CONSTANT TENSIONING SYSTEM AND METHOD FOR HOISTING TENDERS

Abstract

The invention relates to a constant tensioning system to compensate wave motion of a tender, comprising: - a first conduit having an outlet operatively connectable to a crane or winch thereof; - a second conduit having an outlet operatively connectable to a crane or winch thereof; - a third conduit extending between the first conduit and the second conduit and fluidly connected to both; and - a regulator valve in the third conduit being switchable between a closed position, in which a fluid flow between the first conduit and the second conduit is prevented, and an open position in which the first conduit and the second conduit are fluidly connected to each other to provide and / or maintain a constant pressure between the first and second conduit. The invention also relates to a tender deployment system and a method for compensating wave motion of a tender during deployment of retrieval thereof.

Description

The invention relates to a constant tension system for hoisting tenders, in particulartenders for pleasure yachts and research vessels, and to amethod for hoisting such tenders. Ship tenders, or simply tenders, are small boats that are used to transport people and / or supplies between a ship and shore and are for example used on (luxury) yachts and exploration and / or research ships. In most cases, tenders are either stored on deck or in a specially designed garage or hangarbay inside the ship that comprises an openable door in the ships to provide access to and from the garage or hangar bay. To deploy and retrieve the tender(s), a tender deployment system comprising one ormore cranes is used. This could be deck cranes (in case ofdeck storage) or garage cranes, when an inboard garage or hangar bay is present. The deployment system is congured to move the tender out over the water and subsequently lower the tendertowards (and into) the water. Overthe years, one ofthe main problems with these deployment systems has been the presence ofwaves or sea swell. When the tender is positioned in the water, the waves cause the tender to move up- and downwards. As long as the reeled out cables are still attached, this results in differentiation of the length ofthe cables on which the tender is suspended. In particular, slack in the reeled out cable occurs at the momentthe tender is at awave crest, in some cases resulting in the hook and / orthe cables dropping uncontrollably into the tender. This leads to damage ofthe tender and / orthe people inside the tender. An additional risk is that peoples extremities get caughtby the cable and / or the hook when the tender descents from the wave. It that case, the dropped hook and / or cable is being pulled tight and any extremities, such as ngers or hands, may get caught and hurt. To obviate these problems, in particular the unwanted detachment ofthe cables from the tender, constant tensioning or CT systems were developed. These CT systems are congured to apply a constant tension to the cables throughout the rise and fall ofthe tender on the waves, which prevents slack in the cables and consequently the detachment thereof. This ensures that the cables are reeled in when the tender is rising on awave and lowered when the tender is descending from awave. To achieve such constant tensioning, most constant tensioning systems contain a main drive and an auxiliary drive, with the latter being congured to provide a constanttension to the cables. Such systems are however relatively large and thus take up (valuable) space on a ship. This is in particular a problem for (luxury) yachts and research vessels in which technical systems should be as compact as possible. Therefore, there is a need for an effective and more simple constant tensioning system to prevent slack in the cables ofa tender deployment system. The present invention is aimed at obviating or at least reducing the aforementioned problems by providing a simple and effective constant tensioning system that can be used in atender deployment system to deploy a tender to and retrieve a tender from the water. To that end, the invention provides a constant tensioning system congured for wave motion compensation of a tender in a tender deployment system, the constant tensioning system comprising: 1 - a rst conduit having an outlet that is operatively connectable to at least one crane, and preferably to awinch thereof, - a second conduit having an outlet that is operatively connectable to the at least one crane, and preferably to awinch thereof, - athird conduitthat extends betweenthe rst conduitandthe second conduitand is uidly connected to both, and - a regulator valve that is positioned in the regulator conduit and that is switchable between a closed position, in which a uid ow between the rst conduit and the second conduit is substantially prevented, and an open position in which the rst conduit and the second conduit are uidly connected to each otherto provide and / ormaintain a constant pressure between the rst and second conduit. The constant tensioning system, by virtue ofthe regulator valve, provides and / or maintains a constant pressure between the rst and second conduits, and in particular between the outlets thereof. This in turn results at a constant line pull on awinch cable ofthe at least one crane to which the tender is connected. The constant line pull allows compensation for the movement ofa tenderthat is connected to the at least one crane when it is moving with wave motion, in particular the rise and fall ofthe waves. The regulator valve is congured to be closed during normal operation, which is hoisting the tender from and lowering the tender to the water surface. During operation ofconstant tensioning (i.e. a constant tensioning or CT-mode), the regulator valve is congured to be in the closed positionwhen the tender is moving up on a wave. The constant line pull achieved with the constant pressure causes the winch to reel in the cable to prevent slack. The regulator valve is congured to be in the open position during descent ofthe tender on awave. The weight ofthe tender will, during descent, overcome the internal (mechanical and hydraulic) resistance ofthe system allowing the tenderto reel outthe cable. To maintain the pressure in the system during this reeling out, the regulator valve is opened to allow hydraulic uid ow from the rst conduit to the second conduit. An advantage ofthe constant tensioning system according to the invention is that it provides a compact and efcient constant tensioning system having a small footprint. This is mainly due to the fact that the CT-system according to the invention only requires a single regulator valve to maintain the constant tension. In particular, the CT-system can be provided in a housing, such as a (small) container, that can be connected to or provided in a crane ofatender deployment system. Therefore, the footprint ofthe CT-system according to the invention is smaller than that of existing CT-systems in which an auxiliary drive specically designed for constant tensioning is applied. Another advantage ofthe constant tensioning system according to the invention is that it the use of (complex) electronics and / or sensors is obviated. The CT-system according to the invention requires a single valve to provide the constant tension to the cable(s). This reduces complexity and increases reliability and robustness ofthe CT-system, especially compared to existing CT-systems. 