CA1220039A - Pressurized liquid filled tendons - Google Patents
Pressurized liquid filled tendonsInfo
- Publication number
- CA1220039A CA1220039A CA000457508A CA457508A CA1220039A CA 1220039 A CA1220039 A CA 1220039A CA 000457508 A CA000457508 A CA 000457508A CA 457508 A CA457508 A CA 457508A CA 1220039 A CA1220039 A CA 1220039A
- Authority
- CA
- Canada
- Prior art keywords
- tendon
- liquid
- recited
- pressure
- sea water
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
- B63B21/50—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers
- B63B21/502—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers by means of tension legs
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- Ocean & Marine Engineering (AREA)
- Earth Drilling (AREA)
- Examining Or Testing Airtightness (AREA)
- Revetment (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Pressurized liquid filled tubular tendons provide a means for detecting leaks therein. Filling the tendon with a liquid having a specific gravity less than that of sea water provides increased buoyancy and reduces the weight supported by the buoyant structure. The use of a corrosion inhibiting liquid reduces the corrosion of the interior tendon wall.
Pressurized liquid filled tubular tendons provide a means for detecting leaks therein. Filling the tendon with a liquid having a specific gravity less than that of sea water provides increased buoyancy and reduces the weight supported by the buoyant structure. The use of a corrosion inhibiting liquid reduces the corrosion of the interior tendon wall.
Description
~22~3~
PRESSURIZED LIQUID FILLED TENDONS
_ 05 INT~ODUCTION
The present invention relates generally to tension leg platform tendons. More particularly, the present invention relates to pressurized liquid filled tendons for detecting leaks, providing buoyancy and resisting corrosion. A change in pressure denotes a structural deficiency. An increase in tendon buoyancy reduces the weight supported by the buoyant structure.
Corrosion resistance extends the useful life of the tendon.
BACKG~OUND OF THE INVENTION
In deep water, the use of bottom-founded structures for oil well drilling and production operations is cost prohibitive due to the expense for fabrication and installation of such large structures. For ~ater depths in excess of 1,000 feet, buoyant offshore structures moored
PRESSURIZED LIQUID FILLED TENDONS
_ 05 INT~ODUCTION
The present invention relates generally to tension leg platform tendons. More particularly, the present invention relates to pressurized liquid filled tendons for detecting leaks, providing buoyancy and resisting corrosion. A change in pressure denotes a structural deficiency. An increase in tendon buoyancy reduces the weight supported by the buoyant structure.
Corrosion resistance extends the useful life of the tendon.
BACKG~OUND OF THE INVENTION
In deep water, the use of bottom-founded structures for oil well drilling and production operations is cost prohibitive due to the expense for fabrication and installation of such large structures. For ~ater depths in excess of 1,000 feet, buoyant offshore structures moored
2~ to the sea floor can be used to perform drilling and pro-duction operations cost effactively.
As water depth exceeds 1,000 feet, the tension leg platform (TLP) concept can be introduced to perform oil drilling and production operations. A TLP consists of a buoyant offshore structure moored to fixed sea floor anchor points with vertical tension legs; also referred to as tendons. Drilling, producing and processing equipment as well as crewls quarters are contained in or on the buoyant offshore structure.
Tendon designs include both cable and tubular leg elements. U~S. Patent 4,285,615, issued August 25, 19~1 to Frederick J. Radd discloses, "A mooring apparatus for a structure floating on a body of water, comprising:
a corrosion resistant cable system, including a multi-strand cable, having voids between adjacent strands;".
U.S. Patent 4,226,555, issued october 7, 1980 to Henry Ao Bourne, Jr. discloses, "A mooring system for a tension leg platform, comprising~ a tension leg, including a plural-ity of tubular leg elements having threaded connections between adjacent leg elements;".
The use of pre-tensioned vertical mooring elements prevents vertical motion but permits lateral motion o the floating structure during the passage of waves. Pre tensioning is accomplished by deballasting the buoyant oEEshore structure after the tendons are connected between the buoyant structure and fixed sea floor anchor bases.
