Note: Descriptions are shown in the official language in which they were submitted.
CA 02714831 2013-02-01
TITLE
SYSTEM FOR DISPENSING ABRASIVES INTO A GAS STREAM FOR CLEANING PIPE
INTERIORS
FIELD
[0001] The present invention relates to a system and method for
dispensing abrasive
particulate material into a stream of air or gas that is introduced into a
pipe for the purpose of
cleaning the internal pipe walls, as well as preparing surfaces of the
internal pipe
circumference for the later application of an immediate, protective coating or
lining.
BACKGROUND
[0002] It is well known that contaminants and corrosion products, such as
tubercles,
rust, scale and the like, can form inside metallic water mains and pipes as a
result of
corrosion, and can form layers, which can build up over time to form lumps and
mounds,
masking areas of internal metal loss.
[0003] These occlusive build ups can severely reduce the internal bore of
pipes, leading
to reduced flow capacity and a necessary increase in pumping pressure to
maintain a
sufficient supply of water or other fluid flowing through the pipe. Moreover,
the build-up of
corrosion products can adversely affect the quality of the fluid flowing in
the pipe, creating
problems such as "red water" in drinking water systems.
[0004] The use of abrasives in a flowing air or gas stream for pipe
cleaning to remove
the above-noted contaminants and corrosion products is well known. The generic
process of
1
CA 02714831 2013-02-01
"sandblasting" is a mature technology frequently used in larger-diameter, man-
entry pipes for
surface preparation, and the process of injecting garnet grit (beach-sand
consistency) into a
flowing compressed airstream has been used previously in small diameter pipes
to facilitate
the removal of corrosion products as well as the surface preparation of the
internal pipe
circumference for immediate, protective coating. In fact, the U.S. Navy used
this process for
numerous years to remove corrosion from the internal bore of small-diameter
pipes installed
on its aircraft carrier fleet, after which, the pipes were remotely coated
with a protective
epoxy. Recently, various combinations of gases and abrasives, such as the use
of frozen gas
pellets and different propllant gases, have been combined to attempt to remove
contaminants
and corrosion products, as well as to prepare surfaces of the internal pipe
circumference for
the later application of an immediate, protective coating or liner.
[0005] The process of abrasive blasting becomes more complex
wherever pipeline
entry is not possible by virtue of pipe diameter (too small) or location
(inaccessible). The
deployment of an abrasive from a single entry point, over medium / long pipe
distances,
requires a novel process. This process uses special equipment and produces a
different
surface blast pattern and outcome.
[0006] More recently, larger-sized abrasives (e.g. stones versus
grit), in combination
with larger air movers (compressors / blowers), have been used to clean
corroded water pipes
in diameter ranges of 4" through 8" in the UK. This process deploys an
abrasive in a gas
stream and was (again) used to remove heavy corrosion products in small
diameter pipes and
prepare the internal circumference for immediate protective coating.
[0007] However, these conventional systems to have drawbacks and
limitations. For
one thing, cleaning systems that deploy an abrasive in a gas stream, such as
that described in
United States Patent Application Publication No. 2009/270016 (Christopher),
disclose the use
2
CA 02714831 2013-02-01
of a pressurized hopper for dispensing the abrasive particulate material into
the air or gas
stream. Such pressurized vessels require periodic inspections, maintenance and
testing to
preclude deterioration and rupture that could pose a significant safety
hazard. Pressurized
vessels that contain rocks are potentially unsafe and are therefore typically
fabricated with
heavy-walled, welded steel.
[0008] Furthermore, with such pressurized vessels, when that vessel
has been filled
(charged) with rocks and abrasive particulate matter, and is thereafter
pressurized, it is not
possible to add more rock or material to the pressurized hopper without de-
energizing the
feed system altogether, thus slowing down the system operation.
[0009] In addition, such conventional abrasive blasting systems
utilize an axial-feed
screw for dispensing abrasive particulate material from the pressurized hopper
into the air or
gas stream. While the use of such systems provides a steady controlled rate of
insertion of
abrasive particulate, the operator cannot visually observe the process. As
such, operators of
such systems cannot visually perceive problems such as hang-ups or jamming of
or other
sensory cues, or de-energize the system to investigate a feed problem.