2 A further advantage is that the constant tensioning system according to the invention can be integrated in deck cranes and / or in garage cranes, thus allowing tenders to be deployed and / or retrieved from the deck (using one ormore deck cranes) or from a garage (using one ormore garage cranes). Another advantage ofthe constant tensioning system according to the invention is that the use ofsensors can substantially be obviated. In principle, the single valve operation is sufcient to achieve proper functioning ofthe CT-system. It is noted thatthe rst, second and third conduit are congured to transport hydraulic uid and have appropriate characteristics therefore. In use ofthe constant tensioning system, the outlets ofthe rst and second conduits are connected to the at least crane, preferably to awinch thereof, and the crane preferably is a crane of a tender deployment system. It is further noted that the rst conduit is also referred to in the application as a hoisting conduit. The terms rst conduit and hoisting conduit are used interchangeably throughout the application. The second conduit is also referred to in the application as a lowering conduit. The terms second conduit and lowering conduit are used interchangeably throughout the application. The third conduit is also referred to in the application as regulator conduit and these terms are used interchangeably in throughout the application. It is also noted that the terms constant tensioning and its abbreviation CT are used interchangeably throughout the application and both refer to the same. It is furthermore noted that the term conduit should not be interpreted in a restrictive manner and relates to an object that forms a channel or is capable of channeling hydraulic uid. In this application this also embodies alternatives such as hoses, lines, pipes or other similar suitable synonyms. In an embodiment ofthe constant tensioning system, the regulator valve is switchable between a rise mode, in which a connected tender moves upward on a wave and the regulator valve is in the closed position, and a descentmode in which the connected tendermoves downward on or from awave and the regulator valve is in the open position. An advantage ofthe rise and descentmodes is that each ofthese modes is related to a specic wave motion to allow compensation for said wave motion. In an embodiment ofthe constant tensioning system according to the disclosure, the regulator valvemay be anormally closed valve that, during operation, is congured to switch to the open position when the pressure in the rst conduit exceeds apredetermined regulator pressure. An advantage ofthis type ofvalve is that the regulator valve is only openedwhen necessary for function ofthe CT-system. In practice, the regulator valve will thus only open when the tender, during CT-mode, is descending on awave. The risk ofthe valve being opened during normal (i.e. deployment) operation is therewith obviated (in contrast to the risk being presentwhen using anormally open valve). In an embodiment ofthe constant tensioning system according to the disclosure, the system may further comprise a CT-pressure line that is connected to the regulator valve and that is congured to provide the predetermined regulator pressure to the regulator valve. 3 An advantage of providing a CT-pressure line is that the regulator pressure of the regulator valve, that is the pressure at which the regulator valve is congured to switch from the closed to the open position, can be adapted to the desired value. The desired value may for example be determined by the characteristics ofthe at least one crane, such as maximum safe working load (SWL) and / or the weight ofthe tender that is going to be used in conjunction with the CT-system. Another advantage is that the CT-system is useable in a wide range of different tender deployment systems, which reduces the cost ofthe manufacturing compared to systems in which a set value is used. The latter would require different unit to be produced (resulting in higher production costs). In an embodiment ofthe constant tensioning system according to the disclosure, the regulator valve may be a pilot-operated balanced piston reliefvalve. An advantage ofthis particular valve is that it provides a reliable, substantially leak-free valve that is capable to perform the required operation in the CT-system. Due to the pilot-operated nature, the predetermined pressure can be easily applied. In an embodiment ofthe constant tensioning system according to the disclosure, the constant tensioning system may have a deploymentmode, in which the regulator valve is inoperative, and a CT- mode in which the regulator valve is switchable between the open and the closed position such that the constant pressure is provided and / or maintained. It is noted that the CT-mode may comprise, and preferably does comprises, both the rise mode and the descent mode of the system to compensate for respectively upward motion on a wave and downward motion from a wave by the tender. In other words, the CT-mode comprises both the rise mode and the descent mode, which are preferably alternated to compensate for respectively up- and downward motion ofthe tender on the waves. An advantage ofhaving both abovementioned modes is that the regulator valve is that the risk ofaccidental switching ofthe regulatorvalve to the open position is substantially obviated. It alsomeans that the use ofthe constant tensioning system, for the purpose of obviating wave movement, is only possible after the CT-mode has been selected. The use ofthe CT-mode therewith is a conscious choice of an operator. This increases the safety of the CT-system even further. In addition, it prevents any damage to the CT-system (orthe associated crane ordeployment system). It is noted thatthe CT-system, which is connected to the associated crane (in particular the winch thereof) is thus capable ofproviding, by virtue ofthe constant pressure between 1St and 211d conduit, a constant line pull to a cable to which the tender is connected only in the CT-mode. In the deployment mode, a cable of the at least one associated crane is lowerable or hoistable to respectively lower or hoist a tender that is connected to the cable, wherein the cable movement preferably is based on user input that is received and processed by a control unit. 4 In an embodiment ofthe constant tensioning system according to the disclosure, the CT-system may further comprise an enable valve that is operable to switch the constant tensioning system between the deploymentmode and the constant tensioning mode. An advantage of an enable valve, which preferably is user operatable or user-controllable, is that the CT-system can easily be switched (back and forth) between the deploymentmode and the CT- mode. In an embodiment ofthe constant tensioning system according to the disclosure, the CT-system may further comprise a safety release unit that is congured to transfer the constant tensioning system from the CT-mode to the deploymentmode based on one ormore predetermined conditions. An advantage of a safety release unit, which operates based on a predetermined condition, is that the safety ofthe CT-system is increased even further. In particular, it prevents potentially harmful situations by disabling the CT-mode and switching to the deployment mode. The safety release unit may be used for various different predetermined conditions or even combinations thereof. The safety release unitmay also be used in conjunction with a controller to regulate and / or control it. In an embodiment of the constant tensioning system according to the disclosure, the one or more predetermined conditions may comprise one ormore of: - the at least one associated crane being in an unextended state, wherein the unextended state comprises abeam extension ofless than 95% ofthemaximum extension ofan extendable beam of the at least one associated crane, and / or user input comprising a hoist or lower command congured to respectively hoist or lower a tender connected to a cable ofthe at least one associated crane. The constant tensioning system is only required when the tender is positioned on the waves during deployment or retrieval thereof. In particular with garage cranes, this also means that the crane must be fully extended in order to be able to safely deploy / retrieve the tender. Therefore, it may be prevented to bring the CT-system in the CT-mode ifthe crane is not fully extended. In particular, full extension preferably