Tendon inspection is necessary as both a maintenance expenditure and safety precaution. Tendon repair and replacement are both very expensive and laborious operations. Cracks and corrosion due to exposure to sea water decrease the failure load and working lifetime of the tendon. The desirability of minimizing tendon corrosion has been recognized in the art.
Previou~ly cited United States Patent 4,285,615 discloses an invention for providing a corrosion resistant design for a tension leg cable which isolates the steel wire cable from the sea water environment.
The present invention provides a method and means for detecting structural deficiencies in a tubular tendon, increasing its buoyancy and extending its useful life.
SUMMARY OF THE INVENTION
The present invention provides an aparatus for detecting a leak in a tension leg platform tendon, comprising: a fluid-tight tensioned tubular tendon, said tendon connected on its upper end to a buoyant offshore structure and on its lower end to an anchor means, said anchor means connected to the sea floor; means for supplying liquid to said tendon; means Eor pressurizing said liquid in e~cess of the maximum hydrostatic - 2 ~
~2~ 3~
pressure exerted by the sea w~ter on said tendon, and means or monitoring pressure, said means monitoring variations in liquid pressure in said tendon.
According to another aspect of the present invention there is provided an appara~us for detecting a leak in a tension leg platform tendon, comprising: a buoyant offshore structure:
anchor means connected to the sea floor; at least one tensioned tubular tendon connected between said buoyant offshore structure and said anchor means, said tendon being a fluid-tight tubular member; means for supplying liquid to said tendon in excess of the maximum hydrostatic pressure exerted by the sea water on said tendon; means ~or monitoring pressure, said means monitoring variations in liquid pressure in said tendon.
According to yet another aspect of the present invention there is pro~ided a method for detecting a leak in a tension leg platform tendon, comprising the steps ofo connecting a tensioned tubular tendon between a buoyant offshore structure and an anchor means connected to the sea floor, said tendon being a fluid-tight tubular member, supplying a liquid to said tendon;
pressurizing said liquid in excess of the maximum hydrostatic pressure exerted by the sea water on said tendon; monitoring liquid pressure in said tendon to detect leaks therein.
- 2a -~%~
Ol _3_ PRINCIPAL OBJECT OF THE INVENTION
The object of the present invention i5 to provide a ~5 method and means for detecting leaks in a tubular tendon, increasing its buoyancy and extending its useful life. A
method and means for detecting leaks indicating structural deficiencies promotes safety and reduces routine maintenance expenditures. Increasing the buoyancy of the tendon reduces the weight supported by the buoyant offshore structure; per-mitting a more efficient design. Increased tendon lifeprovides more cos~ effective deep water drilling by reducing maintenance, repair and replacement of the tendons.
Another object of the present invention is ~o provide an improved design for a tension leg platform incorporating the invention described herein.
Additional objects and advantages of the present invention will become apparent from a detailed reading of the specification and drawings which are incorporated herein and made a part of this invention BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevation schematic view, partially in section, of a tension leg platform.
FIG. 2 is an enlarged detailed view of the tendon of FIG. 1~
FIG. 3 is a section view of the tendon of FIG~ 2 taken about line 3-3.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows an elevation schematic view, partially in section, of a tension leg platform (TLP) 1 deployed at a drilling site. A lower platform 2 is provided on which may be mounted crew's living quarters, well test equipment and processing equipment. An upper platform 3 is provided on which may be mounted a pilot house, cranes, the drilling derrick, skid base, the drill string and a helicopter landing site. Similar conven-iences as are known to those skilled in the art of oil exploration and production may also be stored on the lower and upper platforms. Platforms 2 and 3 are supported by a plurality of annular support columns 4. When the TLP is 01 _4_ in its illustrated bouyant condition, columns 4 and pontoons 5 extend beneath the surface of the waterO A
05 plurality of tendons 6 extend from each support column 4 to anchor means consisting of a foundation template 7 secured to the sea floor 8 with friction piles 9, thereby restricting movement of the structure. A drill s~ring 10 and risers 11 extend from platform 1 or 2 between pontoons 5 to the sea floor 8 during drilling and pro-ducing operations. Well template 12 maintains the risersin a stationary position relative to the sea floor 8.
