The present invention relates to a marine instrument protective housing resistant to mechanical forces such as punching, bending and scraping.
Underwater structural devices such as large mooring anchors or templates must be lowered and installed to predetermined positions. In order to improve safety, predictability, and speed of operations, the offshore oil and gas industry has grown ever more demanding on the supply of accurate location for underwater equipment. In order to provide such data, during installation, permanent monitoring, or before removal, it has been common to link an acoustic transponder to the submerged equipment, and to locate it thanks to a corresponding transducer on board a related vessel.
However, such transponder, typically a cylinder of a few centimetres diameter and a few decimetres lengths, may be subject to very rough handling. This is in particular the case for transponders designed to locate anchors mooring drilling vessels or platforms. The mooring line usually comprises very heavy chains or very large diameter ropes of polypropylene or similar high strength rope. Subject to a mechanically rough descent while following a mooring chain or an anchor from the ship's deck to the sea bottom, rough treatment when the anchor, possibly with the transponder instrument, penetrates the sediments, and to the same extreme handling during recovery, transponders in the field have shown low robustness and reliability, resulting in loss of positioning accuracy of the anchors, higher costs and reduced safety.
The common practice for attaching transponder beacons for anchors and the like has been to use protection and floatation collars. Two half-floating shells are clamped around the body of the beacon. These buoys do leave both ends free and unprotected from bad treatment. The bowline may be attached directly to an end portion with an attachment eye on the instrument housing. The connection may be made using a chain portion, which induces a risk of breaking the attachment eye or the end of the instrument while handling the instrument in a deck crane. The unprotected end portion of the instrument housing is also subject to hitting the deck, chain links, delta plates or any mechanical component during its handling while connected to the anchor or anchor line. Prior art has the significant disadvantage that the bowline, often a chain or a carabine hook or other metal shackle which is connected directly to one end, usually the lower portion of the instrument, which damages the end of the instrument during deck handling or lowering. The buoyant housing of some of the prior art does not form part of the connection to the bowline.
WO2010/062184 describes a protection housing rigidly attached to the shank of an anchor, the protection housing holding a sensor and transmitter device. Such a protection housing rigidly attached to the anchor will require modifications to the anchor and will further be subject to strong mechanical forces when the anchor is dragged through the sediments and there is a risk of damage to the sensor and transmitter. Furthermore, the sensor and transmitter will necessarily end up at the same depth as the anchor, which may be rather deep in the sediments, and may thus not be able to communicate with surface vessels.
Brief summary of the invention
In a material aspect of the invention, it is a marine housing for a submersible instrument (2), comprising:
two or more shell portions (3a, 3b, 3c) for mechanically protecting said instrument (2), wherein the novel features are:
said shell portions (3a, 3b, 3c) arranged for being assembled as an enveloping shell (1) forming a cavity (11) for mechanically protecting said instrument (2),
two or more of said shell portions (3a, 3b, 3c) comprising one or more ropes (5) for binding said shell portions (3a, 3b, 3c) together in their assembled positions forming said shell (1).
In a preferred embodiment of the invention two or more of said shell portions (3a, 3b, 3c) are provided with channels (4) for threading or guiding said one or more ropes (5). This stabilizes the shell during assembly and also during use both while in the sea and particularly protects the rope against wear.
In a preferred advantageous embodiment of the invention the one or more ropes (5) are arranged for reinforcing said shell (1) under tension of said one or more ropes (5) by providing compressive forces to said shell portions (3a, 3b, 3c).
In another aspect of the invention, it is a method for housing a marine submersible instrument (2), comprising: providing two or more shell portions (3a, 3b, 3c) for forming a complete shell (1) with a cavity (11), assembling said shell portions (3a, 3b, 3c) around said instrument (2) thereby forming an enveloping shell (1), and arranging one or more ropes (5) to bind said two or more said shell portions (3a, 3b, 3c) together in their assembled positions about said instrument (2).