means extended over a distance ofat least95% and preferably over a distance of 100% orvery near to it (i.e. maximum extension). Similarly, the regulator valve is notmeant to be opened during hoisting and / or lowering ofthe tender (i.e. for operations other than to compensate wave motion). Therefore, it is advantageous to enable the safety release when an operator, purposefully or inadvertently, controls (i.e. instructs or operates) the system to hoist or lower the tender. In an embodiment ofthe constant tensioning system according to the disclosure the rst and the second conduit each further comprise an inlet side that is connectable to a hydraulic power supply. The constant tensioning system preferably is positioned between the at least one crane and the hydraulic power supply to regulate the hydraulic powerprovided to the at least crane. In an embodiment ofthe constanttensioning system according to the disclosure, the CT-system may further comprise one or more: 5 - a rst conduit pressure sensor that is operatively connected to the rst conduit and that is congured to measure a pressure in the rst conduit, and / or - a second conduit pressure sensor that is operatively connected to the second conduit and that is congured to measure a pressure in the second conduit. In order to monitor and / or provide improved control over the constant tensioning system, pressure sensors may advantageously be used. The pressure data collected from the pressure sensors may be used for monitoring and / or may be used as input for one or more different components ofthe CT-system or atender deployment system in which the CT-system is applied. In an embodiment ofthe constant tensioning system according to the disclosure, the constant tensioning systemmay further comprise a control unit that: - is congured to controlthe safety release unitbased on data relating to the predetermined condition, and / or - is operatively connected to the rst and / or the second pressure sensor and is congured to receive pressure data therefrom. An advantage ofa control unit is that an integrated control overthe CT-system can be realised. In particular, it is advantageous to have a control unit that is coupled to (and capable ofcontrolling) the safety release system and / or the pressure sensors. The data obtained from these sensors and / or unit further improves the operation and efciency ofthe CT-system according to the disclosure. In an embodiment ofthe constant tensioning system according to the disclosure, the constant tensioning systemmay further comprise a brake outlet that is operatively connected to the rst and / or the second conduit and that is congured to selectively release a brake ofan associated winch. An advantage ofproviding a brake outlet is that the constant tensioning system is then usable to also operate and / or control the brake operation. This improves control over the hoisting, lowering and compensation operations ofthe CT-system per se and the tender deployment system as a whole. In an embodiment ofthe constant tensioning system according to the disclosure, the constant tensioning system may further comprise a housing that is connectable to or integratable in a crane ofa tender deployment system, wherein the housing preferably is congured to contain all components of the CT-system. An advantage of a housing is that it provides protection of the components from the environment, in particular a saline environment as present on ships. In addition, the housing allows the constant tensioning system to be easily connected and / or disconnected to a tender deployment system, in particularthe at least one crane (orwinch) thereof. To that end, the housingmay comprise connection means that are congured for connecting the housing to an aforementioned (crane / winch of a) deployment system. In an embodiment ofthe constant tensioning system according to the disclosure, wherein the systemmay further comprise a non-retum valve that is positioned in the third conduit and that, when viewed from the rst conduit towards the second conduit, is positioned before the regulator valve, 6 whereinthe non-retum valve is congured to only allowaow from the rst conduittowards the second conduit. In an embodiment ofthe constanttensioning system according to the disclosure, the CT-system may further comprise a regulator that is positioned in the rst conduit and that is, when viewed from the inlet to the outlet, positioned upstream ofthe connection ofthird conduit to the rst conduit, wherein the regulator is congured to control the ow (and ow direction) in the rst conduit. An advantage ofthe regulator is that is assists in the ow control through the rst conduit, in particular the direction of the ow during operation. It is noted that, when the constant tensioning system is in the deploymentmode, the ow is congured from the inlet towards the outlet. Preferably, the regulator is also operatively connected to the second conduit and is congured to, based on a pressure in the second conduit, allow a ow reversal in the rst conduit. In an embodiment, the regulatormay comprise a directional valve to provide aow towards the outlet and a normally closed valve that is openable under pressure from the second conduit. The disclosure also relates to atender crane comprising a constant tensioning system according to the disclosure. The tender crane according to the disclosure provides similar effects and advantages as the constant tensioning system according to the disclosure. It is noted that the embodiments as described for the CT-system may be applied, alone or in combination, in the tender crane according to the disclosure. The invention also relates to a tender deployment system comprising: - a constant tensioning system according to the disclosure, - at least one tender crane comprising: - at least one winch that is operatively coupled to the constant tensioning system, preferably to the outlets ofthe rst and the second conduits, for receiving hydraulic uid therefrom, and - a beam, preferably an extendable and / or hingeable beam, that is congured to support a cable to which atender is connectable, - at least one hydraulic power supply that is operatively coupled to the constant tensioning system, preferably to the inlet side thereof, for supplying hydraulic uid to the constant tensioning system and the at least one tender crane. The tender deployment system according to the disclosure provides similar effects and advantages as the constant tensioning system andthe tender crane according to the disclosure. It is noted that the embodiments as described for the CT-system and the tender crane may be applied, alone or in combination, in the tender deployment system according to the disclosure. In some cases, similar embodiments ofthe tender deployment system and the CT-system may include similar components or even share such components as part ofthe system. It is further noted that the at least one tender crane and the at least one winch may also be provided as separate parts rather 7 than as an integral unit. This does not change the working of the deployment system and both congurations are considered equivalents that fall within the scope ofthis application. In an embodiment of the tender deployment system according to the disclosure, the tender deployment system may further comprise a controller that is congured to, based on a user input, transfer the system between one of: - a switched-offmode in which the tender deployment system is inactive, and - an operational mode in which the tender deployment system is active, wherein the operationalmode comprises: - a deployment mode in which a cable ofthe at least one tender crane is hoistable or lowerable and the CT-system is inoperative, and - aCT-mode in which the regulator valve ofthe constanttensioning system is switchable between the open and the closed position such that the constant pressure is provided and / or maintained to the at least one winch such that a constant line pull on the cable is