Apparatus for cleaning the interior of an above ground storage tank

Abstract

An apparatus and method for cleaning the interior of an above ground storage tank includes a nozzle assembly mounted to a cover on the storage tank sidewall having a horizontally extending wash pipe fixedly and a suction pipe for recirculation of spent fluids. The wash pipe has an interior segment which can be extended to a tank floor and is configured with a bend to extend along the tank sides all to which is attached a submersible swivel joint fitted with a choked nozzle. A control assembly is provided to direct from the nozzle from the exterior of the storage tank. The nozzle vibrates in response to flow of wash fluid from the wash pipe.

Claims

1. In a storage tank having a vertical sidewall that separates the tank exterior from the tank interior and a horizontally oriented tank floor, a nozzle assembly comprising: (a) a nozzle section said nozzle section having a wash pipe extending through said sidewall of said storage tank into said interior of said storage tank and a nozzle connected to said wash pipe whereby said nozzle will vibrate in response to a flow of wash fluid through said nozzle; (b) a suction section said suction section having a draw nine extending through said sidewall of said storage tank; (c) wherein said nozzle is adjustably positionable adjacent said tank floor; (d) wherein a plurality of compression springs is positioned between said nozzle and said wash pipe; (e) wherein each said compression spring of said plurality of compression springs is a coiled compression spring; and wherein each said compression spring of said plurality of coiled compression springs is mounted on a threaded connector.

2. The nozzle assembly as recited in claim 1 wherein said nozzle has a flange and said nozzle flange is attached to said wash pipe by said threaded connectors.

3. In a storage tank having a vertical sidewall that separates the tank exterior from the tank interior and a horizontally oriented tank floor, a nozzle assembly comprising: (a) a nozzle section said nozzle section having a awash pipe extending through said sidewall of said storage tank into said interior of said storage tank and a nozzle connected to said wash pipe whereby said nozzle will vibrate in response to a flow of wash fluid through said nozzle; (b) a suction section said suction section having a draw pipe extending through said sidewall of said storage tank; (c) wherein said nozzle is adjustably positionable adjacent said tank floor; (d) wherein a plurality of compression springs is positioned between said nozzle and said wash pipe; and (e) wherein each said compression spring of said plurality of compression springs is comprised of conical spring washers mounted around a threaded connector.

4. The nozzle assembly as recited in claim 3 wherein said nozzle has a flange and said nozzle flange is attached to said wash pipe by said threaded connectors.

5. In a storage tank having a vertical sidewall that separates the tank exterior from the tank interior and a horizontally oriented tank floor, a nozzle assembly comprising: (a) a nozzle section said nozzle section having a wash pipe extending through said sidewall of said storage tank into said interior of said storage tank adjacent said tank floor and a nozzle connected to said wash pipe; (b) a nozzle flange attached to said nozzle; (c) a wash pipe flange attached to said wash pipe; (d) a plurality springs positioned between said nozzle flange and said wash pipe flange whereby said nozzle will vibrate in response to a flow of wash fluid through said nozzle; (e) a swivel joint attached to said wash pipe; (f) a control assembly whereby said nozzle may be pivoted about said swivel joint to sweep above said tank floor from said exterior of said storage tank; (g) a suction section said suction section having a draw pipe extending through said sidewall of said storage tank; (h) a high pressure fluid supply line fitted to said wash pipe; (i) a fluid pump system connected to said fluid supply line; (j) a vacuum line fitted to said draw pipe; (k) a vacuum system connected to said vacuum line; and (l) wherein each said spring of said plurality of springs is a compression spring mounted with a threaded connector positioned between said nozzle flange and said wash pipe flange.

6. The nozzle assembly as recited in claim 5 wherein each said compression spring of said plurality of compression springs is a coiled compression spring.

7. The nozzle assembly recited in claim 5 wherein each said compression spring of said plurality of compression springs is a stack of conical spring washers.

8. The nozzle assembly as recited in claim 6 wherein at least said nozzle flange or said wash pipe flange has a plurality of elongated holes for receiving said threaded connectors.

9. The nozzle assembly as recited in claim 7 wherein at least said nozzle flange or said wash pipe flange has a plurality of elongated holes for receiving said threaded connectors.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cutaway perspective view of a storage tank fitted with the articulating nozzle assembly described herein.

(2) FIG. 2 is an outside elevation view of the above ground storage tank cleaning assembly shown in FIG. 1.

