US3799092A

US3799092A - Emergency buoyancy system

Info

Publication number: US3799092A
Application number: US00189383A
Authority: US
Inventors: A Patterson; E Barakauskas
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1971-10-14
Filing date: 1971-10-14
Publication date: 1974-03-26
Anticipated expiration: 1991-03-26
Also published as: FR2162851A5; CA951185A; GB1354197A; JPS4846501A; JPS526241B2; NL7213212A

Abstract

Gases from a solid propellent rocket fuel unit are mixed with carbon dioxide from a pressure vessel to inflate an inflatable buoy, which is connected to a riser pipe utilized in drilling a hole in the bottom of the ocean. The structure buoy is fastened to the riser pipe, about 300 feet below the water, at a level unaffected by wave action, but accessible to divers and is adapted to be rapidly inflated to support the riser pipe, if there is a severe storm and it becomes necessary to cut the drilling platform loose from the riser pipe.

Description

United States Patent Patterson, Jr. et al.

[451 Mar. 26, 1974 EMERGENCY BUOYANCY SYSTEM 3,566,426 3/1971 Davidson et a1. 9/9

[75] Inventors: Arthur E. Patterson, Jr., Cupertino;

Edward J. Barakauskas, Saratoga, Pmrary Emm" 1er Duane Reger both of Calif Asszstant Exammer-Jesus D. Sotelo Attorney, Agent, or FirmF. J. Baehr, Jr. [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, 57 ABSTRACT [22 Filed: Oct. 14, 1971 Gases from a solid propellent rocket fuel unit are mixed with carbon dioxide from a pressure vessel to 7 189383 inflate an inflatable buoy, which is connected to a riser pipe utilized in drilling a hole in the bottom of [52] U.S. Cl ll4/0.5 D the ocean. The structure buoy is fastened to the riser [51] Int. Cl B63b 35/44 pipe, about 300 feet below the water, at a level unaf- [58] Field of Search 114/.5 R, .5 D, 16.4, 16.5, fected by wave action, but accessible to divers and is 114/166, 16.7, 16.8; 9/8 R, 8.3 E, 9 adapted to be rapidly inflated to support the riser pipe, if there is a severe storm and it becomes neces- [56] References Cited sary to cut the drilling platform loose from the riser UNITED STATES PATENTS P P 3,210,785 10/1965 Ward 9/9 3 Claims, 4 Drawing Figures e a II II EMERGENCY BUOYANCY SYSTEM The invention hereinafter described was made in the course of, or under a contract for, the National Science Foundation, an agency of the U.S. Government.

BACKGROUND OF THE INVENTION This invention relates to deep water drilling and more particularly to an emergency buoyancy system for supporting the riser casing if the drilling platform must be cut loose from the hole.

Development of offshore drilling began in the 1930s and developed simultaneously in California and Louisiana, however the early drilling platforms, which support the familiar oil derricks, were either on artificial islands or supported by legs extended to the bottom of the sea. By the mid l950s floating platforms with legs that were jacked to the bottom to raise the platform above the water came into use along with floating platforms, which were held in place by mooring lines fastened to buoys anchored to the floor of the sea. The latter arrangement could be utilized to drill holes under water several hundred feet deep. In 1961 the first deep sea holes were drilled in water over 10,000 feet deep, demonstrating the feasibility of dynamically positioning a drilling platform in the ocean. For additional infomiation on the development of deep sea drilling, reference may be made to A Hole In The Bottom Of The Sea by Willard Bascom, published in 1961, which relates to the story of the Mohole Project.

SUMMARY OF THE INVENTION In general, an emergency buoyancy system made in accordance with this invention comprises a tank for containing pressurized fluid, an exothermic gas generator, a mixing chamber for mixing fluid from the tank with gas produced by the gas generator to form a gaseous mixture and an inflatable buoy adapted to contain the gaseous mixture and provide a predetermined amount of buoyancy.