achieved. An advantage of the tender deployment system according to the disclosure is that it can be switched off (i.e. to be inactive) or can be provided in an operational mode. The operational mode is characterized by two different modes of operation. This includes the deployment mode and the CT- mode, which were both also referred to in relation to earlier described embodiments ofthe constant tensioning system. The advantages recited earlier are also applicable here. In an embodiment ofthe tender deployment system according to the disclosure, the at least one tender crane may comprise at least one extendable beam, wherein the extendable beam has an unextended state and a fully extended state in which an extension ofthe beam is between 95% and up to and including 100% of itsmaximum extension range. In general, the constant tensioning system should, for safety reasons, only be used when the extendable beam is fully extended. Fully extended in this respect preferably means substantially 100% extension, butmay in some cases be viewed as a relative extension of95% or higher. In an embodiment of the tender deployment system according to the disclosure, the safety release system may be congured to transfer the system from the constant tensioning mode to the deploymentmode ifthe extendable beam is transferred from the extended state to the unextended state. An advantage of a safety release unit is that it increases the safety ofthe tender deployment system even further, because it prevents the use ofthe CT-system when the beam is not fully extended. It therewith prevents potentially harmful situations by disabling the CT-mode and switching to the deploymentmode. The safety release unitmay also be used in conjunction with a controller to regulate and / or control it. In an embodiment ofthe tender deployment system according to the disclosure, the at least one crane may comprise an extension sensor that is congured to measure the extension ofthe extendable beam, wherein the safety release system is congured to be operated based on the measurement data provided by the extension sensor. 8 An advantage of an extension sensor is that it provides accurate information relating to the distance overwhich the (beam ofthe) crane is extended. This may be related to an absolute distance or may relate to a relative distance compared to the maximum available extension distance (i.e. a percentage ofmaximum extension). The information of the extension sensor can advantageously be used in determining whetherthe predetermined condition for enabling the safety release unit is fullled. In an embodiment ofthe tender deployment system according to the disclosure, the systemmay further comprise a brake that is operatively coupled to the constant tensioning system, preferably to a brake outlet thereof. An advantage ofabrake, ormultiple brakes, is thatthe cable orcables associatedwiththe tender deployment system can be held steady. The brake or brakes are preferably coupled to the hydraulic drive to disengage the brake(s) at the moment the system is operated. In an embodiment ofthe tender deployment system according to the disclosure, themaximum load capacity (SWL) ofthe at least one crane is adapted to the weight ofthe tender, such that the tender weight is between 30% and 90% ofthe SWL, preferably between 40% and 85% ofthe SWL and more preferably between45% and 80% ofthe SWL. An advantage ofadapting SWL ofthe at least one the crane to the weight ofthe tender is that the safety ofthe deployment system is increased even further. The disclosure also relates to a method for compensating wave motion of a tender during deployment of retrieval thereof, the method comprising the step of providing a tender deployment system comprising a constant tensioning system according to the disclosure or a tender deployment system according to the disclosure, and further comprising, during a deployment, the steps of: - lowering a tender into the water using the deployment system, - activating the constant tensioning mode of the tender deployment system, wherein the constant tensioning mode comprises providing a constant pressure to each winch associated with the one or more cranes to achieve a constant line pull on each cable associated with the one ormore cranes, and - releasing the tender from the tender deployment system, or further comprising, during a retrieval, the steps of: - connecting a tender to be retrieved to a cable ofthe tender, - activating the constant tensioning mode of the tender deployment system, wherein the constant tensioning mode comprises providing a constant pressure to each winch associated with the one or more cranes to achieve a constant line pull on each cable associated with the one ormore cranes, and - hoisting the tender from the water. The method for compensating wave motion of a tender according to the disclosure provides similar effects and advantages as the constant tensioning system, the tender crane and the tender 9 deployment system according to the disclosure. It is noted that the embodiments as described for the CT-system, the tender crane andthe tender deployment systemmay be applied, alone or in combination, in the method for compensating wave motion ofa tender according to the disclosure. In particular, the method provides the advantage a constant line pull is achieved on the (cable connected to the) tender during the movement ofthe tender on the waves with only a single valve. This provides a simplied method for compensating wave motion. This is mainly achieved by the steps of holding the regulator valve in a closed position during rising ofthe tender on a wave and opening the regulator valve during the descent ofthe tender from a wave. The latter equalizes the pressure in the rst and second conduit, therewith allowing a constant line pull to be achieved. In an embodiment ofthe method for compensating wave motion ofa tender during deployment ofretrieval thereofaccording to the disclosure, the step ofactivatingmay comprise the steps of: - keeping the regulator valve in a closed position ifthe tender that is operatively connected to the constant tensioning system is moving upwards on a wave; - switching the regulator valve from the closed position to the open position upon the tendermoving downward on awave, therewith allowing hydraulic uid to ow from the rst to the second conduit to maintain a constant line pull to a cable connected to the tender, and - optionally repeating abovementioned steps during wave motion ofthe tender, and - further optionally deactivating the constant tensioning system. An advantage ofthe abovementioned steps is that a constant line pull is achieved on the (cable connected to the) tender during the movement of the tender on the waves by virtue of only a single valve. This is mainly achieved by the steps ofholding the regulator valve in a closed position during rising ofthe tender on awave and opening the regulator valve during the descent ofthe tender from a wave. The latter equalizes the pressure in the rst and second conduit, therewith allowing a constant line pull to be achieved. The method therewith provides a robust and efcient manner ofcompensating wave motion ofa tender. In an embodiment ofthe method for compensating wave motion ofa tender during deployment of retrieval thereof according to the disclosure, the step of activating the constant tensioning system comprises transferring the constant tensioning system from the deployment mode to the CT-mode, preferably based on user input and / orthe step ofdeactivating the constant tensioning system comprises transferring the constant tensioning system from the CT-mode to the deployment mode, preferably based on user input. An advantage of both abovementioned steps, and in particular the switching between the deployment mode and the CT-mode, is that the risk of accidental opening of the regulator valve is substantially obviated, thus leading to an even safermethod. The separate step ofactivating also means that the CT-mode is used as a conscious choice of an operator. This increases the safety of the CT- system even further. In addition, the steps ofactivating and deactivating also preventdamage to the CT- system or the deployment system as a whole. 