CA2061153A1 - Line leak detector and method - Google Patents
Line leak detector and methodInfo
- Publication number
- CA2061153A1 CA2061153A1 CA 2061153 CA2061153A CA2061153A1 CA 2061153 A1 CA2061153 A1 CA 2061153A1 CA 2061153 CA2061153 CA 2061153 CA 2061153 A CA2061153 A CA 2061153A CA 2061153 A1 CA2061153 A1 CA 2061153A1
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- CA
- Canada
- Prior art keywords
- line
- test
- reservoir
- leak rate
- temperature
- Prior art date
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Abstract
LINE LEAK DETECTOR AND METHOD
Abstract of the Disclosure An apparatus and method for employing the apparatus in testing underground fluid containing lines for leaks. The apparatus comprises (a) a differential pressure transducer mounted to a reservoir for indicating volumetric change in the reservoir; (b) a temperature transducer mounted in the reservoir for monitoring temperature fluctuation in the reservoir; (c) a gauge pressure transducer mounted in the reservoir; (d) a remote temperature sensor and a data acquisition and processing system. The method for employing the apparatus comprises of connecting the apparatus to the line under test and entering certain parameters of a line under test and product temperature into the test computer. The test system then monitors volumetric change in the reservoir as well as pressure and temperature fluctuations in the line under test at 30 second intervals. At the end of the predetermined test period, the system calculates the leak rate during each five minute interval of the test as well as a cumulative leak rate. The trends in the leak rate data during the test are then analyzed to determine whether the calculated cumulative leak rate is accurate.
Abstract of the Disclosure An apparatus and method for employing the apparatus in testing underground fluid containing lines for leaks. The apparatus comprises (a) a differential pressure transducer mounted to a reservoir for indicating volumetric change in the reservoir; (b) a temperature transducer mounted in the reservoir for monitoring temperature fluctuation in the reservoir; (c) a gauge pressure transducer mounted in the reservoir; (d) a remote temperature sensor and a data acquisition and processing system. The method for employing the apparatus comprises of connecting the apparatus to the line under test and entering certain parameters of a line under test and product temperature into the test computer. The test system then monitors volumetric change in the reservoir as well as pressure and temperature fluctuations in the line under test at 30 second intervals. At the end of the predetermined test period, the system calculates the leak rate during each five minute interval of the test as well as a cumulative leak rate. The trends in the leak rate data during the test are then analyzed to determine whether the calculated cumulative leak rate is accurate.
Description
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LINE L~AK DETECT~R ~ND METHOD
Backqround of the Invention Field of the Invention This invention pertains generally to an apparatus and method for detecting leaks in underground supply lines for gasoline and other hydrocarbon fuels. More specifically, the invention pertains to detecting leaks in a supply line between a fuel pump and an underground reservoir containing gasoline at a gasoline service station.
Description of the Prior Art Today's society is becoming increasingly dependent on transportation fueled by hydrocarbons while failing to significantly develop alternative fuel sources. At the same time, society is becoming more concerned with the quality of the natural environment. The first condition has led to a virtual explosion in the number of gasoline service stations in the last couple of decades that shows no signs of abating. The latter condition has manifested itself in stricter governmental regulations to avoid or minimize environmental contamination from operation of service station facilities.
Each service station is essentially a self-contained gasoline dispensing unit. While large pipeline networks are employed in petroleum production fields to connect various units of the field to a central distribution point, t~e same is not true in the distribution of refined petroleum to service stations. Each service station ,c , :
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typically has one or more reservoirs buried under the ground for storing gasoline that are periodically resupplied with gasoline trucked in from various locations.
The fuel is pumped from the storage tank to the dispenser by a submersible pump which is activated when the dispenser switch is turned on and deactivated at the end of the dispensing operation. Normally, a check valve is incorporated in the pump assembly so that at the end of a dispensing cycle, the product line retains the fuel that has been pumped into it, thus permitting the gasoline to be delivered immediately at the start of the next dispensing cycle. A pressure relief valve built into the pump as-sembly is used to relieve the product line pressure to a level of 11-15 psi following the end of each dispensing cycle. Because of the positive pressure that is ~aintained in the product line, any leaks in the piping between the check valve and the dispenser can result in significant amounts of fuel leaking from the product line and contami-nating the subsoil and groundwater.
The lines have therefore become a source of concern for man~ environmentalists. The primary concern arises from the potential for contamination of underground water supplies caused by leaking gasoline or other refined petroleum products. In response to political pressures exerted by environmental and other interest groups, govern-mental authorities have imposed strict controls on the operation of such underground reservoirs to prevent contam-ination and to help arrest the deteriorating state of the environment.
Enforcement of these regulations, coupled with the increasing number of gasoline service stations, has created a new and significant demand for testing procedures and e~uipment capable of detecting ever smaller amounts of leaking gasoline. For instance, current United States governmental regulations specify that the maximum allowable .
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leakage in underground reservoirs and associated lines be no greater than 0.1 gallons per hour and it is expected that future standards will be even lower.
Most of the equipment and procedures currently known in the art for testing the line between the underground reservoir and the dispensing pump are not suffi~iently accurate, and lack the greater resolution and precision required, to test against the lower standards. Improved methods such as that described in United States Letters Patent 4,46~,249 have made it possible to test the underground reservoir for leaks even smaller than the 0.1 gal/hr maximum, but so far as is known, no methods capable of such precision are available for testing the lines for such leaks.
The test equipment and method now in use involves a pressurized reservoir that is graduated for volumetric measurement. The pressurized reservoir is connected to the line under test which is then pressurized. After the line is pressurized, the reservoir is monitored for fluid loss into the line. Vapor pockets sometimes form in the line under test but are normally removed by repeatedly pressurizing and depressurizing the line until the vapor collects at one end of the line whereupon it is bled off.
This system and method of testing is adversely impacted by volumetric changes caused by temperature variations in the line, the difficultly in accurate determination of volumetric change in the reservoir, human error in operator measurements and calculations, and the operator's exercise of judgment at the end of the test.
Another approach is found in United States Letters Patent 3,439,837 issued to Hearn et alia on April 22, 1969.
This patent teaches testing for leaks by measuring the differential pressure between the line under test and another line in which a reference pressure is first estab-lished. However, on information and belief, the apparatus 2 ~
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disclosed in that patent is relatively complex and diffi-cult to calibrate for the simple measurements obtained and the method disclosed does not obtain information with sufficient resolution to test against the new stan-dards. Furthermore, the determining measurements areindirect relative to the line under test and therefore more subject to error.
United States Letters Patent 4,876,530 is directed to a method and apparatus for detecting leakage from under-ground fuel tanks and also from the pressurized lines whichdeliver the fuel to the dispensers. The specification of describes the use of "special measures" which are said to be taken to distinguish thermal contraction from an actual leak in the line which rely upon "the physical fact that the pressure of volume decay caused by thermal contraction decreases with time, whereas the volume decay caused by a leak does not." The method described therein, however, isolates the line(s) under test from the rest of the product storage and delivery system, introducing a number of situations into the line leak test which decrease the reliability and precision of the test. In short, so far as is known, no accurate, reliable, and simple leak test for just the lines is available, and there is a need for such a test of both for environmental reasons and in light of the above-described, exacting governmental regulations.
It is therefore a feature of this invention that it will measure leakage with sufficient accuracy to meet the precision required under governmental standards.
It is a further feature of this invention that it will account for the effects of temperature deviations in the line and the system during the test run.
It is still a further feature of this invention that it incorporates a more accurate method of determining volumetric change in the test reservoir.
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It is still a further feature of this invention that it automates a lar~er portion of the testing in order to eliminate or reduce opportunity for introducing human error into the procedure.
Summary of the Invention The invention comprises an apparatus and a method for testing the leakage rate of fluid from a liquid fluid containing line such as the line between the liquid containing underground reservoir of a gasoline service station and the impact valve to which the line is connected. The apparatus comprises an instrument package modified to include (a) a differential pressure transducer mounted to a reservoir for indicating volumetric change in the reservoir; (b) a temperature transducer mounted in the reservoir for monitoring temperature fluctuation in the reservoir; (c) a gauge pressure transducer mounted in the reservoir; (d) a remote temperature sensor and a data acquisition and processing system. The method comprises the steps of connecting the apparatus to the line under test, isolating the line from the impact valve and underground reservoir, and pressurizing the fluid in the isolated line having the test apparatus connected thereto.
The test system then monitors volumetric change in the reservoir as well as pressure and temperature fluctuations in the system and line under test at preselected time intervals. At the end of a predetermined test period, the system calculates the leak rate during each five minute interval of the test as well as a cumulative leak rate.
Fluctuations and trends in the leak rate data during the test are examined against preselected criteria of change to determine whether the calculated cumulative leak rate is an accurate measurement of the actual rate of leakage of the liquid fluid from the fluid filled line.
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Brief Description of the Drawinqs So that the manner in which the above recited features of the invention, as well as others that may become apparent, are attained and can be understood in detail, a more particular description of the invention briefly summarized above may be had by reference to the exemplary preferred embodiment thereof illustrated in the drawings that form a part of this specification. The appended drawings nevertheless illustrate only a preferred embodiments of the invention and are not to be considered limiting of its scope.