BRIEF DESCRIPTION OF THE DRAWINGS The objects and advantages of this invention will be come more apparent from reading the following detailed description in connection with the accompanying drawings, in which:

FIG. 1 is a partial elevational view of a floating drilling platform and an emergency buoyancy system made in accordance with this invention;

FIG. 2 is an enlarged sectional view taken on line ll-II of FIG. 1;

FIG. 3 is an enlarged sectional view taken on line III- -III of FIG. 2; and

FIG. 4 is an enlarged sectional view of a quick opening valve and mixing chamber made in accordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in detail, FIG. 1 shows a floating drilling platform 1 having a derrick 3 disposed thereon and a riser pipeor casing 5 depending from the drilling platform 1. A drill pipe or drill string 7 having a boring bit at the lower end thereof extends downwardly through the casing to bore a hole beneath the floor of the ocean in several thousand feet of water. In the event of a severe storm it may be necessary to detach the drilling platform 1 from the riser pipe 5. With the drilling platform removed, additional buoyancy may be required to support the riser pipe. The amount of buoyancy would vary depending on the length of the riser pipe, its size, the desired tension, and many other factors. The additional buoyancy is preferably added at a level not appreciably affected by wave action and yet accessible to divers.

As shown in FIG. 1, an emergency buoyancy system 8 adapted to provide gases to an inflatable buoy 9 is disposed approximately 300 feet below the water level. Utilizing compressed gases to inflate the buoy would produce undesirably low temperatures, which could cause freezing and malfunction of the system 8, while utilizing a gas generator, such as a solid propellent fuel unit, would produce a large quantity of compressed gases at elevated temperatures, which are difficult to handle and would cool over a period of time, reducing the buoyancy. Therefore a workable system must produce gases at the ambient pressure and temperature at a depth of 300 feet below the surface of water.

As shown in FIGS. 2 and 3, such an emergency buoyancy system comprises a C0 tank or pressure vessel 11, an exothermic gas generator 13 having a solid fuel rocket propellent unit 14, commercially known as a Jato unit (jet assist take-off unit as manufactured by Hercules Powder Corporation, Radford, Va.), disposed therein and a combination quick opening valve and mixing chamber 15 adapted to mix the CO fluid with the gaseous products of combustion from the gas generator l3 tempering both fluids so that the gaseous mixture has a temperature of approximately F as it enters the inflatable buoy 9, which is fastened to the riser pipe 5 at a depth of approximately 300 feet below the surface of the water.

Each CO tank 11 and gas generator 13 will produce a predetermined amount of buoyancy so that by providing the proper size inflatable buoys 9 and a plurality of CO tanks 11 and gas generators 13, the amount of buoyancy can be varied in increments providing a flexible system capable of responding to various buoyancy needs.

An ignition control system which monitors the amount of CO in each tank 11 and provides an ignition system for each gas generator 13 is operable from the drilling platform 1 above the water, and contains monitors which inform the operator that the system has functioned.

As shown in FIGS. 2 and 3, each CO tank 11 and gas generator 13 is cooperatively associated with a mixing chamber 15, which is connected to the inflatable buoy 9 by a manifold 17. As will be hereinafter described in detail, the tank 11, gas generator 13 and mixing chamber 15 are removably fastened to the manifold 17 and riser pipe 5 so that after they have functioned, they can be easily removed and recharged, and subsequently reinstalled to provide buoyancy in future emergencies.

As shown in FIG. 4, the combination quick opening valve and mixing chamber 15 comprises an outer cylindrical shell or tubular housing 19 disposed generally horizontally, an inlet port 21 in communication with the CO tank 11 and a cylindrical or tubular sleeve member 23 disposed within the outer cylindrical shell 19. The sleeve member 23 is axially aligned with the outer shell 19 and is flange mounted to one end thereof. The flanged end 25 of the sleeve member 23 has an orifice 27 disposed therein for receiving the discharge end of the Jato unit 14 and a seal 29 disposed to seal one end of the annular chamber 31 formed between the shell 19 and sleeve 23. An annular seal ring 33 is seal welded to the shell 19 and has a circumferential groove 35 adapted to receive an O-ring type seal 37, which engages the outer peripheral surface of the sleeve 23 to seal the other end of the chamber 31. A plurality of openings or ports 39 are circumferentially spaced adjacent the central portion of the sleeve placing the annular chamber 31 into communication with the bore or inner surface of the sleeve 23.