According to a preferred embodiment of the invention the method of the invention comprises threading or guiding the one or more ropes (5) through channels (4) in two or more of the shell portions (3a, 3b, 3c). Further preferred embodiments are described in the dependent claims.
Connecting a bowline from the shell holding the instrument, generally directly to a part of an anchor line such as a shackle or chain link or triple plate may provide a significant advantage as the housing of the invention allows the instrument to mechanically tolerate being dragged through sediments, thus the anchor may be more precisely positioned. This is an advantage over the prior art instruments which may not withstand being dragged through sediments. It may also be advantageous to connect the shell (1) directly but releasably to the anchor line already on deck of the vessel in order to remain in a controllable position to avoid beatings from chain being dragged along the deck, and subsequently to be extended in the entire length of the bowline when the anchor has landed.
The background art has been illustrated together with the invention in the following drawing figures. The drawings are meant to illustrate the invention.
The invention will be described in detail with reference to the attached series of drawing Figures and accompanying descriptive text referring to transponder-based underwater location for anchors. The purpose of the invention is however broader, including all type of instruments, and various environments.
In its broadest definition, the invention is a marine housing for a submersible instrument (2), comprising two or more shell portions (3a, 3b, 3c) for housing and mechanically protecting the instrument (2). Particular features of the invention are represented by the facts that the shell portions (3a, 3b, 3c) are arranged for being assembled as a generally completely enveloping shell (1) forming a cavity (11) for mechanically protecting the instrument (2), and that two or more of the shell portions (3a, 3b, 3c) are provided with a rope (5) or two, or any number of ropes (5) arranged for binding the shell portions (3a, 3b, 3c) together in their assembled positions forming the shell (1).
According to a preferred embodiment, the invention concerns the protective housing for a transponder or other instrument designed to locate the anchor for a vessel or a rig, during installation, removal, or at anchored location, please see
A shell comprising only one shell portion may be envisaged by the person skilled in the art, but does not have all the advantages of the invention due to the lack of modularity. The multiple-shell portions (3a, 3b, 3c) of the invention will allow several instrument module volumes or lengths of the cavity (11) formed by the shell (1) and may be adapted to several lengths of the instrument and its accompanying batteries, etc. The shell portions (3a, 3b, 3c) are in a preferred embodiment of the invention rigid and durable against wear, at least the front shell portion (3a), but one or more may be made in a softer, though wear-resistant.
According to a preferred embodiment of the invention, the marine housing of claim 1, the shell portions (3a, 3b, 3c) are provided with channels (4) for threading and/or guiding one or more of the ropes (5). The channels (4) may have several different embodiments depending on the actual implementation of the instrument buoy, such as the need for the shell to protect the ropes from wear or vice versa.
In the marine housing of the invention, one or more of said shell portions (3b) may have an internal pipe-shape forming and surrounding part of said central cavity (11). One or more of the channels (5) may extend through a significant part of one or more of the shell portions (3a, 3b, 3c). Alternatively, but with more exposed ropes, the channels (5) may be formed as eye-shaped protrusions on the outward facing surface of one or more of the shell portions (3a, 3b, 3c). The channels (5) may partly be open channels or furrows along the outward facing surface of one or more of the shell portions (3a, 3b, 3c), such as illustrated in
One significant advantage of the invention in one preferred embodiment is the fact that one or more of the ropes (5) are arranged for reinforcing the shell (1) under tension of said one or more ropes (5) by providing compressive forces to the shell portions (3a, 3b, 3c). As is shown in
The marine housing of the invention may be tapered slightly off behind the bow shell portion (3a) for reducing friction and wear of the remainder shell portions (3b, 3c).
