Wet Abrasive Blasting System with Self-Venting Assembly

Abstract

The invention is directed toward wet-abrasive blasting systems used for cleaning, preparing surfaces, removing coatings, and other abrasive blasting applications. The wet abrasive basting system has a blast pot that includes a venting system. The venting system may be a self-venting system that allows gases to be vented during charging and prevents gases from accumulating in the blast pot during operation. In wet abrasive blasting systems a slurry is conveyed via a piping system, hoses, etc. to a mixer connected to a source of pressurized gas where slurry and compressed air/gas are combined and directed through the blast hose and blast nozzle.

Claims

1.-10. (canceled)

11. A method of operating wet abrasive blasting system, comprising: charging a blast pot of the wet abrasive blasting system with a liquid and solid abrasive to form a slurry, wherein the blast pot comprises: a cylindrical side wall, an inwardly sloping top in the general shape of a basin an upper most portion of an inner volume of the blast pot defined between the underside of the inwardly sloping top and an inside top of the cylindrical side wall of the blast pot, an outlet connected to the cylindrical side wall at the upper most portion of an inner volume of the blast pot, and a self-venting assembly, wherein the self-venting assembly is connected to the outlet in the cylindrical side wall; sealing the blast pot during the final stage of charging the blast pot with liquid; after sealing the blast pot, filling the blast pot with additional liquid and removing substantially all of the trapped air from within the blast pot through the self-venting assembly until the fluid level fills the tank and the self-venting, assembly is sealed; and pressurizing the blast pot with a fluid pump.

12. The method of claim 11, wherein the wet abrasive blasting system comprises: a mixer; a blast hose in fluid communication with the mixer; a slurry piping system connecting the bottom outlet of the blast pot to the mixer; and a pressurized air piping system capable of connecting a source of pressurized air to the mixer.

13. The method of claim 11, wherein the self-venting assembly, comprises: an automatic vent valve that operates based upon a sensor measuring air within the blast pot.

14. The method of claim 13, wherein the automatic vent valve opens to release air from the blast pot that may become trapped in the upper most portion of the blast pot, without releasing a significant amount of fluid, through the automatic vent valve until the fluid level fills the blast pot and the automatic vent valve is automatically sealed to prevent escape of liquid.

15. The method of claim 13, wherein a pipe connects the outlet in the cylindrical side wall and the automatic vent valve.

16. The method of claim 11, wherein the self-venting assembly comprises one of a float type vent valve, a diaphragm-type vent valve or an electronic vent valve.

17. The method of claim 11, wherein air accumulating in the blast pot after purging due to worn pump seals, a suction leak in the fluid pump's inlet hose or from a fluid source that includes trapped air bubbles is vented through the self-venting assembly.

18. The method of claim 11, wherein the self-venting assembly, comprises: an automatic vent valve that operates based upon a sensor measuring air within the blast pot, wherein the automatic vent valve opens to release air from the blast pot that may become trapped in the upper most portion of the inner volume, without releasing a significant amount of fluid, through the automatic vent valve until the fluid level fills the tank and the automatic vent valve is automatically sealed to prevent escape of liquid, wherein the automatic vent valve is a float type vent valve comprising a chamber, a vent seal, a float and a seat, wherein if air enters the automatic vent valve, the float moves to a lower position to allow the air or other gases to escape the chamber.

19. The method of claim 11, wherein sealing the blast pot comprises closing a spring-loaded bung.

20. The method of claim 19, wherein charging the blast pot of the wet abrasive blasting system with the liquid and the solid abrasive comprises charging the blast pot through a sealable inlet hole in the inwardly sloping top.

21. The method of claim 20, wherein during charging air may escape through the sealable inlet hole in top.

22. The method of claim 20, wherein during charging air may escape through the sealable inlet hole in top until a water level reaches the seal.

23. The method of claim 13, wherein the automatic vent valve prevents the accumulator effect.

Description

BRIEF DESCRIPTION OF THE FIGURE

[0015] The invention will now be described with the reference to the drawing wherein:

[0016] The FIGURE depicts an embodiment of a blast pot comprising a self-venting assembly.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0017] The invention relates to wet abrasive blasting systems. Embodiments of the wet abrasive blasting system may comprise a blast pot having a self-venting assembly. The self-venting assembly is capable of purging air from the blast pot without operator action during pressurizing and operation of the wet abrasive blasting system. In some embodiments, the wet abrasive blasting system comprises a blast pot and an automatic air vent valve connected to a top portion of the blast pot. The automatic air vent valve is capable of releasing air from the blast pot without releasing a significant amount of fluid. The automatic air vent valve may be positioned in a top portion of the blast pot such that the blast pot remains substantially full of liquid and abrasive.