A spool shaped valve member 41 is slidably disposed within the sleeve 23. The spool member 41 has end flanges 43, which slidably engage the inner surface of the sleeve 23 and each flange 43 has a groove 45 shaped to receive an O-ring 47, which forms a seal at the end flanges 43. The spool member 41 is so disposed with respect to the ports 39 as to form a seal on opposite sides thereof closing or plugging off the ports 39. A small diameter lock wire 49 is fastened to the spool member 41 and to the sleeve member 23 limiting relative movement therebetween. The lock wire 49 is sufficiently strong to hold the spool member 41 in plugging relation with the ports 39 under severe operating conditions, however, the lock wire 49 is designed to break when subjected to the pressure produced by the gas generator 13 when it is ignited. A counter-bore forms a step 50 in the inner surface of the sleeve forming a unidirectional valve, which only responds to a pressure build-up on one side thereof.

The other end of the shell 19 is closed by a cupshaped cap 51 having an outer flange 53, which is fastened to an inwardly directed flange 55 at the end of the shell forming a seal therebetween. The cap 51 is of the proper diameter and depth of receive the spool member 41 and has a plurality of fingers 57 extending outwardly to the sleeve 23. The fingers 57 have tip ends, which taper outwardly to provide a guideway for receiving the spool member 41 as it leaves the sleeve 23, to assist in directing the spool member 41 towards the cup-shaped cap 51, when the gas generator 13 is ignited.

A discharge port 58 is disposed in the shell 19 adjacent the fingers 57. A short nozzle 59 connects the discharge port 57 to the manifold 17. Quick disconnecting mating flanges 61 are provided and are held in sealing relation by a quick disconnect clamp 62. A portion of the discharge nozzle 59 extends downwardly into the manifold, the lower end of the discharge nozzle 59 is tapered inwardly to assist in aligning the flanges 61 so that they can be assembled under water.

As shown in FIG. 4, the inlet port 21 is placed in communication with the CO tank 11 by a short nozzle 13 welded to the tank 11 and to the shell 19. FIG. 4 also shows the Jato unit 14 mounted in the gas generator 13, which comprises a tubular shell portion 67 having a flanged end closure 69. The Jato unit 14 is suspended from mounting brackets 71 and 73 fastened to the shell portion 67. The mounting brackets locate the Jato unit 14 within the shell so that the discharge nozzle extends through the orifice 27 and withstand the thrust of the Jato unit 14 after it is ignited. The mounting bracket 71 is formed from interconnecting portions 75 and 77 which are bolted together to fix the position of the Jato unit 14 within the shell 67 and allow it to be easily replaced.

The CO; tank 11, gas generator 13, and mixing chamber 15 are fastened together to form a unitized structure or assembly, which is supported from a pair of

collars

79 and 81 fastened to the riser pipe 5. The upper collar 79 has a pair of semicircular plates 83 extending radially therefrom. The plates 83 have arcuate scalloped peripheral edges for receiving the CO tanks 11 and a plurality of holes 85 adapted to receive a tapered pin 87, which is fastened to the upper end of the CO, tank 11 by a bracket 89. The lower collar 81 is encircled by an l-beam 91, which is fastened thereto by a plurality of struts 93 extending radially outwardly from the lower collar 81. The l-beam 91 is disposed under the flanges of the end closures 69 and has a pair of wedge-shaped blocks 95 fastened thereto to form a cradle for each gas generator. The CO tanks 11 and gas generators 13 have lifting

lugs

97 and 99, respectively, properly disposed so that when the quick disconnect flange clamp 62 is removed the assembly can be removed from the manifold 17. An isolation valve 102 is disposed in the manifold upstream of the inflatable buoy so that portions thereof may be shut off.