[0010] It would, therefore, be advantageous to have an improved
system and method
for dispensing abrasive particulate material into a stream of air or gas that
utilizes a hopper
(containing the abrasive particulate material) that is open to the atmosphere
(unpressurized),
whereupon an operator can readily add more abrasive particulate material into
the air or gas
stream as required or needed, without the need to de-energize the system or
shut down, thus
increasing the efficiency and speed of the system in accomplishing the task.
[0011] It would be further advantageous to have an improved system
and method for
dispensing abrasive particulate material into a stream of air or gas that
provides no pressure
3
CA 02714831 2013-02-01
blow black, by virtue of using a hopper that is open to the atmosphere, and
which is easily
portable, lighter in weight, and safer than current pressurized screw feed
system
configurations.
[0012] It would also be further advantageous to have an improved system and
method
for dispensing abrasive particulate material into a stream of air or gas that
utilizes a valve
body and a sliding gate (two controls) to keep variable control of the
introduction of abrasive
particulate material into the hopper, rather than a feed screw, thus giving an
operator better
control of the dosing rate into the hopper, both mechanically and visually,
and thus better
control of the pipe cleaning and preparation process.
[0013] Accordingly, there is a need for an improved system and
method of delivery of
abrasive material into a gas stream for the purpose of cleaning, preparing and
coating or
lining the interior surface of in-service, small-diameter pipes. There is a
further need for a
pipe cleaning system which is operably able to introduce abrasive from a
vessel under one set
pressure (for example, atmospheric pressure), into a gas stream in a measured,
highly-
controlled and safe manner. To this end, the present invention effectively
addresses these
needs.
SUMMARY
[0014] An important advantage and object of the present invention is
that it provides
an improved system and method for dispensing abrasive particulate material
into a stream of
air or gas that utilizes a hopper (containing the abrasive particulate
material) that is open to
the atmosphere, through use of which an operator can add more abrasive
particulate material
into the air or gas stream as required or needed, without the need to de-
energize the system
or shut down, thus increasing the speed of the system in accomplishing the
task.
4
CA 02714831 2013-02-01
[0015] Another important advantage and object of the present
invention is that it
provides an improved system and method for dispensing abrasive particulate
material into a
stream of air or gas that provides no potential for pressurized abrasive blow-
back, by virtue
of using a hopper that is open to the atmosphere, and which is lighter in
weight than the
current, pressurized configurations, and therefore more flexible (portable) in
use.
[0016] Another important advantage and object of the present
invention is that it
provides an improved system and method for dispensing abrasive particulate
material into a
stream of gas that utilizes a valve body and a sliding gate (two controls) to
keep variable
control of the introduction of abrasive particulate material into the hopper,
rather than a feed
screw, thus giving an operator better control of the dosing rate into the
hopper, and thus the
pipe to be cleaned.
[0017] According to a first broad aspect of an embodiment of the present
invention,
there is disclosed a system for dispensing abrasive particulate material into
a stream of gas to
be introduced into a pipe for cleaning an interior of the pipe, comprising an
air blower
coupled to the pipe, the air blower generating the stream of gas to be
introduced into the
pipe; a hopper for dispensing the abrasive particulate material, the hopper
being constructed
and arranged for operation at atmospheric pressure and constructed and
arranged for
connection and fluid communication with each of the pipe and the air blower,
the hopper
further comprising a housing having an inlet for receiving the abrasive
particulate material
and an outlet for delivery of the abrasive particulate material from the
hopper; and valve feed
means positioned within the hopper and in fluid transporting the abrasive
particulate
material from the hopper into the stream of gas for introduction into the
pipe.
[0018] According to a second broad aspect of an embodiment of the
present invention,
5
CA 02714831 2013-02-01
there is disclosed a method for cleaning an interior of a pipe, said method
comprising
providing an air or gas stream and connecting it to the pipe to be cleaned;
providing a hopper
at atmospheric pressure in fluid communication with each of the air or gas
stream and the
pipe; providing valve feed means in communication with the hopper for
regulating a flow of
abrasive particulate material from the hopper to the air or gas stream and the
pipe;
dispensing abrasive particulate material into the hopper; and selectively
operating the valve
feed means so as to transport the abrasive particulate material from the
hopper into the air or
gas stream and the pipe.