10 In an embodiment ofthe method for compensating wave motion ofa tender during deployment of retrieval thereof according to the disclosure, the method may further comprise one or more ofthe steps of: - transferring, using the safety release unit, the constant tensioning system from the CT-mode to the deploymentmode ifthe predetermined condition is met, and / or - providing and / or adjusting the predetermined regulator pressure, wherein the predetermined regulator pressure is preferably adapted to a weight ofa tender to be operatively connected to the constant tensioning system The step oftransferring provides the advantage that the constant tensioning system is protected from damage to (accidental) actions such as hoisting and / or lowering. An advantage ofthe adjusting step is that the CT-system can be adapted for different types of tenders and / or for tenders having different weight. In an embodiment ofthe method for compensating wave motion ofa tender during deployment ofretrieval thereofaccording to the disclosure, themethodmay comprise the step ofloading passengers and / or goods to be disembarked in the tender. An advantage ofthe method is that the loading ofpassengers and / orgoods can be performed in a safer and more efcient manner. In an embodiment ofthe method for compensating wave motion ofa tender during deployment of retrieval thereof according to the disclosure, the method may further comprise extending the extendablebeam ofone ormore cranes ofthe tender deployment system to a fully extended state before engaging the constant tensioning mode. An advantage ofactivating the CT-system onlywhen the beam ofthe at least one crane is fully extended increases safety ofboth the system and the ship on which the system is installed. Further advantages, features and details ofthe invention are elucidated on the basis ofpreferred embodiments thereof, wherein reference is made to the accompanying drawings, in which: Figure 1 shows a schematic view ofan example ofa constant tensioning system according to the disclosure, Figure 2 shows a schematic view ofa control unit and associated components according to the disclosure, Figure 3 shows aschematicview ofasecond example ofa constanttensioning system according to the disclosure with the CT-system in the deploymentmode, Figure 4 shows a schematic view ofthe second examplewhen the CT-system is in the rise mode ofthe CT-mode, Figure 5 shows a schematic view ofthe second example when the CT-system is in the descent mode ofthe CT-mode, Figure 6 shows a schematic view of an example of a tender deployment system according to the disclosure, and 1 1 Figure 7 shows a schematic view ofan example ofthe method according to the disclosure for compensating wave motion ofa tender during deployment ofretrieval thereof. In an example, constant tensioning system 2 comprises rst uid conduit 4, second uid conduit 6 and third uid conduit 8. First uid conduit4 extends from uid inlet 10, which is operatively connectable to (schematically indicated) hydraulic power source 12, to uid outlet 14, which is connectable to at least one crane (schematically indicated with 500). Similarly, second uid conduit 6 extends from an associated uid inlet 16, which is operatively connectable to (schematically indicated) hydraulic power source 12, to associated uid outlet 18, which is connectable to at least one crane (schematically indicated with 500). Third uid conduit 8 extends between rst uid conduit 4 and second uid conduit 6 and uidly connects them to each other. Constant tensioning system 2 further comprises regulator valve 20, which is positioned in third uid conduit 8 and that has a closed position (shown as solid arrow S) and a closed position (shown as dotted arrow A). Constant tensioning system 2 in this example also comprises CT-pressure conduit 22, which extends between an CT-pressure conduit inlet 24 and regulator valve 20. CT-pressure conduit 22 is congured to provide the predetermined regulator pressure to regulator valve 20. Furthermore, constant tensioning system 2 in this example also contains non-retum valve 26, which is positioned between regulator valve 20 and rst conduit 4 and which is congured to allow ow towards regulator valve 20. Both rst conduit 4 and second conduit 6 are also connected via respective brake lines 28, 30, which both are connected to outlet brake line 34 that emanates in brake outlet 32, which is connected to a (schematically shown) brake B. In this example, all brake lines 28, 30, 34 are connected to valve 36 to selectively regulate the ow to and from brake B. In this example, each of rst uid conduit 4 and second uid conduit 6 is provided with respectively pressure sensor 38, 40. Constant tensioning system 2 is further provided, in this example, with control unit 42 (schematically shown in gure 3), which is connected to several components of constant tensioning system 2. This includes for example pressure sensors 38, 40. In this example, it is also connected to enable valve 44, although enable valve 44 may also be controlled in another manner, such as with (hydraulic) pressure or spring force. Control unit 42 is also connected to safety release unit 46, which is congured to transfer constanttensioning system 2 from the CT-mode to the deploymentmode based on one ormore predetermined conditions. Thismay for example concern that the at least one crane of the tender deployment system 500 is an unextended state. The unextended state comprises a beam extension of less than 95% of the maximum extension of an extendable beam of the at least one associated crane, which may for example be measured with schematically indicated extension sensor 48, which is not part ofCT-system 2 yetmay provide input to control unit 42 thereof. Control unit 42 may also be connected to user interface 50, which is operable to receive and transmit operator input to control unit 42. Safety release unit 46may transfer constant tensioning system 2 from the CT-mode to the deploymentmode based on user input received from user interface 50, such as a hoist or lower 12 command. It is noted that alternative method for providing safety release unit 46 are also possible. This may for example concern hydraulic or spring-based variants. In this example, constant tensioning system 2 also comprises regulator 52 that is positioned in rst conduit 4 and that, in this example, is also operatively connected to second conduit 6 by means of line 62. Regulator 52 may, based on a pressure in the second conduit, allow aow reversal in the rst conduit, although the ow in deployment mode is directed towards the outlet. In this example (see gure 1), constant tensioning system 2 is further provided with additional valves 54, 56 that regulate the ow from CT-pressure line 22 to drain line 58 and drain outlet 60. In a second example (see gures 3 to 5), constant tensioning system 102 is shown in various modes of operation. In deployment mode (see gure 3), hydraulic uid is transported between uid supply 112 and (schematically indicated) crane 500 through rst uid line 104 and second uid line 106. Fluid is allowed to ow from inlet 110 via (directional) regulator 152 to outlet 114 and regulator valve 120 is in a closed position and, as such, inoperative. Flow is also directed through second uid line 106. Similarly, ow ofuid through valves 154 and 156 is restricted as these are also closed. When constant tensioning system is transferred from the deploymentmode (gure 3) to the CT- mode (gures 4, 5), regulatorvalve 120becomes operative. The regulatorpressure foropening regulator valve 120 is applied through CT-pressure line 122 that is fed from CT-pressure line inlet 124. When the CT-mode is active and a (not shown) tender rises on a wave, constant tensioning system 102 will be in