This is most conveniently provided on a wider outer frame portion. For ease of use it is preferably for the scale to be on the front face of the probe that is in the face remote from the face carrying the water-finding paste.

The invention will now be described with reference to the accompanying drawings in which Figure 1 is a diagrammatic representation (not to scale) of the front face of a water-finding probe according to the invention, and Figure 2 is a cross-section of the probe of Figure 1 along the line II-II.

Referring to Figure 1 a water-finding probe comprises an outer frame (I) comprising a cross-piece (2) and two frame members (3, 4) integral with the cross-piece. The cross-piece is provided with a hole (5) by which a line may be attached to suspend the probe. The frame (1) is constructed of brass.

Sandwiched within frame (1) are four elongated rectangular strips (6) of transparent plastics material (polymethyl methacrylate). Between the strips (6) are rectangular strips of brass (7). The rectangular strips of brass abut against the cross-piece (2) and are thus in electrical contact with it.

The transparent plastic strips and the brass strips are held together by two screws (8, 9) which extend through openings in the frame member (4) and extend through the transparent strips (6) and brass strips (7) to the member (3).

As can be seen in Figure 2 the transparent strips (6) and brass strips (7) are arranged relative to frame (1) so that the top surfaces are all at the same level. Because the transparent strips (6) are less deep than the brass strips (7) recesses are formed on the back face of the probe into which water-finding paste can be inserted.

The depth of the recesses need not be very great, and may be less than 1 mm. The width of the transparent members may for example be between 2 and 5 mm. The width of the conducting members (7) may be between 4 and 5 mm.

Claims (9)

Claims:

1. A probe suitable for determining the depth of water in an oil storage tank and having a back surface for receiving a water-finding paste and a front surface through which the water-finding paste can be viewed comprises (a) a plurality of elongated transparent members, (b) a plurality of elongated conducting members, each transparent member being adjacent to a conducting member, the conducting members being in electrical contact with one another, the transparent and conducting members being so arranged as to constitute a smooth face on the front side of the probe and wherein on the back side of the probe the outer surface of the elongated transparent members lies below the outer surfaces of the adjacent conducting members so as to define grooves in which water-finding paste may be placed, and (c) a support connecting means for connecting a line to support the probe and to allow electrical contact to the conducting members of the probe.

2. A probe according to claim 1 wherein the transparent members are in the form of strips of polymethyl methacrylate.

3. A probe according to claims 1 or 2 wherein the conducting members are made of brass.

4. A probe according to any of the preceding claims wherein the conducting and transparent members are approximately the same width.

5. A probe according to any of the preceding claims wherein the support connecting means is provided by a conducting cross piece extending across one end of the probe and in contact with the conducting members.

6. A probe according to any of the preceding claims wherein the support connecting means is provided with a hole for connecting a line to support the probe.

7. A probe according to any of the preceding claims wherein the outer elongate members are conducting members of increased cross-section.

8. A probe according to any of the preceding claims wherein a graduated scale is provided on the front face of an outer conducting member.

9. A probe as claimed in any one of the preceding claims and as hereinbefore described with reference to the accompanying drawings.