US1827574A - Method and apparatus for gauging the contents of tank cars and the like - Google Patents

Description

ct. 13, 1931. L. E. FRAzlER I 1,827,574

METHD AND APPARATUS FOR GAUGING THE CONTENTS OF TANK CARS AND THE LIKE Y adict wail;

Oct. 13,. 1931. L. E. FAzlER METHOD AND APPARATUS FOR 'x-AUGING THE CONTENTS OF TANK CARS AND THE LIKE Filed Feb. 25, 1928 3 Sheets-5119#l 2 Fuss FIEJD n (ai Lucius E.1"`razer Oct. 13, 1931. E. FRAZIER METHOD AND APPARATUS FOR GAUGING THE CONTENTS OF TANK CA'RS'AND THE LIKE Filed Feb. 25., 1928 3 Sheets-Shea?l 3 Fna-.5. /f' 40 Patented Oct. 13,l 1931 .PATENT OFFICE I IQUCIUS E. FRAZIEB, F BARTLESVILLE, OKLAHOHA, ASSIGNOB T0 HILLIPS PETROLEUM COMPANY, 0F BABTLESVILLE, OKLAHOMA1 A CORPORATION METHOD AND APPARATUS FOR GAUGING THE CONTETS OF TANK CABSAND rTHE LIKE.

Application led February 25, 1928.l Serial No; 256,958.

rIhis invention relates to improved means.

tor-gauging the contents of receptacles, and has particular relation to the gauging of the contents of tank cars adapted to contain volatile liquids.

The primary object of this invent-ion is the provision of improved means for gauging the contents of tank cars which are adapted to receive volatile liquids, such as liquefied petroleum gas, and which enables an accurate gauge reading of the contents of the car without removing dome covers and the like from the tank car.

A further and important object of this invention is the provision of improved means for lgauging the contents of tank cars, such as class IV--A and V tank cars, in a practical manner which complies with statutory p'rovisions that the -cover of the car shall not be opened; the improved gauging means permitting an accurate level readingr of the contents wthin the car without permitting any appreciable loss lof the contents within the car which is under high pressure.

A further object of this invention is the provision of an improved method and apparatus for determining the liquid level within r a receptacle containing liquid under pressure greater than external pressure.

Heretofore gauging o the contents of tank cars has been effected in the practical art by either gauge pole measurements or by weighing on suitable track scales. The gauge pole measurement of tank car contents involves the removal of dome covers and the like, and whfle this is legal in connection. with the handling of certain hydrocarbons, it is not 49` "hazard and loss-of material being shipped,

only illegal but impracticable to so measure the tank car contents where highly volatile shipments are in transit, due to the extreme by va-porizatfon.- The weighing of tank cars tank cars to ascertain their contents, a small error very often seriously affects the volume of shipment in the tankv car, to the loss`of the shipper, in cases of reduced volume, or in- I 'l f 1 A i l1, i i i i D increased volume. Other methods consist of providing dome covers with sight holes and the like,'which method of ascertaining tank car contents is highly inaccurate. With the present invention I overcome many of the difculties heretofore Vencountered in the accurate gauging of the highly volatile contents of tank cars, such as are adaptable for shipping liquefied petroleum gas and the like.,

The rapid and accurate determination of the volume in the tank car is obtained broadly by lowering from externally of the receptacle compartment, an open tube of known length or dimensions, into the tank compartment, above the liquid level, until a lower opening immerses into the top of the liquid, so that the liquid will be pressure forced to externally of the tank car, into a visible relation. This is done without the removal of dome lcovers and the like, and thus many of the proved gauging device in position upon the tank dome cover plate. Figure 2 is a view, partly in section, taken horizontally across the dome housing substantially on the line 2 2 of Figure 1, showing in plan view the relief valve: the eduction valves; vapor vent valve, and the improved liquid level gauging device, v

' Figure 3 is a horizontal sectional view taken through the upper portion of the improved gauging device. f

Figure 4^ is a vertical sectional 'view showing details of the improved gaugingdevice and its mounting qndpperating means.

taken through-the upper portion of the irnproved gauging devi-ce', 'showing means for raising and lowering the gauge tube.

Figure 6 is a vertical sectional view of fletails lof the improved gauging device, taken in vertical plane at a 90 angle with respect to the section of Figure 4.