In the drawin~s:
Figure 1 is an illustration of the apparatus of the invention as is set up and employed for use in testing.
Figure 2 is a more detailed depiction of the instrument package of the apparatus in Figure 1.
Figure 3 is a perspective view of a portion of the submersible pump as it is depicted in Figure 1 with an isolation plug installed.
Figure 4 is an enlarged depiction of the computational package of the apparatus as viewed from the top and as depicted in Figure 1.
Figure 5 is a schematic diagram of the temperature data and acquisition circuitry housed in the instrumentation package of Figure 2.
Figure 6A and 6B are a schematic diagram of the data processing, analog-to-digital converting, and input/output circuitry of the computational package of Figure 4.
Figure 7 is a schematic diagram of the keypad and associated connectors of the computational package of Figure 4.
Figure 8a and 8b are schematic diagrams of the power circuits of the computational package of Figure 4.
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Figure 9 is flow chart summarizing selected steps of a presently preferred embodiment of the method of the present invention.
Description of the Preferred Embodiment Figure 1 illustrates the lnvention as it is employed to test an underground line. Line 10, reservoir 1~, submersible pump 30, impact va:Lve 17, and dispensing pump 12 are all standard equipment commonly found installed at gasoline service stations as is shown. Isolation plug 35, instrument package 20, computational package 40, and lines 11, 13, and 16 in the preferred embodiment are transported to different service stations by truck 18 and assembled for testing.
The apparatus of the invention in its preferred embodiment comprises instrument package 20, line 11, line 13, computational package 40 and line 16. Instrument package 20 is connected to line 10 when line 10 is under test via line 11 and through isolation plug 35 (see Figure 3) installed in submersible pump 30. Submersible pump 30 normally pumps gasoline from underground reservoir 14 to dispensing pump 12 via line 10 and impact valve 17 but instead isolates line 10 from reservoir 14 when modified using isolation plug 35. Instrument package 20 is further connected to computational package 40 via line 13 and to a pressurized source of nitrogen aboard truck 18 through line 16.
Figure 2 illustrates instrument package 20 of the presently preferred embodiment shown in Figure 1 in greater detail. Instrument package 20 is a modification of a prior art device constructed and used by Tanknology Corporation International of Houston, Texas. The prior art device has been adapted by the addition of temperature transducer 26, gauge pressure transducer 60, differential pressure trans-ducer 62, remote temperature sensor 52, and signal pro-.
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~e~f;inq system loo, th~ latter three beilly looatcd b~neat.h cov~r 28 and ~ elnq :~ihown ~ch~matical l y in ~igure 5 .
l~emDerature tr~nsdllc~r 2 6 i n ~he pre~erred e~}~odi~en~. i s a ~3tandard th~rmistor or a ther~ocouple ~ remot~ tempera-.~ ture s~nsor 52 that i5 c~onnected ts instrum0nt pacXage 20and ja~k 50 by plug 38 ~hrough ~;able. 54 ~or a p~rpo~e ko be descri~3ed bcl~w. Gat~ge pr~ssu:re tran~duoQr 6n is used ~o me?~s~lre the ~res~ure ~xQrted C~R the f luid by ~h~
in~t g?~;, the pr~ssure being mea~urcd rQlat~ve ~o atms:~-10 3pher.ic pres~ure, Dif~renti?~ pressur~ tran~ducQr 6~ is used tode~ermlne th~ mas3 of f luid captureO in a te~t rceervoir, or graduated cylinder 32 as ~ re ftllly d~cribed below ~y measuring the ~ifferences in pre~sur~ be~ween th~3 top ~n~
15 bottom of cylinder 32. Differential pre..~ure transducer G2 may b~ any one of ~v~r~1 commerci~lly av~ ble transduc ers~ ~or example, ~odel SCXOlD (Sensym, Inc., Su~ le, ~a) ~ 10 RC ~crie6 (Mi~.r~switc~ Divl~ion o~ Honeyw~ll, Inc~, Freeport, lL~ an~ P3061-20 ~D (~ucas ~chaevitz, Inc., ~e~n~ukcn, NJ) tr~nsducers h~ all b6cn u~ed t.o varyin0 de.g~ees or ~vantage. Th~ Mi~ros~iCc~ t~ansducer i6 sensitive to c~m~on mo~e pr~ssureJ c~g7, outp~t c~anges ~v~r ~ne r~llge of ~hc pr~sure. ~ifrerenti~l, suc~ th~ ~hR
outpu~ fro~ pressure tran~duccr 60 mu6~ be u~d to cor~e~t 2~ t~e output ~rom that pa~ti~ r transd~c~r 62.
The ~.~ntral compon~nt of instrum~n~ pacXage 20 i the t2~t reserv~ir, whi~h in t~e pre~erred embodim~n~
graduate.d cylin~er 32. The contant of ~raduated cylinder 32 ls controlled by fi~ling wlt~ uid fluid contalned in holdi.ng tan~ z2 through lin~ 2~ wh~n iiller v~lve 34 i~
opened. Th~ con~.~nt is al~o c~ntrolled by i~jecting nitrogen ~r s~m~ other suitable ~s into cylillder 32 fro~
a pre~suri~d s~l1rce via guio~-connector 27, valv~ 25, an~
l~ne 33~ In addi~ion to nitrogen, any lne~t gas th~t i~
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non-flammable is also suitable. Pressure exerted by the contents of cylinder 32 is reduced by bleeding gas through relief valve 23 or line 33. Outlet valves 29a-b are used to drain the liquid content of cylinder 32. Outlet valve 29a is a one-~uarter inch outlet valve with a quick disconnect and outlet valve 29b is a one-half inch outlet valve with a quick disconnect, both as are well known in the art.
Figure 3 illustrates submersible pump 30 having the isolation plug 35 installed therein. Line 10 is isolated from underground reservoir 1~ by the installation of isolation plug 35 in submersible pump 30 and is consequently placed in fluid flow communication with line 11. Such isolation pluys and their use are commonly known among those skilled in the art. In strumentat ion package 20 of Figures 1-2 is connected to isolation plug 35 via line 11. Isolation plug 35 requires either quarter-inch or half-inch connectors on line 11 and thus the necessity for having both outlet valve 29a and b on instru-mentation package 20. Thus, modifying submersible pump 30with isolation plug 35 isolates line 10 and places it in fluid flow communication with line 11.
Impact valve 17 shown in Figure 1 is designed to shut off excessive fluid flow through line 10 during normal operation to prevent large gasoline spills that may occur if dispensing pump 12 is damaged or malfunctions. ~alves such as impact valve 17 are required by federal regulations for each pump such as dispensing pump 12. As is well known in the art, impact valve 17 also has a manual switch that will also block fluid flow when appropriately set in order to perform routine maintenance and inspection of dispensing pump 12. Impact valve 17 is used in this manner to isolate line 10 from dispensing pump 12. Line 10 is therefore isolated from both underground reservoir 14 and dispensing pump 12 for testing purposes.
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Computational package 40 of Figure 1 is illustrated in greater detail in Figure 4. Computational package 40 in its preferred embodiment is a formed aluminum case manufactured for housing inst:rumentation. The case of computational package 40 includes several electrical circuits depicted schematically in Figures 6A-B with some interactive components mounted on the top and whose schematic is shown in Figure 7.
The operator enters and receives test control data with computational package 40 using display 45, keypad 48, and printer 42. In the pre~erred embodiment, display 45 is a liquid crystal display displaying two lines of twenty (20) characters each, keypad 48 is a 16 key, ~ x 4 matrix unit, and printer 42 is a standard 40 column dot-matrix printer. Keypad 48 communicates with micro-controller 72 of Figure 6A via connectors 78 and 80 of Figure 6A and connector 82 of Figure 7. Keypad 48 further communicates with printer 42 via connector 84 of Figure 7. Computation-al package 40 also includes power on-off switch 46 (Figures 4 and 8a) and reset button 44 (Figure 6A).
Computational package 40 interfaces with and receives multiplexed analog data in parallel from the signal processing system 100 of instrument package 20 via line 13 and connector 66. Signal processing system 100 is located under cover 28 of instrument package 20 in Figures 1-2 and is a data acquisition and signal transmitting system as depicted schematically in Figure 5. System 100 translates the output of temperature transducer 26, remote temperature transducer 52, differential pressure transducer 62, and gauge pressure transducer 60 to a voltage between 0-5 volts for transmission to computational package 40 tFigure 4).
Signal conditioning is accomplished with integrated circuit operational amplifiers in signal processing system 100 in any one of several common circuit designs for acquisition and transmission of data. All testing and data .
