CA1112888A

CA1112888A - Offshore/subsea flares

Info

Publication number: CA1112888A
Application number: CA313,105A
Authority: CA
Inventors: John F. Straitz, Iii
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-01-11
Filing date: 1978-10-11
Publication date: 1981-11-24
Also published as: GB2012407A; JPS5495027A; IT1113492B; IT7947565A0; FR2414690A1; FR2414690B1; GB2012407B

Abstract

ABSTRACT
An ignitor is provided for offshore-subsea flares in which a flare, floating or fixed, is provided separated from an offshore drilling platform but connected by a subsea conduit or connection, preferably flexible, through which fuel gas is delivered to the flare for pilots and for ignitor gas for the pilots and which has provisions for insulated conductors for control of the pilot gas, the ignitor gas and for the ignition of the ignitor gas and indication of operating conditions.

Description

~4~

This invention relates to offshore gas flares and more particularly to apparatus for igniting waste gas for combustion at a location spaced from an offshore well.
It has heretofore been proposed as in U.S. Patent ~o.
1,087,112, to burn gas on the surface of the water released below the surface through a nozzle carried on a buoy. In order to ignite the gas a lump of potassium, sodium or calcium phosphid is released from below the water surface by the pressure -of the fuel, rises to the surface of the water and ignites to ignite the gas. Only a single ignition is intended, or possible, combustion ~eing maintained by continuous supply of gas.
Flares for offshore use and capable of accommodation to changes of depth due to wind, tides and the like are shown in U.S. Patent ~o. 2,894,269 to Dodge; ~o. 3,6~2,196 to Marion et al.; ~o. 3,666,395 to Kubasta; ~o. 3,902,843 to Genini et al., and No. 3,920,378 to Castela.
Of these only Castela et al. in u.S. Patent No. 3,920,378, undertake to provide a lighting device which is shown only diagrammatically and is described only as of the type producing electrical impulses to produce sparks at the level of the night lights and which apparently require the intervention at the 1are of a wor~man for actuating the lighting circuits.
Reference is also made to the intended use of a fuse on FIG. 1 but this is not otherwise shown nor described.
If the flow of gas to be burned to an offshore flare is continuous, a single ignition may be adequate but if the flow is interrupted then difficulties are encountered. Various expedients have been resorted to for ignition of offshore flares including the use of ~oman candles, flare pistols, and tracer bullets but these have not proven satisfactory.

Hazards to personnel, because of combustible liquid carry-over, vapor clouds and high radiation from burning flares add to the problem. ~-~,~

It has been common practice to ignite flares supportedabove the ground by the use of flame fronts to ignite gas fired pilots. My prior U.S. Patent No. 3,816,059 shows such a system. These are not feasible with offshore flares because of chilling of the flame carrying pipe by the surrounding water and condensate build-up in subsea pipes.
In accordance with the invention an ignition system is provided for offshore flares with provisions at the offshore platform for monitoring the condition of and treating the fuel gas for pilots and ignition and for supply of electrical energy, with provisions at the flare for pilot and pilot ignitors, and with a suitable conduit or connector between the platform and the flare for supply of fuel gas, electric power and for signals ~o indicate pilot conditions.
It is the principal object of the invention to provide an ignition system for offshore flares which are separated from offshore wells and platforms and which will be reliable in use and not hazardous to personnel.
It is a further object of the invention to provide an ignition system for offshore flares which is easy to install.
It is a further object of the invention to provide an ignition system for offshore flares in which a supply of fuel gas is provided for pilot gas and for ignitor gas and in which the condition of the fuel gas is monitored and the gas is preconditioned prior to departure from the platform.
It is a further object of the invention to provide an ignition system for offshore flares which are separated from offshore wells and platforms which includes a back up battery.
It is a further object of the invention to provide an ignition system for offshore flares which are separated from offshore wells and platforms having a simple but effective conduit or connection between the platform and the flare.