Figure 7 is a fragmentary vertical sectional 1giew taken through the improved gauging tu e.

Figure 8 is a side elevation showing vthe graduated gauge tube as used with this invention.

Figure 9 is a fragmentary view, partly in section, showing means for venting of pressure from within the housing which covers the gauge device, prior to entire removal of the housing.

Figure 10 is a plan view of the gauging de.- vice cover or housing.

ln the drawings, wherein for the purpose of illustration is shown only a preferred eml bodiment of my invention, the letter A may contents'of-the tank car after an improved method.

The tank car A includes the ordinary cylindrical inner shell 15, disposed on a horizontal axis, surrounded in spaced relation by an outer jacket 16, and between which insulation 17 is disposed, preferably either cork or asbestos cement. On the top of the tank car the dome header 18 is suitably Welded or otherwise sealed at a joint 19; the header 18 being disposed on a vertical axis, and being relatively short, and having a passageway 193 therethrough. The dome header 18 is annularly flanged at 20, to receive bolts 21, by

means of which to detachably bolt the dome cover plate 21 in place; the dome cover plate 21 having an annular sealed gasket connection at 22'upon the flange 20, as shown in Figure 1. The passageway 19a is relatively shallow, and is not intended to be used similar to the vapor dome of an ordinary petroleum tank car, since the dome structure of the tank car A is -onlyus'ed to receive valves and measuring accessories. A 'cvlindrical shaped dome housing 23is bolted at 24 upon the outer marginal portion of the dome cover plate 21, and the compartment 25 therein is adapted to receive details of the valves C, D, E and F andthe gauge device G. The dome housing cover 27 is pivoted or otherwise suitexcess pressure relief valve C is known as the safetyvalve, while the valve D vents exhaustive vapors int-o the dome housing compartment 25 and therefrom thru an opening 30,

under conditions understood in this art.

-Referring to the gauging device G, the

same includes a base 35 of substantially discshaped formation, attached by a plurality of lbolt devices 36 upon the cover plate 21. The

bolt devices 36 each include a shank 38 screw threaded at opposite ends, and preferably including an intermediate smooth portion for free disposal thru a passageway 39 in the base plate 35, as illustrated in Figur screw threaded shank of each of the bolt devices 36 detachably threads into a socket provided therefor in the cover plate 21, and the opposite screw threaded end thereof extends upwardly above the top surface of the base plate 35, for receiving a cap screw 40. The bolt devices 36 are eccentrically placed upon the base plate 35, and at the center e6. Une' of the plate 35 is provided astuiiing box 42, for slidably receiving the Gauge rod or tube 44 therethrough with a leash-proof connection. The base plate 35is of course provided with a passageway 44a therethrough for slidably receiving the gauge tube 44, and the plate is provided with an upstanding screw threaded 'shank or collar 47 for detachably receiving the packing nut 48, by means of which a follower 49 may be clamped down upon packing material, to compress the latter about i the gauge tube 44 which extends through the base plate 35 at opposite sides thereof.

The dome cover plate 21 is of course provided with a passageway 50 therethrough,

through which the gauge tube 44 may operate to extend into the compartment of the tank car A. In order to prevent leak of contents from the tank car A, wherein the liquid is ordinarily under superatmospheric pressure, I prefer to provide an annular flange or protuberance 51, extending'from the bottom surface of the plate 35, and surrounding the passageway 44, which is adapted to telescope into an annular groove proy vided inwardly of the top surface of the dome cover plate 21; suitable packing 52 being placed between the facing bottom surface of the groove and the lower edge of the annular langel, as shown'in Figures V4 and 6 of thedrawings, to provide an effective seal, when the bolts 36 clamp the baseplatel 35 upon the cover plate 21, in the position illusu trated.