[0019] According to a third broad aspect of an embodiment of the present
invention,
there is disclosed a method of cleaning an interior of a pipe, said method
comprising isolating
the pipe from other pipe sections; providing an air or gas stream and
connecting it to the pipe
to be cleaned; utilizing the air or gas stream to dry out the pipe; de-
energizing the air or gas
stream; providing a hopper at atmospheric pressure in fluid communication with
each of the
air or gas stream and the pipe providing valve feed means in communication
with the hopper
for regulating a flow of abrasive particulate material from the hopper to the
air or gas stream
and the pipe; re-energizing the air or gas stream; dispensing abrasive
particulate material into
the hopper; and selectively operating the valve feed means so as to transport
the abrasive
particulate material from the hopper into the air or gas stream and then into
the pipe.
DRAWINGS
[0020] The embodiments of the present invention will now be
described by reference to
the following figures, in which identical reference numerals in different
figures indicate
identical elements and in which:
[0021] Figure 1 is a perspective view of an embodiment of the system
and method of
6
CA 02714831 2013-02-01
the present invention;
[0022] Figure 2 is a side view of the embodiment of the system and
method of the
present invention shown in Figure 1;
[0023] Figure 3 is a top view of another embodiment of the system
and method of the
present invention; and
[0024] Figure 4 is a side view of the embodiment of the system and
method of the
present invention shown in Figure 3.
DESCRIPTION
[0025] The invention will be described for the purposes of
illustration only in
connection with certain embodiments; however, it is to be understood that
other objects and
advantages of the present invention will be made apparent by the following
description of the
drawings according to the present invention. While a preferred embodiment is
disclosed, this
is not intended to be limiting. Rather, the general principles set forth
herein are considered to
be merely illustrative of the scope of the present invention and it is to be
further understood
that numerous changes may be made without straying from the scope of the
present
invention.
[0026] The present invention consists of an improved system and
method for
dispensing abrasive particulate material into a stream of gas that is
introduced into a pipe for
the purpose of cleaning the internal pipe walls, as well as to prepare
surfaces of the internal
pipe circumference for the subsequent application of a protective coating or
liner.
7
CA 02714831 2013-02-01
[0027] Referring to Figures 1 and 2, there is shown a first
exemplary embodiment of
the present invention. In a preferred embodiment, as hereinafter described,
the system and
method of the present invention comprises a hopper 1, a gate valve 2, a rotary
airlock valve 3,
a shut off valve 4, and an air blower / drier 8, as hereinafter described.
[0028] In operating the system of the present invention, in an
exemplary embodiment,
a target pipe section 9 is taken out of service and then accessed at either
end of the pipe using
dug pits. Once the pipe section 9 is opened and isolated, it is then drained
and visually pre-
inspected, such as through closed circuit television or a remote camera (not
shown). As
would be readily apparent to one skilled in the art, typically all service
taps are opened so
that they can back-drain into the pipe. The upstream and downstream in-service
piping is
then capped with protective, pressure sleeves (not shown). The target pipe
section is
inspected to verify the extent of the contaminants and corrosion products that
are present,
although usually the extent of blockage can be pre-determined from service
records.
[0029] An air blower / drier is then coupled, by way of pressure-
rated piping
connections, to the isolated pipe section 9 at 11 (shown in Figures 3 and 4)
and the air blower /
drier 8 is used to clean out excess water and dry the in situ contaminants and
corrosion
products (e.g. tubercles) on the interior of the pipe section 9. It is
conveniently thought that
the application of high-volume, low-pressure, clean, heated air from the
outset will speed
drying and make the contaminants and corrosion products (not shown) more
brittle / friable
in preparation for the introduction of a selected grade / size of abrasive
particulate material,
as hereinafter described.
