GB1568865A - Sensitive j-tube and application thereof - Google Patents

Description

PATENT SPECIFICATION ( 11) 1 568 865

tn ( 21) Application No 32489/77 ( 22) Filed 3 Aug 1977 ( 19), O ( 31) Convention Application No 713087 ( 32) Filed 9 Aug 1976 in, ( 33) United States of America (US)

O ( 44) Complete Specification Published 11 Jun 1980

I ( 51) INT CL G 011 F 23/16 G Ol L 7/18 ( 52) Index at Acceptance G 1 H 3 G 1 L 3 D 2 ( 54) SENSITIVE J-TUBE AND APPLICATION THEREOF ( 71) We, Texaco Development Corporation, a Corporation organized and existing under the laws of the State of Delaware, United States of America, of 135 East 42nd Street, New York, New York 10017, United States of America, 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 concerns a sensitive J-tube instrument and a particular application thereof.

More specifically it concerns an application of the principles involved to provide a novel manometer that has increased sensitivity Also, a particular application is that of measuring the change in liquid level of a tank of liquid over a predetermined period of time, which 10 change may indicate the presence of a leak.

The testing of underground tanks for leakage has always been a difficult problem Heretofore, two known methods which have been used have had various drawbacks A first method required the product to be removed from the tank and the vent lines to be sealed Then the tank was pressurized with air to several pounds per square inch The pressure would then be monitored over a given period of time for indications of a leak Obvious drawbacks of that 15 arrangement included the fact that changes in pressure indicated would not necessary mean that the tank was leaking but it might just as well be in the connecting lines or dispensor from the tank Furthermore, the removal of products from the tank was time consuming and costly, and the pressurizing of the tank risked damage thereto.

A second procedure which has been employed involved the fitting of the fill pipe of the 20 tank with a four or five foot high standpipe, and then the tank would be filled with product to the top of the standpipe Any leakage would then be detected by observing the drop in level of the standpipe This method had a bad tendency to stress the tank and could expand the ends of the tank Also since product had to be added to the tank for this test the temperature would not be stable, and consequently considerable variations would have to be taken into consid 25 eration to make an accurate determination.

Consequently, it is an object of this invention to provide an instrument and/or method for determining leaks in large product tanks, such as underground storage tanks for gasoline or the like It involves the principles of this invention which provides an amplification of the difference in surface levels of a pair of liquid columns that are connected by a U-tube 30 The invention provides a J-tube device for measuring change in the surface level of a fluid, comprising a U-tube portion containing an indicator-fluid therein, said Utube portion having a predetermined inside cross-sectional area and one leg of said Utube portion being connected to a larger inside cross-sectional area tube to form the taller leg of said J-tube, and valve means for connecting each of said U-tube portion legs with a fluid to be measured in 35 which, in use, said device is immersed with the larger cross-sectional area tube extending above the surface of the fluid, said valve means being connected above the tops of said indicator fluid.

Therefore the invention provides a sensitive J-tube device for measuring change in the surface level of a fluid It comprises a relatively small inside diameter U-tube containing a "predetermined quantity of a coloured indicator-fluid that is immiscible with said fluid the Resurface level of which is to be measured The said indicator-fluid has a density which is approximately the same but heavier than said fluid being measured The combination comprises a relatively large inside diameter tube connected to one leg of said U-tube and forming therewith the taller leg of said J-tube The said large tube is long enough to extend 45 1,568,865 from above the maximum surface level of said fluid being measured to below the minimum surface level thereof It also comprises, in a preferred embodiment, a three-way valve having three ports for connection to each of the legs of said U-tube and to the body of said fluid being measured, and it comprises means for connecting said U-tube leg ports to said U-tube at a location that is above the maximum height of said indicator-fluid therein The said three-way valve having at least three positions one for connecting all three of said ports together and one for connecting only the shorter leg of said J-tube to the body of said fluid being measured and one for closing said U-tube leg ports It also comprises, according to another preferred feature, a reservoir connected into the shorter leg of said J-tube at a location above the maximum expected height of said indicator fluid, in order to contain any overflow without 10 loss of indicator fluid It further comprises, according to a further preferred feature, an elongated support for holding said J-tube device in a fixed position when measurement is being taken Moreover, it comprises, according to a further preferred feature, an elongated handle for actuating said three-way valve from a location above the surface of said fluid being measured 15 The invention also provides a method of measuring a change in the surface level of a fluid, comprising the steps of taking a relatively small inside cross-sectional area U-tube having an indicator-fluid therein, and having a larger inside cross-sectional area tube connected to one leg of said U-tube, immersing said tubes into said fluid with said larger area tube extending above said surface level, connecting both legs of said U-tube with said fluid at a location on 20 said tubes which is above the maximum height of said indicator-fluid therein, said connection being made while said tubes are immersed, disconnecting said one leg from said fluid to isolate said leg and said larger area tube from said fluid at the beginning of a measuring time period, and determining the difference in height of the tops of said indicator-fluid levels in said U-tube at the end of said measuring time period whereby the change in surface level of 25 said fluid is magnified.