Referring to FIG. 2, an enlarged detailed view of tendon 6 depicts the tendon as a tubular element. A
plurality of tendon segments, each consisting of a tubular element and sealable couplings, are joined to provide a single elongated tubular tendon. The tubular element typically has a relatively thin wall compared to its overall diameter. A tubular element has been designed utilizing inside and outside diameters oE 18 and 20 inches, respectively. FIG. 3 shows a section view of the tendon of FIG. 2 taken about line 3-3.
In accordance with the present invention, a liquid; preferably corrosion inhibiting and having a specific gravity less than that of sea water, enters the tendon through a conduit located at its upper end. A
liquid mixture of fresh water and hydrazine fulfill the preceding criteria.
Subsequen' to the introduction of liquid to the tendon, compressor 13 supplies pressure through the conduit to the tendon's contents~ A pressure in excess of the maximum hydrostatic pressure exerted by the sea water on the tendon is recommended to avoid the instance where the pressure inside the tendon is equal to the sea water pressure at the same elevation. A positive net internal pressure is utilized to detect a leak. A valve is closed to retain the pressurized contents. Pressure gauges monitor the pressure therein. Reductions in pressure, in excess of a predetermined value, activate a signal to inform crew members of a deficient tendon.
As water depth exceeds 1,000 feet, the tension leg platform (TLP) concept can be introduced to perform oil drilling and production operations. A TLP consists of a buoyant offshore structure moored to fixed sea floor anchor points with vertical tension legs; also referred to as tendons. Drilling, producing and processing equipment as well as crewls quarters are contained in or on the buoyant offshore structure.
Tendon designs include both cable and tubular leg elements. U~S. Patent 4,285,615, issued August 25, 19~1 to Frederick J. Radd discloses, "A mooring apparatus for a structure floating on a body of water, comprising:
a corrosion resistant cable system, including a multi-strand cable, having voids between adjacent strands;".
U.S. Patent 4,226,555, issued october 7, 1980 to Henry Ao Bourne, Jr. discloses, "A mooring system for a tension leg platform, comprising~ a tension leg, including a plural-ity of tubular leg elements having threaded connections between adjacent leg elements;".
The use of pre-tensioned vertical mooring elements prevents vertical motion but permits lateral motion o the floating structure during the passage of waves. Pre tensioning is accomplished by deballasting the buoyant oEEshore structure after the tendons are connected between the buoyant structure and fixed sea floor anchor bases.
Tendon inspection is necessary as both a maintenance expenditure and safety precaution. Tendon repair and replacement are both very expensive and laborious operations. Cracks and corrosion due to exposure to sea water decrease the failure load and working lifetime of the tendon. The desirability of minimizing tendon corrosion has been recognized in the art.
Previou~ly cited United States Patent 4,285,615 discloses an invention for providing a corrosion resistant design for a tension leg cable which isolates the steel wire cable from the sea water environment.
The present invention provides a method and means for detecting structural deficiencies in a tubular tendon, increasing its buoyancy and extending its useful life.
SUMMARY OF THE INVENTION
The present invention provides an aparatus for detecting a leak in a tension leg platform tendon, comprising: a fluid-tight tensioned tubular tendon, said tendon connected on its upper end to a buoyant offshore structure and on its lower end to an anchor means, said anchor means connected to the sea floor; means for supplying liquid to said tendon; means Eor pressurizing said liquid in e~cess of the maximum hydrostatic - 2 ~
~2~ 3~
pressure exerted by the sea w~ter on said tendon, and means or monitoring pressure, said means monitoring variations in liquid pressure in said tendon.