(3) FIG. 3 is an interior elevation view of the above ground storage tank cleaning assembly shown in FIG. 1.

(4) FIG. 4 is a side partial cross-section of the above ground storage tank cleaning assembly shown in FIG. 1.

(5) FIG. 5 is a top partial cross-section view of the above ground storage tank cleaning assembly shown in FIG. 1.

(6) FIGS. 6A and 6B are a side partial cross-section view of the vertical articulation of the nozzle assembly shown in FIG. 1.

(7) FIG. 7 is a schematic diagram of the vacuum system assembly of the above ground storage tank cleaning assembly shown in FIG. 1.

(8) FIG. 8 is a schematic view of the vacuum assembly above ground storage tank cleaning assembly.

(9) FIG. 9 is an isometric view of the suction section of the above ground storage tank cleaning assembly being articulable above the tank floor of an above ground storage tank.

(10) FIG. 10 is side partial cross-section view of an alternate embodiment of the nozzle section of the nozzle assembly shown in FIG. 1.

(11) FIG. 11 is a top view of the alternate embodiment of the nozzle section of the nozzle assembly shown in FIG. 10.

(12) FIG. 12 is a side view of a flange attachment mechanism of the nozzle section of the nozzle assembly shown in FIGS. 10 and 11.

(13) FIG. 13 is a top view of the alternate embodiment of the nozzle section of the nozzle assembly shown in FIG. 10 provided with conical spring washers.

(14) FIG. 14 is an elevation view of the nozzle attachment flange for the nozzle of the alternate embodiment of the nozzle section shown in FIG. 10 and FIG. 13.

(15) FIG. 15 is a top view of the alternate embodiment of the nozzle section of the nozzle assembly shown in FIG. 10 provided with tension springs.

DESCRIPTION OF EMBODIMENT

(16) FIG. 1 shows a cutaway perspective view of an above ground storage tank (40) having a vertically extending sidewall (42) that separates the tank exterior (43) from the tank interior (45). The sidewall (42) of the storage tank (40) is fitted with one embodiment of an articulating nozzle assembly (10) comprised of a nozzle section (12), a suction section (13), and a nozzle steering or control section (14). The nozzle assembly (10) is used for cleaning the interior of the storage tank (40). The nozzle assembly (10) may be permanently or removably fitted on the storage tank (40) by attachment to a manway cover, hatch, or port (30) of an opening (32) in the sidewall (42) of the storage tank (40). The nozzle assembly (10) may also be permanently or removably fitted on the storage tank (40) by attaching it to a separate hatch, port cover, or other opening positioned in the vertically extending sidewall (42).

(17) The nozzle section (12) of the assembly (10) is fitted to a high pressure fluid supply line (50) that is attached to a fluid supply, such as a water or crude oil supply, and pump system (52) so that wash fluid may be injected into the storage tank (40). The suction section (13) is attached to a vacuum system (54) which recirculates suctioned fluids to fluid supply and pump system (52).

(18) As shown in FIG. 2 and FIG. 3 the nozzle assembly (10) is fitted to the tank sidewall (42) where nozzle section (12) will be positioned adjacent tank floor (45A). However, the storage tank (40) may also be provided with a separate hatch, opening, or port, not shown, positioned in a desired location in the sidewall (42) where the apparatus (10) might also be attached.

(19) FIG. 4 shows a side partial cross-section view of the storage tank (40) with the tank sidewall fitted with the articulating nozzle assembly (10). In the interest of clarity, suction section (13) is shown at a position above nozzle assembly (12) though suction section (13) will be preferably positioned on the tank sidewall at a position in line with or below nozzle assembly (12) as needed in order to achieve adequate suction of fluids.

(20) The nozzle section (12) of the nozzle assembly (10) is comprised of a horizontally extending wash pipe (34) that is fixedly mounted to the vertically extending sidewall (42) of the storage tank (40). The wash pipe (34) extends through the tank sidewall (42) so that the wash pipe (34) protrudes into the interior (45) of the storage tank (40) in a direction generally perpendicular to the tank sidewall (42) and has an exterior portion (34A) that extends away from the storage tank sidewall (42) on the tank exterior (43) of the storage tank (40) and an interior portion (34B) that extends from the storage tank sidewall (42) into the tank interior (45) of the storage tank (40).

