CA2287732A1

CA2287732A1 - Portable flare knockout

Info

Publication number: CA2287732A1
Application number: CA002287732A
Authority: CA
Inventors: Marlin Romeo
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-10-28
Filing date: 1999-10-28
Publication date: 2001-04-28

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.

Description

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;

(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.

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 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.

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.

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.

Claims

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.

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.