The gauge tube 44 is of novel construction, including the main tube body 60, ordinarily formed of stock material, which has disposed therein a small tube 61, preferably spot welded in place, in order that the gauging -tube may have avery small passa eway4 62 Y therethrough, best suited to determine liquid -vided a valve device 70, including a valve casing 71, of preferably the angle type, screw l threaded at 72 upon the top ofthe tube body 60, and having a needle valve 73 screw threaded therein, provided with a needle point 74 adapted to seat at 75 in the valve casing to close olf the passageway 62 from atmospheric communication. The 'needle valve 73 has a handle 76 exterior'ly of the valve casing, to permit its convenient adjustment, and the anglenozzle 77 is of course provided with a relatively large duct 78 therethrough, into which contents passing the needle'valve seat 75 from the passageway 62 may enter to pass oifexteriorly at the top of the gauging tube or device.V For a purposewhich will be subsequently men- -tioned it is .preferred to provide a calibrated member 80 over the outlet end of the nozzle 77, ha-ving a ne passageway or duct 81 therethrough equal to or less than the cross area of the passageway 62. The tube body 60 is externally graduated, as shown in Figures 1 and 8 of the drawings; the same being preferably graduated in inches and lg-inch divisions therebetween, the graduations increasing from zero upwardly along the tube, from a location intermediate the ends, for reasons which will be subsequently apparent; the graduations continuing .to the needle angle valve structures 70. a A

The gauge tube 44 is adaptable for vertical sliding in a line normal to the liquid level within the4 tank car. In order to maintain the line of movement of the gauge tube vertical within the tank car compartment, it is preferred to provide a'steadying guide tube or pipe 85, having a screw threaded connection at 86 in the cover plate so as to align the passageway of the pipe 85 with the passageway 50 thru which the gauge tube slides. The guide tube 85 preferably has a step bearing `89 in the lower portion ofthe tank compartment, so that the guide tube is positioned truly vertical against swaying, and may guide frame or yoke 100 is provided, comprising supporting'legs 101 and 102, connected at their upper ends by a cross plate 103, provided with an opening thru which the gauge rod device 44 may lslideupwardly, without obstruction. The legs 101 and 102 are outwardly iianged at 107, at their lower ends,

and apertured, for receiving the outwardly extending screw threaded Shanks 108 of two of the diametrically opposed cap nuts 40. Nuts 109 adjust on the screw threaded Shanks 108, to clamp the flanges 107 in place, and

support the frame 100 in a stationary position with the legs 101 and 102 straddling the stuffing box 42.

It is preferred to adjustably clamp a rack bar to the upper portion of the gauge tube 44, and to this end a sleeve .,115 receives the upper portion of the body tube 61 therethrough; the sleeve 115 being split at its upper and lower ends 116 and 117a respectively; the' sleeve 115 at 'opposite sides of these splits being provided with ears for receiving Abolts 117 by means of which to draw the split sleeve at its upper and lower ends into a clamping engagement with the gan e tube device 44 which extends therethroug Integral with the sleeve 115 is the rack 120, comprising teeth arranged vertically along the split sleeve 115. A shaft 125 is rotatably supported at its opposite ends in the frame legs 101 and 102, as shown in Figures 4 and 6 of the drawings; the `shaft 125 having a pinion 126 keyed therewith in a meshing relation with'the rack bar 120. A crank 127 is rigid on the shaft 125, at the outer side of the leg 102. and the crank 127 preferably has a collapsible handle 128 thereon by means ofv poses. The body 141 is screw threaded and open at its lower end for screw ,threading at 145 upon the peripherally screw threaded base plate 35, las shown in Figures 4, 6 and 9 of the drawings. The base plate 35 is provided with an annular flange 146 annularly projecting beyond the screw threaded con-` iis viding a seat for supporting a asket 147,

upon which the lower edge of t e housing 140 may seat in a sealing relation, to'prevent escape of vapor contents from the compartment within the' housing 140 past the connection of the said housing with the base late 35, as is-perfectly apparent. Some o the connections of the details of the gauging device may be leaking, and hence the sealed housing construction 140 has been provided to prevent escape of the high volatile contents of the tank car by vaporization. Inasmuch as the pressure in the housing compartment is superatmospheric, it is preferred that some means be provided to vent the same to atmosphericpressure prior to entire removal of the housing 140. To this end I prefer to provide right angled shaped ducts 150,' in the base plate 35, having outlets on the top surface thereof and at the screw threaded periphery thereof, which are unseated in the course of unscrewing of the housing or cap 140, andv o'f course will releasethe pressure from within the housing prior to entire removal thereof from the base plate 35, as can readily be understood from the arrangement of parts in Figure 9.

ln order to provide a further seal a ainst escape of contents of the housing when c osed, the cap' nuts 40 may be clamped against suitable lead washers 160, to prevent leak of pressure past the bolts 38.

