Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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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
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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
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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
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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
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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
21
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
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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.
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