[0030] Once the pipe section 9 is suitably dry, the air blower / drier 8
is then de-
energized and a suitably designed three component feeder assembly, comprised
of a hopper
1, gate valve 2 and rotary air lock valve 3, and is connected at the upstream
end of the pipe.
8
CA 02714831 2013-02-01
In an exemplary embodiment, the feeder assembly is positioned between the air
blower /
drier 8 and the target pipe section 9 using a portable transport device such
as a truck 10, as
shown in Figures 1 and 2. Hopper 1 is not pressurized, as opposed to other
conventional feed
design systems, but rather is at atmospheric pressure. In this embodiment,
such a feeder
assembly comprised of hopper 1, gate valve 2 and rotary air lock 3 can be
loaded onto a truck
10, as shown in Figure 4, and moved about quite readily and easily.
[0031] The air blower / drier 8 is then energized so as to provide
an air or gas stream
(seen in Figure 1 at 6), and suitable quantities of abrasive particulate
materials (not shown are
progressively introduced into the hopper 1 at hopper opening 5 for later
propulsion in a
downstream flow 7 of the air or gas stream (as shown in Figure 1). Examples of
abrasive
particulate material that could be used are flint, chert, granite, sand, rock,
though it will be
understood that numerous variations to these are possible, as would be readily
apparent to
one skilled in the art.
[0032] In an exemplary embodiment, the feeder assembly comprises
hopper 1, gate
valve 2 and a rotary air lock valve 3, which work in conjunction so as to
allow the operator to
meter out a selected quantity of abrasive particulate material from the hopper
1 to enter the
air or gas stream 6 and be directed downstream 7 to the target pipe section 9,
as hereinafter
described.
[0033] During the start of the pipe cleaning process it is desirable
not to "flood" or
"choke" the pipe with too much abrasive particulate material and potentially
create a
blockage. As such, when beginning to progressively introduce abrasive
particulate materials
into the hopper 1, only a minimal amount of this material is first introduced,
with the
material that is introduced going to the bottom of the hopper 1 through
gravity and first
coming to contact with the gate valve 2 at the bottom of the hopper, which is
fundamentally a
9
CA 02714831 2013-02-01
slide gate through which the operator can initially regulate the amount of
abrasive particulate
materials that the rotary air lock valve 3 will be exposed to. When it is
desired to add
additional abrasive particulate material into the system, the operator turns
handle 13,
wherein the gate valve 2 slides horizontally to allow the abrasive particulate
material to fall
into the rotary air lock valve 3, which operates essentially as a sealed
dispensing device, in
that when a certain level of material accumulates, the rotary air lock valve
can be rotated by
the operator to introduce the abrasive particulate material downstream 7 (as
shown in Figure
1) to the pipe section 9. The gate valve 2 and the rotary air lock valve 3
could be hydraulically
powered, if desired, or may be mechanically driven or driven by any other
suitable means
known to the skilled person. In an exemplary embodiment, not only does the
rotary air lock
valve 3 meter the amount of abrasive particulate material introduced, but it
also, in doing so,
moves this material from (atmospheric) into another (in this example, a pipe
having a
pressure higher than atmospheric pressure). Because of the tolerances and the
number of
vanes on the valve, there is a sealing effect from the inlet to the outlet
side of the valve.
Typically, this is in the range of between 15 ¨ 40 pounds per square inch
(psi), though
variations to this will of course be possible.
[0034] In this manner, the operator is able to keep visual contact
with and variable
control of the introduction of abrasive particulate material into the air or
gas stream 6 from
hopper 1, rather than using a pressurized, enclosed feed screw, thus giving an
operator better
control of the dosing process into the pipe section 9 to be cleaned. Further,
the operator can
add more abrasive particulate material into the air or gas stream 6 as
required or needed,
without the need to de-energize the system or shut down, thus increasing the
speed of the
system in accomplishing the task. Moreover, the advantage of introducing
abrasive
particulate material through a rotating air-lock valve delivery such as that
disclosed in the
present invention, as opposed to a more conventional Archimedes axial-feed
screw, is that the
rotating air-lock valve acts as the pressure block while, by its design, an
Archimedes axial-
CA 02714831 2013-02-01
feed screw cannot. Hence, there is a need for such conventional, axial-feed
screw systems
and their supplies of abrasive particulate stone supply to be contained within
a pressurized
zone, such as pressurized hopper, in order to function. Operators or such
conventional axial-
feed screw systems can achieve a good rate of control in introducing abrasive
particulate
matter into the system by screw rotation, but they cannot visually observe the
dosing process.