[0018] The wet abrasive blasting system may further comprise a slurry piping system, a pressurized air piping system and a mixer. Typically, the slurry piping system will connect a bottom outlet of the blast pot to a mixer. In certain embodiments of the wet abrasive blasting system, the blast pot contains a mixture of a solid particulate and a fluid (hereinafter slurry), and the slurry piping is capable of conveying the desired flow rate of slurry from the blast pot to the mixer to be combined with the pressurized gas. The pressurized gas piping system connects a source of pressurized gas to the mixer and is capable of conveying the desired flow rate of pressurized gas at a desired pressure to the mixer. Typically, the gas will be air and the fluid will be water, but other gases and fluids may be used. In addition, additives may be added to the fluid or the gas, as desired. The abrasive media may include media in the range of United States Standard Sieve Screen Size 10010. The media and water are mixed into the pressure vessel; the ratio is inconsequential. A blast pot, typically, comprises a cone-shaped bottom with an outlet at the lowest point of the vessel. Since the media is heavier than water, the slurry is funneled into a hose or pipe that connects the blast pot to the input piping of the control panel. The slurry piping system and/or the pressurized gas piping system may be comprised of pipe and other components as desired to control the flow and pressure.

[0019] The inventor's discovered that wet abrasive blast systems operate and should be designed on the principle that the fluids in the slurry cannot be compressed. Therefore, the volume of abrasive slurry pushed out of the blast pot and mixed into the compressed air stream is controlled by the amount of fluid forced into the substantially filled pressure vessel. In such a case, as a volume of water is pumped into the blast pot, an equal volume of wet-abrasive media must be forced out of the pressure vessel. However, air trapped in the pressure vessel during filling or air that may accumulate in the pressure vessel or blast pot after purging due to worn pump seals, or a suction leak in the fluid pump's inlet hose, or from a fluid source that includes trapped air bubbles, will compress and cause fluctuations in the flow and/or the pressure of slurry stream. These fluctuations in flow and pressure may be at least partially due to the accumulator effect caused by the trapped compressed air/gas. As used herein, accumulator or accumulator effect is defined as a storage reservoir in which fluid is held under pressure with a compressible gas which can be further compressed or pressurized without forcing fluids out of the vessel when additional fluid is added to the reservoir. Since the compressible gas may be further compressed the reservoir may hold an additional volume of fluid as the volume of compressible gas is reduced.

[0020] In conventional dry blasting, this pressure vessel would contain both abrasive and compressed, air or other gas in a top portion of the blast tank, the trapped compressed air/gas forces the dry media out of the bottom of the tank to the blast hose. However, in wet-abrasive blasting systems, the pressure vessel contains a slurry of abrasives and fluid (usually water) when charged. Gas trapped in the pressure vessel above the slurry is undesirable as the trapped air results in a accumulator affect in the blast pot and is detrimental to the consistent and efficient means of forcing the wet-abrasive media into the mixer with the compressed air.

[0021] The air or other gas may become trapped in the space between the underside of the basin-shaped enclosure and the inside top of the cylinder, which makes up the cylindrical body of the pressure vessel (for example, the air space AS shown in the FIGURE). Some blast pots are equipped with a manual vent valve to remove air from the air space. However, this manual method has its shortcomings due to the fact that the operator may not realize the blast pot has accumulated air and that manually venting also allows fluid to escape along with the trapped air/gas. Wet abrasive blasting system operators typically will rely on the release of fluid from the vent valve to ensure the air and other gases is released. The operator has no other visible means of determining the exact moment when all of the air/gas has been expelled and the operator waits to see the escaped flow of liquid as an indication of when to manually close the valve. This is a major concern, especially in states or other locations where a run-off of liquid could be deemed as a violation of their ecology protection laws.