(21) The exterior portion (34A) of the wash pipe (34) has an exterior end (36) configured for attachment to and fluid communication with the high pressure fluid line (50) at the tank exterior (43) by means of an attachment flange (38) or other attachment means. The interior portion (34B) of the wash pipe (34) has an interior end (35) configured for attachment to and fluid communication with a pipe segment (31) in order to extend the interior portion (34B) of the wash pipe (34) along the vertically extending tank sidewall (42) in the tank interior (45).

(22) Pipe segment (31) has a discharge end (35A) that is configured for attachment to the swivel end segment (33A) of a submersible joint (33), such as a Chiksan swivel joint manufactured by FMC Technologies, Inc. The swivel joint (33) has a discharge end (37) that is fitted with a choked nozzle (39). In this configuration, the choked nozzle (39) will be rotatably positionable within the interior (45) of the tank (40) by means of the swivel joint (33). The wash pipe (34) can be adjusted, preferably by lengthening pipe segment (31), to allow the choked nozzle (39) of the nozzle section (12) to be extended adjacent to, and in use sweep slightly above, the tank floor (45A).

(23) Highlighted area 6 shown in FIG. 4 refers to articulating nozzle (39) which is shown in FIGS. 6A and 6B. FIG. 6A shows nozzle (39) in a horizontal position and FIG. 6B depicts an alternate position of the articulating nozzle (39) offset at a desired downward angle () to follow the downward sloped surface of the tank floor (45A. Offsetting nozzle (39) at downward angle () allows improved mixing at the floor, without creating potential for damaging the floor by directing fluid forces at a relatively perpendicular angle to the tank floor (45A) or at an angle where the fluid forces generated by the nozzle (39) will cause wear or damage to the floor surface. The angular adjustment of nozzle (39) in combination with the adjustment of interior end (35) to position the nozzle section (12) to sweep slightly above the tank floor (45A) will provide a means to clear adherent sludge, oil, or other petroleum slurry from the surface of the tank floor (45A) while improving the mixing at the tank floor (45A) without creating a potential for damaging the floor by projecting high velocity fluids against the tank surface.

(24) The high velocity fluids projected by the nozzle section (12) may be any water, crude oil, or other fluid substance which may be directed in a jet or plume to dissolve and suspend accumulated sludge from a tank floor (45A).

(25) The suction section (13) of the nozzle assembly (10) is comprised of a horizontally extending draw pipe (44) that is fixedly mounted to the vertically extending sidewall (42) of the storage tank (40). The draw pipe (44) extends through the tank sidewall (42) so that the draw pipe (44) protrudes into the interior (45) of the storage tank (40) in a direction generally perpendicular to the tank sidewall (42). The exterior portion (44A) of the draw pipe (44) extends away from the storage tank sidewall (42) on the tank exterior (43) of the storage tank (40) and the interior portion (44B) of the draw pipe (44) extends from the storage tank sidewall (42) into the tank interior (45) of the storage tank (40).

(26) The suction section (13) is attached to a collection hose or pipe, shown as disposed vacuum line (26), having a vacuum connection (26a) for connecting the vacuum line (26) to the vacuum system (54) for producing a vacuum force () at the suction section (13) to suction the adherent sludge (81) freed by nozzle section (12).

(27) The exterior portion (44A) of the draw pipe (44) has an exterior end (47) configured for attachment to the vacuum line (26) at the tank exterior (43) by means of an attachment flange (38) or other attachment means. The interior portion (44B) of the draw pipe (44) has an intake end (49) that is fitted with a vacuum nozzle or funnel (46). In this configuration, the funnel (46) will be capable of clearing obstructions from around opening (32), can add cutter stock to the amalgam within the storage tank (40), or can be used to suction recirculating product from the tank (40) to water supply and pump system (52) in order to redistribute the recirculating product back through the nozzle (39) into the interior of the tank (40). Cutter stock may be any chemical or substance for aid in dissolving and breaking up of adherent fluid from the tank floor (45A).

(28) FIG. 3, FIG. 4, and FIG. 5 show the control section (14) of the nozzle assembly (10). Control section (14) is fitted to the nozzle section (12) so that the position of the choked nozzle (39) by means of the swivel section (34A) of the submersible joint (33) can be manipulated by a user from the exterior of the storage tank (42). The control assembly (14) is generally comprised of a rotatable control shaft (24) that has an exterior end (23) extending generally perpendicular from the vertically extending sidewall (42) of the storage tank (40) and an interior end (25) that extends into the interior (45) of the storage tank (40). The control shaft (24) is fitted through a control bushing (22) mounted on the tank sidewall (42) of the storage tank (40) at a position adjacent to the exterior portion (34A) of the wash pipe (34).