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proc~3ing i6 per~ d in accord~llce with softwarQ :tored in a 64 K~it EPROM ~4 and run usin~ ~-blt micro-controller 72 ~rhioh i6 an 80'i~.A~IBA~lC: proc~;sor produo~d ~y In'cel t~or-porat~on (S~nta Cl~ra, CA~. Th~ \~se or the above-descr~bed 5 Luaa6 Scha~vitz pressure Ir~nsducer a~ the differentia}
pre~su~ tr~n~duccr 62 permits a reso}ution of ten (10) bit~ with minimal hardw~re or 90~t~are chan~e.~.
~uch h~rdwar~ and æl~tware cllang~s car~ bo ea~ily reco~nized anO re~ made by tho~e slci 1 led in the ~rt 10 ha~ring thG benç~fit of t.his discl.~sure. ~or in~:~anc~, A/D
con~rer~or 70 c~n },e either an 8-bit or 1 O-bit convert:,~r dependirlg upon the r~solution of ~ ociat~d tranc~u~er~:.
Furthermore, iî tha differ~ntial tran~d~cer 62 produc~cl by ~uc~ Sch~ovitz, wh ich has ~el~-contained 6ignal con-lS ditioninq circuitry~ iG u'cilized, t.he signal condi~:ioningcircuitry shnwn in ~ ~ gure 5 as2;0ciated with di~f@r~ntial transduc~r 62 can bc omi~ted.
Da~a i ~ receiVed by computational packag~ 4n from instrument package ~0 via 1 i ne l l and corlnector 66 i~;
2n mul~iple~ed ~y mult~pl~xor 68, convcrted to digi~.~l form by A/D conver~er 70. Beth ~ra s~ored in 6~ it ~1 76 and ~on~.emporaneously prlnted during t~ting by E~rin~er 42 w~ lso print~ the r~.~ults o~ tl~e te~iting once t:~s~ing i~ com~let~a. Mi~:ro-controllor 72 CommUni~?~tes witn the 25 other integrated circuit C~ips ln Figures CA-B ~ia thrz~
~uses, eacl~ ~us being d~dicated ~or on~ or contro~., data, or addre~ signal~:, res~ectlv~31y. F~r the s~kc of clarity, thege bu~ re not dcpictQd in their entlr~ty but are eimply lab~l Rd as ~ucn on t:h~ appropri~tc leads to ~.h~
30 lndivi~ual chip~.
~ ompl~t?~tional pack~g~ 40 i~ powercd by a ~2 vol~. dc gel?-cell bat~cry 90 (~own in Fig-lre sa) oS a type produced ~y any of ~ever~l ~nasluf~otur~rs ThQ 12 volt sign~ rcduced to 5 ~l~l ts by voltaqe limiter 92, and 35 bf~th 9 an~ 12 v~ signal ~nd a ~5 vol~. signal are -, ,.
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transmitted to other components via connector 94. The battery supply of battery 90 is capable of powering all electrical components of instrument package 20 via line 13 as well as those of computational package 40 for an entire day. Further, the battery supply can be recharged from the electrical system of truck 18 via a jack in the side of computational package 40 that is also not shown. Separate +12 volt and +5 volt signals are generated by the circuit depicted schematically in Figure 8b for the purpose of producing a clean, independently generated reference signal for A/D converter 70 in Figure 6 and trans~itted by connector 96.
In conventional testing operations, the test unit comprised of instrumentation package 20 and computation package 40 is set up in the configuration illustrated in Figure 1 and as previously described herein except that the test unit is not yet connected to line 10 or submersible pump 30. Selected steps in the subsequently described method of the invention are summarized in the flow chart of Figure 9.
Once the test equipment is set up, the operator must first enter selected test system parameters before the test begins (the step shown at reference numeral 100 in Figurs 9). These parameters include the diameter and length of line 10, the type of product contained in line 10 (which should be the same as that in underground reservoir 14), and the period of time over which the test will be conducted. This is done using keypad 48 and display 45 of computational unit 40. Computational package 40 then calculates the standard line volume of the line under test (line 10) and the cubic thermal expansion rate for the product contained in underground reservoir 14 in calculations during the test from the entered information (step 102).
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Thi3 ~eloctcd in~ormation must be ~nt:ered oorrec:tly for ~e sys~em to ac~ l,ely ~ccount ~or th~ e~cot of t~pcrature on ~olumetric chanc;~ detec~:ed during ~he test.
It iS a well kllewll scientific prinoipal ~hat tllQ vo1u~Q, 5 t;e~mp~rature, and ~rR~ re o~ rlle conte~ts of any ~;lo~;~d syst~ ar~ interrelated a~ ae:;cr~bc!d by Boyla~ law. Thus, err~:rs in ~ny of the en~ere~ guantl~ies will ~r~nsla~e in~o errors in volumetric measurcment. An ~rror in the calc~-lated v~ me Or line 1~) wlll, .rOr inst~n~:e, t~lU~; cause an 10 error in temperaturG: correotiorl.
~ olding tanX ~ of lns~rumentation p~c,kage 20 shown in Figure 2 muzt bc filled with th~2 same type of flui~ that ~tored in unaer~round reserv~ir 14. A con-.reni~nt ~ay ~o ob~ain ~illing fluid i5 to c>~tAin ~ ~m?Jl 1 amount o~ flui~
rom reservoir 14 via dispensing pump 12, line lO and ~ub~ner~:ibls pump 3~. Obtainins t.h~ fluid in ~ni~ manner also has ~h~ lv~ntage of ensuring that the line 10 ie r~1a.tiv~ly ~u11 of fl-.litl, t.h~reby reducing the am~unt o~
~por in ~ e 10; eYen so, line 10 i~ likely ~o cont~in enough vapor t.o ~ffect the ~est such tha~ ~ur'c31er re~uctions in the a~nount of vapor proson~ in the line 10 a~
d~ rihed below is bene~icia1. Also, 1t 1s because of th~
pr~:sence of the vapor in lin~ 10 that line 10 is ~Q~erred ta herein as li~auid flui~ containin~ line. If th~3 rilling 25 f1uid from hol~ing tank 2`' is obtainQd in this ~anner, it:
mus~ be done before line 10 is iso1~tecl ~rbm unaergxoulld re3crvoir 14 and di6pen~ing pump 12.
The temperature o th~: yrosluct in 1ine 10 i~ me~surod (~tep 10~) b~fore tes~in~ r~rdlesfi of whether f1uid is 30 ob~ained for l~ g tank 22 ~s described A~Ove. In the pr~Qrred embodim~nt c~f t.h~ h~d of the inven~i on, ~he t;emper~ture i5 measured be~ore line 10 i~ isol;~t~d ~rom ~i~her d i ~;~Qnc~ i ng pump 12 or ~eservoir 14 . 'l'o mea~ure t2~8 temper~ture, r emote temper~turc ccncor 5~ i6 in6erted ir~to :~ 1 ine 10 throu~h ~n~ aperture ln submersible pump 30 into , 3 TANB,016 PATEN~
which isolation plug 35 is fitted (shown in Figure 3) when line 10 is isolated from reservoir 14 whereupon the temperature is taken and recorded. Once the temperature is taken, remote temperature sensor 52 is removed. If fluid is obtained for holding tank 22 in the manner described above, the temperature of the product in line 10 may alternatively be taken by simply inserting remote temperature sensor 52 into the product received through dispensing pump 12.
Since line 10 is the line to be tested for leaks, it must be isolated from the remainder of the pumping dispensing system (step 106). This is accomplished by manually closing impact valve 17 and modifying submersible pump 30 with isolation plug 35 as heretofore described.
Line 10 must be filled with fluid to as great an extent as is practically possible during testing since air pockets or other gaseous deposits adversely impact the results of the test. Once line 10 is isolated, instrumentation package 20 is then placed in fluid flow communication with line 10 via 20 line 11 and isolation plug 35. Instrumentation package 20 is then used to pressurize and depressurize the content of line 10 to cause vapor pockets to coalesce at either end of line 10 where they are bled off in order to remove any such gaseous pockets as is well known in the art.
Once instrumentation package 20 is connected to line 10 via line 11, fluid is allowed to drain from holding tank 22 into test reservoir 32 via filler line 21 and filler valve 34. Nitrogen valve 25 is opened, thereby allowing nitrogen to be received via nitrogen quick connect 27 into test reservoir 32 from the source of pressurized nitrogen aboard truck 18 and via line 13, thereby placing the entire test system under pressure (step 108). Vapor pockets in the isolated system will coalesce and flow to one end of the isolated system or the other where they are bled and eliminated. Repetition of this process will increase its - , . .
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PATEN~r ef ~ec~iveness ~ hough the pr~ rred e.mbodiment of the ir~vention contemp].~tes only tWo or three repetition6~ Once t~e vapor pock~ts ~e rcmoved from ~.h~ sys~em unaer t~:st, tc~t rQser~roir 32 iS again îill~d and pl~ocd undQr 5C~ p~:i pressure: using nitrogen. In t he even~ of over-prc~-suri2ation, press~lre ls bl~d ~:;ing relief valve 23. The sy~it~m ls then rca~ly for testl ng.