The scale upon the gauge tube so calibrated with respect to the dimensions of ythe tank car that when the open lower end of the gauge tube 44 is at the top of the tank car where the maximum level of liquid is to be placed, such as at the point 160a shown in Figure l, the zero reading of the scale will appear opposite the pointer 170, shown in Figures 3 and 6 of the drawings, as located on the top plate or portion 103 of the frame 100. When in this position the gauge device indicates that there is no outage.v rlhe gauge tube 44 is of course raised and lowered through the rack and pinion arrangement carried b the frame 100, in a Amanner which is obvious from the above description.

if al@ tank car ist@ be fined, the housing 140 is of course removed from the base plate, andthe handle v128 swung'downwardly into position, andthe gauge tube 44 moved up' wardly through the stuiiing YboX 42 by turnfing-vthe crank 127, which rtates the pinion '126 and elevatesrthe rack 120to move the gauge rod 44 upwardly. The operation is repeated until the zero'mark appears opposite vthe pointer-170. 'The tank is then filled by applying the vline connection with one or be forced upwardly through the restricted passageway 62, inasmuch as the air space or .its seat the liquid will be forced into the nozzle 77, and visibly appear through the open-v in'g 81, and after which the needle valve is closed andV the gaugetube 'lowered and the housing 140 applied, for the tank car has been filled With its volatile liquid content to the maximum level. The gauge tube' 44 is provided of the heavy walledxsmall bore type, so that the passageway therethrough is of small volumetric capacity, which consequently diminishes the time lag factor in making observations." The bore of the passageway 62, by way of example only, may range from End of an inch in diameter to a quarter of an inch. It had been previously found that when opening the needle valve 7 3 to a certain extent, the pressure within the tank car forced the contents of the tank car with too great a velocity past the needle valve seat, sometimes freezing the' opening due to lowering of temperature incident to expansion. Therefore, the cap 80 was placed so as to provide aA smallduct 81, which may range from .0135 to .125 inches indiameter, so as to prevent this 'expansion at the needle valve seat.

The vapor pressure on the volatile liquid in the car, at normal temperatures of from 30 to 120 F. issuperatmospheric, ranging from' atmospheric pressure to 200 pounds pressure per sq. inch.

In order to determine the outage in the tank car, it is merely necessary to lower the gaugeitube 44 byits operating ineans, and the needle valve 76 being open, it is apparent that when the lower open end of the tube reaches the liquid level., the liquid will be pressure forced quickly through the small diametered duct or passageway of the gauge tube, and inform the observer exteriorly of the tankcar that the top level of the volatile liquid hasbeen reached. rlhe reading on the 'gauge rdd scale may then he taken opposite the pointer 170, which indicates the Y outage in inches or the like. From this the vvolumetric contents of the tank car can be. vreadily calculated. if the scale is not graduated to immediately determine the contents. v

It is entirely practical to use theimproved vgauge tube in a simpler manner than that shown in the drawings, by Vproviding merely a sealed connection of the tube with the tank. thru which it maybe slid into and. out of the tank without the intervention Iof rack A,and bar and other mechanical expediente.

The check valve at theA bottom of the gauge tube has been provided to 'increase the safetv factor, and prevent escape of the volatile contents of the car through the gauge tube,-

lll

in event of serious accident to the tank car, such as if the superstructure of the improved device is torn away by wreckage. This check valve may be dispensed with if found desirable. l

It is -apparent from the foregoing that a vmethodand improved apparatus have been provided for accurately gauging the. liquid contents of tank cars receiving highly volatile liquids, in a manner which is both practical and legal. Among other advantages, there are four which are important in relation to the shipment of volatile liquids, such as lique- 2. .It enables the carrier to cessories. i

While the drawings portray the present invention in a good practical form, it is to be understood that the proportions and materials of the device as set forth are not a vital embodiment of the invention; that changes may be made from time to time to conform with the rulings of those agencies controlling common carriers or other reasons and that various changes in the shape,'and

arrangement of parts "ma be made to the form of invention without epartin from the spirit of the same or the scope of t e claims.

I claim:

1. In a, tank car gauging device the combination with a tankcar, of a hollow tube, means mounting the tube for upright slidable movement in the tank car for partial insertion thereinto to various degrees, a housing externally on the tank car for enclosing the exposed portion of the tube, means to seal the compartment in the housing againstrelease of pressure therefrom, said housing and said last mentioned means cooperating in structure to provide vent ducts which opento revlease pressure from within the housing duringremoval of the latter and prior .to entire lremoval thereof.