According to another aspect of the present invention there is provided an appara~us for detecting a leak in a tension leg platform tendon, comprising: a buoyant offshore structure:
anchor means connected to the sea floor; at least one tensioned tubular tendon connected between said buoyant offshore structure and said anchor means, said tendon being a fluid-tight tubular member; means for supplying liquid to said tendon in excess of the maximum hydrostatic pressure exerted by the sea water on said tendon; means ~or monitoring pressure, said means monitoring variations in liquid pressure in said tendon.
According to yet another aspect of the present invention there is pro~ided a method for detecting a leak in a tension leg platform tendon, comprising the steps ofo connecting a tensioned tubular tendon between a buoyant offshore structure and an anchor means connected to the sea floor, said tendon being a fluid-tight tubular member, supplying a liquid to said tendon;
pressurizing said liquid in excess of the maximum hydrostatic pressure exerted by the sea water on said tendon; monitoring liquid pressure in said tendon to detect leaks therein.
- 2a -~%~
Ol _3_ PRINCIPAL OBJECT OF THE INVENTION
The object of the present invention i5 to provide a ~5 method and means for detecting leaks in a tubular tendon, increasing its buoyancy and extending its useful life. A
method and means for detecting leaks indicating structural deficiencies promotes safety and reduces routine maintenance expenditures. Increasing the buoyancy of the tendon reduces the weight supported by the buoyant offshore structure; per-mitting a more efficient design. Increased tendon lifeprovides more cos~ effective deep water drilling by reducing maintenance, repair and replacement of the tendons.
Another object of the present invention is ~o provide an improved design for a tension leg platform incorporating the invention described herein.
Additional objects and advantages of the present invention will become apparent from a detailed reading of the specification and drawings which are incorporated herein and made a part of this invention BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevation schematic view, partially in section, of a tension leg platform.
FIG. 2 is an enlarged detailed view of the tendon of FIG. 1~
FIG. 3 is a section view of the tendon of FIG~ 2 taken about line 3-3.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows an elevation schematic view, partially in section, of a tension leg platform (TLP) 1 deployed at a drilling site. A lower platform 2 is provided on which may be mounted crew's living quarters, well test equipment and processing equipment. An upper platform 3 is provided on which may be mounted a pilot house, cranes, the drilling derrick, skid base, the drill string and a helicopter landing site. Similar conven-iences as are known to those skilled in the art of oil exploration and production may also be stored on the lower and upper platforms. Platforms 2 and 3 are supported by a plurality of annular support columns 4. When the TLP is 01 _4_ in its illustrated bouyant condition, columns 4 and pontoons 5 extend beneath the surface of the waterO A
05 plurality of tendons 6 extend from each support column 4 to anchor means consisting of a foundation template 7 secured to the sea floor 8 with friction piles 9, thereby restricting movement of the structure. A drill s~ring 10 and risers 11 extend from platform 1 or 2 between pontoons 5 to the sea floor 8 during drilling and pro-ducing operations. Well template 12 maintains the risersin a stationary position relative to the sea floor 8.
Referring to FIG. 2, an enlarged detailed view of tendon 6 depicts the tendon as a tubular element. A
plurality of tendon segments, each consisting of a tubular element and sealable couplings, are joined to provide a single elongated tubular tendon. The tubular element typically has a relatively thin wall compared to its overall diameter. A tubular element has been designed utilizing inside and outside diameters oE 18 and 20 inches, respectively. FIG. 3 shows a section view of the tendon of FIG. 2 taken about line 3-3.
In accordance with the present invention, a liquid; preferably corrosion inhibiting and having a specific gravity less than that of sea water, enters the tendon through a conduit located at its upper end. A
liquid mixture of fresh water and hydrazine fulfill the preceding criteria.
Subsequen' to the introduction of liquid to the tendon, compressor 13 supplies pressure through the conduit to the tendon's contents~ A pressure in excess of the maximum hydrostatic pressure exerted by the sea water on the tendon is recommended to avoid the instance where the pressure inside the tendon is equal to the sea water pressure at the same elevation. A positive net internal pressure is utilized to detect a leak. A valve is closed to retain the pressurized contents. Pressure gauges monitor the pressure therein. Reductions in pressure, in excess of a predetermined value, activate a signal to inform crew members of a deficient tendon.