Once ~le vap~r p~)ckets ~re r~:~oved, t~s~in~ i ~ begun ar~d i~3 ~ctually conduct.~ ~y sc)ftware :itored in dat~
~0 prQcessin~ clrcuitry h~used in computational pac:k~ge 40 (step llo) a~- morc~ ully t1escribed below. Pressure and temperature dat~ al~ collected by diferenti~1 pres5ure tr~nGducer located lln(9er cover 28, temperature tran~duocr 26, gauge pc~ssure ~rar~sduccr locatQd und~r ~:over 28 and 15 :~cmote tQmperatur~. ~en50r ~;~, and tr~nsmitted by ~ gnal processiny system 2~ ~rom in~trumentation pac~age 20 to computa~ion~l F)acka~e 4~ through line 13. The prc!~6ur~
exe.rt;ed l~y the fluid in the r~sorv~ir, the pressu~e a~ the top of ~.he. reservoir, and the ~mperakure of thc fluid in ~ reservoir, ar~ sampled ~Ye~y thirt.y s~conds (step 112~
for th~ dur~tion of the test ~nd per~nently rooorded ~ith pr~nter 4~. Thic data i~ al~o ~t.~red in ~step 114) rand~
access memory 76 in ~m~utatio~al pacXa~c 40. Typical te3t run~ in ~h~ pre~erred embo~iment are of thi~ty or ~ixty mlnutes, bu~ ~e~t run~ ~ay be.o~ differQnt duratian~.
Thc ~y~em reads th~ ~ta at thirty second i~ter~als and ls:~g it ~o pr~n~e~ 42.
once the test ls over ~ 116), the temp~ra~ure of the product in the lin~ is then m~sured again uslng the re.m~te ~empera~ure sen~o- 52. Once thc po~ st te~p~raturc iE ta~.en, the ~oft.w~re then calculates the volumetrlc chan~e in ~ fluid in te~t roc~rvoi~ ~2 and in l~n~ lo duQ to temper~t.~re fl~ctuations ~s determi~i~d ~rom pQSt-test ~ pr~-test readings. ~hi6 volumetrio c.hælng~.
3~ due to temp~. at.-lrR is t~en u~e~ to corr~,t the o~er~11 2 ~ $ ~ 3 TANB,016 PATENT
measured change in volume of the total amount of fluid found in both reservoir 32 and line 10 (step 118).
Theoretically, line lo WclS completely fluid filled when testing began and any fluid loss is the result of leakage of liquid fluid from the sealed test system, and is reflected in the change in fluid level in test reservoir 32. Total volumetric change can therefore be derived from the height of fluid in test reservoir 32. The current invention calculates the column height as measured by the differential pressure transducer of fluid in graduated cylinder/test reservoir 32 at any given time during the test procedure from the weight of the column of fluid in test reservoir 32. The weight, in turn, is determined by the difference in pressures exerted by the fluid in test reservoir 32 at the top of the column and at the bottom as measured by differential pressure transducer 62. The weight of the fluid is then calculated from the differential pressure with the product's particular specific gravity in accordance with the known formula.
The micro-controller of computational package 40 calculates the algebraic sum of all the measured volumetric changes and converts that sum to a cumulative leak rate measured in gallons per hour. The leak rate for each five minute period of the test is also calculated (step 120) and the standard deviation of the leak rate for each such period is divided by the average leak rate of all the five minute periods to obtain an arbitrary comparison value for each five minute period. Each of these values is logged by printer 42.
The micro-controller of computational package 40 therefore outputs not only data indicating the overall or cumulative performance of the system under test, but also information broken down into five minute "trending"
periods. Thus, the validity of the measured cumulative leak rate is determined by analyzing the trending 2~ L~'~,3 P~'rl3NT
inro~tion (3tcp 1~) to a~c~rt~in whetI~er t~e tren~:liny inEormation meets preself~cted criteria o:E ohang~. If the trending in~ormation is erratic or s~ows t~t the leak rate has not leveled of~, then tho m~a3ur~d cu~ulative le~k ra~e from that particular ~.Q,e:t is sU~2~eC~ and the ~ e~iting ~;hould b~ con~lucted ~y~in (s~ep 12~).
presel~.c~.Qd cri~cerium ln tha prererred embodiment is Operdtor selectable to acooIQmodate 'ch~ dQTnands 0~ the CUstQmer whi.12 comDlylng with ~vernmental regul~tory r~guirements. For instance, when conduc~.ing the me~ho~ ~or a cust.-)mer in the lJnlteà Stat~; who wi~ihe3 ~o comply with minimal governmontal ~equirement~ ., maximum leak rate ~f 0.1 gallons per hour) Vl~l~ mi~ht spec:ify a c~umulativQ
lea}c ~ate o~ not more than 0.00~2~ g~llons over two succes-~ive ~ive minute lnterv~ls. ~owever, if thc aalclllat~d leRk rat~:s ~re tr~nding t~ z6~rc. ~r ar~ o~he~w~ se decreas-ing, t~en lt is gen~rally appropri~te to a66u~e ~hat no lc~k exi6t8 and that ~h~ ca lculated leaJc rates are ~h~:
result o~ el~ ronic noi~ in ~h~ ~yctam.
The pr~.ferr~d embo~iment 03~ thç~ inv~ tion zllso cont~lpl2~tes using a ~;ound ala~m all:hough it i~ nt~lt nQcQssary to t.hP. practice o~ the lnvention. The al~rm SV~SI(l~; when either ther¢ i~; an in~:uffi~ient ~mcunt~ ~f liquid f J tl i d in t~s~ reservoir/qradu~t~ll cylinder 32 to continue the te~t or ~hon tha tost is o~er. In t~.h~. firs~
situAtion, circUitry i~ provided t~ onitor pressurs~ dat~, recei~red from inetrument package 20, ~.o insure ~hat tne liquid ~lU1~ lev~ a}~OVe a pre~electe~, ~inisnu~
throshold level and sounds ~n ~1 ~rm if it is r~ot . In the l~tter sltuation, ~ lar~ is 5i~ply aounded at ~ha end of the t~st Alth~ }~ cribed in term~ of tho 2~bove pr~ rr~d embodi~n~nts, thQ ~n~t.hod and apparatu~; o~ the present inventio-~ is not so limited, ~hc ~bov~ de6c~iption havlng been set ~ut. ;3,s heing illustratiVe o~ t~e inventic)n for th~
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purpose of compliance with the disclosure requirements of the Patent Statute. Those skilled in the art who have the benefit of this disclosure may wlell be able to make certain changes in the described embodiments which do not change the manner in which the various elements of these embodiments function to achieve the results desired. All such changes are intended to fall within the scope of the following claims.
TANB,016 PATENT
LINE L~AK DETECT~R ~ND METHOD
Backqround of the Invention Field of the Invention This invention pertains generally to an apparatus and method for detecting leaks in underground supply lines for gasoline and other hydrocarbon fuels. More specifically, the invention pertains to detecting leaks in a supply line between a fuel pump and an underground reservoir containing gasoline at a gasoline service station.
Description of the Prior Art Today's society is becoming increasingly dependent on transportation fueled by hydrocarbons while failing to significantly develop alternative fuel sources. At the same time, society is becoming more concerned with the quality of the natural environment. The first condition has led to a virtual explosion in the number of gasoline service stations in the last couple of decades that shows no signs of abating. The latter condition has manifested itself in stricter governmental regulations to avoid or minimize environmental contamination from operation of service station facilities.
Each service station is essentially a self-contained gasoline dispensing unit. While large pipeline networks are employed in petroleum production fields to connect various units of the field to a central distribution point, t~e same is not true in the distribution of refined petroleum to service stations. Each service station ,c , :
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typically has one or more reservoirs buried under the ground for storing gasoline that are periodically resupplied with gasoline trucked in from various locations.
The fuel is pumped from the storage tank to the dispenser by a submersible pump which is activated when the dispenser switch is turned on and deactivated at the end of the dispensing operation. Normally, a check valve is incorporated in the pump assembly so that at the end of a dispensing cycle, the product line retains the fuel that has been pumped into it, thus permitting the gasoline to be delivered immediately at the start of the next dispensing cycle. A pressure relief valve built into the pump as-sembly is used to relieve the product line pressure to a level of 11-15 psi following the end of each dispensing cycle. Because of the positive pressure that is ~aintained in the product line, any leaks in the piping between the check valve and the dispenser can result in significant amounts of fuel leaking from the product line and contami-nating the subsoil and groundwater.
The lines have therefore become a source of concern for man~ environmentalists. The primary concern arises from the potential for contamination of underground water supplies caused by leaking gasoline or other refined petroleum products. In response to political pressures exerted by environmental and other interest groups, govern-mental authorities have imposed strict controls on the operation of such underground reservoirs to prevent contam-ination and to help arrest the deteriorating state of the environment.
Enforcement of these regulations, coupled with the increasing number of gasoline service stations, has created a new and significant demand for testing procedures and e~uipment capable of detecting ever smaller amounts of leaking gasoline. For instance, current United States governmental regulations specify that the maximum allowable .
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leakage in underground reservoirs and associated lines be no greater than 0.1 gallons per hour and it is expected that future standards will be even lower.