[0022] The inventors were the first to realize the advantages of a wet abrasive blasting system comprising a blast pot having a self-venting system wherein air and other gas is automatically vented during the filling and pressurizing of the pressure vessel without allowing fluid to escape. The self-venting system additionally has the advantage of venting any air or other gas that may unknowingly be introduced into the purged, pressurized vessel during use or idle time via worn pump seals, a suction leak in the pump's fluid source hose or piping, or even due to natural air bubbles that are trapped in the fluid being fed to the fluid pump, for example. Because wet abrasive blasting system operators generally do not manually re-purge the pressurized vessel of new air/gas (because there is no direct indicator when there is air in the system and venting could cause fluid run-off due as the fluid escapes simultaneously or after the air is purged), the inventors realized an automatic vent valve would provide a wet blasting system that prevents the accumulator effect and has improved efficiency and performance.

[0023] In wet abrasive blasting systems wherein the blast pot is experiencing an accumulator effect, the pressure fluctuations at the mixer may result in uneven mixing ratios of slurry and air moving through the blasting hose and/or slurry backing up into the air supply piping system. Embodiments of the wet blasting systems comprising a self-venting assembly prevents this accumulator effect by allows air to escape from the blast pot before problems are realized.

[0024] Embodiments of the wet abrasive blasting system may comprise a vertically mounted, cylindrical pressure vessel with the inwardly sloping top welded enclosure in the general shape of a basin as shown in the FIGURE. The basin comprises a sealable inlet hole allowing access into the inner volume of the blast pot. The sealable hole may be sealed by a pressure tight lid that is secured by any means such as, but not limited to, spring loaded, bolts, threaded, swing bolts, clamps, or other securing means. (Some models of the EcoQuip wet abrasive blasting systems comprise a spring-loaded bung to seal the inlet hole.) The purpose of the inward sloping top or basin is to provide a convenient means to fill the blast pot with abrasive media and fluid (the basin serves as a funnel to guide the particulate blast media and fluid into the hole in the top of the vessel).

[0025] The blast pot may be of any design capable of storing the slurry and maintaining the pressure of the system. Typical blast pots for wet abrasive blasting systems comprise cylindrical side walls and a conical shaped bottom leading to the bottom slurry outlet of the blast pot and into the slurry piping system, though other configurations may be used. The top and/or the bottom of the blast pot may be any configuration such as, but not limited to, flat, round, conical, elliptical, inward sloping, basin shaped, or upward sloping, for example. In one embodiment, the blast pot comprises a threaded outlet such as outlet 15 in the FIGURE to be located as high as possible in the inner volume of the tank, for example, in the area below the welding of the basin shaped top to the cylindrically shaped outer housing. The outlet may be any outlet capable of connecting the self-venting assembly or automatic vent valve to the blast pot and in fluid communication with its inner volume. The outlet may be a welded connection, threaded connection, flanged connection, quick connector, and/or tubing connector. The self-venting assembly may further comprise a piping system between the blast pot and the automatic vent valve. In an embodiment of the wet abrasive blasting system, the outlet is in communication with a top portion of the inner volume of the blast pot and, in a more specific embodiment, the outlet is in fluid communication with the highest point of the inner volume within the blast pot.

[0026] An automatic vent valve may be connected to the outlet. The automatic vent valve may be any type of valve capable of venting air from a pressurized vessel. The valve may be a float type valve or an automatic control valve that operates based upon a sensor measuring air within the pressurized vessel.

[0027] For example, the automatic vent valve may be a float type valve as shown in FIG. 1. During the final stage of charging or filling the blast pot, the blast pot is sealed. For example, the spring-loaded bung as shown in the FIGURE is released from its open, position and allowed to seal the pot under the biasing force of the spring. (Pressurization of the fluids cannot take place unless the pot is sealed). As additional fluid/water is pumped to fill or charge the blast pot, the air or other gas will escape through the self-venting system's vent until the fluid level fills the tank and the vent is sealed. In an embodiment of the wet abrasive blasting system with a float-type vent valve, the fluid level raises thereby lifting the float and causing its vent seal to tightly press against the vent's seat. Should new air/gas be introduced into the pressurized vessel, after it has been filled, sealed, and purged, the air/gas physically rises to the top portion of the vessel (in the air space between the underside of the basin shape and the cylindrical outer shell, for example) and temporarily causes the float to release its seal from the vent's seat enough to vent the gas. The air would continue to vent until the float is again lifted by the rise of fluid and the seal would again engage the vent's seat and prevent any significant amount of fluid from escaping.

[0028] As used herein, pipe shall mean any fluid containment device used to convey liquid or gas, such as a tube, hose, duct, pipe, or other similar structure. The pipe may have any cross-sectional shape, including rectangular, square, circular, or other shape. The flow area of the pipe is defined by its internal cross-sectional area.