~ t is a further ob~ect of the inYention to provide an ignition sy~tem ~or o~shore flares~ whi~ch are separated from offshore weIls and platorms and in w~ich a supply of fuel gas to the flare is utilized and controlled for pilots and for ign~tion~
It is a further object of the invention to provide an ignition system for offs~ore flares which are separated from offshore wells and platforms and in which the temperature conditions prevailing at the flame are utilized to control the ignition of a pilot ~ n accordance with a broad aspect, the invention relates to an offshore-subsea flare comprising:
~ a) an offshore flare for com~ustion of waste gas/
said flare comprising a burner, at least one pilot means for igniting the waste gas delivered to said burner, at least one gas ignitor means for igniting said pilot means, and an automatic ignition control means to control said pilot means and said ignitor means;
(b) an offshore platform located separately and remotely from said flare, said platform having associated therewith a source of combustible waste gas, means for supplying fuel gas to said pilot means and said ignitor means, and automatic activation means for activation of said ignition control means;
(c) a first su~merged conduit means for delivering waste gas from said source to said burner;
(d~ a second submerged conduit means for delivering fuel gas to said pilot means and said ignitor means, and ~ e~ a submerged connecting means hetween said control ~e~ns ~s50ciated with s~id flare and said ~cti~atin~ means associated w-ith said platform.
Other ob~ects~and advantageous ~eatures of the invention will be apparent from the des~r~ptl~Dn and claims.
The nature and characteristic features of the invention will be more readily understood from the following description taken in connection w-ith t~e accompanyi`ng drawings forming part hereof in whi`ch:
FIG 1 is a view in elevation of an offshore platform, an offshore flare of the buoy type, and the connection there-between in accordance with the invention;
FI~. 2 is a diagrammatic view o~ the fuel supply line for ignition and controls therefor which are located at the offshore platform;
FIG. 3 is a view in elevation of a flare in accordance with the invention which is supported from the sea floor;
FIG 4 ~s an enlarged view in elevation, parts being broken away, and showing the details of the waste gas burner, the pilot gas supply, the ignition gas supply and the ignitor;
FIG. 4A is a fragmentary view in elevation showing the control box of FIG. 4;
FIG. 5 is an enlarged vertical sectional view of the pilot;
FIG, 6 is a horizontal sectional view taken approximately on the line 6~6 of FI~. S;

- 3~ -FIG. 7 is an enlarged view of a portion of the pilot gas -supply pipe showing the thermocouple conduit carried thereby FIG. 8 is a view in elevation on a larger scale than FIG.
4 and showing details of the ignitor pipe and ignitor, FIG. 9 is a transverse sectional view, taken on the line 9-9 of FIG. 4 and showing the details of the connector or conduit between the offshore platform and the offshore flare;
and FIG. 10 is a diagrammatic view of the controls located at the flare.
It should, of course, be understood that the description and drawings herein are illustrative merely and that various modifications and changes can be made in the structure disclosed without departing from the spirit of the invention.
Like numerals refer to like parts throughout the several views. ~`
Referring now more particularly to the drawings and first to FIG. 1, an offshore platform is shown at P having a drilling rig 11, and fuel gas supply and control equipment 12 with a connecting conduit 13, hereinafter described, for ignition, extending to an offshore flare 14.
The offshore flare 14 can be of the buoy type with a - bottom anchor 15 and buoy 16 as illustrated in FIG. 1, or can be supported by an anchored base frame 17 extending upwardly as illustrated in FIG. 3, with a step off platform 18 and ladder and cage 19 to the access platform 18a, of the flare 14.
The flare 14 preferably has a waste gas supply pipe 20 extending thereto from the platform P which may have a flexible section 20a for a free floating type flare 14 as shown in FIG.
30 1. The pipe 20 can have a burner end 21 with flame retention members 22 at the burner end 21.