The invention further provides a method of magnifying the measurement of a change in surface level of a first fluid by employing a U-tube containing a second fluid which is immiscible with said first fluid, comprising the steps of providing a relatively large crosssection area tube connected to one leg of said U-tube at a location that is higher than a 30 predetermined maximum level of rise of said second fluid in one of the legs of said U-tube, opening valve connections to both legs of said U-tube at a location above said maximum level prior to the commencement of a measurement time period, immersing said Utube and said large area tube in said first fluid to equalize the level of said first fluid inside of said large area tube with that outside and equalize the levels of said second fluid in said U-tube legs, isolating 35 said one leg and the large cross-section area tube from said first fluid at said commencement of said measurement time period, and determining the difference in fluid levels of said second fluid in said U-tube legs at the termination of said measurement time period.

The foregoing and other objects and benefits of the invention will be more fully set forth below in connection with the best mode contemplated by the inventor of carrying out the 40 invention, and in connection with which there are illustrations provided in the drawings, wherein:

FIG 1 is a schematic diagram illustrating a J-tube structure according to one embodiment of the invention; FIG 2 is a schematic diagram like that of FIG 1 but showing the fluid level modified in 45 accordance with changes in the level of a bulk fluid that is having its surface level change measured; FIG 3 is a longitudinal elevation not according to scale, illustrating one embodiment of an instrument in accordance with the invention; and, FIGS 4 and 5 are schematic diagrams illustrating two operative positions of the three-way 50 valve that is employed in the instrument according to FIG 3.

It has been discovered that a change in the level of a body of liquid may be amplified by employing a J-tube instrument according to this invention The basic principles are illustrated and will be explained in connection with the schematic showings of FIGS 1 and 2 Both of these figures illustrate a body of liquid 11 that has a surface 12, which may change in height, as 55 indicated in FIG 2 A change in the height of the surface 12 of liquid body 11 may be because of a leak in the tank (not shown), or other container for the liquid 11 However, such change would be slow and small in many instances And, particularly where an underground tank of gasoline or the like is concerned, the change in level is difficult to detect.

It will be noted that the instrument includes a U-tube portion 15, which has a shorter leg 16 60 connected by the U-shaped bottom with a longer leg 17, on the other side.

Connected to the top of the leg 17 of the U-tube, there is a larger crosssectional area tube that is long enough to extend up above the maximum level of surface 12 of the liquid body 11.

There are two valves 23 and 24 that are connected as indicated, so that the top of leg 16 has 65 valve 23 controlling the opening or closing of the interior of this leg through the top, in regard to connection thereof with the body of fluid 11 The valve 24 is connected so as to similarly control a fluid connection from the inside of the leg 17 of the U-tube 15 to the body of fluid 11 In this case there is a schematic indication of a pipe or other fluid conduit 27 from the upper portion of the U-tube leg 17, to one side of the valve 24 The other side of valve 24 is 5 connected directly into the body of liquid 11, similarity as is the other side of the valve 23, which is connected to the top of the leg 16 of the U-tube 15.

In the U-tube 15 there is an indicator fluid 30, which is immiscible with the liquid 11 As will appear from the explanation which follows, the indicator liquid 30 may be slightly heavier than the liquid 11 However, so long as the immiscibility is maintained, there appears to be no 10 reason why the density of the indicator liquid 30 might not be the same or even less than the density of the liquid 11.

It will be observed that the larger tube 20 has an inside cross-sectional area which is indicated by an arrow across the diameter It has reference No 31 applied thereto This area is greater than the inside cross-sectional area of the legs 16 and 17 of the U-tube The latter 15 area is indicated by the dimension d 2 which has arrows with reference numeral 32 applied thereto (in FIG 1).