(29) The interior portion (25) of the control shaft (24) has a perpendicularly extending control rod (27) pivotally fitted to a steering linkage (28) that is pivotally attached to the swivel joint (33). The exterior end (23) of the control shaft (4) is fitted with a steering wheel (29) to facilitate rotation of the rotatable control shaft (24). A handle projecting from the control shaft such as a crank, lever or other device for turning the control shaft (24) may be utilized as a replacement for else steering wheel (29). When interior end (35) is adjusted to place nozzle section (12) adjacent the tank floor (45A), interior portion (25) of the control shaft (24) will be proportionately adjusted in order to articulate swivel joint (33).

(30) As shown in FIG. 5, a top partial cross-section view of a storage tank fitted with the articulating nozzle assembly (10), rotation of the control shaft (24) of the nozzle assembly (12) will move the control rod (27) and by the associated steeling linkage (28) control position of the choked nozzle (39) and thereby the direction of flow from the choked nozzle (39) as the swivel joint (33) pivots about the swivel segment (33A).

(31) The control assembly (14) and associated steering linkage (28) can be any suitable steering mechanism such as an eccentric gear drive, rack and pinion, cam, or wheel mechanisms. An automated device or a powered turning mechanism may also be incorporated into the control assembly (14). For example, the control assembly (14) may be fitted with a motor, such as an electric or hydraulic motor, to rotate the control shaft (24) or to otherwise manipulate the steering linkage (28) as a substitute for the manual steering wheel (39).

(32) As shown in FIGS. 7 and 8, the vacuum system (54) is comprised of a motor (58) and vacuum pump (55) connected to a vacuum tank (56) by an associated vacuum line (60c). The vacuum tank (56) is connected at entry (70c) to a vacuum line (60b) that is connected at entry (70b) to a fluids collection chamber (62). The fluids collection chamber (62) is further connected, at entry (70a) to a fluids vacuum line (60a). The fluids Vacuum line (60a) is connected to the vacuum connection (58) of vacuum line (26) shown in FIG. 1. When activated the vacuum pump (55) will create a vacuum within vacuum tank (56) via vacuum line (60c), a vacuum within the fluids collection chamber (62) via vacuum line (60b), and provide a desired suction force () at the funnel (46) via fluid vacuum line (60a) which is in communication with vacuum line (26) by means of vacuum connection (26a). The suction force () at the funnel (46) will draw the freed adherent sludge (81) from the tank (40) into the fluids collection chamber (62).

(33) The adherent sludge (81), drawn by suction through funnel (46) and Vacuum line (26) into vacuum line (60a), is delivered through entry (70a) into the fluids collection chamber (62). The collected sludge (81), and an extraneous fluids drawn along with the sludge (81), will then spill into the fluids collection chamber (62) where it will be collected. The fluids collection chamber (62) is provided with an airtight fluids exit port (64a) having an associated fluids dump valve (61). The fluids exit port (64a) is in communication with a fluids discharge line (64b). A discharge outlet (65) from the discharge line (64b) delivers fluids discharged from the fluids collection chamber (62) into a fluid holding tank (66) or to another desired location for ultimate disposal. A dump pump (68) may be provided with the discharge line (64b) to facilitate removal of the sludge (81) and any extraneous fluids from the fluids collection tank (62). The fluids dump valve (61) may be an automatic or manually operated valve such as a butterfly valve, a gate valve, or a ball valve.

(34) The vacuum tank (56) may be provided with a vacuum control port (57) in communication with, a vacuum control or relief valve (59). The vacuum relief valve (59) is used to regulate the suction created in the vacuum tank (56) and thus the suction created in the vacuum line (26) and ultimately the suction force () created at the funnel (46).

(35) Pressure monitors (72) may be positioned at desired locations throughout the vacuum system (54) such as in the vacuum tank (56), the fluids collection chamber (62), or the vacuum line (26) to monitor and generate pressure signals (71). These pressure signals (71) may be delivered to a control panel (70) from which control signals (73a) may be generated and transmitted to the vacuum control valve (59), pump (55), or motor (58) as necessary to regulate the vacuum created in the vacuum tank (56) and the quantity of fluids delivered to the fluids collection chamber (62) and to otherwise control the vacuum system (54). The control panel (70) may also be used to receive, generate, and transmit control signals (73b) to and from the fluids dump valve (61) at the fluids exit port (64a) of the fluids collection chamber (62) and to the dump pump (68) to regulate removal of the collected fluids from the fluids collection chamber (62).