The flame retention members can be of any desired type ~s heretoore employed or can be as shown and described in my U~S, Letters Patent No. 4,116,618 issued September 26, 1978. :-. . ... . . . . .. ..
The flare 14, at the burner end is preferably provided with a windshield 24 having a plurality of spaced ver~ical slats ~5 and a bottom wall 26 through which one or more pilot gas supply pipes 27 extend for supplying a gas/air mixture to pilots 28. In the particular embodiment illustrated in FIG.
4, two pilots 28 are shown, but the number of pilots 28 will be determined in a specific design by the diameter of the pipe 20 and wind conditions at the burner end 21 of the pipe 20.
Within the interior of ~he pipe 20 and preferably spaced downwardly from the flame retention mem~ers 22, a fluidic diode 23 is provided which permits free upward flow of the gas to be burned but interposes a resistance to downward flow in the pipe 20. The fluidic diode can be that shown in my prior U,S. Patent No. 3,730,673.
T~e pilot gas supply pipes 27 are supplied with fuel gas from a fuel gas supply ring 30 through air inspirating venturis 31.
Air for the venturis 31 is preferably supplied through an air inlet 33 which includes, in a housing 34, an apertured air-adjustment member 34a.
An ignitor pipe 40 is provided for each pilot 28 and extending thereto with an ignitor ~as supply pipe 41 connected thereto through a venturi 42, similar to the venturi 31, and having an air inlet 33 which includes, in a housing 34, an apertured plate 35 with a valve plate 36 normally urged to open position by a spring 37 but movable to closed position in the event of an explosion beyond the air inlet 33. A
handle 38 can be provided to check the mov~ment of the plate T