The marine housing of the invention may comprise a liner pipe (21) to be arranged about said instrument (2) in the cavity (11), please see
In a preferred embodiment of the invention one or more of the shell portions (3a, 3b, 3c) have one or more sensor windows (6, 6′) for a sensor or transmitter of the instrument (2). The window (6) must be transparent for the sensor or transmitter, i.e. should be an open aperture or transparent, i.e. the aperture or window (6) having the same signal propagation properties as surrounding water or sediments. The window (6) may be an aperture, or a material piece being transparent to the signal in question, such as a cover being transparent to acoustic signals, or even having an acoustic velocity near the acoustic velocity of water. The window (6) may even be the material of the shell portion in question covering the sensor or transmitter. The buoy may contain an acoustic receiver or transmitter (22), an electromagnetic receiver or transmitter (23), a pressure sensor (24), or a sampling device (25). Alternatively, the window (6′) may be arranged laterally on the housing, such as illustrated in
According to a preferred embodiment, the invention concerns the protective housing for a transponder designed to locate the anchor for a vessel or a rig, during installation, removal, or at anchored location, please see
Each subsequent body segment may have a slightly smaller diameter protruding end (31), designed to engage in the larger diameter end (32) of the neighbouring body segment, or end section, please see
The rope (5), please see
In an embodiment of the invention the rope is passed through four holes for each of the body pieces and end plate and nose portions(
All housing pieces are preferably made of hard polymer material, designed to protect the transponder from mechanical forces, such as shocks and scraping in particular. As an acoustic transponder preferably is be held generally nearly vertical, please see
Several advantages are provided by having a design with several housing segments such as shown in
End sections and particularly the bow section and also the top plate should be hard, in order to resist shocks and scraping. They need also to be in a material easy to machine or shape to required characteristics.
The top plate, please see
The front, nose or “bottom” section, please see
As shown generally in all Figs., the marine housing of the invention is provided with the bow shell portion (3a) arranged closest to said bowline portion (7) having a pyramidal or conical shape with an apex portion (31a) directed towards said bowline portion (7), please see
In a preferred embodiment, top and bottom sections are made of nylon. One advantage of this design is that an increasing traction on the rope will improve the rigidity and strength of the assembly, by setting all pieces under compression. This does of course only apply until the rope breaks. Thus parallel independent ropes (or wires) may be used in order to have redundancy if one rope breaks.
In order to position the beacon in the buoy, spacers may be added. They may compensate for a beacon shorter than the available room: one may use an additional plastic pipe in the continuity of the beacon, please see
A preferred installation is quite simple. Beacon, shell sections and, if required, spacers are assembled, then secured using rope and wire clamps, please see
There are many other possible embodiments to this invention. For example, one end section and the body shell pieces may be replaced by one single piece, a container to be locked with a cover thanks to the rope. However, as mechanical properties required for the body piece(s) and distal plate(s) may not be the same, such design may require a composite structure for such container. One will also lose the practical advantages of modularity cited above. Finally, should this container be very long, it may not give the expected protection against shocks and bending, as several articulations may act as energy absorbers.
Several ropes may be used in locking a shell of the invention. However, one single rope appears to allow faster assembly and higher strength.
The problems related to the general lack of robustness of transponders has triggered the invention. However, the housing of the invention may apply to several types underwater instruments, such as sensitive equipment with much electronics and sensors designed to perform collection of data or emit or receive various signals. Such equipment is in nature quite fragile, and effective mechanical protection is required when rough handling cannot be avoided. Many underwater instruments may benefit from the invention.
Not all instruments will need to be held vertical, and buoyancy is not an absolutely required property of all embodiments of the present invention. The buoy has been tested in traction in a dry trench pulled by an excavator.
The described solution may be used for transponders that are used for precise location of equipment underwater, such as anchors. One example is USBL, or Ultra Short Base Line acoustics, commonly used in the offshore oil and gas industry. USBL may even be integrated in a data system supporting the positioning of equipment underwater. Thanks to the transponder and tight integration in the positioning system such as those supplied by the assignee of this patent, the anchor can be located in real-time and visible to rig and tug boat positioning operators during installation and removal, contributing to an accurate and safe operation.
Number | Date | Country | Kind |
---|---|---|---|
20092906 | Aug 2009 | NO | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/NO2010/000321 | 8/30/2010 | WO | 00 | 4/16/2012 |
Number | Date | Country | |
---|---|---|---|
61255561 | Oct 2009 | US |