Most of the equipment and procedures currently known in the art for testing the line between the underground reservoir and the dispensing pump are not suffi~iently accurate, and lack the greater resolution and precision required, to test against the lower standards. Improved methods such as that described in United States Letters Patent 4,46~,249 have made it possible to test the underground reservoir for leaks even smaller than the 0.1 gal/hr maximum, but so far as is known, no methods capable of such precision are available for testing the lines for such leaks.
The test equipment and method now in use involves a pressurized reservoir that is graduated for volumetric measurement. The pressurized reservoir is connected to the line under test which is then pressurized. After the line is pressurized, the reservoir is monitored for fluid loss into the line. Vapor pockets sometimes form in the line under test but are normally removed by repeatedly pressurizing and depressurizing the line until the vapor collects at one end of the line whereupon it is bled off.
This system and method of testing is adversely impacted by volumetric changes caused by temperature variations in the line, the difficultly in accurate determination of volumetric change in the reservoir, human error in operator measurements and calculations, and the operator's exercise of judgment at the end of the test.
Another approach is found in United States Letters Patent 3,439,837 issued to Hearn et alia on April 22, 1969.
This patent teaches testing for leaks by measuring the differential pressure between the line under test and another line in which a reference pressure is first estab-lished. However, on information and belief, the apparatus 2 ~
TANB,016 PATENT
disclosed in that patent is relatively complex and diffi-cult to calibrate for the simple measurements obtained and the method disclosed does not obtain information with sufficient resolution to test against the new stan-dards. Furthermore, the determining measurements areindirect relative to the line under test and therefore more subject to error.
United States Letters Patent 4,876,530 is directed to a method and apparatus for detecting leakage from under-ground fuel tanks and also from the pressurized lines whichdeliver the fuel to the dispensers. The specification of describes the use of "special measures" which are said to be taken to distinguish thermal contraction from an actual leak in the line which rely upon "the physical fact that the pressure of volume decay caused by thermal contraction decreases with time, whereas the volume decay caused by a leak does not." The method described therein, however, isolates the line(s) under test from the rest of the product storage and delivery system, introducing a number of situations into the line leak test which decrease the reliability and precision of the test. In short, so far as is known, no accurate, reliable, and simple leak test for just the lines is available, and there is a need for such a test of both for environmental reasons and in light of the above-described, exacting governmental regulations.
It is therefore a feature of this invention that it will measure leakage with sufficient accuracy to meet the precision required under governmental standards.
It is a further feature of this invention that it will account for the effects of temperature deviations in the line and the system during the test run.
It is still a further feature of this invention that it incorporates a more accurate method of determining volumetric change in the test reservoir.
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It is still a further feature of this invention that it automates a lar~er portion of the testing in order to eliminate or reduce opportunity for introducing human error into the procedure.
Summary of the Invention The invention comprises an apparatus and a method for testing the leakage rate of fluid from a liquid fluid containing line such as the line between the liquid containing underground reservoir of a gasoline service station and the impact valve to which the line is connected. The apparatus comprises an instrument package modified to include (a) a differential pressure transducer mounted to a reservoir for indicating volumetric change in the reservoir; (b) a temperature transducer mounted in the reservoir for monitoring temperature fluctuation in the reservoir; (c) a gauge pressure transducer mounted in the reservoir; (d) a remote temperature sensor and a data acquisition and processing system. The method comprises the steps of connecting the apparatus to the line under test, isolating the line from the impact valve and underground reservoir, and pressurizing the fluid in the isolated line having the test apparatus connected thereto.
The test system then monitors volumetric change in the reservoir as well as pressure and temperature fluctuations in the system and line under test at preselected time intervals. At the end of a predetermined test period, the system calculates the leak rate during each five minute interval of the test as well as a cumulative leak rate.
Fluctuations and trends in the leak rate data during the test are examined against preselected criteria of change to determine whether the calculated cumulative leak rate is an accurate measurement of the actual rate of leakage of the liquid fluid from the fluid filled line.
2 ~ 3 TANB,016 PATENT
Brief Description of the Drawinqs So that the manner in which the above recited features of the invention, as well as others that may become apparent, are attained and can be understood in detail, a more particular description of the invention briefly summarized above may be had by reference to the exemplary preferred embodiment thereof illustrated in the drawings that form a part of this specification. The appended drawings nevertheless illustrate only a preferred embodiments of the invention and are not to be considered limiting of its scope.
In the drawin~s:
Figure 1 is an illustration of the apparatus of the invention as is set up and employed for use in testing.
Figure 2 is a more detailed depiction of the instrument package of the apparatus in Figure 1.
Figure 3 is a perspective view of a portion of the submersible pump as it is depicted in Figure 1 with an isolation plug installed.
Figure 4 is an enlarged depiction of the computational package of the apparatus as viewed from the top and as depicted in Figure 1.
Figure 5 is a schematic diagram of the temperature data and acquisition circuitry housed in the instrumentation package of Figure 2.
Figure 6A and 6B are a schematic diagram of the data processing, analog-to-digital converting, and input/output circuitry of the computational package of Figure 4.
Figure 7 is a schematic diagram of the keypad and associated connectors of the computational package of Figure 4.
Figure 8a and 8b are schematic diagrams of the power circuits of the computational package of Figure 4.
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TANB,016 PATENT
Figure 9 is flow chart summarizing selected steps of a presently preferred embodiment of the method of the present invention.
Description of the Preferred Embodiment Figure 1 illustrates the lnvention as it is employed to test an underground line. Line 10, reservoir 1~, submersible pump 30, impact va:Lve 17, and dispensing pump 12 are all standard equipment commonly found installed at gasoline service stations as is shown. Isolation plug 35, instrument package 20, computational package 40, and lines 11, 13, and 16 in the preferred embodiment are transported to different service stations by truck 18 and assembled for testing.
The apparatus of the invention in its preferred embodiment comprises instrument package 20, line 11, line 13, computational package 40 and line 16. Instrument package 20 is connected to line 10 when line 10 is under test via line 11 and through isolation plug 35 (see Figure 3) installed in submersible pump 30. Submersible pump 30 normally pumps gasoline from underground reservoir 14 to dispensing pump 12 via line 10 and impact valve 17 but instead isolates line 10 from reservoir 14 when modified using isolation plug 35. Instrument package 20 is further connected to computational package 40 via line 13 and to a pressurized source of nitrogen aboard truck 18 through line 16.
Figure 2 illustrates instrument package 20 of the presently preferred embodiment shown in Figure 1 in greater detail. Instrument package 20 is a modification of a prior art device constructed and used by Tanknology Corporation International of Houston, Texas. The prior art device has been adapted by the addition of temperature transducer 26, gauge pressure transducer 60, differential pressure trans-ducer 62, remote temperature sensor 52, and signal pro-.
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~e~f;inq system loo, th~ latter three beilly looatcd b~neat.h cov~r 28 and ~ elnq :~ihown ~ch~matical l y in ~igure 5 .
l~emDerature tr~nsdllc~r 2 6 i n ~he pre~erred e~}~odi~en~. i s a ~3tandard th~rmistor or a ther~ocouple ~ remot~ tempera-.~ ture s~nsor 52 that i5 c~onnected ts instrum0nt pacXage 20and ja~k 50 by plug 38 ~hrough ~;able. 54 ~or a p~rpo~e ko be descri~3ed bcl~w. Gat~ge pr~ssu:re tran~duoQr 6n is used ~o me?~s~lre the ~res~ure ~xQrted C~R the f luid by ~h~
in~t g?~;, the pr~ssure being mea~urcd rQlat~ve ~o atms:~-10 3pher.ic pres~ure, Dif~renti?~ pressur~ tran~ducQr 6~ is used tode~ermlne th~ mas3 of f luid captureO in a te~t rceervoir, or graduated cylinder 32 as ~ re ftllly d~cribed below ~y measuring the ~ifferences in pre~sur~ be~ween th~3 top ~n~
15 bottom of cylinder 32. Differential pre..~ure transducer G2 may b~ any one of ~v~r~1 commerci~lly av~ ble transduc ers~ ~or example, ~odel SCXOlD (Sensym, Inc., Su~ le, ~a) ~ 10 RC ~crie6 (Mi~.r~switc~ Divl~ion o~ Honeyw~ll, Inc~, Freeport, lL~ an~ P3061-20 ~D (~ucas ~chaevitz, Inc., ~e~n~ukcn, NJ) tr~nsducers h~ all b6cn u~ed t.o varyin0 de.g~ees or ~vantage. Th~ Mi~ros~iCc~ t~ansducer i6 sensitive to c~m~on mo~e pr~ssureJ c~g7, outp~t c~anges ~v~r ~ne r~llge of ~hc pr~sure. ~ifrerenti~l, suc~ th~ ~hR
outpu~ fro~ pressure tran~duccr 60 mu6~ be u~d to cor~e~t 2~ t~e output ~rom that pa~ti~ r transd~c~r 62.
