CA2035026C

CA2035026C - Separator for producing moist, granular blasting agent

Info

Publication number: CA2035026C
Application number: CA002035026A
Authority: CA
Inventors: Sigrid Keizers
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-06-24
Filing date: 1990-06-09
Publication date: 2001-10-09
Anticipated expiration: 2010-06-09
Also published as: ATE88940T1; CA2035026A1

Abstract

The invention relates to a device for blasting with a moist granular me-dium in which a water/blasting agent mixture with a relatively high moisture content is conveyed by a stream of air to a blasting pipe. The invention is aimed at keeping the sand fluid with a relatively high addition of water as far as its entry (1) into the conveyor agent pipe and ensuring that after its exit (2) from the blasting pipe it contains only just enough residual moisture to pre-vent dust formation either through the discharging blasting agent or from sur-face particles removed. This aim is achieved by the invention in that a device (5) is fitted in the conveyor circuit of the device for blasting with moist granu-lar agents in front of the blasting agent entry to separate out the superfluous water.

Description

11/14/00 18:29 FAg 2a2 5831 SEABY-ASSOCIATES ~ 003/012 This invention relates to a separator for providinD a moist, granular blasting agent.
Specifically, the invention relates to a separator which yields a moist, granular blasting agent from a t't~lxture of blasting agent, water and compressed b air for discharge through a blasting nozzle.
When treating technical-grade surf:~ces to prepare them for painting, scrubbing building facades or removing rust, a particulate or granular agent, e.9.
dry sand is accelerated onto the surface being treated using a high-energy propehar~t such as air. In order to prevent dust, which can be hazardous to healtft and to the environment In general, a liquid, (usually water) is commonly added to the agents. The water is conveyed along with the agent and its propellant through a hose and discharged through a nozzle. In a conventional process, the agent Is contact~d with the propellant by injecting th~ agent into the propellant. One essential requirement for proper functioning cf the system has been that the sand or granules remain pertectly dry until arriving at the nozzle, and perfect dryness is expensive to achieve. When on the other hand, moist agents such as wet sand are employed, the expense of procurement and management are reduced and the ran~a of ~pplications is increased. This approach, however, involves the problem of kae~ping the wet agent sufficicntiy mobile for conveying through hoses to the nozzle. The problem is usually solv~d by fluidizing they sand in a tank with enough water to force it Into a propellant tube.
The above described approach makes it possible to convey the agent over long distances as well as offering the advantages of much lower costs and 11/14/00 18:29 FAg 232 5831 SEABY-ASSOCIATES 1004/012 improved physiologlc~l and environmental r,~mpatibility due to the absence of dust. There is, however, a drawback in that it takes a large quantity of water to adequately tTuldize the agent. This leaves undesirable water at the site of operations which combines with the agent and with material abraded from the surtace being treated to yield a muddy mixture, promotes the corrosion of steel components, prevents the surface from drying rapidly and n~cessitates further prvressir~g.
The object of the present invention Is to mix enough water with the agent to keep it fluid until it ~nters the propellant pipe, and to leave just enough water in the mixture once it has left the nozzle to prevent the agent and particles abraded from the surface b~ing treated turning into dust.
Accordingly, the invention relates to a separator for providing a moist, granular blasting agent from a mixture of prope~lant, water and granular agent comprising= a housing; a screen in sari housing dividing the interior of the ~ 5 housing Into an upper chamber and a lower chamber; a first inlet in said housing for Introducing the mixture into said upper chamber above said screen; at least one of an impact plate and a deflector in said upper chamber for decelerating the mixture flowing Into said upper chamber through said first inlet whereby water is caused to drop from the mixture through said screen into the lower chamE'er leaving moist, granular blasting agent ; and an outlet in said housing for discharging said moist, granular blasting agent from the housing.