36 if desired.
In FIG. 4 only one ignitor assembly is shown but each pilot 28 is provided with its own ignitor assembly.
Fuel gas is supplied through a pipe 41 to the inlet of the venturi 42 by means of solenoid valve 51 and pipe 43.
The ring 30 and the pipe 43 are supplied with fuel gas from a pipe 44 having a pressure gage 45 connected thereto.
An ignition fitting 48 is provided in the pipe 40 beyond the venturi 42 having an igniting spark plug 49 therein and a viewing opening 50 to observe conditions at the spark plug 49.
The pipe 43 has a solenoid controlled valve 51 therein and a solenoid controlled valve 52 is provided between the pipe 44 and the ring 30.
Referring to FIG. 8, a bypass pipe 54 can be provided around the valve 51 and to the ignition fitting 48, controlled by a solenoid valve 55 for supplying gas under pressure directed against the gap of the spark plug 49 for cleaning the plug.
Referring now to FIG. 2 a fuel gas supply pipe 56 is provided connected to a source of fuel gas for pilot operation and ignitor operation.
The pipe 56, as shown in FIG. 2, is connected through a manual shut-off valve 57, a strainer 58, and a pressure regu-lating valve 59 for adjustment of the delivered pressure of the fuel gas to the desired pressure level. A pressure gage 60 is connected to pipe 56 ahead of the pressure regulator 59 and a pressure gage 61 is provided downstream of the pressure regulator 59 for observation of the fuel gas pressure. The 30 pipe 56 also has a connection 62 to a pressure switch 63.
The pipe 56 extends to a drier 64 of any desired type, such as a refrigerated or a chemical drier, for elimination of liquid from the fuel gas. A dew point sensor 65 is provided in the pipe 56 which is connected to an audible dew point alarm 66 and a visual dew point alarm 67.
The pipe 56 also has a solenoid valve 68 therein which is connected to the power supply as hereinafter described.
The fuel gas supply and control equipment, as shown in FIG. 2, includes power leads 70 and 71 which are connected t~ro~h ~n ~n~ witch 72 and through a step ~gw~ ~rans~ormer and rectifier 73 to provia~ the aes~,rea ~c, t~ye ~or ~ a~
purposes, such as 24 volts. A rechargeable ~attery pack 75 can be provided, controlled by a manually operable switch 76 for emergency power suppl~.
The output lines from the transformer and rectifier 73 are connected to a controller 78 and to the pressure switch 63, indicat ng lights 79 and 80 being provided to indicate high gas pressure or low gas pressure in the pipe 56. Pilot indicator lights 77, 77a, 77b and 77c are provided activated by the controller 78.
The power leads 70 and 71 have connected thereto a 20 conductor 82 with a switch 83 and a conductor 84.
The controller 78 also has a signal input connection 81 for signal input determined by operation of the pilots 28, as hereinafter explained.
A conductor 87, connected to the conductor 70, and with a pushbutton 87a therein can be provided for spark plug cleaning of the pilots 28, as hereinafter explained.
As shown in FIG. 9, a connecting conduit 13 is provided, preferably flexible, with an outer sheath 85 which may be of teflon or other suitable waterproof material and with a spiral wound flexible corrosive resistant metal sheath 85a within which a flexible fuel gas pipe 86 is disposed. The pipe 86 is connected to the pipe 56 and within the sheath 85 through a fluid tight connector 88 and at the other end through a fluid tight connector 88a to the pipe 44 for supply of pilot gas and ignitor gas.
Within the conduit 13 a plurality of insulated flexible conductors 90, 91, 92 and 93 are provided connected respectively to the conductors 82, 84, 81 and 87. The space within the sheath 85 and surrounding the pipe 86 and the conductors 90, 91, 92 and 93 can be filled with any desired heat insulating and electrical insulating material 94 such as synthetic plastic pellets for flexibility of the conduit 13.
Referrin~ now to FIG. 10 the control equipment there shown is located within a control station box 96 at the lower part of the flare 14 which is protected against radiation by a radiation shield 97.
Conductors 90, 91, 92 and 93 extend through the fluid tight connector 88a, and are connected respectively to conductors 100, 101, 102 and 103 for the station box 96.
Each of the pilots 28 has a thermocouple 105 (see FIG. 5) carried therein in a guide tube 106, which at its upper end is mounted in a pilot flame retention nozzle 107. The nozzle 107 has a plurality of flame retention ports 108 therein.
The thermocouple leads extend through a gas tight coupling 109 (FIG. 7) on each pipe 27 and into the box 96.
In FIG. 4 only two pilots 28 are shown but in FIG. 10 three thermocouples 105 are illustrated diagrammatically and shown as connected respectively to temperature switch relays 110. The relays 110 have supply conductors 100 and 101 connected thereto and the relays provide signals through their conductors 1l1 if the thermocouple 105 indicates that there is a flame at its pilot 28 and through conductors 112 to provide signals to their ignition timers 113 and to an associa~ed ignition transformer 114 if the signals indicate there is no flame at J~;3 the respective pilot 28. Each transformer 114 is connected through a spark plug wire 115 to its respective spark plug 49.
The signals through the conductors 111 are also delivered to a controller 116 from which a signal is delivered through the conductor 102 to the conductor 81 and controller 78 for activation of the pilot indicating lights and as determined by the summation of the voltages of the signals through the conductor 81.
The controller 116 takes the signals in the conductors 111 and connects them to a lower voltage which can be summed up for measurement and indication of pilot status. The controller 116 produces a voltage signal which equals voltage from transformer 73 x num~er of pilots operating total num~er of pilots The controller 78 measures the voltage and gives an indication by means of the lamps 77, 77a, 77b, 77c. If all the pilots are out there is no voltage signal to controller 78. The controller 78 will activate a red pilot failure lamp 77.
The energization of the power leads 100 and 101 is also effective through conductors 117 and 118 to open the solenoid valve 52 to supply pilot gas to all the pilots 28.
The signals in the conductors 112 are also effective through conductors 120 and 121 to open the solenoid valve 51 to supply ignition gas delivery to the venturi 42 so that the gas-air mixture at the spark plug 49 will be intermittently ignited as determined by the timer 113 to provide a series of flame fronts through the ignitor pipe 40 to ignite the gas-air mixture delivered to the pilots 28.

The solenoid 55 for each gas bypass 54 is connected by the signal conductor 103 and by conductor 123 to the conductor 101 so that upon energization of the signal conductor 101 a *~ 3 gas jet cleaning action is available at the spark plug 49 of each ignitor assembly.
The mode of operation should be clear from the foregoing but will be summarized briefly.
Combustible waste gas from the offshore platform P is delivered through the pipe 21 to the offshore flare 14 for discharge through the burner end 21.
Fuel gas supplied through the pipe 56, with valve 57 open, advances through strainer 58 for removal of solids and partial removal of entrained liquid and the delivered pressure is regulated by adjustment of the pressure regulator 59.
The fuel gas pressure as delivered from the pressure regulator 59 is available through the pipe 62 at the pressure switch 63.
The fuel gas advances through the drier 64 for removal of any liquid content which could condense when subjected to underwater temperatures between the platform P and the flare 14.
If there is vapor content above a predetermined level the sensor 65 will activate an audible alarm 66 and visual alarm signal 67.
The flow is also controlled by the solenoid valve 68 energized from the power output of the transformer 73.
As the fuel gas passes through the pipe 56 it advances into the gas pipe 86 in the connecting conduit 13 and through the pipe 44, at the o~fshore flare 14, is divided. Part of the fuel gas is delivered under the control of the solenoid valve 52 to the fuel gas ring 30 and then through the venturis 31 for air admixture for delivery to the pilots 28.
Part of the fuel gas, under the control of the solenoid 51 passes to the venturi 42 for air admixture and for ignition by the spark plug 40 to deliver intermittent igniting flame r ~L~5.~.a~