rise mode. In rise mode, the cable to which the tender is connected is reeled in and the valves 154 and 156 connected to CT-pressure line 122 are opened, whereas regulator valve 120 remains closed to allow the cable to be reeled in under the constant pressure on the cable that exceeds the weight ofthe tender at that time. Ifthe wave motion changes from rising to descending, the tender will descent as well. At that moment, constant tensioning system 102 will switch from rise mode to descentmode, because the force on the cable to which the tender is suspended is higherthan the hydraulic (constant) pressure in constant tensioning system 2 and the tender will lower (i.e. descent with the wave). When constant tensioning system 2 is in descentmode, the pressure in third conduit 108 on the side ofrst conduit 104 exceeds the regulator pressure exerted on regulator valve 120 applied through CT-pressure line 122, causing regulator valve to switch to an open position. This allows uid to ow from rst conduit 104 to second conduit 106. In the descent mode, both valves 154, 156 to drain line 158 and drain outlet 160 also remain open. In an example oftender deployment system 500 (see gure 6), tender deployment system 500 comprises constant tensioning system 502 ofwhich rst output 514 is uidly connected to crane drive 560 by means of rst uid conduit 504. Second output 518 is uid connected to crane drive 560 by means of second uid conduit 506. First uid conduit 504 and second uid conduit 506 are, on the respective inlets 510, 516 connected to hydraulic uid supply 512, whichmay in turn be connected to 13 power source 562, such as electric motor(s) 562, via one ormore lines 564, 566, 568. Hydraulic uid supply 512 is further uidly connected to CT-pressure line inlet 524 by means ofuid line 570. Crane drive 560 comprises winch 572 that is connected to (or integral part of) crane 574. In this example, crane 574 is extendable crane 574 that comprises extendable beam 578 which can be extended using hydraulic cylinder 580 that is part of crane 574. The rate of extension can be measured using extension sensor 582, which in this example is provided on beam 758. Beam 574 is further provided with cable 584 and hook 586 for suspending a (non shown tender). Crane 574, in particular hydraulic cylinder 580 ofbeam 578 is in this example operated using hydraulic supply 512 via hydraulic lines 588 and 590. An intermediate regulator 592, switch 592 or other component 592 may be positioned between hydraulic cylinder 580 and hydraulic supply 512. Further, uid drain or container 594 is also schematically shown. In an example, method 1000 for compensating wave motion ofa tender during deployment of retrieval thereof, method 1000 comprises the step of providing 1002 a tender deployment system comprising a constant tensioning system according to the disclosure or providing 1002 a tender deployment system according to the disclosure. Method 1000 relates to both deploying or lowering 1004 ofa tender to the water as well as to retrieving 1006 a tender from the water. The steps of method 1000 relating to deploying 1004 a tender comprise the base steps of lowering 1008 a tender into the water using the deployment system, activating 1010 the constant tensioning mode of the tender deployment system and releasing 1012 the tender from the tender deployment system. The step ofactivating 1008 results in providing a constant pressure, by the constant tensioning system, to each winch associated with the one ormore cranes to achieve a constant line pull on each cable associated with the one ormore cranes. The steps relating to retrieving 1006 a tender from the water comprise the base steps of connecting 1014 a tender to be retrieved to a cable ofthe tender deployment system, activating 1016 the constant tensioning mode ofthe tender deployment system, and hoisting 1018 the tender from the water. The step ofactivating 1016 results in providing a constant pressure, by the constant tensioning system, to each winch associated with the one or more cranes to achieve a constant line pull on each cable associated with the one ormore cranes. The step ofactivating 1010, 1016 may comprise one ormore ofthe following substeps.A rst substep is keeping 1020 the regulator valve in a closed position if the tender that is operatively connected to the constant tensioning system is moving upwards on a wave. A second substep, which precedes or follows the step ofkeeping 1020, is the step ofswitching 1022 the regulator valve from the closed position to the open position upon the tendermoving downward on a wave, therewith allowing hydraulic uid to ow from the rst to the second conduit to maintain a constant line pull to a cable connected to the tender. Method 1000 also comprises, due to the continuous wave motion, repeating 14 1024 abovementioned steps during wave motion ofthe tender. Further optionally, method 1000 may comprise the step ofdeactivating 1026 the constant tensioning system. Additionally or alternatively, the step of activating 1010, 1016 may also comprise the step transferring 1028 the constant tensioning system fromthe deploymentmode to the CT-mode, preferably based on user input. Further additionally or alternatively, the optional step of deactivating 1026 the constant tensioning system may comprise transferring 1030 the constant tensioning system from the CT-mode to the deploymentmode, preferably based on user input. Even further optionally, which may be additionally or alternatively, method 1000 may comprises the step of transferring 1032, using the safety release unit, the constant tensioning system from the CT-mode to the deployment mode if the predetermined condition is met. Also optionally, which may be additionally or alternatively, method 1000 may comprise the step of providing 1034 and / or adjusting 1034 the predetermined regulator pressure, wherein the predetermined regulator pressure is preferably adapted to a weight of a tender to be operatively connected to the constant tensioning system. Further also additionally or alternatively, method 1000 may comprise the step of extending 1036 the extendable beam ofone or more cranes ofthe tender deployment system to a fully extended state before engaging the constant tensioning mode. This step is thus performed, in this example, prior to the step of activating 1010, 1018 and, when lowering, preferably also before the step of lowering 1008. The present invention is by no means limited to the above described preferred embodiments and / or experiments thereof. The rights sought are dened by the following claims within the scope of which many modications can be envisaged. 15 CLAUSES 1. Constant tensioning system congured for wave motion compensation ofa tender in a tender deployment system, the constant tensioning system comprising: - a rst conduit having an outlet that is operatively connectable to at least one crane, and preferably to awinch thereof, - a second conduit having an outlet that is operatively connectable to the at least one crane, and preferably to awinch thereof, - athird conduitthat extends betweenthe rst conduitandthe second conduitand is uidly connected to both, and - a regulator valve that is positioned in the third conduit and that is switchable between a closed position, in which a uid ow between the rst conduit and the second conduit is substantially prevented, and an open position in which the rst conduit and the second conduit are uidly connected to each otherto provide and / ormaintain a constant pressure between the rst and second conduit. 2. Constant tensioning system according to clause 1, wherein the regulator valve is a normally closed valve that, during operation, is congured to switch to the open position when the pressure in the rst conduit exceeds a predetermined regulator pressure. 3. Constant tensioning system according to clause 2, further comprising a CT-pressure conduit that is connected to the regulator valve and that is congured to provide the predetermined regulator pressure to the regulator valve. 