The above defined object is achieved using the separator by removing excess water at a location in the hose carrying the moist granular agent upstream of where the agent is discharged through the node. -This approach exploits the 11/14/00 18:30 FAg 232 5831 SEABY-ASSOCIATES ~ 005/012 fact that water or any liquid Is denser than air and will flow under the force of gravity through an essentially horizontal screen, which is fine enough to retain the agent (the sand or grant~late~ and advance it along with the propellaryt. The method will be sucxessful only wh~n the flow of propellant and agent can be decelerated. Otherwise, most of the liquid w111 remain entrained with the agent and the propellant due to high speed- An apparatus of this type must ~nsure that not only the excess water but also only a little of the air needed as a propellant can escape, and that the screen does not become clogged or that there Is same way of cleaning the screen.
1 o The invention is desrxibed below with reference to the accompanying drawings, wherein: .
Figure 1 is a partly sectioned, front view of one embodiment of the invention and Figure 2 is a partly sectioned, exploded, isometric view of another embodiment of the Invention.
Referring to Fig. 1, one embodiment of the separator of the present Invention includes a housing defined by a cylindrical tank 5 with an inlet 1, which is in fluid communication with a propellant hose 3. The hose 3 supplies a mixture of granular agent and excess water. A line 6 is connected to a reservoir (not shown) for fluidized agent, which is forced into hose 3. The propellant and drained granular agent leave the tank 5 through an outlet 2.
A screen 7 mounted in tha tank 5 beneath the inlet 1 and the outlet 2 divides the tank into an upper chamber 10 and a lower chamber 11. A deflector 13, which also acts as an impact plate for the mixture entering the upper 11/14/DO 18:30 FAg 232 5831 SEABY-ASSOCIATES ~JOD6/012 chamber, and divertera 14 extend from the screen 7 to the top wall 12 of the tank 5. Gaps 15 ar~ provided between the ends of the deflector 13 and the Interior surface of the side wall of the tank 5 which permit blasting agent and propellant to flow around the deflector. The oNter ends of the diverters 14 abut the interior surface of the tank side wall, but a gap 17 between their inner end$ permits the flow of the blasting agent and propellant past the dlverters.
A drain 19 containing a valve 16 is provided in the bottom wall i 8 of tank 5. A line 8 containing a valve iB extends into the drain 19. The drain 18 can alternatively ba located on the side wall of the tank 8 immediately above the bottom wall 18 without adversely affecting the operation of the apparatus.
The separator is located at any point in a hose or line carrying the mixture of propellant and blasting agent. in operation, water, propellant and the agent travel through the hose 3 into the upper chamber 10 of the tank 5, where the mixture encounters the deflectorlirrlpaCt plate 93. The deflector 13 diverts the mixture through the gaps 15. Since the cross-section of the tank 5 Is much larger than that of the hose 3, the propellant will be consld~rably decelerated and excess liquid will drop through the screen 7. Once It has passed the gaps 15, the mi~dure of agent and propellant encounters another obstacle in the form diverters 14 and exits the tank 5 through the gyp 17 and the outlet 2.
It has been found that a thin layer of granular agent forms on top of the screen 7 and especially in tt~e front corner of the deflector 13 and in the corners between the divertera 14 and the interior of the tank side wall. The layer does not become progressively thicker and remains permeable to water. Separated water drops to the floor of the tank and leaves the tank through the valve 16 and 11/14/00 18:31 FAg 292 5831 SEABY-ASSOCIATES ~ 009/012 the line 8 along with a small quantity of air and any particles of agent fine enough to penetrate the screen 7.
A cushion of air becomes established In the space between the bottom wall 18 of the tank 5 and the saeen 7 and can be exploited to unclog the screen in conjunction with a safety mechanism that apparatuses of this type already have in order to suddenly depressurize the agent supply hose, which is often very long and accordfnDly has a large volume. When this procedure is initiated, the cu$hion of air in the lower chamber 11 will expand upwardly through the screen 7, lifting the layer of agent from the screen 7 and carrying it away.
