Note: Descriptions are shown in the official language in which they were submitted.
CA 02782672 2012-07-04
PIG LAUNCH AND RETRIEVAL SYSTEM
TECHNICAL FIELD
[0001] Pigging tubes
BACKGROUND
[0002] It is known to use pigs in furnaces, including when the furnaces
are online,
see for example US patent 6,569,255, which is incorporated by reference, by
the same
inventor. However, an improved launch and retrieval of a pig was desired over
the system
disclosed in US patent 6,569,255.
SUMMARY
[0003] There is disclosed a method of retrieving a pig in a flow system
having an
inlet, an outlet, a pig catcher, an intermediate section through which the pig
travels, and a
first flow path from a downstream end of the intermediate section to the
outlet, the first flow
path not passing through the pig catcher, by opening a second flow path from
the
downstream end of the intermediate section to the outlet, the second flow path
passing
through the pig catcher, restricting flow on the first flow path to force the
pig into the second
flow path, and retrieving the pig in the pig catcher as it enters the pig
catcher on the second
flow path.
[0004] In various embodiments, there may be included any one or more of
the
following features: the restriction of flow on the first flow path may be a
complete stopping
of flow. The first flow path may be restricted when the pig approaches the end
of the
intermediate area. The restriction to the first flow path may be ended once
the pig enters the
second flow path. The restriction to the first flow path may be ended once the
pig is
retrieved. The second flow path may be opened when the pig approaches the end
of the
intermediate area. The second flow path may be closed once the pig is
retrieved. The pig
catcher may be a pig catcher/launcher.
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[0005] There is disclosed a method of launching and retrieving a pig in a
flow system
having an inlet, an outlet, a pig catcher/launcher, an intermediate section
through which the
pig travels, a first flow path from a downstream end of the intermediate
section to the outlet,
the first flow path not passing through the pig catcher/launcher, and a third
flow path from
the inlet to an upstream end of the intermediate section, the third flow path
not passing
through the pig catcher/launcher, by opening a fourth flow path from the inlet
to the
upstream end of the intermediate section, the fourth flow path passing through
the pig
catcher/launcher, restricting flow on the third flow path to force fluid to
flow on the fourth
flow path to launch the pig, removing the restriction to flow on the third
flow path after the
pig is launched, closing the fourth flow path, opening a second flow path from
the
downstream end of the intermediate section to the outlet, the second flow path
passing
through the pig catcher/launcher, restricting flow on the first flow path to
force the pig into
the second flow path, and retrieving the pig in the pig retriever as it enters
the pig
catcher/launcher on the second flow path.
[0006] In various embodiments, there may be included any one or more of
the
following features: the restriction of flow on the third flow path may be a
complete stopping
of flow. The restriction of flow on the first flow path may be a complete
stopping of flow.
The first flow path may be restricted when the pig approaches the end of the
intermediate
area. The restriction to the first flow path may be ended once the pig enters
the second flow
path. The restriction to the first flow path may be ended once the pig is
retrieved. The second
flow path may be opened when the pig approaches the end of the intermediate
area. The
second flow path may be closed once the pig is retrieved.
[0007] These and other aspects of the device and method are set out in the
claims,
which are incorporated here by reference.
BRIEF DESCRIPTION OF THE FIGURES
[0008] Embodiments will now be described with reference to the figures, in
which
like reference characters denote like elements, by way of example, and in
which:
[0009] Fig. 1 is a drawing in schematic form of an embodiment of an
apparatus for
online pigging of a furnace;
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[0010] Fig. 2 is a drawing in schematic form of the apparatus of Fig. 1 in
normal
operation with no pig deployed;
[0011] Fig. 3 is a drawing in schematic form of the apparatus of Fig. 1
when
launching a pig; and
[0012] Fig. 4 is a drawing in schematic form of the apparatus of Fig. 1
when
retrieving a pig.