2. In a tank car gauging device the combination with a tank car, ofa tube slidable upon the tank car in a substantially vertical lline from the upper part'of the tank car, ya

normally open check valve in the lower end of said tube adapted to close under abnormal lforces placed thereon, and a manuall oper- "mated valve on the tube externally of t e tank Car. r

3. In a gauging' device fox-,tank cars the nozzle having a calibrated opening for combination with a tank car having a compartment therein, a .guide tube connected with the tank carin a stable vertical osition within the compartment of the tan v car, a

auge -tube slidable within said guidetube irom externally of the tank car and opening in; said guide tube, the guide tube having openings therein to the compartment of the tank car to permit entry of the contents of the tank car into the guide tube into contact with the gauge tube, means providing a pressure sealed sliding connection of the gauge tube relatively to the tank car to permit movement of the gauge tube into or out of the tank car guide tube, a rack on the gauge tube externally of the tank-car compartment, a pinion meshing with the rack, means rotatably supporting the pinion so that upon rotation of the latter the rack moves longitudinally for elevating and lowering said gauge tube, and a valve 'on the gauge tube for regulating escape of iiuids from the tank.

4. As an article of manufacture a gauge-` tube of the class .described comprising an tube for registering liquid levels and liquid depths comprising an upright elongated thick walled tube having a fine bore assageway longitudinally therethrough, t e 'tube externallytherealong havin a scale, a normally open gravity operate check valve at the lower `end of the tube, and an adjustable needle valve for regulating the opening of the'passageway at the upper end of the tube.

6., As an articlel of manufacture a gauge tube .for testing liquid levels of pressure liquid's within tank cars the combination of an elongated upright graduated tube having a passageway therethrough, valve means at the upper end of the tube for regulating the opening 'of the passageway, the valve means having'an outlet nozzle, andl a device on the reventing too fast expansion of iiui as t ey enter the passageway and pass said'valve.

7. In a gaugetube an elongated upright tubular graduated body havingl a fine bore passageway therethrough, a valve including a casing at the upper end of the tube and a needle adjustable inthe casing for re ulating the opening of the passageway of ty el tube, said valve casing having an outlet, and a device attachable over the outlet opening of the so a passageway through the top wall,

valve casing having av calibrated opening amount of liquid within receptacles an tank cars and the like comprisin a vbase carried by the top of said tank car an having a stuing box thereon, a graduated upright tube slidable relative to said base in the stuling box, means on thebase and the tube for ositive sliding of the tube with respect to t e base, and a housinghaving a releasable sealed connection with the base for enclosing ina sealed relation the last mentioned means and the end of the tube associated therewith.

amount of liquid within receptacles a 9. A gauge device for determin'ngthe n tank cars and the like comprising a base carried by the top of said tank car and havin a stufng box thereon, a graduated uprig t Atube slidable relative to said base in theestung box, means on the base and the tube for positive sliding of the tube with respect to the base, a housing having a releasable sealed connection with the base for enclosing in a sealed lrelation the last mentioned means and the end of the tube associated therewith, and means carried by the base for attaching the base in a sealed connection with a tank car. l1 0. In combination with. atank car having a p assageway throu h the top wall, a base plate, means detacha ly connecting the base plate in a. sealed connection with the tank car, the base plate having a stung box there'- on provided with a passageway alignin with the passageway of the tank car, a gra uated tube slidable inthe stung box through the passageway thereof and through the passageway of the tank car so as to be extended into the tank car, a frame 'carried bythe base,

a rack, means mounting the rack upon the upper portion of the gaugetube for longitudinal adjustment thereon, a crank shaft rotatable on the frame havinga pinion meshing with said rack, and a release valve carried by the upper portion of the gauge tube for opening the latter to the atmosphere.

115. In combination with a tank car having a base plate, means detachably connecting the base plate in a sealed connection with the tank Fear, the base'plate having a stullingbox thereon provided with a'passageway aligning with' the passageway ofthe tank car, a graduated tube slidable in the stuling box through theI passageway thereof and through the passagewayof the. tank car so as to be extended into the ytank car, a frame carried by the base, a rack, means mounting the lrack upon the upper portion of the gauge tube for longitudin'al adjustment thereon, a crank shaft rotatable on the frame havinga pinion meshing with said rack, a releasevalve carried by the the latter to the atmosphere, and a housing A' attachable with the base in a sealed connection to house the stuiing box, frame, rack and inion and upper portion of the gauge rod t erein in a sealed compartment.