(36) A suction force () is then created at the funnel (46) by the vacuum system (54) and directed by the funnel (46) to suction the floating sludge (81), thereby clearing the area about the tank sidewall (42) of tank (40), drawing the floating sludge (81) into the fluids collection chamber (62) of the vacuum system (54).

(37) The vacuum system (54) is assembled with motor (55) connected to the vacuum pump (58), vacuum pump (58) connected to vacuum tank (56) via vacuum line (60c), fluids collection tank (62) connected to vacuum tank (56) via vacuum line (60b), and vacuum line (26) connected to fluids collection tank (62) via fluids vacuum line (60a).

(38) With the vacuum system (54) attached to the vacuum line (26) of the suction section (13), the motor (55) and vacuum pump (58) is then activated to create a vacuum in vacuum tank (56). Creating a vacuum in the vacuum tank (56) will create a vacuum in the fluids collection tank (62), a suction force () in fluid vacuum line (60a) and in vacuum line (26), and a suction force () at the funnel (46) whereby the sludge (81) will be drawn through funnel (46), vacuum line (26), and fluid vacuum line (60a) into fluids collection chamber (62) where the suctioned sludge (81) will be collected.

(39) Controlling the suction force () and the flow of sludge (81) into and out of the fluids collection chamber (62) may be accomplished by manually controlling the vacuum relief valve, the dump valve (61), the dump pump (68), the motor (55), and the vacuum pump (58). Controlling the suction force () and the flow of sludge (81) into and out of the fluids collection chamber (62) may also be accomplished by automatically controlling the vacuum relief valve, the dump valve (61), the dump pump (68), the motor (55), and the vacuum pump (58) by providing a generating control signals (71 and 73a, 73b) to and from the control panel (70) and the associated valves, pumps, and motors.

(40) Further, the funnel (46) will be capable of adding cutter stock to the amalgam within the storage tank (40) by providing cutter stock to vacuum line (26) and causing a positive pressure to be applied to the vacuum line (26). After addition of cutter stock to tank (40), typical washing procedures through nozzle assembly (12) may proceed after which funnel (46) may then be used to suction recirculating product and cutter stock from tank (40) to fluid holding tank (66) wherein recirculating product may be filtered from the sludge (81) and cutter stock and reintroduced into water supply and pump system (52) in order to redistribute the recirculating product back through the nozzle (39) into the interior of the tank (40).

(41) In use, the nozzle assembly (12) and suction pipe (13) of the apparatus (10) are permanently or removably mounted to the vertically extending sidewall (42) of the storage tank (40) containing adherent sludge (81). The wash pipe (34) and draw pipe (44) extend through the tank sidewall (42) of tank (40) with the exterior portions (34A) of the wash pipe (34) and (44A) of the draw pipe (44) on the exterior (43) of the storage tank (40) and an interior portions (34B) of the wash pipe (34) and (44A) of the draw pipe (44) extend into the tank interior (45) of the storage tank (40). The swivel segment (33A) of the submersible swivel joint (33) is then attached to the end (35) of the interior portion (34B) of the wash pipe (34) and the discharge end (37) of the swivel joint (33) is fitted with a choked nozzle (39). The nozzle assembly (12) is then positioned adjacent to the floor (45A) of tank (40). The steering linkage (28) of the control assembly (14) is then attached to the swivel joint (33) in a configuration that will allow rotation of the choked nozzle (39) about the centerline of the interior wash pipe (34B) by means of the swivel joint (33) when the steering wheel (29) is turned to rotate the control shaft (24).

(42) Flow from the choked nozzle (39) is accomplished by attachment of exterior portion (34A) of the wash pipe (34) to the fluid line (50) at the tank exterior (43) by means of the attachment flange (38) or other attachment means. The swivel joint (33) with the attached control shaft (24) by means of the associated steering linkage (28) will then allow the nozzle (39), and any associated flow, to be directed to a desired position and location in the interior (45) of the storage tank (40) by rotation and manipulation of the control shaft (24) and associated steering linkage (28).