DETAILED DESCRIPTION
[0013] Fig. 1 is a drawing in schematic form of an embodiment of an
apparatus for
online pigging of a furnace. Fluid flows through the apparatus via tubes 30
from the
upstream feedstock inlet 10, to furnace inlet 12, through the furnace (not
shown), and from
furnace outlet 14 to downstream feed stock outlet 16. The fluid flow is
directed by means of
valves 1-6. In normal operation with no pig deployed, valve 1 is closed, valve
2 is closed,
valve 3 is closed, valve is 4 open, valve is 5 open, and valve 6 is closed.
This allows fluid
flow from the upstream feedstock inlet 10, to furnace inlet 12, through the
furnace (not
shown), and from furnace outlet 14 to downstream feed stock outlet 16 while
isolating the
pig launcher/retriever 18. Fig. 2 shows the apparatus of Fig. 1 in this state.
When it is desired
to launch a pig (not shown), first a pig is inserted into the pig
launcher/retriever 18 (if not
already present) and the opening (not shown) through which the pig is inserted
into the pig
launcher/retriever 18 from the outside is sealed. If the pig
launcher/retriever 18 is not already
filled with fluid, valve 1 is then opened to allow fluid to flow into the pig
launcher/retriever
18. Valve 1 may be a variable flow control valve and may be opened partially
to allow the
fluid to enter the pig launcher/retriever 18 slowly. Pig launcher/retriever 18
may have a vent
(not shown) to allow air to escape as it is filled with fluid. Then, valve 1
is opened if not
already open and valve 3 is opened to allow the fluid to flow through the pig
launcher/retriever 18 to the furnace inlet 12. If valve 1 is in a partially
open state, valve 1
may be opened more fully. To ensure that the pig launches successfully, valve
4 is closed to
force fluid flow to occur on the path through the pig launcher/retriever 18.
Fig. 2 shows the
apparatus of Fig. 1 in this launching state. Optionally, valve 4 can be
reopened when the pig
passes junction 20 as detected by a sensor (not shown) or assumed due to the
passage of
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time. Valve 1 and valve 3 can then be closed. If valve 4 is reopened and
valves 1 and 3
closed, then a drain valve (not shown) can optionally be opened in order to
allow fluid to
drain from the launcher after the pig is launched.
[0014] Before the pig reaches junction 22, but after the pig has past
junction 20, as
detected by a sensor or assumed based on the passage of time, valve 4 is
opened if not
already open, and valves 1 and 3 closed if not already closed. If the pig
launcher/retriever 18
is not already filled with fluid, valve 6 is then opened to allow fluid to
flow into the pig
launcher/retriever 18. Valve 6 may be a variable flow control valve and may be
opened
partially to allow the fluid to enter the pig launcher/retriever 18 slowly.
Pig
launcher/retriever 18 may have a vent (not shown) to allow air to escape as it
is filled with
fluid. Then, valve 6 is opened if not already open and valve 2 is opened to
allow the fluid to
flow through the pig launcher to the downstream feedstock outlet 16. If valve
6 is in a
partially open state, valve 6 may be opened more fully. To ensure that the pig
travels on the
correct route at junction 22, valve 5 may be closed to force fluid flow to
occur on the path
through the pig launcher/retriever 18. Fig. 4 shows the apparatus of Fig. 1 in
this retrieving
state. Valve 5 can be reopened when the pig has passed junction 22 or when the
pig has been
retrieved. Once valve 5 is reopened and the pig has returned to the pig
launcher/retriever 18,
valve 6 and valve 2 may be closed. If it is desired to re-launch the pig
immediately, valves 1
and 3 can then be opened. If it is desired to remove the pig from the pig
launcher/retriever
18, a drain valve (not shown) may be opened to remove fluid from the pig
launcher/retriever
18 and once the pig launcher/retriever 18 is empty it may be opened to remove
the pig.
[0015] Immaterial modifications may be made to the embodiments described
here
without departing from what is covered by the claims. In the claims, the word
"comprising"
is used in its inclusive sense and does not exclude other elements being
present. The
indefinite articles "a" and "an" before a claim feature do not exclude more
than one of the
feature being present. Each one of the individual features described here may
be used in one
or more embodiments and is not, by virtue only of being described here, to be
construed as
essential to all embodiments as defined by the claims.
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