121 In a tank car gauging device the com- `binatio'n with a tank car, of a tube movable in an upright relation upon thetank car in a sealed connection therewith so that the tube may extend to various degrees into the tank car, external valve means for regulating the passageway inthe tube, and a check valve in the tube normally open by gravity to permit tank car fluids to pass through the tube to the valve means first mentioned, and adapted to' operate incident to abnormal pressures to close said passageway.

13. In a tank car gauging device the combination with a tank car, of a tube movable on the tank car for partial insertion thereinto to various degrees, a housing externally ing and said portion having associated port' means which will permit release of pressures when the housing 1s unscrewed on the plate to a predeterminedv .degree and prior -to entirev removal of the housing from said plate.

Y lei. In combinationa tank for receiving a high pressure huid under pressure greater than atmospheric, a gauge tube, means slidably mounting the gauge tube upon the tank in pressure sealed relationtherein for movement to various degrees into the tank in line normal to the level tained in the tank, the tube being open in the tank,l an escape valve carried upon the tube externally of the tank for regulating escape of pressure duid from within the tank to the atmosphere, and calibrated vent means for regulating escape of the pressure duid in an expansion preventing relation at theloeation where the escape valve regulates the exit of thedpr'essure fluid from the passa eway of sai tube, to prevent freezing adyacent the escape valvewhen the latter is open in said tube.

-15'.'In a'tank car gauging device, the combination with a tank car, of a tube movable in an upright relation upon the tank car for partial insertion thereinto. to r.various detube therein which is external of the ank, vgasket means against which the .housing @19H-IPS, t0 Seal the' compartment of the heus.

from within'the housing to the atmospherel of pressure liquids eon- Y ing from the atmosphere, saidraised portion having ducts opening thereupon within the,l

housing compartment and at their opposite ends openingv on the screw threaded portion of the housing ati the housing side of 'said gasket means whereby to be opened when the `housing is partially unscrewed from the raised portion to unseal the housing compartment from the gasket means but prior to entire disconnectionof the housing` from the screw threads of said raised portion..

. 16. In an'outagegauge Vfor tanks the combination ofa tank, a graduated tube, means slidably mounting the tubeon the top vof the tank in pressure sealed relation therewith,

the tube being open within the tank and extending externally'of the tank, escape valve car and containing therein the upper portion ofthe tube and its valve when the tube is lowered into the tank car and surrounding and sealing therein the stuffing box connection whereby to prevent leakage of contents atl the connection of the stuling box and the tube with the tank car. f

LUCIUS FRAZIER.

means on the tube externallyof thetank for i 17. In gauge apparatus for determining s the amountv of liquid within tank cars and the like, the combination of a, tank car, a stuiling box mounted on the top thereof, a hollow slidable gauge tube slidable in an upright relation through said stuing box so that the tube may be inserted to various depths in the tank car, sa-id tube being open at its lower end in the tank car and being of a length so that the same may be substantial- 1y entirely inserted within the tank car with a short upper end projecting above the top of the tank car, valve means on the upperl portion of the tube externally of the tank for opening or closing'the tube, means carf ried by the tank externally thereupon to positively withdraw the tube .or lower it into the tank car, and a housing carried by the'top of the tank car for releasably sealing therein. the upper portion of the gauge tube and said last mentioned means, when the latter is substantially' completely lowered into .the tank car, said housinvhaving a sealed connection with the top of tzlie tank car surrounding said stuliingbox to prevent leakage of tank c ar contents from said housing.

18. In a gauge device thecombination of a tank, a stuiiing box. carried at the top ofthev tank, an upright hollow gauge tube slidable in a sealed relation through said stung box and of a length to permit the same to b'e slid into the tank forV substantially its entire length withvbut a small portion of the-tube extending externally of the tank, valve means on the upper `portion of the tube externally of the tank -for regulating discharge of tank contentsI therethrough, and a dome-like cap of imperforate construction havingv a removable sealed connection at the top of the tank

Images