10. When fine granular agents are employed for an extended period of time, the layer of agent on top of the screen 7 can become solid and almost impermeable to water. To avoid clogging, the valve 16 is opened to open an inlet line 9 for admitting water or air under pressure. A jet of water or air will loosen the deposits and remove them via the hose 3 and the outlet 2 which have been detached from the source of fluid and the nozzle, raspeckively.
Referring to Figure 2, a second embodiment of the invention includes an elongated housing generally Indicated at 20 defined by upper and lower boxes and 22, respectively. The upper box 21 defines a chamber 23 with an open bottom end. Deflectors 25 and 26 are mounted in grooves 24 in the side walls of the box 21. The deflectors 25 and 2t3 are perpendicular to the direction of flow of fluid In the box 21. Openings 27 in the deflectors 25 and 26 permit water and sand to flow through the deflectors. Th~ openings 27 are approximately 30 mm in diameter, and are staggered, i.e. displaced alternately on either side of the central longitudinal axis of the box 21 such that they force the flow to undergo 11/14/00 18:31 FAg 232 5831 SEABY-ASSOCIATES ~I008/012 acute deflections. The flow is thus decelerated considerably and most of the water drops down. The lower box 22 of the housing is in the form of a trough with a screen 28 on the top thereof, where the box 22 comes into contact with the upper box 21. The screen 28 includes several layers, specifically a coarse mesh b top layer 29, a fine mesh middle layer 30, and a supporting layer 31, which rests against a shoulder along the edge of the lower box 22. The upper box 21 is secured to the lower box 22 by screws 32 mating with threaded bores 33 in the lower box. A very wet mixture of sand aryd water enters the upper box 21 via an intake 34 and Is decelerated by deflectors 25 end 26. Mast of the water drops, by grawlty, Into the lower box 22 and leaves through an outlet 35. The sand, with just enough water left mixed with it to make it fluid, is supplied to the nozzle (not shown), through a conneckor 36. The housing 20 is designed to allow the flow to be generated by compressed air. The air will not enter the lower box 22 of the housing but will remain in the upper box 21 to ensure that the sand arrives at the nozzle. Other types of deflectors, with different types of perforations, can be used.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A separator for providing a moist, granular blasting agent from a mixture of propellant, water and granular agent comprising:
a housing;
a screen In said housing dividing the interior of the housing into an upper chamber and a lower chamber;
a first inlet in said housing for introducing the mixture into said upper chamber above said screen;
at least one of an impact plate and a deflector in said upper chamber for decelerating the mixture flowing into said upper chamber through said first inlet whereby water is caused to drop from the mixture through said screen into the lower chamber leaving moist, granular blasting agent; and an outlet in said housing for discharging said moist, granular blasting agent from the housing.

2. The separator of claim 1, including an impact plate in said upper chamber for decelerating a mixture entering the upper chamber through said first inlet; and a deflector in said upper chamber downstream of said impact plate in the direction of fluid flow to the outlet for diverting the flow of moist, granular agent to the outlet.

3. The separator of claim 2, wherein said impact plate extends between a top wall of said housing and said screen.

4. The separator of claim 3, including gaps between the ends of said impact plate and the side wall of said housing.

5. The separator of any one of claims 1 to 4, including a drain in the bottom of Bald housing for discharging water from said lower chamber; a second inlet for introducing a fluid into the lower chamber for cleaning said screen;
and a valve in said second inlet for opening and closing said second inlet.

6, The separator according to claim 1, including a plurality of deflector plates extending across said upper chamber perpendicular to the direction of fluid flow between the first inlet and the outlet, and staggered openings in said deflector plates far diverting and decelerating the flow of fluid through said upper chamber.

7. The separator of claim 6, wherein said housing includes an upper elongated box defining said upper chamber; and a lower elongated box defining said lower chamber, said upper box having an open bottom, and said lower box having an open top supporting said screen.

8. The separator of claim 7, wherein the screen includes an upper coarse mesh screen, and a lower fine mesh screen.