3~3 01 _5_ The corrosion inhibiting liquid protects the interior walls of the tubular tendon from exposure to sea 05 water. A liquid having a specific gravity less than that of sea water provides buoyancy and reduces the tendon weight supported by the offshore buoyant structure. Barring any pressurizing malfunctions, a change in pressure indicates a leak in the tendon attributable to a crack or puncture through the tendon or an inadequate coupling seal.
While a certain preferred embodiment has been specifically disclosed, it should be understood that the invention is not limited thereto, as many variations will be,readily apparent to those skilled in the art and the S invention is to be given its broadest possible interpre-tation within the terms of the following claims~
While a certain preferred embodiment has been specifically disclosed, it should be understood that the invention is not limited thereto, as many variations will be,readily apparent to those skilled in the art and the S invention is to be given its broadest possible interpre-tation within the terms of the following claims~
Claims (15)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for detecting a leak in a tension leg plat-form tendon, comprising:
a fluid-tight tensioned tubular tendon, said tendon connected on its upper end to a buoyant offshore structure and on its lower end to an anchor means, said anchor means connected to the sea floor;
means for supplying liquid to said tendon;
means for pressurizing said liquid in excess of the maximum hydrostatic pressure exerted by the sea water on said tendon, and means for monitoring pressure, said means monitoring variations in liquid pressure in said tendon.
a fluid-tight tensioned tubular tendon, said tendon connected on its upper end to a buoyant offshore structure and on its lower end to an anchor means, said anchor means connected to the sea floor;
means for supplying liquid to said tendon;
means for pressurizing said liquid in excess of the maximum hydrostatic pressure exerted by the sea water on said tendon, and means for monitoring pressure, said means monitoring variations in liquid pressure in said tendon.
2. Apparatus as recited in claim 1, wherein:
said liquid is water.
said liquid is water.
3. Apparatus as recited in claim 1, wherein:
said liquid is a hydrocarbon.
said liquid is a hydrocarbon.
4. Apparatus as recited in claim 1, wherein:
said liquid includes a corrosion inhibitor mixed therewith.
said liquid includes a corrosion inhibitor mixed therewith.
5. Apparatus as recited in claim 1, wherein:
said liquid has a specific gravity less than that of sea water.
said liquid has a specific gravity less than that of sea water.
6. Apparatus for detecting a leak in a tension leg plat-form tendon, comprising:
a buoyant offshore structure;
anchor means connected to the sea floor;
at least one tensioned tubular tendon connected between said buoyant offshore structure and said anchor means, said tendon being a fluid-tight tubular member;
means for supplying liquid to said tendon in excess of the maximum hydrostatic pressure exerted by the sea water on said tendon;
means for monitoring pressure, said means monitoring variations in liquid pressure in said tendon.
a buoyant offshore structure;
anchor means connected to the sea floor;
at least one tensioned tubular tendon connected between said buoyant offshore structure and said anchor means, said tendon being a fluid-tight tubular member;
means for supplying liquid to said tendon in excess of the maximum hydrostatic pressure exerted by the sea water on said tendon;
means for monitoring pressure, said means monitoring variations in liquid pressure in said tendon.
7. Apparatus as recited in claim 6, wherein:
said liquid is water.
said liquid is water.
8. Apparatus as recited in claim 6, wherein:
said liquid is a hydrocarbon.
said liquid is a hydrocarbon.
9. Apparatus as recited in claim 6, wherein:
said liquid includes a corrosion inhibitor mixed therewith.
said liquid includes a corrosion inhibitor mixed therewith.
10. Apparatus as recited in claim 6, wherein:
said liquid has a specific gravity less than that of sea water.
said liquid has a specific gravity less than that of sea water.