4. Constanttensioning system according to any one ofthe preceding clauses, whereinthe regulator valve is a pilot-operated balanced piston reliefvalve. 5. Constant tensioning system according to any one ofthe preceding clauses, wherein the constant tensioning system has a deploymentmode, in which the regulator valve is inoperative, and a CT-mode in which the regulator valve is switchable between the open and the closed position such that the constant pressure is provided and / or maintained. 6. Constant tensioning system according to clause 5, further comprising an enable valve that is operable to switch the constant tensioning system between the deployment mode and the constant tensioning mode. 16 7. Constant tensioning system according to clause 5 or 6, further comprising a safety release unit that is congured to transfer the constant tensioning system from the CT-mode to the deploymentmode based on one ormore predetermined conditions. 8. Constant tensioning system according to clause 7, wherein the one or more predetermined conditions comprise one ormore of: - the at least one associated crane being in an unextended state, wherein the unextended state comprises abeam extension ofless than 95% ofthemaximum extension ofan extendable beam of the at least one associated crane; and / or user input comprising a hoist or lower command congured to respectively hoist or lower a tender connected to a cable ofthe at least one associated crane. 9. Constant tensioning system according to any one ofthe preceding clauses, wherein the rst and the second conduit each further comprise an inlet side that is connectable to a hydraulic power supply. 10. Constant tensioning system according to any one ofthe preceding clauses, further comprising one or more: - a rst conduit pressure sensor that is operatively connected to the rst conduit and that is congured to measure a pressure in the rst conduit, and / or - a second conduit pressure sensor that is operatively connected to the second conduit and that is congured to measure a pressure in the second conduit. 11. Constant tensioning system according to any one ofthe preceding clauses, further comprising a control unit that: - when dependent on clause 7, is congured to control the safety release unit based on data relating to the predetermined condition, and / or - when dependenton clause 10, is operatively connected to the rst and / or the second pressure sensor and is congured to receive pressure data therefrom. 12. Tender deployment system comprising: - a constant tensioning system according to any one ofthe preceding clauses; - at least one tender crane comprising: - at least one winch that is operatively coupled to the constant tensioning system, preferably to the outlets ofthe rst and the second conduits, for receiving hydraulic uid therefrom, and - a beam, preferably an extendable and / or hingeable beam, that is congured to support a cable to which atender is connectable, 17 - at least one hydraulic power supply that is operatively coupled to the constant tensioning system, preferably to the inlet side thereof, for supplying hydraulic uid to the constant tensioning system and the at least one tender crane. 13. Tender deployment system according to clause 12, further comprising a controller that is congured to, based on a user input, transfer the system between one of: - a switched-offmode in which the tender deployment system is inactive, and - an operational mode in which the tender deployment system is active, wherein the operationalmode comprises: - a deployment mode in which a cable ofthe at least one tender crane is hoistable or lowerable and the CT-system is inoperative, and - aCT-mode in which the regulator valve ofthe constanttensioning system is switchable between the open and the closed position such that the constant pressure is provided and / or maintained to the at least one winch such that a constant line pull on the cable is achieved. 14. Tender deployment system according to clause 12 or 13, wherein the at least one tender crane comprises at least one extendable beam, wherein the extendable beam has an unextended state and a fully extended state in which an extension ofthe beam is between 95% and up to and including 100% of itsmaximum extension range. 15. Tender deployment system according to clause 13, when dependent on clause 7, wherein the safety release system is congured to transfer the system from the constant tensioning mode to the deploymentmode ifthe extendable beam is transferred from the extended state to the unextended state. 16. Tender deployment system according to any one ofthe clauses 12 to 13, wherein themaximum load capacity (SWL) ofthe at least one crane is adapted to the weight ofthe tender, such that the tender weight is between 30% and 90% ofthe SWL, preferably between 40% and 85% ofthe SWL and more preferably between45% and 80% ofthe SWL. 17. Method for compensating wave motion ofa tender during deployment ofretrieval thereof, the method comprising the step ofproviding atender deployment system comprising a constant tensioning system according to any one ofthe clauses 1 to 11 or a tender deployment system according to any one ofthe clauses 12 to 16, and further comprising, during a deployment, the steps of: - lowering a tender into the water using the deployment system; - activating the constant tensioning mode of the tender deployment system, wherein the constant tensioning mode comprises providing a constant pressure to each winch associated with the one or 18 more cranes to achieve a constant line pull on each cable associated with the one ormore cranes, and - releasing the tender from the tender deployment system; or further comprising, during a retrieval, the steps of: - connecting a tender to be retrieved to a cable ofthe tender deployment system, - activating the constant tensioning mode of the tender deployment system, wherein the constant tensioning mode comprises providing a constant pressure to each winch associated with the one or more cranes to achieve a constant line pull on each cable associated with the one ormore cranes, and - hoisting the tender from the water. 18. Method according to clause 17, wherein the step ofactivating comprises the steps of: - keeping the regulator valve in a closed position ifthe tender that is operatively connected to the constant tensioning system is moving upwards on a wave; - switching the regulator valve from the closed position to the open position upon the tendermoving downward on awave, therewith allowing hydraulic uid to ow from the rst to the second conduit to maintain a constant line pull to a cable connected to the tender, and - optionally repeating abovementioned steps during wave motion ofthe tender, and - further optionally deactivating the constant tensioning system. 19. Method according to clause 17 or 18, wherein: - the step ofactivating the constant tensioning system comprises transferring the constant tensioning system from the deploymentmode to the CT-mode, preferably based on user input, and / or - when dependent on clause 18, the step of deactivating the constant tensioning system comprises transferring the constant tensioning system from the CT-mode to the deploymentmode, preferably based on user input. 20. Method according to any one ofthe clauses 17 to 19, further comprising one or more ofthe steps of: - transferring, using the safety release unit, the constant tensioning system from the CT-mode to the deploymentmode ifthe predetermined condition is met; and / or - providing and / or adjusting the predetermined regulator pressure, wherein the predetermined regulator pressure is preferably adapted to a weight ofa tender to be operatively connected to the constant tensioning system. 19 21. Method according to any one of the clauses 17 to 20, further comprising extending the extendablebeam ofone ormore cranes ofthe tender deployment system to a fully extended state before engaging the constant tensioning mode. 20

