PORTABLE FLARE KNOCKOUT

LANCE-FUSEES ECLAIRANTES PORTATIF

English Abstract

The invention provides for a method of depressurizing a blocked pipeline at a
producing well
site. The invention permits depressurization in a vapour-tight manner and
facilitates the disposal
of any fluids and lethal gases present. In accordance with this method, there
is provided a
portable vapour-tight depressurizing apparatus with a pressure vessel and
flare stack for
incinerating gases, all mounted on a portable trailer. The pressure vessel is
connected to the
pipeline by means of a flow line at the blow down point. Incoming fluids are
directed to the
vessel where the pressurized fluid separates into liquid and gaseous phases.
The fluids are
removed from the vessel through a liquid outlet. The gas is removed through a
gas outlet. The
gas outlet leads to flare stack where the gas is incinerated. Fluid and gas
flow is regulated by a
number of sensors and control valves.

Claims

WHAT IS CLAIMED IS:
1. An apparatus comprising:
(a) a portable platform;
(b) a pressure vessel mounted on the platform, said vessel comprising a fluid
inlet, a
liquid outlet, a gas outlet and a gas sensor;
(c) an inlet line including a shut-off valve;
(d) control means for activating the shut-off valve, said control means
operatively
connected to the shut-off valve and the gas sensor; and
(e) a flare stack connected to the gas outlet of the pressure vessel by a gas
outlet line.
2. The apparatus of claim wherein the vessel further comprises a liquid sensor
which is
operatively connected to the control means.
3. The apparatus of claim 1 further comprising a phase separator disposed in
the flow path
of the fluid inlet of the pressure vessel.
4. The apparatus of claim 1 or claim 2 wherein the flare stack is pivotally
mounted to the
platform and moveable between a horizontal position and a vertical position.
5. The apparatus of claim 1 or claim 2 wherein the pressure vessel is an
elongate cylindrical
vapour-tight vessel.
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6. The apparatus of claim 1 wherein the control means is operative to close
the shut-off
valve upon receiving a signal from the gas sensor that the gas pressure within
the vessel has
reached a pre-determined level.
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Description

CA 02287732 1999-10-28
CANADIAN PATENT
Docket No. 12608-001
PORTABLE FLARE KNOCKOUT
FIELD OF THE INVENTION
The present invention relates to a portable depressurizing and gas flaring
apparatus for
vapour tight applications, which may be referred to as a portable flare
knockout.
BACKGROUND OF THE INVENTION
Pipelines which carry oil and/gas from a producing wellsite sometimes become
blocked
with hydrate or water and require depressurizing, referred to as "blow down",
so as to dehydrate
or deice the blockage with methanol to bring the pipeline back on stream.
There is a need in the art for an apparatus which may be used to depressurize
a blocked
pipeline in a vapour-tight manner and dispose of any fluids including any
lethal or poisonous
gases which may be present. The apparatus may also be useful in providing a
flaring system for
use at the wellhead.
SUMMARY OF THE INVENTION
The present invention is directed to a portable vapour-tight depressurizing
apparatus with a pressure vessel and a flare stack for capturing and
incinerating gases from a
wellhead or a pipeline.
Accordingly, in one aspect of the invention, the invention comprises an
apparatus
comprising:
(a) a portable platform;