If there is a problem, or if the feed rate needs to be altered in any manner,
the operator is
limited to making adjustments by rotating the feed screw forwards or backwards
to address
these matters; otherwise, the feed system must be de-energized, thus slowing
down the entire
operation. By contrast, the present invention, by using gate valve 2 and
rotary air lock valve 3
in conjunction with unpressurized hopper 1, the operator has two methods of
feed control;
visual contact with the feed process, and the ability to make adjustments
without de-
energizing the feed system, thereby realizing increasing operational
efficiencies through
decreased probability of system shut downs.
[0035] Once the abrasive particulate materials have been metered from the
three-
component feed system (hopper 1, gate valve 2 and rotary air lock valve 3)
into air or gas
stream 6 and downstream 7 (as shown in Figure 1) to the pipe section 9, these
charged
abrasive particulate materials impact the contaminants and corrosion products
on the interior
of the pipe section 9 and remove them from the pipe walls. Of course, it will
be understood
that the downstream "receiving pit" excavation) can be,.before the air blower
/ drier 8 is
energized, covered (at surface) to prevent or substantially inhibit any
energized abrasive
particulate materials from escaping the downstream excavation. Abrasive
particulate,
corrosion products, and dust can otherwise be collected in the "receiving pit"
from pipe
section 9 using conventional collection boxes and dust separators known to
those skilled in
this cleaning process.
[0036] In addition, the movement and action of the hardened angular
abrasive
11
CA 02714831 2013-02-01
particulate materials also scrapes the internal walls of the pipe section 9,
thereby providing a
degree of surface preparation for a subsequently applied, protective coating
or liner. The
hot / warm / dry air that propels the abrasive also acts to heat the pipe to a
temperature that
will keep it dry and prevent condensation.
[0037] Once the cleaning process is completed, the upstream hardware
(air blower /
drier 8, three-component feed system comprising hopper 1, gate valve 2 and
airlock valve 3
and connecting pipes) is de-energized, disconnected and removed from the
upstream
location. The target pipe section 9 is then ready for immediate coating or
lining using a
variety of methods including, for example, cement mortar, sprayed epoxy,
sprayed advanced
polymers (polyurethane or polyurea) or cured-in-place pipe lining, though it
will be
understood that numerous variations to this are possible, as would be readily
apparent to one
skilled in the art.
[0038] In an alternative embodiment, the system further comprises a shut
off valve 4
(as shown in Figures 1, 2 and 4) and preferably is manually operated. The
purpose of the
shut off valve 4 is to isolate the rotary airlock valve 3 from the system,
when system
troubleshooting or maintenance is required, or when higher pressures will be
used to dry and
clean out the pipe. For example, when the air blower / drier 8 is used at
higher pressures
during the process of using the air blower / drier 8 to clean out excess water
and dry the in
situ contaminants and corrosion products, the air lock valve 3 can be isolated
by engaging
shut off valve 4, minimizing the potential for pressure loss out through the
hopper 1 at these
higher drying pressures. Similarly by engaging shut off valve 4 anytime during
feed system
operation, blockage or feed problems with abrasive particulate can be quickly
rectified
without system shutdown.
[0039] It will be apparent to those skilled in this art that various
modifications and
12
CA 02714831 2013-02-01
variations may be made to the embodiments disclosed herein, consistent with
the present
invention, without departing from the spirit and scope of the present
invention.
[0040] Other embodiments consistent with the present invention will
become apparent
from consideration of the specification and the practice of the invention
disclosed therein.
[0041] Accordingly, the specification and the embodiments are to be
considered
exemplary only, with a true scope and spirit of the invention being disclosed
by the following
claims.
13