Each CO tank 11 and gas generator 13 will produce a predetermined amount of buoyancy so that by varying the number of units activated incremental buoyancies can be obtained. To activate a portion of the system a Jato unit 14 is ignited by operating a switch at the surface to commence burning of the solid fuel propellent. The products of combustion are gases so that the pressure in the shell 67 of the gas generator 13 builds up rapidly causing the lock wire 49 holding the spool valve 41 in place to break, allowing the valve member 41 to slide into the cup-shaped cap 51, and liquid CO to begin to flow through the ports 39 and into the mixing chamber 15, wherein it vaporizes and mixes with the products of combustion from the Jato unit 14 to reduce the temperature of the products of combustion and raise the temperature of the CO so that the temperature of the mixture leaving the discharge port 57 is approximately F, which is generally equal to the temperature of the water at a depth of 300 feet. Once the Jato unit 14 is ignited it burns without external oxygen until it is burned out. The CO; tank is sized to provide sufficient cooling for the Jato unit. The CO begins to flow into the mixing chamber shortly after combustion of the Jato unit 14 is initiated and continues to flow during combustion and for a short period after combustion is completed to insure that no hot gases flow through the manifold and into the inflatable buoy 9. As noted hereinbefore, the spool valve 41 is unidirectional so that no other valving is required in the manifold and activation of one unit will not cause spool valves of other units to operate. Thus, the apparatus hereinbefore described advantageously produce incremental quantities of noncondensable gaseous mixtures at the ambient temperature and pressure expected to exist approximately 300 feet below the surface of the water to provide incremental amounts of emergency buoyancy.

What is claimed is:

1. An emergency buoyancy system comprising a pressure vessel for pressurized fluid; an exothermic gas generator; a mixing chamber fluidly connected to said pressure vessel and said gas generator for producing a gaseous mixture of pressurized fluid from said pressure vessel and gas from said gas generator; said mixing chamber comprising an outer tubular shell, a sleeve disposed within the outer shell, the sleeve being fastened to one end of said shell, a circumferential seal between the shell and the sleeve, the gas generator being disposed to discharge into said sleeve, a second circumferential seal between said sleeve and said shell cooperating with said first mentioned circumferential seal to form an annular chamber between said sleeve and said shell, said shell having an opening placing the pressure vessel in communication with said annular chamber, said sleeve member having at least one port placing said annular chamber in communication with the inner side of said sleeve, means for plugging said port, means for holding said plugging means in plugging relation under normal conditions and operable to allow said plugging means to move out of plugging relationship oxide.

Claims

1. An emergency buoyancy system comprising a pressure vessel for pressurized fluid; an exothermic gas generator; a mixing chamber fluidly connected to said pressure vessel and said gas generator for producing a gaseous mixture of pressurized fluid from said pressure vessel and gas from said gas generator; said mixing chamber comprising an outer tubular shell, a sleeve disposed within the outer shell, the sleeve being fastened to one end of said shell, a circumferential seal between the shell and the sleeve, the gas generator being disposed to discharge into said sleeve, a second circumferential seal between said sleeve and said shell cooperating with said first mentioned circumferential seal to form an annular chamber between said sleeve and said shell, said shell having an opening placing the pressure vessel in communication with said annular chamber, said sleeve member having at least one port placing said annular chamber in communication with the inner side of said sleeve, means for plugging said port, means for holding said plugging means in plugging relation under normal conditions and operable to allow said plugging means to move out of plugging relationship with said port, when said gas generator is activated, and an opening in said shell for discharging the gaseous mixture from said shell at ambient temperature; and means for containing said gaseous mixture under water to provide a predetermined amount of buoyancy.

2. An emergency buoyancy system as set forth in claim 1, wherein the plugging means is slidably disposed within the sleeve.

3. An emergency buoyancy system as set forth in claim 1, wherein the gas generator comprises a Solid propellent rocket fuel and the fluid is liquid carbon dioxide.