It has been discovered that the changes in the level or height of the surface 12 of the body of liquid 11, will produce a differential in the levels of the indicator liquid 30 in U-tube 15 And, 2 the ratio of the change in level of surface 12, to the differential in the levels of the indicator 20 liquid 30 in the legs 16 and 17, is in accordance with the ratio of the inside cross-sectional area of the legs 16 and 17 to the inside cross-sectional area of the tube 20 Consequently, there is a substantial amplification of the change in the level of the surface 12 Furthermore, with the density of the indicator liquid 30 being the same or close to the same density as the body of liquid 11, the changes in levels are substantially all on account of the ratios of cross-sectional 25 areas As will appear below, this is because the volumne of liquid which must move during the establishment of a new balance, is the major factor in the change in liquid levels.

The foregoing relationship was discovered to exist while employing an indicator liquid that was made of a mixture of water and methanol, and with the body of liquid having its surface level measured being gasoline 30 An explanation of why the amplification of liquid level change takes place, may be made clear by reference to the schematic diagrams of FIGS 1 and 2 Thus, with relation to the various liquid level changes and the sizes of the J-tube structure, consider the following The procedure involves first the immersion of the J-tube structure, i e Utube 15 and the larger tube 20 connected to leg 17 thereof, all into the body of liquid 11 The immersion is done with 35 valves 23 and 24 both open Then the liquids in both legs of the J-tube system are permitted to equalize and the surface of the indicator liquid 30 will be at the same level This level is indicated in the diagrams by a dashed line 35.

Next, when it is desired to commence a fluid level measuring time period, the valve 24 2 i 11 be closed so as to isolate the liquid inside of tube 20 and the connecting leg 17 of the U-tube 40 Thereafter, following some predetermined period of time it may be found that the fluid level 12 of the body of liquid 11 has fallen to the position of the surface 12 which is indicated in FIG 2 The difference between these levels is indicated by the symbol in FIG 2.

The change A h in the level of surface 12 will cause a difference in pressure on the indicator-liquid 30 in the two legs of the U-tube 15, because of the fact that the liquids in tube 45 and the leg 17 are isolated from the body of liquid 11 Consequently, the indicator liquid will be pushed down in the leg 17 of the U-tube 15, and a corresponding change must take place in raising the liquid level of the indicator liquid 30 in leg 16 Since the liquid 11 and indicator liquid 30 are immiscible, all of the liquid which was isolated from the body of liquid 11 in the long leg of the i-tube structure remains isolated and there must be an equal volume 50 of the liquid displaced on the leg 16 side of the U-tube as the volume which has moved down from the tube 20 into the leg 17 of the U-tube, as the change in liquid levels took place.

Because of the foregoing conditions, the changes in fluid levels will be directly in proportion to the ratios of the cross-sectional areas of the fluid columns involved or to the square of the diameter of each of the fluid columns 55 The foregoing relationship may be proved mathematically in the following manner, with reference to the dimensions indicated on FIGS 1 and 2, and assuming that the tube 20 and the legs 16 and 17 are circular in cross-section Thus, it will be observed that:

Ah = h 6 + h, ( 1) Then, h 6 can be obtained in terms of h 2 from the fact that the volumne of liquid that has left 60 the large diameter tube 20 is equal to the volume of liquid that has entered the small diameter leg 17 The latter is the distance h 2 divided by two This may be expressed by the following equations:

ir/4 d,12 h 6 = 7 r/4 d 22 h 2/ 2 ( 2) 6 which may be solved for h 6 and will result in the equation: 65 1,568,865 1,568,865 4 h 6 = (d 2/dl)2 h 2/12 ( 3) Then, h 7 can be obtained in terms of h 2 from the fact that:

h 7 = h 4 (h 3 + h 2) = (h 4 h 3) h 2 ( 4) It will be noted that the quantity h 4 h 3 can be expressed in terms of h 2 as follows, and involving the fluid pressures: the pressure at the depth h 3 may be expressed as 5 h 3 = h 3 pg ( 5) wherein pg = the density of the liquid 11.

Then considering the other side (isolated portions) of the U-tube columns, the pressure at depth h 4 which is due to the isolate head of liquid 11 above the indicator fluid level in the leg 17 of the U-tube may be expressed as h 4 = h 4 Pg ( 6) 10 And, since we have a static balance, we can express the difference in pressure between the depths h 3 and h 4 as being equal to the expression h 2 pw, wherein pw = the density of the indicator liquid 30 Thus:

h 4 pg-h 3 pg = h 2 pw 15 or, 1 h 4 h 3 = h 2 pw/pg ( 7) Next, it is clear that:

h, = (h 4 h 3)-h 2 ( 8) and substituting in that equation for the quantity h 4 h 3 from the foregoing equation ( 7) we have 20 h 7 = h 2 pw/pg h 2 = h 2 (pw/pg1) ( 9) Now, since Ah = h 6 + h 7, it may be rewritten by substitutions from equations ( 3) and ( 9) to be Ah = (d 2/dl)2 h 2/2 + h 2 (pw/pg -1) 25 h 2 l 1/2 (d 2/d 1)2 + pw/pg 1 l ( 10) From this it can be seen that if the densities, i e pw and pg are substantially equal, the difference in liquid levels from the beginning to the end of a measurement time period, i e.