11. A method for detecting a leak in a tension leg plat-form tendon, comprising the steps of:
connecting a tensioned tubular tendon between a buoyant offshore structure and an anchor means connected to the sea floor, said tendon being a fluid-tight tubular member;
supplying a liquid to said tendon;
pressurizing said liquid in excess of the maximum hydro-static pressure exerted by the sea water on said tendon;
monitoring liquid pressure in said tendon to detect leaks therein.
connecting a tensioned tubular tendon between a buoyant offshore structure and an anchor means connected to the sea floor, said tendon being a fluid-tight tubular member;
supplying a liquid to said tendon;
pressurizing said liquid in excess of the maximum hydro-static pressure exerted by the sea water on said tendon;
monitoring liquid pressure in said tendon to detect leaks therein.
12. The method of claim 11 such that said liquid is water.
13. The method of claim 11 such that said liquid is a hydrocarbon.
14. The method of claim 11 such that said liquid includes a corrosion inhibitor mixed therewith.
15. The method of claim 11 such that said liquid has a specific gravity less than that of sea water.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US50876483A | 1983-06-28 | 1983-06-28 | |
| US508,764 | 1983-06-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1220039A true CA1220039A (en) | 1987-04-07 |
Family
ID=24023975
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000457508A Expired CA1220039A (en) | 1983-06-28 | 1984-06-27 | Pressurized liquid filled tendons |
Country Status (6)
| Country | Link |
|---|---|
| CA (1) | CA1220039A (en) |
| ES (1) | ES533817A0 (en) |
| FR (1) | FR2548367B1 (en) |
| GB (1) | GB2142286B (en) |
| NO (1) | NO842599L (en) |
| YU (1) | YU46143B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4626136A (en) * | 1985-09-13 | 1986-12-02 | Exxon Production Research Co. | Pressure balanced buoyant tether for subsea use |
| US4630970A (en) * | 1985-09-13 | 1986-12-23 | Exxon Production Research Co. | Buoyancy system for submerged structural member |
| CN107235121B (en) * | 2017-04-29 | 2019-04-05 | 大连理工大学 | A kind of monitoring device and installation method based on sound transmission tension leg VIV |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL250591A (en) * | 1959-04-17 | |||
| GB888247A (en) * | 1960-11-11 | 1962-01-31 | Conch Int Methane Ltd | Device for the storage of liquids at very low temperatures |
| US3517517A (en) * | 1968-09-19 | 1970-06-30 | Pan American Petroleum Corp | Encapsulated cable for marine use |
| US4116044A (en) * | 1977-04-28 | 1978-09-26 | Fmc Corporation | Packoff leak detector |
| GB1599491A (en) * | 1978-01-07 | 1981-10-07 | Fmc Corp | Pipe swivel joints |
| US4226555A (en) * | 1978-12-08 | 1980-10-07 | Conoco, Inc. | Mooring system for tension leg platform |
| US4285615A (en) * | 1978-12-13 | 1981-08-25 | Conoco, Inc. | Corrosion resistant tension leg cables |
-
1984
- 1984-06-20 FR FR848409692A patent/FR2548367B1/en not_active Expired
- 1984-06-27 GB GB08416341A patent/GB2142286B/en not_active Expired
- 1984-06-27 NO NO842599A patent/NO842599L/en unknown
- 1984-06-27 CA CA000457508A patent/CA1220039A/en not_active Expired
- 1984-06-28 YU YU112684A patent/YU46143B/en unknown
- 1984-06-28 ES ES533817A patent/ES533817A0/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| NO842599L (en) | 1985-01-02 |
| ES8601469A1 (en) | 1985-10-16 |
| GB2142286B (en) | 1986-05-14 |
| FR2548367A1 (en) | 1985-01-04 |
| YU112684A (en) | 1987-04-30 |
| GB2142286A (en) | 1985-01-16 |
| YU46143B (en) | 1993-05-28 |
| ES533817A0 (en) | 1985-10-16 |
| FR2548367B1 (en) | 1989-04-21 |
| GB8416341D0 (en) | 1984-08-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |