The present invention generally relates to a mixing device and method. More particularly, the present invention pertains to a device and method for mixing a fluid disposed in a tank.
It is generally known that fluids stored in tanks will often settle. Settling of some fluid may be of no consequence or even desirable. However, in other fluid, settling may be detrimental. For example, in petroleum product, settling may cause basic components to precipitate or concentrate at or near the bottom of the tank—damaging the tank and reducing the quality of the petroleum product stored therein. In general, this problem is referred to as basic sediment and water (BS&W).
Gasoline and crude oil storage tanks are generally agitated for product blending, uniformity and suspension of sediment and water. Since this type of storage vessel is typically very large diameter with relatively short height, top entry agitators are generally not practical and side entry agitators are used.
Side entry agitators penetrate through the side wall of the vessel and project several feet into the tank. There is currently no provision to extract the shaft and impeller from the tank without breaking the vessel seal which could result in a substantial spillage from the vessel.
Environmental requirements for gasoline tanks in particular have shifted the tank designs to use floating roofs. This allows for the minimization of the vapor space above the fluid and hence volatilization. Due to the presence of the current design side entry agitators, floating roofs cannot be dropped to the bottom of the vessel and a significant perpetual inventory must be maintained in each tank.
Accordingly, it is desirable to provide a system, device and method capable of overcoming the disadvantages described herein at least to some extent.
The foregoing needs are met, to a great extent, by the present invention, wherein various respects a system, device, and method of mixing fluid in a tank is provided.
An embodiment of the present invention pertains to a system for mixing a fluid in a tank. The system includes a mixer assembly, a housing, and an actuator. The mixer assembly has a motor, a shaft, and an impeller. The housing is disposed in a side wall of the tank. The housing has sufficient volume to contain the impeller. The actuator is configured to retract the mixer assembly and draw the impeller into the housing. The mixer assembly has a first conformation and a second conformation. In the first conformation the impeller is disposed in a main portion of the tank and configured to mix the fluid in response to rotation of the impeller via the motor and shaft. In the second conformation the impeller is disposed in the housing and out of the main portion of the tank.
Another embodiment of the present invention relates to a mixer assembly. The mixer assembly includes an impeller, a motor to rotate the impeller, and a shaft affixed to the impeller and convey torque from the motor to the impeller. The mixer assembly additionally includes housing having sufficient volume to contain the impeller, a seal, and an actuator. The seal is disposed in the housing. The seal is configured to facilitate rotation of the shaft and being configured to facilitate longitudinal sliding the shaft while reducing leakage of a fluid across the seal. The actuator is configured to urge the shaft to move longitudinally. The impeller is drawn into the housing in response to the actuator moving the shaft.
Yet another embodiment of the present invention pertains to a method of drawing a fluid from a tank having a floating roof. In this method, if it is determined the roof is below a predetermined minimum level an impeller is retracted from the tank and into a chamber affixed to a side of the tank. In this manner, additional fluid may be drawn from the tank and the roof is allowed to descend below the impeller in response to the impeller being in the housing and out of a main portion of the tank.
There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.
The present invention provides a retractable impeller for a tank mixing system and method of retracting an impeller from a tank. For the purposes of this disclosure, the term “tank” and variations thereof refer to a container or vessel of any suitable size or shape and to contain any suitable fluid. In a particular example, the tank or tanks described herein may be suitable for containing many tens, hundreds, thousands, millions etc. of liters of fluid. In a specific example, the fluid may be a petroleum product stored in a tank having a relatively large volume such as, hundreds to millions of barrels.
The impeller assembly 14 is configured to mix or otherwise generate a flow of the fluid 16 in the tank 12 to prevent or reduce separation of components within the fluid 16. In general, the impeller assembly 14 includes an impeller 22, shaft 24, seal 26, housing 28, motor 30 and support 32. As shown herein, various examples of seals, housings, and supports are envisioned in this or other embodiments of the invention. The impeller 22 is configured to urge the fluid 16 to flow in response the being rotated. The shaft 24 is configured to transfer torque from the motor 30 to the impeller 22. The seal 26 is configured to prevent or reduce leakage of the fluid 16 around the shaft 24. In addition, the seal 26 is configured to facilitate retracting the shaft 24 from the tank 12 and inserting the shaft into the tank 12. As shown herein, the seal 26 may include one seal or a plurality of seals operable to facilitate sliding the impeller assembly 14 and rotation of the shaft 24.
The housing 28 is configured to provide a recess or chamber of sufficient volume for the impeller 22 and/or at least a portion of the shaft 24 to be retracted from a main volume of the tank 12 and allow the roof 20 to descend below the level of the impeller 22. The motor 30 is configured to generate sufficient torque to rotate the impeller 22 via the shaft 24. In general, the motor 30 may include any suitable motor or actuator such as, for example, electric, pneumatic, hydraulic, combustion driven, and the like. The support 32 is configured to support the motor 30 and/or reduce lateral forces on the shaft 24 and/or the seal 26. Optionally, the support 32 is configured to facilitate refraction and/or insertion of the impeller assembly 14.
In addition, the tank mixing system 10 optionally includes an actuator 34, sensor 36, and/or controller 38. If included, the actuator 34 may be configured to draw the shaft 24 and impeller 22 into the housing 28 and/or urge the shaft 24 and impeller 22 out of the housing 28 and back into the tank 12. In various examples, the actuator 34 may include a hydraulic or pneumatic actuator, threaded rod and follower, geared rack and pinion, or other such linear actuator. The sensor 36 may include any suitable sensor such as, for example, a pressure transducer, electrical resistance, or the like. The controller 38 may be configured to receive signals from the sensor 36 and/or a user. The controller 38 may be further configured to send and/or receive signals from the actuator 34 to modulate the actuator 34 and/or monitor the actuator 34 for position, resistance to movement, etc. The control of retraction and/or insertion may be manual and/or automatic. For example, a user may utilize the controller 38 to modulate the actuator 34. In addition or alternatively, the controller 38 may automatically send signals to the actuator 34 in response to signals from the sensor 36. In this manner, the impeller 22 may automatically be drawn into the housing 28 in response to the roof 20 falling below a predetermined minimum level and/or the impeller 22 may automatically be inserted into the tank 12 from the housing 28 in response to the roof 20 rising above the predetermined minimum level.
Alternatively or in addition, the level of the roof 20 may be determined by monitoring an amount of the fluid 16 in the tank 12. For example, based on an amount of the fluid placed 16 in the tank 12 verses an amount of the fluid 16 drawn from the tank 12, an amount of the fluid 16 currently remaining in the tank 12 can be estimated. If is determined the level of the fluid 16 is below the predetermined minimum, the impeller 22 may be retracted into the housing 28 either manually or automatically.
To urge the sled 42 to slide relative to the housing 40, the impeller assembly 14 may include the actuator 34. The actuator 34 may include any suitable device operable to urge the sled 42 to move relative to the housing 40. Examples of suitable actuators include hydraulic cylinders, screw drives, and the like. In a particular example, the actuator 34 includes a hydraulic cylinder with a piston 52 configured to mate with a cylinder 54 and driven by a hydraulic fluid in a generally understood manner.
The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
This application claims priority to U.S. provisional application entitled, RETRACTABLE MIXING DEVICE AND METHOD, filed Jul. 15, 2013, having Ser. No. 61/846,264, the disclosure of which in hereby incorporated by reference in its entirety.
Number | Date | Country | |
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61846264 | Jul 2013 | US |