The ~.~ntral compon~nt of instrum~n~ pacXage 20 i the t2~t reserv~ir, whi~h in t~e pre~erred embodim~n~
graduate.d cylin~er 32. The contant of ~raduated cylinder 32 ls controlled by fi~ling wlt~ uid fluid contalned in holdi.ng tan~ z2 through lin~ 2~ wh~n iiller v~lve 34 i~
opened. Th~ con~.~nt is al~o c~ntrolled by i~jecting nitrogen ~r s~m~ other suitable ~s into cylillder 32 fro~
a pre~suri~d s~l1rce via guio~-connector 27, valv~ 25, an~
l~ne 33~ In addi~ion to nitrogen, any lne~t gas th~t i~
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non-flammable is also suitable. Pressure exerted by the contents of cylinder 32 is reduced by bleeding gas through relief valve 23 or line 33. Outlet valves 29a-b are used to drain the liquid content of cylinder 32. Outlet valve 29a is a one-~uarter inch outlet valve with a quick disconnect and outlet valve 29b is a one-half inch outlet valve with a quick disconnect, both as are well known in the art.
Figure 3 illustrates submersible pump 30 having the isolation plug 35 installed therein. Line 10 is isolated from underground reservoir 1~ by the installation of isolation plug 35 in submersible pump 30 and is consequently placed in fluid flow communication with line 11. Such isolation pluys and their use are commonly known among those skilled in the art. In strumentat ion package 20 of Figures 1-2 is connected to isolation plug 35 via line 11. Isolation plug 35 requires either quarter-inch or half-inch connectors on line 11 and thus the necessity for having both outlet valve 29a and b on instru-mentation package 20. Thus, modifying submersible pump 30with isolation plug 35 isolates line 10 and places it in fluid flow communication with line 11.
Impact valve 17 shown in Figure 1 is designed to shut off excessive fluid flow through line 10 during normal operation to prevent large gasoline spills that may occur if dispensing pump 12 is damaged or malfunctions. ~alves such as impact valve 17 are required by federal regulations for each pump such as dispensing pump 12. As is well known in the art, impact valve 17 also has a manual switch that will also block fluid flow when appropriately set in order to perform routine maintenance and inspection of dispensing pump 12. Impact valve 17 is used in this manner to isolate line 10 from dispensing pump 12. Line 10 is therefore isolated from both underground reservoir 14 and dispensing pump 12 for testing purposes.
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TANB,016 PATENT
Computational package 40 of Figure 1 is illustrated in greater detail in Figure 4. Computational package 40 in its preferred embodiment is a formed aluminum case manufactured for housing inst:rumentation. The case of computational package 40 includes several electrical circuits depicted schematically in Figures 6A-B with some interactive components mounted on the top and whose schematic is shown in Figure 7.
The operator enters and receives test control data with computational package 40 using display 45, keypad 48, and printer 42. In the pre~erred embodiment, display 45 is a liquid crystal display displaying two lines of twenty (20) characters each, keypad 48 is a 16 key, ~ x 4 matrix unit, and printer 42 is a standard 40 column dot-matrix printer. Keypad 48 communicates with micro-controller 72 of Figure 6A via connectors 78 and 80 of Figure 6A and connector 82 of Figure 7. Keypad 48 further communicates with printer 42 via connector 84 of Figure 7. Computation-al package 40 also includes power on-off switch 46 (Figures 4 and 8a) and reset button 44 (Figure 6A).
Computational package 40 interfaces with and receives multiplexed analog data in parallel from the signal processing system 100 of instrument package 20 via line 13 and connector 66. Signal processing system 100 is located under cover 28 of instrument package 20 in Figures 1-2 and is a data acquisition and signal transmitting system as depicted schematically in Figure 5. System 100 translates the output of temperature transducer 26, remote temperature transducer 52, differential pressure transducer 62, and gauge pressure transducer 60 to a voltage between 0-5 volts for transmission to computational package 40 tFigure 4).
Signal conditioning is accomplished with integrated circuit operational amplifiers in signal processing system 100 in any one of several common circuit designs for acquisition and transmission of data. All testing and data .
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Ns~ 016 PAT~;NT
proc~3ing i6 per~ d in accord~llce with softwarQ :tored in a 64 K~it EPROM ~4 and run usin~ ~-blt micro-controller 72 ~rhioh i6 an 80'i~.A~IBA~lC: proc~;sor produo~d ~y In'cel t~or-porat~on (S~nta Cl~ra, CA~. Th~ \~se or the above-descr~bed 5 Luaa6 Scha~vitz pressure Ir~nsducer a~ the differentia}
pre~su~ tr~n~duccr 62 permits a reso}ution of ten (10) bit~ with minimal hardw~re or 90~t~are chan~e.~.
~uch h~rdwar~ and æl~tware cllang~s car~ bo ea~ily reco~nized anO re~ made by tho~e slci 1 led in the ~rt 10 ha~ring thG benç~fit of t.his discl.~sure. ~or in~:~anc~, A/D
con~rer~or 70 c~n },e either an 8-bit or 1 O-bit convert:,~r dependirlg upon the r~solution of ~ ociat~d tranc~u~er~:.
Furthermore, iî tha differ~ntial tran~d~cer 62 produc~cl by ~uc~ Sch~ovitz, wh ich has ~el~-contained 6ignal con-lS ditioninq circuitry~ iG u'cilized, t.he signal condi~:ioningcircuitry shnwn in ~ ~ gure 5 as2;0ciated with di~f@r~ntial transduc~r 62 can bc omi~ted.
Da~a i ~ receiVed by computational packag~ 4n from instrument package ~0 via 1 i ne l l and corlnector 66 i~;
2n mul~iple~ed ~y mult~pl~xor 68, convcrted to digi~.~l form by A/D conver~er 70. Beth ~ra s~ored in 6~ it ~1 76 and ~on~.emporaneously prlnted during t~ting by E~rin~er 42 w~ lso print~ the r~.~ults o~ tl~e te~iting once t:~s~ing i~ com~let~a. Mi~:ro-controllor 72 CommUni~?~tes witn the 25 other integrated circuit C~ips ln Figures CA-B ~ia thrz~
~uses, eacl~ ~us being d~dicated ~or on~ or contro~., data, or addre~ signal~:, res~ectlv~31y. F~r the s~kc of clarity, thege bu~ re not dcpictQd in their entlr~ty but are eimply lab~l Rd as ~ucn on t:h~ appropri~tc leads to ~.h~
30 lndivi~ual chip~.
~ ompl~t?~tional pack~g~ 40 i~ powercd by a ~2 vol~. dc gel?-cell bat~cry 90 (~own in Fig-lre sa) oS a type produced ~y any of ~ever~l ~nasluf~otur~rs ThQ 12 volt sign~ rcduced to 5 ~l~l ts by voltaqe limiter 92, and 35 bf~th 9 an~ 12 v~ signal ~nd a ~5 vol~. signal are -, ,.
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2 ~ 3 TANB, 016 PATENT
transmitted to other components via connector 94. The battery supply of battery 90 is capable of powering all electrical components of instrument package 20 via line 13 as well as those of computational package 40 for an entire day. Further, the battery supply can be recharged from the electrical system of truck 18 via a jack in the side of computational package 40 that is also not shown. Separate +12 volt and +5 volt signals are generated by the circuit depicted schematically in Figure 8b for the purpose of producing a clean, independently generated reference signal for A/D converter 70 in Figure 6 and trans~itted by connector 96.
In conventional testing operations, the test unit comprised of instrumentation package 20 and computation package 40 is set up in the configuration illustrated in Figure 1 and as previously described herein except that the test unit is not yet connected to line 10 or submersible pump 30. Selected steps in the subsequently described method of the invention are summarized in the flow chart of Figure 9.
Once the test equipment is set up, the operator must first enter selected test system parameters before the test begins (the step shown at reference numeral 100 in Figurs 9). These parameters include the diameter and length of line 10, the type of product contained in line 10 (which should be the same as that in underground reservoir 14), and the period of time over which the test will be conducted. This is done using keypad 48 and display 45 of computational unit 40. Computational package 40 then calculates the standard line volume of the line under test (line 10) and the cubic thermal expansion rate for the product contained in underground reservoir 14 in calculations during the test from the entered information (step 102).
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Thi3 ~eloctcd in~ormation must be ~nt:ered oorrec:tly for ~e sys~em to ac~ l,ely ~ccount ~or th~ e~cot of t~pcrature on ~olumetric chanc;~ detec~:ed during ~he test.
It iS a well kllewll scientific prinoipal ~hat tllQ vo1u~Q, 5 t;e~mp~rature, and ~rR~ re o~ rlle conte~ts of any ~;lo~;~d syst~ ar~ interrelated a~ ae:;cr~bc!d by Boyla~ law. Thus, err~:rs in ~ny of the en~ere~ guantl~ies will ~r~nsla~e in~o errors in volumetric measurcment. An ~rror in the calc~-lated v~ me Or line 1~) wlll, .rOr inst~n~:e, t~lU~; cause an 10 error in temperaturG: correotiorl.