CA 02287732 1999-10-28
(b) a pressure vessel mounted on the platform, said vessel comprising a fluid
inlet, a
liquid outlet, a gas outlet and a gas sensor;
(c) an inlet line including a shut-off valve;
(d) control means for activating the shut-off valve, said control means
operatively
connected to the shut-off valve and the gas sensor; and
(e) a flare stack connected to the gas outlet of the pressure vessel by a gas
outlet line.
In one embodiment, the vessel further comprises a liquid sensor which is
operatively connected
to the control means. The vessel may further comprise a phase separator
disposed in the flow
path of the fluid inlet of the pressure vessel. The flare stack may be
pivotally mounted to the
platform and moveable between a horizontal position and a vertical position.
The pressure vessel
may be an elongate cylindrical vapour-tight vessel. The control means is
operative to close the
shut-off valve upon receiving a signal from the gas sensor that the gas
pressure within the vessel
has reached a pre-determined level.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of an exemplary embodiment with
reference to the accompanying simplified, diagrammatic, not-to-scale drawings.
In the drawings:
Figure 1 is a schematic depiction of an embodiment of the apparatus.
Figure 2 is a side view of an embodiment including a trailer.
Figure 3 is a schematic view of an embodiment.
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CA 02287732 1999-10-28
DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION
The present invention provides for a portable depressurizing unit for vapour
tight
applications that recovers and combusts any gases accumulated in the
depressurizing operation.
The apparatus (10) according to the Figures comprises a trailer (12) which has
mounted
onto it a flare stack (30) and a pressure vessel (50). The pressure vessel
(50) is mounted on some
vessel supports (14) and includes a fluid inlet (52), a gas outlet (56), a
liquid outlet (58). In basic
operation, pressurized fluid consisting of liquids and gases enters the fluid
inlet (52) and
separates into a liquid phase which settles to the bottom of the vessel and a
gas phase. A wedge
demister (54) or other device which aids in phase separation may be placed in
the path of the
incoming fluid stream. The accumulated liquid may be withdrawn through the
liquid outlet (58)
and the liquid outlet valve (59). The gas may be withdrawn through the gas
outlet (56), the gas
outlet valve (57) and into the flare stack (30) where it may be disposed of by
combustion.
Flow line (70) to be used in connecting the vessel to the fluid source is
stored and
transported on the trailer ( 12) on flow line racks (20) which are mounted to
the trailer ( 12) as is
shown in Figure 2.
The flare stack (30) comprises a main stack (32) of an appropriate length
which has a
drain valve (33) at the bottom end thereof. The flare stack (30) mounts to a
pivot (34) which is
mounted to a flare stack pivot support ( 16) which is rigidly attached to the
trailer ( 12). When
being transported to the work site, the flare stack (30) may be pivoted
downwards to be in a
substantially horizontal position as is shown in Figure 2, where it rests on a
flare stack travelling
cradle (18). The flare stack may then be raised to its operative vertical
position by a winch (24)
which has a cable (26) attached to the lower end of the flare stack by a
snatch block (36). The
top end of the flare stack is a burner (40), an igniter (44) and a pilot light
and line (42). The pilot
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CA 02287732 1999-10-28
line carries propane gas from propane bottles (23) carned on racks (22) on the
trailer (12). The
igniter (44) includes a shot tube (45) which is closed at the bottom and has a
meshed opening at
the top. A flare within the shot tube may be used to ignite the pilot light.
Alternatively, the shot
tube may be lowered to manually place a flame on the igniter and then raised
into position to
ignite the pilot.
The vessel (50) includes an access hatch (60) to allow visual inspection of
the vessel and
its components.
Incoming fluids are directed to the vessel (50) by the flow line (70) and may
be regulated
by a manual shut-off valve (76) and an automatic shut-off valve (78)
controlled by gas and liquid
sensors in the vessel. A liquid level sensor and gauge (62, 66) may activate
the valve (78) in
response to a high level of liquid within the vessel. A gas pressure sensor
and gauge (64) may
also activate closure of the valve (78) by control means (79) which are well
known in the art, in
response to gas pressures within the vessel (50) in excess of a predetermined
level. Optionally, a
one-way check valve (80) may be provided to prevent backflow of fluid through
the flow line
(70)
The pressure vessel (50) includes a fail-safe pressure safety relief valve
(68) which
automatically releases gas to the flare stack and burner by safety relief line
(46). These safety
valves are well-known in the art and may be set to open at a pre-determined
pressure to prevent
overpressurization in the vessel (50).
A pressure gauge (69) may be prominently mounted to the vessel allowing for
the
operator to visually monitor the pressure within the vessel (50).
All piping should be connected by hammer unions which have a high pressure
rating. All
materials used should preferably have corrosion allowance where it is known
that the apparatus
( 10) will be used in a corrosive environment.
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CA 02287732 1999-10-28
In operation, the apparatus (10) is towed or otherwise transported to an area
close to the
affected site and set up on level ground. Preferably, the location should be a
safe distance from
the wellhead or source of flow and chosen with prevailing winds in mind. The
trailer (12) may
be stabilized with jacks (not shown). The apparatus may be grounded using a
ground rod and
electrical ground cable (not shown). The winch (24) may then be used to
elevate the flare stack
(30) to its vertical operative position. The connecting spool (38) may then be
connected between
the vessel and the flare, completing the connection between the gas outlet
(56) and the safety
relief valve to the flare stack (30).
The connection to the wellhead or pipeline is made at the blowdown point (72)
with an
adjustable choke (74) which is rigged in directly off source of flow
connection. Flow line (70) is
then rigged to the choke from the manual valve (76). Fluid dump line (not
shown) is rigged to
the liquid outlet valve (59) to the liquid storage tank (not shown). A ammonia
scrubber (not
shown) should be used if the liquid is degassing to the atmosphere.
The entire system should be purged of oxygen as the failure to do so may cause
explosion. Also, the sight glasses (not shown) should be prepared for use
using a hand-held
pump such as a Baker pump.
The vessel may then be pressurized to a low level by opening the manual choke
(74) and
the valve (76) and the burner (40) ignited using the pilot and ignitor (44).
The depressurizing
operation may then be continuously operated by operating the manual choke (74)
while
monitoring the pressure and level gauges (62, 64, 66, 69)
When rigging out, the vessel should be purged with propane or nitrogen to
eliminate any
residual sour gas. All liquids should be emptied from the vessel (50). The
operator should
confirm that the flare is extinguished. It is preferably that the flowline
into the vessel is flushed
with water after disconnection from the source and the water in the vessel
flushed back out.
After lowering the flare stack onto the travelling cradle (18), it should be
secured. All pipe or
flow line (70) should be racked and secured.
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CA 02287732 1999-10-28
As will be apparent to those skilled in the art, various modifications,
adaptations
and variations of the foregoing specific disclosure can be made without
departing from the scope
of the invention claimed herein.
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Representative Drawing