Ah, will be reflected at the levels of the indicator-liquid 30 surfaces as one half of h 2 times the ratio of the inside diameter d 2 divided by d,, squaredOr: 30 Ah = h 2/ 2 (d 2/d M 2 ( 11) In other words, the change in level 12 of the liquid 11, will be small compared to the change in the level of the surfaces of the indicator liquid columns of liquid 30, in the U-tube legs 16 and 17 Thus, the latter is an amplification of the former, in accordance with a ratio that is mostly related to the inside cross-sectional areas of the larger and smaller columns when the density 35 of the indicator liquid 30 is nearly the same as that of the body of liquid 11.

An instrument constructed in accordance with the invention, which may be employed for measuring change in the surface level of a fluid, is illustrated in FIG 3 This includes the various elements which will be described in more detail below The instrument will be 40 immersed in a body of liquid 40 which is to have any change in surface level thereof measured.

There is a relatively small inside diameter U-tube 41 which has a pair of legs 44 and 45 The U-tube 41 contains a predetermined quantity of an indicator liquid 48 therein, which is immiscible with the liquid 40 In addition, the indicator liquid 48 will preferrably have a color added thereto for aiding observation of the surface levels thereof 45 An instrument that was tested, employed as the indicator liquid 48, a mixture of methanol and 5 % water, which was dyed slightly to make it distinguishable visually from the body of liquid 40 which was gasoline Of course, the legs 44 and 45 of the U-tube portion 41, were transparent.

In the instrument illustrated in FIG 3, a relatively large inside diameter tube 51 is 50 connected to the top of the leg 45 of the U-tube 41 The large tube 51 is long enough to extend from above the maximum surface level of the body of liquid 40, during a measurement, to below the minimum surface level thereof.

There is a three-way valve 52 that is schematically indicated in FIGS 4 and 5 This valve 52 has three ports 56, 57 and 58 These ports are connected to the legs 44 and 45 of the U-tube 55 41 as well as to the body of liquid 40, in the manner indicated by the schematic diagrams of, FIGS 4 and 5.

Valve 52 is located on the instrument so that the connections to U-tube legs 44 and 45 are above the maximum height of the surfaces of indicator liquid 48 therein Also, it has at least three different positions, two of which are indicated by the schematic showings in FIGS 4 and 60 One position is like that shown in FIG 4 which connects the port 57 directly with common internal passages that are indicated schematically by three arrows 60 Consequently, the port 57 is connected to port 58 and port 56 together Thus, in this position the leg 45 of the J-tube instrument is connected to the leg 44 and to body of liquid 40 Therefore the indicator liquid 48 will stabilize its surfaces at equal levels, so that the indicator liquid 48 has equal height 65 columns in the legs 44 and 45.

A A It will be observed that the instrument also has a reservoir 61 that is connected into the leg 44 of the U-tube 41 This reservoir 61 is provided in order to contain any overflow of the indicator liquid 48, in case the response becomes too great.

Also, there is an elongated support member 62 which, has the tubes of the J-tube instrument attached in any convenient manner It is for handling the instrument and to 5 support it when a measurement is being taken.

There is an elongated handle 65 which connects to the three-way valve 52 and extends upward sufficiently to rise above the surface of the liquid 40 for manual manipulation of the valve.

It will be appreciated that a measurement procedure to detect a change in surface level of 10 the liquid 40 will involve an instrument like that described above, and a step of immersing the J-tube instrument into the body of liquid 40 Then the instrument will be held at a fixed position to allow equalization of the columns of indicator liquid 48 in the legs 44 and 45 This equalization will take place with the valve 52 in the position indicated by FIG 4.

At the commencement of a measuring time period the valve 52 will be shifted to the 15 position indicated in FIG 5, and consequently the liquid column on the long side (tube 51 and leg 45) of the J-tube instrument will be isolated from the liquid 40 After a predetermined period of time, any change in the level of the body of liquid 40 will be reflected by the amplified change in levels of the surfaces of indicator liquid 48, in the manner indicated above This change will take place while the valve 52 is in a position shown in FIG 5 20 Then, in order to take a reading of the indicator fluid surface levels in the U-tube legs 44 and 45, the situation may be held at then existing conditions by shifting the valve 52 to a position (not illustrated) which will close both ports 57 and 58 This holds the liquid levels in legs 44 and 45 at the positions they had reached Then the instrument may be raised bodily up out of the liquid 40 in order to take a reading of the difference in levels of the surfaces of 25 indicator liquid 48.