fronts controlled by the timer 113 through the pipe 40 to ignite the gas-air mixture at the pilot 28.
The temperature at each thermocouple 105, if no flame is present at its pilot 28, will be efective to open the solenoid valve 51 for delivery of igniting gas to the spark plug 49, and for actuation of the timer 113 and through the ignition transformer 114 provide a spaced series of sparks at spark plug 49.
When there is a flame at the pilot 28, the timer 113 is shut off and a signal is delivered through the controller 116 and the signal conductors 102, 92 and 81 to the controller 78 to provide a visual indication at the lamps 77, 77a, 77b and 77c which is responsive to the number of pilots 28 in operation.
If cleaning of the spark plugs 49 is desired this may be effected by pressing the pushbutton 87a (FIG. 2) which provides for energization of the solenoid 55 to supply gas jets directed to the points of the spark plugs 49.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An offshore-subsea flare comprising:
(a) an offshore flare for combustion of waste gas, said flare comprising a burner, at least one pilot means for igniting the waste gas delivered to said burner, at least one gas ignitor means for igniting said pilot means, and an automatic ignition control means to control said pilot means and said ignitor means;
(b) an offshore platform located separately and remotely from said flare, said platform having asso-ciated therewith a source of combustible waste gas, means for supplying fuel gas to said pilot means and said igni-tor means, and automatic activation means for activation of said ignition control means;
(c) a first submerged conduit means for deli-vering waste gas from said source to said burner;
(d) a second submerged conduit means for de-livering fuel gas to said pilot means and said ignitor means, and (e) a submerged connecting means between said control means associated with said flare and said acti-vating means associated with said platform.

2. The offshore-subsea flare defined in claim 1 wherein means is provided for reducing the liquid content of the fuel gas.

3. The offshore-subsea flare defined in claim 2 wherein dew point sensing means is provided on said plat-form in advance of said submerged connecting means.

4. The offshore-subsea flare defined in claim 3 wherein an alarm member is provided responsive to said dew point sensing means.

5. The offshore-subsea flare defined in claim 2 wherein gas drier means is provided in advance of said submerged connecting means.

6. The offshore-subsea flare defined in claim 1 wherein fuel gas pressure control means is provided at said offshore platform.

7. The offshore-subsea flare defined in claim 1 wherein pressure responsive means is provided for con-trolling the delivered pressure of said fuel gas.

8. The offshore-subsea flare defined in claim 1 wherein said control means associated with said offshore flare comprises a member responsive to the temperature at said pilot.

9. The offshore-subsea flare defined in claim 1 in which said ignitor means includes a spark member, means for supplying fluid for cleaning said spark member, and said activation means associated with said platform includes means for activating said means for supplying cleaning fluid.

10. The offshore-subsea flare defined in claim 1 in which power supply means is provided on said platform for said activation means, and an auxialary power supply is provided on said platform.

11. The offshore-subsea flare defined in claim 1 wherein said second submerged conduit means and said sub-merged connecting means are contained together in a cable.

12. The offshore-subsea flare defined in claim 11 wherein at least part of said cable is flexible.

13. The offshore-subsea flare defined in claim 11 wherein at least part of said cable is provided with a protective sheath.

14. The offshore-subsea flare defined in claim 13 wherein said protective sheath comprises a metallic material.

15. The offshore-subsea flare defined in claim 1 wherein a shield is provided for said flare.