[0029] As used herein, piping system shall mean pipe and other components used to connect one part of a system to another. The other components may include, but are not limited to: valves, check valves, elbows, tees, reducers, regulators, connectors, gauges or sensors such as flow, temperature or pressure gauges, and control valves.

[0030] As used herein, fluid or fluids are liquids, preferably substantially incompressible fluids, such as water.

[0031] An embodiment of a blast pot 10 comprising a self-venting assembly is shown in the FIGURE. The blast pot 10 comprises vertical cylindrical side wall 11 and top 12. Top 12 forms a basin with a filling hole able to be sealed by a spring loaded bung 13. The spring loaded bung 13 forms a pressure tight seal 14 capable of sealing the blast pot 10. Embodiments of the wet abrasive system with a self-venting system may or may not comprise a spring-loaded bung 13 but may comprise another means of charging and sealing the blast pot. The abrasive media and water may be added through the hole in the top 12. As the blast pot 10 is filled with particulate and liquid, air may escape through the same hole in top 12 until the water level reaches the seal 14. At that point, the basin B will begin to fill and an air space AS is trapped in the top portion of blast pot 10. However, the embodiment of the blast pot 10 in the FIGURE comprises a self-venting assembly connected to outlet 15. The self-venting assembly comprises a vent seal 16 that may be sealed closed by seat 17 attached to float 19 on lever 20. The vent seal 16 and seat 17 are in the open position (as shown) as long as float 19 on a lever 20 is in the lower position. As the automatic vent valve chamber 21 fills with liquid, the liquid lifts float 19 to an upper position which raises lever 20 on its hinge 18. This moves seat 17 against vent seal 16 closing the vent. If additional air enters automatic vent valve chamber 21, the float 19 will move to a lower position opening vent seal 16 to allow the pressurized air to escape the chamber 21 and allow chamber 21 to be substantially with liquid, again raising seat 17 to seal vent seal 16 to prevent release of the liquid. As long as the chamber 21 is substantially filled with liquid, seat 17 will prevent escape of liquid from the vent. Other styles of automatic vent valves may also be used on embodiments of the self-venting, assembly.

[0032] In the embodiment shown in the FIGURE, the spring-loaded bung 13 comprises a bracket 22 mounted below the spider plate 23. The spider plate 23 is above the hole in the basin B through which the bung's guide-rod passes. The bracket 22 serves at least two purposes: (1) the bottom of the bracket 22 becomes the lower surface for a locking device to hold the bung 13 in the open position during the filling, process and (2) a center hole in the bracket 22 acts to align the bung's guide-rod 24 and eliminates the need for a bung alignment counterweight. The spring-loaded bung system simplifies the charging of the pressure vessel and makes the process as free from operator error as possible.

[0033] The self-venting system does not require the spring-loaded bung system in order for it to work. The spring-loaded bung keeps the pressure vessel closed during idle time. This spring loaded sealing prevents debris from contaminating the inside of the vessel. This also prevents precipitation from entering the vessel during idle time, which could freeze and be detrimental to ball valves and other components associated with the pressure vessel. The spring-loaded bung and self-venting system enables charging the pressure vessel without any fluid remaining in the top of the basinabove the seal. Therefore, the operator can travel with a sealed pressure vessel (whether charged or uncharged) and avoid spillage, thus not violating ecology laws about run-off in some states.

[0034] The self-venting system and the spring-loaded bung are two separate devices installed on the same pressure vessel to comprise a system that works together to simplify the venting of air/gas from a pressure vessel, and more importantly, it does so without, any excess significant fluid run-off or unnecessary spillage.

[0035] The embodiments of the described wet abrasive blasting systems, self-venting assemblies and methods are not limited to the particular embodiments, components, method steps, and materials disclosed herein as such components, process steps, and materials may vary. Moreover, the terminology employed herein is used for the purpose of describing exemplary embodiments only and the terminology is not intended to be limiting since the scope of the various embodiments of the present invention will be limited only by the appended claims and equivalents thereof.

[0036] Therefore, while embodiments of the invention are described with reference to exemplary embodiments, those skilled in the art will understand that variations and modifications can be effected within the scope of the invention as defined in the appended claims. Accordingly, the scope of the various embodiments of the present invention should not be limited to the above discussed embodiments, and should only be defined by the following claims and all equivalents.