(43) During the process of flow from choked nozzle (39) or after a sufficient flow has been achieved, fluid may be reclaimed through funnel (46) by activating vacuum system (54) which will draw fluid into funnel (46), through draw pipe (44), and into fluid source (52) where the fluid may then be recirculated to clean storage tank (40).

(44) FIG. 9 depicts an isometric view of suction section (13) wherein nozzle section (12) has been omitted to best show the function of the suction section (13) being articulable. As shown in FIG. 9, suction section (13) may be configured in the same manner as nozzle section (12) shown in FIGS. 3, 4, 5, 6A and 6B. In such a configuration suction section (13) will be provided with ninety degree pipe segments (41 & 48), a steering linkage (28A), control rod (27A), and a swivel joint (48) so as to allow funnel (46) to be positioned adjacent tank floor (45A) and articulated and positioned as desired, as described for nozzle section (12), to allow suction force () to draw in adherent sludge.

(45) FIGS. 10 and 11 show an alternate embodiment of the nozzle section (12) of the nozzle assembly (10). In this nozzle (39) is attached to a vibration mechanism (90) that will allow the nozzle (39) to vibrate and flutter, shown as (V) in FIG. 11, in response to the ejection of the wash fluid from the nozzle (39). Vibration mechanism (90) is comprised of nozzle (39) attached to pipe flange (92) which is configured to receive the discharge end (37) of the swivel joint (33). Pipe flange (92) is then attached to pipe flange (94) around swivel joint extension (33B) between a plurality of compression springs (96). The action of the discharge wash fluid, shown as (F) in FIG. 11, through the nozzle (39) will cause the nozzle (39) to vibrate and flutter on springs (96) from side to side as wash fluid is discharged to enhance the washing action of wash fluid. The amount of vibration and flutter of the nozzle (39) may be controlled by changes in the stiffness or spring constant of the springs (96).

(46) FIG. 12 shows an embodiment of a spring bolt (93) for connecting springs (96) between pipe flanges (92) and (94) of vibration mechanism (90). Spring bolt (93) is comprised of a spring (96) welded or otherwise attached between threaded connectors shown as bolt sections (95) and (97). A nut (98) is used to secure spring bolt (98) between attachment flanges (92) and (94).

(47) Springs (96) are shown as coiled compression springs but other types of spring devices that will allow the nozzle (39) to vibrate in response to the flow of wash fluid may also be utilized. One such compression spring device, a stack of conical spring washers (96A), also called Belleville washers or disc springs, is shown in FIG. 13. In use a desired number of conical spring washers (96A) may be mounted around and stacked along the length of a threaded connector such as an attachment bolt (95A) and secured between flanges (92) and (94) by a nut (98) to provide the desired vibration of nozzle (39) in response to the flow of wash fluid. The amount of compression applied to the conical spring washers (6A) by tightening or loosening the nut (98) on attachment bolt (95A) will serve to adjust the amount of vibration of nozzle (39).

(48) In the embodiments of the nozzle section (12) shown in FIGS. 10-13, vibration of the nozzle (39) attached to flange (92) may be enhanced by providing elongated bolt holes (99) for use in conjunction with attachment bolts (95) as shown in FIG. 14 or in conjunction with attachment bolts (95A).

(49) The elongated bolt holes (99) may be rectangular but it is thought that oval or elliptical shaped bolt holes oriented parallel to the floor (45A) of the storage tank (40) will enhance nozzle vibration and removal of sludge from the tank floor. The elongated dimension of bolt holes (99) with respect to the diameter of bolts (95) and (95A) may be adjusted as desired to increase or decrease the vibration of the nozzle (39). Elongated bolt holes (99) for attachment bolts (95) or (95A) shown in FIG. 14 could be provided in either of, or both, flange (92) and (94) for enhancing vibration of nozzle (39) as thought necessary.

(50) FIG. 15 shows a tension spring (96B) as the spring (96) shown in FIGS. 10 and 11. In use tension spring (96B) replaces spring (96) between bolt sections (95) and (97) to provide tension spring bolts (93B) to be secured between flanges (92) and (94) by a nut (98) to provide the desired vibration of nozzle (39) in response to the flow of wash fluid.

(51) It is thought that the proposed apparatus and method for cleaning the interior of an above ground storage tank presented herein and many of its attendant advantages will be understood from the foregoing description. It is also thought that it ill be apparent that various changes may be made in the form, construction and arrangement of the parts and steps of the apparatus and method without departing from the spirit and scope of the invention or sacrificing all of its material advantages.