~ olding tanX ~ of lns~rumentation p~c,kage 20 shown in Figure 2 muzt bc filled with th~2 same type of flui~ that ~tored in unaer~round reserv~ir 14. A con-.reni~nt ~ay ~o ob~ain ~illing fluid i5 to c>~tAin ~ ~m?Jl 1 amount o~ flui~
rom reservoir 14 via dispensing pump 12, line lO and ~ub~ner~:ibls pump 3~. Obtainins t.h~ fluid in ~ni~ manner also has ~h~ lv~ntage of ensuring that the line 10 ie r~1a.tiv~ly ~u11 of fl-.litl, t.h~reby reducing the am~unt o~
~por in ~ e 10; eYen so, line 10 i~ likely ~o cont~in enough vapor t.o ~ffect the ~est such tha~ ~ur'c31er re~uctions in the a~nount of vapor proson~ in the line 10 a~
d~ rihed below is bene~icia1. Also, 1t 1s because of th~
pr~:sence of the vapor in lin~ 10 that line 10 is ~Q~erred ta herein as li~auid flui~ containin~ line. If th~3 rilling 25 f1uid from hol~ing tank 2`' is obtainQd in this ~anner, it:
mus~ be done before line 10 is iso1~tecl ~rbm unaergxoulld re3crvoir 14 and di6pen~ing pump 12.
The temperature o th~: yrosluct in 1ine 10 i~ me~surod (~tep 10~) b~fore tes~in~ r~rdlesfi of whether f1uid is 30 ob~ained for l~ g tank 22 ~s described A~Ove. In the pr~Qrred embodim~nt c~f t.h~ h~d of the inven~i on, ~he t;emper~ture i5 measured be~ore line 10 i~ isol;~t~d ~rom ~i~her d i ~;~Qnc~ i ng pump 12 or ~eservoir 14 . 'l'o mea~ure t2~8 temper~ture, r emote temper~turc ccncor 5~ i6 in6erted ir~to :~ 1 ine 10 throu~h ~n~ aperture ln submersible pump 30 into , 3 TANB,016 PATEN~
which isolation plug 35 is fitted (shown in Figure 3) when line 10 is isolated from reservoir 14 whereupon the temperature is taken and recorded. Once the temperature is taken, remote temperature sensor 52 is removed. If fluid is obtained for holding tank 22 in the manner described above, the temperature of the product in line 10 may alternatively be taken by simply inserting remote temperature sensor 52 into the product received through dispensing pump 12.
Since line 10 is the line to be tested for leaks, it must be isolated from the remainder of the pumping dispensing system (step 106). This is accomplished by manually closing impact valve 17 and modifying submersible pump 30 with isolation plug 35 as heretofore described.
Line 10 must be filled with fluid to as great an extent as is practically possible during testing since air pockets or other gaseous deposits adversely impact the results of the test. Once line 10 is isolated, instrumentation package 20 is then placed in fluid flow communication with line 10 via 20 line 11 and isolation plug 35. Instrumentation package 20 is then used to pressurize and depressurize the content of line 10 to cause vapor pockets to coalesce at either end of line 10 where they are bled off in order to remove any such gaseous pockets as is well known in the art.
Once instrumentation package 20 is connected to line 10 via line 11, fluid is allowed to drain from holding tank 22 into test reservoir 32 via filler line 21 and filler valve 34. Nitrogen valve 25 is opened, thereby allowing nitrogen to be received via nitrogen quick connect 27 into test reservoir 32 from the source of pressurized nitrogen aboard truck 18 and via line 13, thereby placing the entire test system under pressure (step 108). Vapor pockets in the isolated system will coalesce and flow to one end of the isolated system or the other where they are bled and eliminated. Repetition of this process will increase its - , . .
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PATEN~r ef ~ec~iveness ~ hough the pr~ rred e.mbodiment of the ir~vention contemp].~tes only tWo or three repetition6~ Once t~e vapor pock~ts ~e rcmoved from ~.h~ sys~em unaer t~:st, tc~t rQser~roir 32 iS again îill~d and pl~ocd undQr 5C~ p~:i pressure: using nitrogen. In t he even~ of over-prc~-suri2ation, press~lre ls bl~d ~:;ing relief valve 23. The sy~it~m ls then rca~ly for testl ng.
Once ~le vap~r p~)ckets ~re r~:~oved, t~s~in~ i ~ begun ar~d i~3 ~ctually conduct.~ ~y sc)ftware :itored in dat~
~0 prQcessin~ clrcuitry h~used in computational pac:k~ge 40 (step llo) a~- morc~ ully t1escribed below. Pressure and temperature dat~ al~ collected by diferenti~1 pres5ure tr~nGducer located lln(9er cover 28, temperature tran~duocr 26, gauge pc~ssure ~rar~sduccr locatQd und~r ~:over 28 and 15 :~cmote tQmperatur~. ~en50r ~;~, and tr~nsmitted by ~ gnal processiny system 2~ ~rom in~trumentation pac~age 20 to computa~ion~l F)acka~e 4~ through line 13. The prc!~6ur~
exe.rt;ed l~y the fluid in the r~sorv~ir, the pressu~e a~ the top of ~.he. reservoir, and the ~mperakure of thc fluid in ~ reservoir, ar~ sampled ~Ye~y thirt.y s~conds (step 112~
for th~ dur~tion of the test ~nd per~nently rooorded ~ith pr~nter 4~. Thic data i~ al~o ~t.~red in ~step 114) rand~
access memory 76 in ~m~utatio~al pacXa~c 40. Typical te3t run~ in ~h~ pre~erred embo~iment are of thi~ty or ~ixty mlnutes, bu~ ~e~t run~ ~ay be.o~ differQnt duratian~.
Thc ~y~em reads th~ ~ta at thirty second i~ter~als and ls:~g it ~o pr~n~e~ 42.
once the test ls over ~ 116), the temp~ra~ure of the product in the lin~ is then m~sured again uslng the re.m~te ~empera~ure sen~o- 52. Once thc po~ st te~p~raturc iE ta~.en, the ~oft.w~re then calculates the volumetrlc chan~e in ~ fluid in te~t roc~rvoi~ ~2 and in l~n~ lo duQ to temper~t.~re fl~ctuations ~s determi~i~d ~rom pQSt-test ~ pr~-test readings. ~hi6 volumetrio c.hælng~.
3~ due to temp~. at.-lrR is t~en u~e~ to corr~,t the o~er~11 2 ~ $ ~ 3 TANB,016 PATENT
measured change in volume of the total amount of fluid found in both reservoir 32 and line 10 (step 118).
Theoretically, line lo WclS completely fluid filled when testing began and any fluid loss is the result of leakage of liquid fluid from the sealed test system, and is reflected in the change in fluid level in test reservoir 32. Total volumetric change can therefore be derived from the height of fluid in test reservoir 32. The current invention calculates the column height as measured by the differential pressure transducer of fluid in graduated cylinder/test reservoir 32 at any given time during the test procedure from the weight of the column of fluid in test reservoir 32. The weight, in turn, is determined by the difference in pressures exerted by the fluid in test reservoir 32 at the top of the column and at the bottom as measured by differential pressure transducer 62. The weight of the fluid is then calculated from the differential pressure with the product's particular specific gravity in accordance with the known formula.
The micro-controller of computational package 40 calculates the algebraic sum of all the measured volumetric changes and converts that sum to a cumulative leak rate measured in gallons per hour. The leak rate for each five minute period of the test is also calculated (step 120) and the standard deviation of the leak rate for each such period is divided by the average leak rate of all the five minute periods to obtain an arbitrary comparison value for each five minute period. Each of these values is logged by printer 42.
The micro-controller of computational package 40 therefore outputs not only data indicating the overall or cumulative performance of the system under test, but also information broken down into five minute "trending"
periods. Thus, the validity of the measured cumulative leak rate is determined by analyzing the trending 2~ L~'~,3 P~'rl3NT
inro~tion (3tcp 1~) to a~c~rt~in whetI~er t~e tren~:liny inEormation meets preself~cted criteria o:E ohang~. If the trending in~ormation is erratic or s~ows t~t the leak rate has not leveled of~, then tho m~a3ur~d cu~ulative le~k ra~e from that particular ~.Q,e:t is sU~2~eC~ and the ~ e~iting ~;hould b~ con~lucted ~y~in (s~ep 12~).
presel~.c~.Qd cri~cerium ln tha prererred embodiment is Operdtor selectable to acooIQmodate 'ch~ dQTnands 0~ the CUstQmer whi.12 comDlylng with ~vernmental regul~tory r~guirements. For instance, when conduc~.ing the me~ho~ ~or a cust.-)mer in the lJnlteà Stat~; who wi~ihe3 ~o comply with minimal governmontal ~equirement~ ., maximum leak rate ~f 0.1 gallons per hour) Vl~l~ mi~ht spec:ify a c~umulativQ
lea}c ~ate o~ not more than 0.00~2~ g~llons over two succes-~ive ~ive minute lnterv~ls. ~owever, if thc aalclllat~d leRk rat~:s ~re tr~nding t~ z6~rc. ~r ar~ o~he~w~ se decreas-ing, t~en lt is gen~rally appropri~te to a66u~e ~hat no lc~k exi6t8 and that ~h~ ca lculated leaJc rates are ~h~:
result o~ el~ ronic noi~ in ~h~ ~yctam.
