WO1997042470A1

WO1997042470A1 - Level-measuring equipment for liquids

Info

Publication number: WO1997042470A1
Application number: PCT/NO1996/000100
Authority: WO
Inventors: Åge ALBRIGTSEN
Original assignee: Albrigtsen Aage
Priority date: 1995-03-28
Filing date: 1996-04-30
Publication date: 1997-11-13

Abstract

A staff (3) is placed in a measuring well (2) inside a tank (1), and on said staff (3) are arranged float-like level plates (4) in a manner which enables them to rotate around their axles (5) under the influence of the surface of a liquid. On the level plates, symbols (4') are inscribed to indicate the position of the level plates (4) in relation to the lower extremity of the staff (3), these symbols being readable from the upper end of the measuring well (2).

Description

LEVEL-MEASURING EQUIPMENT FOR LIQUIDS

The present invention relates to a level-measuring device for liquids in a tank, especially for explosive liquids stored in underground fuel tanks at petrol stations and the like. All such tanks comprise a measuring well consisting of a vertical tube, which to this day is used for measuring the liquid level. This is done by lowering a dipper rod down to the bottom of the tank. When the rod is lifted again, it is possible to read to which level the liquid has moistened the rod and from this, deduce the level and therefore the volume of liquid.

A large number of methods may be used to determine the level of liquids in tanks. Many such methods involve the use of electricity to the tank and return signals to indicate the level. Such measuring systems will be useful to keep a continuous monitoring of, for example, several underground tanks at a petrol station with indication on a panel inside the station building, showing the available fuel supply at all times. As a rule, for most petrol stations, such continuous monitoring is not necessary. As the liquid to be measured can ignite and explode, this factor must be taken into account in the design of any electronic measuring device. All electronic measuring devices must be designed to the so-called Ex classification. Such continuous electronic monitoring system to Ex classification is costly, especially in view of the number of tanks and of sensors. In general, a petrol station will not require fuel level information more than once a day. It is also desirable to keep the cost of the measuring system down. Monitoring the level of the contents of fuel tanks has a dual purpose; firstly to determine the volume of fuel sales, and secondly to monitor any possible fuel leakage from the tank, which would pollute the environment. Leakage monitoring must be installed in all petrol stations within a certain time. In order to effect this in a cheap and easy but safe manner, a level-measuring system through the existing measuring well in the tank will be able to provide an acceptable solution. A very common level-measuring principle is provided by a float floating on top of the liquid surface This principle applied to indicate a number of determined levels is shown in US patents nos 1,408,218, 3,307,399 and 3,545,272 A series of small floats which follow the level of the liquid are used The detection and indication of the actual liquid level is solved in various ways in the above- mentioned patents In patent 1,408,218, as the floats rise, they close a sight hole in the wall of the tank enabling an observer on the outside of the vat or tank to see how many sight holes are closed and thus determine the liquid level Such a solution cannot be used for an underground tank

US patent no 3,307,399 presents a solution which also aims at open sea or tank, and will not be appropriate for an underground fuel tank

US patent no 3,545,272 has an electric indicator for the float position This entails the transmission of electric signals to and from the inside of the tank, which will increase the costs of the equipment due to the Ex classification The object of the present invention is to provide a solution which satisfies the following requirements

- explosion-proof design - installation and use in all existing and new underground fuel tanks through the measuring well

- easy use

The above is achieved with the help of a staff placed in a measuring well inside a tank, along which staff several level plates are mounted at a certain distance from one another, such plates being on at least one of their surfaces inscribed with symbols indicating the level of the liquid which can be read from one extremity of the rod Each level plate is mounted in such a manner as to rotate around an axle when influenced by the liquid

Further details of the invention will appear from the following description of a preferred embodiment of the invention Figure 1 is a cross-sectional view of an underground fuel tank with measuring well. Figure 2 illustrates the staff with level plates ready for installation in the measuring well.