Claims

1. Constant traction system designed to compensate for the wave motion of a tender in a tender deployment and retraction system; the constant traction system comprising: - a primary pipe fitted with an outlet that can be functionally connected to at least one tap; and preferably the winch thereof; - a second pipe fitted with an outlet that can be functionally connected to at least one crane; and preferably its winch; - a third pipe extending between the first and the second pipe and which in liquid connection with both; and - a control valve installed in the third line that can be switched between a closed position in which a fluid flow between the first pipe and the second pipe is essentially occur; and an open position in which the first pipe and the second pipe are in fluid connection together stands for providing and / or maintaining a constant pressure between the first and the second line.

2. Constant traction system according to conclusion l; where the control valve is a normally closed valve is that; in operation; is configured to switch to the open position if the pressure in the first line a exceeds predetermined regulatory burden.

3. Constant traction system in accordance with claim 2; further comprising a CT pressure line that is connected to the control valve and which is designed to provide a predetermined control pressure at the control valve.

4. Constant traction system according to one of the preceding claims; where the control valve a is a pressure-regulated balanced pressure reducing valve.

5. Constant traction system according to one of the preceding claims; where the system a has an expansion and retraction mode in which the control valve is inactive; and has a constant pressure mode in which the control valve is switchable between the open and closed positions such that the constant pressure is provided and / or retained.

6. Constant traction system according to claim 5; further comprising an activation valve which is configured for switching the constant draft system between extension and retraction modes and the constant pressure mode. 2 1 7. Constant traction system in accordance with claim 5 or 6; further comprising a safety device unit designed for switching the constant tensile force system of the expansion and input mode to constant pressure mode based on one or more predetermined conditions.

8. Constant traction system according to one of the preceding claims; where one or more predetermined conditions comprise one or more of: - that at least one crane is in a non-extended position; whereby the non- extended position an arm extension of less than 95% of the maximum extendability of an extendable arm of the has at least one crane; and / or - a user input comprising a he instruction or four instruction configured for the respectively hoisting or lowering a tender connected to a cable of at least one associated faucet.

9. Constant traction system according to one of the preceding claims; where the first and the second pipe each further have an inlet side that can be connected to a hydraulic power source.

10. Constant traction system according to one of the preceding claims; further comprising one or more from: - a first line pressure sensor that is operationally connected to the first line and that is configured for measuring a pressure in the first line; and / or - a second line pressure sensor that is operationally connected to the second line and that is configured for measuring a pressure in the second pipe.

11. Constant traction system according to one of the preceding claims; further comprising a control unit that: - when dependent on conclusion 7; is structured for the based on the data that relates to the control a predetermined condition of the safety state unit; and / or - when dependent on conclusion; actively connected with the first and / or the second pipe pressure sensor and is configured to receive pressure data from it.

12. Tender staking and delivery system comprising: - a constant traction system according to one of the preceding conclusions; - comprising at least one tender crane: - at least one winch operationally connected to the constant pull system; preferably with the outlets of the first and second lines; for receiving hydraulics from them liquid; and 22 - an arm, preferably an extendable or hinged arm; which is designed to support a cable to which a tender can be connected; - at least one hydraulic power source operationally connected to the constant traction system; preferably an inlet side thereof; for supplying hydraulic fluid to the constant traction system and at least one tender crane.

13. Tender issuing and input system in accordance with claim 12, further comprising a control system that is configured to switch the system between one of the following based on user input: - a disabled state in which the tender issuing and submission system is inactive; - an operating mode in which the tender issuing and submission system is active; where the operating mode includes: - an extension and retraction mode in which a cable of the at least one tender crane is hoistable / reversible is and the constant traction system is not active; and - a constant draft mode in which the control valve of the constant draft system is switchable between an open and a closed state so that the constant pressure at the at least a winch is provided and / or maintained such that a constant cable tension is applied to the cable reaches.

14. Tender placement and supply system in accordance with claim 12 or 13; where the at least one tender cranes comprising at least one extendable arm; where the extendable arm has a non-extended position and has a fully extended position; in which the arm is in the fully extended position extended within a range of 95% and up to 100% of the maximum possible extension.

15. Tender outsourcing and supply system in accordance with Claim 13; when dependent on Claim 7; where the safety device system is configured for switching the constant system pull force mode to extension and retraction mode when the extendable arm is transferred from the fully extended position to the non-extended position.

16. Tender designation and supply system in accordance with one of Claims 12 to 13; whereby the maximum load capacity (SWL) of at least one crane is adapted to the weight of the tender; such that the tender weight is between 30% and 90% of the SWL; preferably between 40% and 85% of the SWL is; and preferably is between 45% and 80% of the SWL.

17. Procedure for compensating wave motion of a tender during launching or removing it from the water; the procedure comprising the step of providing a tender for the deployment and insertion system comprising a constant traction system in accordance with one of claims 1 to 11 or a tendering and supply system in accordance with one of claims 12 to 16; and 23 further comprising, during the launching; the steps of: - lowering a tender into the water using the tender deployment and retrieval system; - activating the constant pull mode for each winch associated with the one or more tender cranes to achieve a constant cable tension on each cable that is associated with the one or more tender cranes; and - detaching the tender from the tender issuing and submission system; and / or further comprising; during removal from the water; the steps of: - connecting the tender to be lifted out of the water to a cable of the tender launching and input system; - activating the constant pull mode of the tender deployment and retraction system; whereby the constant pull mode providing a constant pressure to each winch that is associated with the one or more valves for providing a constant cable tension on any cable that is associated with the one or more taps; and - hoisting the tender out of the water.

18. Method according to conclusion 17; where the step of activation comprises the steps of: - keeping the control valve in the closed position when operating on the constant traction system connected tender moves upwards on a wave; - switching the control valve from the closed position to the open position when the tender is downwards moves on a wave; thereby allowing the hydraulic fluid from the first to the second flow in order to maintain a constant cable tension on a cable connected to the tender cable; and - optionally repeating the above-mentioned steps during the movement of a tender on the waves; and - furthermore, optionally deactivating the constant traction system.

19. Method in accordance with claim 17 or 18; whereby: - the step of activating the constant draft system and the extension and retraction mode transferring the constant traction system to the constant traction mode includes; at preference based on user input; and / or - depending on conclusion 18; the step of deactivating the constant draft system from constant draft mode to extension and insertion mode involves transferring the constant traction system; preferably based on user input.

20. Method of working in accordance with one of claims 17 to 19; further comprising one or more of the steps of: 24 - transferring the constant traction system using the safety device from the constant tension mode to the extension and insertion mode as the predefined condition has been reached; and / or - providing and / or adjusting the predetermined control valve pressure; whereby for the predetermined specific control valve pressure is preferably adjusted to the weight of an operating tender connected to the constant tensile force system.

21. Method of working in accordance with one of the preceding claims 17 to 20; further comprising the extension of an extendable arm of one or more cranes of the tender outrigger and insertion system to a fully extended position for switching on the constant traction mode. 25

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