While particular embodiments of the invention have been described above in considerable detail in accordance with the applicable statutes this is not to be taken as in any way limiting the invention but merely as being descriptive thereof.

Claims (1)

1. WHAT WE CLAIM IS:

   1 A J-tube device for measuring change in the surface level of a fluid, comprising a U-tube portion containing an indicator-fluid therein, said U-tube portion having a predetermined inside cross-sectional area and one leg of said U-tube portion being connected to a larger inside cross-sectional area tube to form the taller leg of said Jtube, and valve means for connecting each of said U-tube portion legs with a fluid to be measured in which, in use, said 35 device is immersed with the larger cross-sectional area tube extending above the surface of the fluid, said valve means being connected above the tops of said indicator fluid.

   2 A measuring device according to claim 1, wherein said valve means comprises a three-way valve having at least two positions in which each leg of the Utube portion is 4 o connected to a fluid to be measured, and only the other leg of the Utube portion is connected 40 to such fluid, respectively.

   3 A measuring device according to claim 2, wherein such valve has a further position in which each leg of the U-tube portion is isolated from said fluid to be measured.

   4 A measuring device according to claim 2 or claim 3, further comprising an elongated 4 S handle for actuating said three-way valve from a location above the surface of said fluid 45 A measuring device according to any preceding claim, further comprising a reservoir connected to the other leg of said U-tube portion at a location above the maximum expected rise of said indicator fluid in order to contain any overflow without loss of indicator fluid.

   6 A measuring device according to any preceding claim, further comprising an elongated 0 support for holding said measuring device in a fixed position 50 7 A measuring device according to any preceding claim, wherein said indicator fluid includes a colouring agent for visually distinguishing from said fluid to be measured.

   8 A method of measuring a change in the surface level of a fluid, comprising the steps of taking a relatively small inside cross-sectional area U-tube having an indicator-fluid therein, and having a larger inside cross-sectional area tube connected to one leg of said U-tube, 55 immersing said tubes into said fluid with said larger area tube extending above said surface level, connecting both legs of said U-tube with said fluid at a location on said tubes which is above the maximum height of said indicator-fluid therein, said connection being made while said tubes are immersed, disconnecting said one leg from said fluid to isolate said leg and said 6 larger area tube from said fluid at the beginning of a measuring time period, and determining 60 the difference in height of the tops of said indicator-fluid levels in said U-tube at the end of said measuring time period whereby the change in surface level of said fluid is magnified.

   9 A method according to claim 8 wherein said indicator-fluid has a density approximately the same but heavier than said fluid being measured.

   An 10 A method according to claim 8 or claim 9 wherein said indicator fluid includes a 65 1,568,865 v J 6 1 568 8656 colouring agent for visually distinguishing from said fluid being measured.

   11 A method of magnifying the measurement of a change in surface level of a first fluid by employing a U-tube containing a second fluid which is immiscible with said first fluid, comprising the steps of providing a relatively large cross-section area tube connected to one leg of said U-tube at a location that is higher than a predetermined maximum level of rise of said second fluid in one of the legs of said U-tube, opening valve connections to both legs of said U-tube at a location above said maximum level prior to the commencement of a measurement time period, immersing said U-tube and said large area tube in said first fluid to equalize the level of said first fluid inside of said large area tube with that outside and equalize the levels of said second fluid in said U-tube legs, isolating said one leg and the large 10 cross-section area tube from said first fluid at said commencement of said measurement time period, and determining the difference in fluid levels of said second fluid in said U-tube legs at the termination of said measurement time period.

   12 A device for measuring change in the surface level of a fluid, substantially as 1 hereinbefore described with reference to, and as illustrated in, Figures 1 and 2 or Figures 3 to 1 of the accompanying drawings.

   13 A method of measuring change in the surface level of a fluid, substantially as hereinbefore described with reference to the accompanying drawings.

   Agents for the Applicants 2 MICHAEL BURNSIDE & PARTNERS 2 Chartered Patent Agents Hancock House 87 Vincent Square London S Wi P 2 PH Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited Croydon Surrey 1980.

   Published by The Patent Office 25 Southampton Buildings, London, WC 2 A IAY,from which copies may be obtained.