Figure 3 is a detailed view of the level plates on the staff. Figure 4 shows the invention placed in a measuring well inside a tank. Figure 5a illustrates an alternative staff equipped with a float and mirror. Figure 5b is the same device as 5a, shown in a vertical longitudinal section.

The present invention consists in placing a level-measuring device in an existing measuring well 2 itself mounted in an enclosed underground tank 1 The level-measuring device consists of a U-profiled staff 3 as shown in a cross-sectional view on figure 3. Along said staff 3 are mounted several level plates 4 at a distance of, for example, one centimeter from one another. Each level plate 4 is mounted on an axle 5 in such a manner that the level plate 4 can rotate when it is influenced by a force. Figure 2 illustrates several such level plates 4 in different positions along a staff 3.

The level plates 2 are designed with a certain buoyancy so as to float upwards when in contact with the liquid contained in the tank. On the plate which is floating closest to the surface of the liquid, a symbol 4' printed on the level plate

4 and indicating the level in centimeters will be clearly observable from the top of the staff 3. The level plates 4 which are above the plate floating in the liquid will, because of the lack of influence from the liquid to create buoyancy, hang downwards and will not hide from sight the plate floating on the surface of the liquid. Figure 3 illustrates how the plates which are totally immersed in the liquid float upwards in one of their extremities. The level plate 4 closest to the surface of the liquid is practically horizontal, and the plates situated above the liquid hang downwards thus making it impossible to observe from above the symbol 4' printed on them. One can imagine the staff 3, with level plates 4, being mounted in the measuring well 2 in an underground tank 1. The level plate 4 which floats on the surface of the water will be readable from the top of the staff 3, i.e. from the top of the measuring well 2. This may be done with the help of a lens 6 mounted at the upper extremity of the measuring well, so as to enable an observer to read the symbols 4'. One can also imagine a light source 7 placed to the side of the lens 6 in order to illuminate the symbols 4' on the level plate 4, or the symbols 4' may be in a phosphorescent material. Such reading devices make it necessary to real the level manually.

It is possible to devise several different mehods permitting reading of the symbols 4¹ on the level plates 4 in a more automatic manner, for example with the help of a camera placed at the top of the measuring well 2. Another method could be to replace the symbols on the level plates 4 with bar codes which may be read by an appropriate code reading head placed at the top of the measuring well 2.

Figures 5 a and b illustrate an alternative and simpler design for the staff 3. In this case, the symbols 4' are position numbers on a measuring tape which is fixed along the inside of the U-profiled staff 3. A float 4" can move along the staff 3 inside the U profile. The upper end of the float 4" is slanting at 45 ° towards the symbols 4' and is covered by a mirror surface in order to allow the symbol 4' which is at any time visible above the mirror surface 8 to be read from the top of the measuring well 2.

Claims

1. Level-measuring equipment for a liquid in a tank where several float-like level plates for the detection of the liquid surface characterized in that a staff (3) is placed inside a measuring well (2) in a tank (1), and several level plates (4) are mounted at a certain distance from one another along the staff (3) and on at least one side of said plates (4) is marked a symbol (4') for the liquid level which can be read from one extremity of the staff (3), and each level plate (4) is mounted in such a manner as to allow movement around an axle (5) under the influence of the liquid.

2. The level-measuring equipment for a liquid in a tank of claim 1, characterized in that the symbol (4') is a number expressing centimeters which can be read through a lens (6) provided at the upper extremity of the measuring well (2) and assisted by a light source (7) placed in the vicinity.

3. The level-measuring equipment for a liquid in a tank of claim 2, ch a ra c terized in that the lens (6) may be replaced by an electronic reading device through a camera.

4. The level-measuring equipment for a liquid in a tank of claim 1, characterized in that the symbol (4¹) is a bar code which may be read electronically by an existing method from the upper extremity of the measuring well (2).

5. The level-measuring equipment for a liquid in a tank of claim 1, characterized by a float (4") mounted so as to move along the staff (3) and provided with an upper surface which is slanting at 45 ° towards the symbols (4') and is made of a mirror material.