The pr~.ferr~d embo~iment 03~ thç~ inv~ tion zllso cont~lpl2~tes using a ~;ound ala~m all:hough it i~ nt~lt nQcQssary to t.hP. practice o~ the lnvention. The al~rm SV~SI(l~; when either ther¢ i~; an in~:uffi~ient ~mcunt~ ~f liquid f J tl i d in t~s~ reservoir/qradu~t~ll cylinder 32 to continue the te~t or ~hon tha tost is o~er. In t~.h~. firs~
situAtion, circUitry i~ provided t~ onitor pressurs~ dat~, recei~red from inetrument package 20, ~.o insure ~hat tne liquid ~lU1~ lev~ a}~OVe a pre~electe~, ~inisnu~
throshold level and sounds ~n ~1 ~rm if it is r~ot . In the l~tter sltuation, ~ lar~ is 5i~ply aounded at ~ha end of the t~st Alth~ }~ cribed in term~ of tho 2~bove pr~ rr~d embodi~n~nts, thQ ~n~t.hod and apparatu~; o~ the present inventio-~ is not so limited, ~hc ~bov~ de6c~iption havlng been set ~ut. ;3,s heing illustratiVe o~ t~e inventic)n for th~
:
::
TANB, 016 PATENT
purpose of compliance with the disclosure requirements of the Patent Statute. Those skilled in the art who have the benefit of this disclosure may wlell be able to make certain changes in the described embodiments which do not change the manner in which the various elements of these embodiments function to achieve the results desired. All such changes are intended to fall within the scope of the following claims.
Claims (4)
1. An apparatus for testing an isolated liquid fluid containing line for the presence of a leak, comprising:
means for measuring the temperature of the liquid in the liquid fluid containing line before and after the testing and transmitting a signal representa-tive thereof;
means for measuring the temperature and pressure of the liquid in a filled test reservoir and trans-mitting a signal representative of the measured temperatures and the measured pressure; and means for receiving the signals from each of said temperature and temperature and pressure measur-ing means for calculating therefrom a cumulative leak rate at selected time intervals and com-paring the calculated leak rates to develop trending information and analyzing the trending information by comparing the calculated leak rate to ascertain whether the trending information meets a preselected criterium of change to deter-mine the rate of liquid fluid leakage from the liquid fluid containing line and the validity of the cumulative leak rate.
means for measuring the temperature of the liquid in the liquid fluid containing line before and after the testing and transmitting a signal representa-tive thereof;
means for measuring the temperature and pressure of the liquid in a filled test reservoir and trans-mitting a signal representative of the measured temperatures and the measured pressure; and means for receiving the signals from each of said temperature and temperature and pressure measur-ing means for calculating therefrom a cumulative leak rate at selected time intervals and com-paring the calculated leak rates to develop trending information and analyzing the trending information by comparing the calculated leak rate to ascertain whether the trending information meets a preselected criterium of change to deter-mine the rate of liquid fluid leakage from the liquid fluid containing line and the validity of the cumulative leak rate.
2. An apparatus for testing an isolated liquid fluid containing line, comprising:
an instrument package further comprising a test reservoir containing fluid, a differential pressure transducer mounted to the test reservoir for measuring the pressure TANB,016 PATENT
exerted by the fluid and generating an electrical signal proportional thereto, a temperature transducer mounted in the test reservoir for measuring the temperature of the fluid and generating an electrical signal proportional thereto, a gauge pressure transducer mounted in the test reservoir for measuring the pressure exerted by the atmosphere in the test reservoir and generating an electrical signal proportional thereto, a remote temperature sensor for measuring the temperature of the ambient atmosphere and generating an electrical signal proportional thereto, and means for transmitting the electrical signals generated by the differential pressure transducer, the temperature transducer, the gauge pressure transducer, and the remote temperature sensor;
a computational package that receives the electrical signals transmitted from said instrument package, records the data transmitted in the electrical signal, and calculates leak rate data of the liquid fluid containing line at preselected intervals during a selected test period and a cumulative leak rate for the entire test period;
means for connecting the test reservoir of said instrument package to the liquid fluid containing line; and means for connecting the test reservoir of said instrument package to a pressurized source of TANB,016 PATENT
gaseous fluid for raising the pressure to the liquid fluid containing line after connecting said instrument package to the liquid fluid containing line.
an instrument package further comprising a test reservoir containing fluid, a differential pressure transducer mounted to the test reservoir for measuring the pressure TANB,016 PATENT
exerted by the fluid and generating an electrical signal proportional thereto, a temperature transducer mounted in the test reservoir for measuring the temperature of the fluid and generating an electrical signal proportional thereto, a gauge pressure transducer mounted in the test reservoir for measuring the pressure exerted by the atmosphere in the test reservoir and generating an electrical signal proportional thereto, a remote temperature sensor for measuring the temperature of the ambient atmosphere and generating an electrical signal proportional thereto, and means for transmitting the electrical signals generated by the differential pressure transducer, the temperature transducer, the gauge pressure transducer, and the remote temperature sensor;
a computational package that receives the electrical signals transmitted from said instrument package, records the data transmitted in the electrical signal, and calculates leak rate data of the liquid fluid containing line at preselected intervals during a selected test period and a cumulative leak rate for the entire test period;
means for connecting the test reservoir of said instrument package to the liquid fluid containing line; and means for connecting the test reservoir of said instrument package to a pressurized source of TANB,016 PATENT
gaseous fluid for raising the pressure to the liquid fluid containing line after connecting said instrument package to the liquid fluid containing line.
3. A method for testing the leakage rate of fluid from a liquid fluid containing line, comprising the steps of:
isolating a liquid fluid containing line having a test apparatus connected thereto from a liquid containing underground reservoir connected to one end of the line and from an impact valve connected to the other end of the line;
pressurizing the fluid in the isolated line having the test apparatus connected thereto;
obtaining data representative of changes in temperature and pressure levels in the isolated line having the test apparatus connected thereto over a preselected test period at preselected time intervals;
calculating a cumulative leak rate from the tem-perature and pressure levels at each time inter-val and comparing the cumulative leak rate at each time interval to develop trending infor-mation from the data; and analyzing the trending information to ascertain whether the trending information meets preselected criteria of change to determine whether the calculated cumulative leak rate is an accurate measurement of the actual rate of TANB,016 PATENT
leakage of the liquid fluid from the fluid filled line.
isolating a liquid fluid containing line having a test apparatus connected thereto from a liquid containing underground reservoir connected to one end of the line and from an impact valve connected to the other end of the line;
pressurizing the fluid in the isolated line having the test apparatus connected thereto;
obtaining data representative of changes in temperature and pressure levels in the isolated line having the test apparatus connected thereto over a preselected test period at preselected time intervals;
calculating a cumulative leak rate from the tem-perature and pressure levels at each time inter-val and comparing the cumulative leak rate at each time interval to develop trending infor-mation from the data; and analyzing the trending information to ascertain whether the trending information meets preselected criteria of change to determine whether the calculated cumulative leak rate is an accurate measurement of the actual rate of TANB,016 PATENT
leakage of the liquid fluid from the fluid filled line.
4. The method of claim 3 wherein the trending information is calculated at five minute intervals of the preselected test period and includes at least one of the leak rate for each respective interval, the standard deviation of each respective interval, the standard deviation of the leak rate for each respective interval, or the ratios of the standard deviation of each respective interval to the average leak rate of all the intervals.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US65493991A | 1991-02-13 | 1991-02-13 | |
| US654,939 | 1991-02-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2061153A1 true CA2061153A1 (en) | 1992-08-14 |
Family
ID=24626832
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2061153 Abandoned CA2061153A1 (en) | 1991-02-13 | 1992-02-13 | Line leak detector and method |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2061153A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113916457A (en) * | 2021-08-25 | 2022-01-11 | 华能国际电力股份有限公司丹东电厂 | System and method for pre-judging water leakage of boiler device |
| CN114135795A (en) * | 2021-11-18 | 2022-03-04 | 慧感(上海)物联网科技有限公司 | Omnibearing leakage monitoring and early warning Internet of things system and early warning method thereof |
-
1992
- 1992-02-13 CA CA 2061153 patent/CA2061153A1/en not_active Abandoned
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113916457A (en) * | 2021-08-25 | 2022-01-11 | 华能国际电力股份有限公司丹东电厂 | System and method for pre-judging water leakage of boiler device |
| CN114135795A (en) * | 2021-11-18 | 2022-03-04 | 慧感(上海)物联网科技有限公司 | Omnibearing leakage monitoring and early warning Internet of things system and early warning method thereof |
| CN114135795B (en) * | 2021-11-18 | 2023-10-24 | 慧感(上海)物联网科技有限公司 | Omnibearing leakage monitoring and early warning Internet of things system and early warning method thereof |
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