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WO1998038082A1 - Procede permettant d'empecher le depot de salissures larvaires sur la coque d'un navire - Google Patents

Procede permettant d'empecher le depot de salissures larvaires sur la coque d'un navire Download PDF

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Publication number
WO1998038082A1
WO1998038082A1 PCT/GB1998/000535 GB9800535W WO9838082A1 WO 1998038082 A1 WO1998038082 A1 WO 1998038082A1 GB 9800535 W GB9800535 W GB 9800535W WO 9838082 A1 WO9838082 A1 WO 9838082A1
Authority
WO
WIPO (PCT)
Prior art keywords
transducers
transducer
phase
hull
time
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.)
Ceased
Application number
PCT/GB1998/000535
Other languages
English (en)
Inventor
Lars Steinar ØSTLIE
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
OET HOLDINGS PLC
Original Assignee
OET HOLDINGS PLC
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by OET HOLDINGS PLC filed Critical OET HOLDINGS PLC
Priority to AU62997/98A priority Critical patent/AU6299798A/en
Publication of WO1998038082A1 publication Critical patent/WO1998038082A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B59/00—Hull protection specially adapted for vessels; Cleaning devices specially adapted for vessels
    • B63B59/04—Preventing hull fouling

Definitions

  • the present invention concerns a method and a means for preventing deposition of larvae on a ship's hull using mechanical vibrations.
  • it is of interest to fight the so-called "barnacle larvae", but other types of marine biological fouling can also be fought using the method and the means in accordance with the invention.
  • vibration systems using low frequency oscillations are capable of providing an effect which inhibits fouling. Because one has previously not realized which physical processes are of importance in connection with prevention of fouling when using low frequency vibrations, these systems have resulted in a relatively poor effect. Is has often been supposed that it is the actual sound pressure which is of importance, in the same manner as in the ultrasound case, but lately more clarity has been achieved regarding the important physical processes. It has turned out that the marine organisms of most interest, namely certain larvae in the size range 0.15-0.4mm, feel uncomfortable with strong water particle movement in the infrasonic vibration range 20- 60 Hz, i.e. when water particles move with amplitudes of ⁇ 0.1 -0.2mm and at a particle maximum velocity which lies above a certain lower limit. Under such conditions, these larvae will try to avoid settling down on the ship's side.
  • the present invention is provided to achieve just this enhanced effect, and to avoid completely standing nodes in any region on the hull.
  • Fig. 1 shows a simplified diagram curve forms for the pressure signals in the water for two transducers in a pair, as a function of time, and additionally a synchronous disclosure of the motions of a swimming larva,
  • Fig. 2 shows the same curve forms as in Fig. 1, however with broken time axes to render the curve forms and the shifts therebetween in a more realistic fashion
  • Fig. 3 shows a diagram of instantaneous pressure conditions in the water just outside a ship's hull in the region adjacent to transducers in a pair, the transducers at the moment oscillating in phase
  • Fig. 4 shows a corresponding diagram to Fig. 3, in which the transducers " at the moment oscillate in opposite phases.
  • the prior art in particular the art disclosed in NO 170.320 which is mentioned above, is based on a type of acoustics which has an effect on a larva approaching the hull, using one single negative stimulus.
  • two negative stimuli are used against the larva, first a stimulus with a combination of low frequency velocity and pressure progressions which influence the deposition pattern of the larvae, and in addition a pressure pulse is emitted in which all oscillators operate in phase, with another type of signal.
  • This last signal affects the swimming pattern of the larvae in such a manner that during a short time lapse (about 0.5 seconds) they stop swimming due to a received pressure pulse with instantaneous frequency in the range 100 Hz-1 kHz.
  • Fig. 1 is shown a diagram containing the curve forms achieved in the water outside two single transducers, SI and S2, a time axis running toward the right side.
  • the signals which are sent to every second transducer sitting in one or two rows on the inside of the ship's hull, are actually signals consisting of synthesized forms, such as shown in the upper left circle in Fig. 1.
  • One transducer, SI, in a pair receives the simplest type- of signal, which in the water results in pressure conditions substantially like a square pulse, in the example indicated in curve SI as a "27.5 Hz signal".
  • the frequency is not necessarily 27.5 Hz, it is preferably within the range 10-50 Hz.
  • the square signal is run for a period of about 5 seconds, and is then succeeded by a different type of signal, indicated as a "27.5 Hz burr".
  • This is a signal in which there is still in essence used square pulses, however, each pulse is so short as to appear as a straight line or a spike in this diagram.
  • the spacing between spikes in this diagram is somewhat erroneous, importance has here only been attached to showing that a different type of signal appears. It is referred to Fig. 2 regarding a more correct showing of the time relations.
  • the "burr" signal is held for a period of about 0.5 seconds, and is then succeeded by the "main signal” which once more lasts for about 4 seconds, and so on.
  • the "burr" signal is shown in closer detail, however still with a somewhat incorrect time ratio, since the spacing (T) between the two double pulses is in reality considerably larger in the example shown.
  • the fundamental frequency i.e. the frequency of occurring double pulses in the "burr” signal given by a frequency 27.5 Hz in this case, which corresponds to a period (T) of 33.4 milliseconds.
  • the duty cycle of the "burr” signal is low, as indicated in the example, a full double pulse takes 1/32 of the complete period (T). This gives a duty cycle of about 3%.
  • the instantaneous frequency attached to the actual double pulse is about 880 Hz in the case shown.
  • the S2 curve is superficially quite similar to the SI curve, and similarity actually exists in the "burr" periods, in which both transducers SI an S2 are driven in full synchronism and quite similarly.
  • the S2 signal deviates from SI in the following manner:
  • S2 is a 27.5 Hz square signal output from the transducer, however in this case a phase sweep is applied in relation to the
  • the S2 square wave may then have a fundamental frequency 27.4 Hz.
  • Fig. 2 shows the same two signals output from transducers SI and S2, however with gaps several places in the time axis in order to present genuine curve forms as a function of time along the axis. Besides, there is an enlargement in the lower part of the figure, corresponding to the upper right circle in Fig. 1, however with a more correct indication of the spacing between two double pulses. In Fig. 2 it is easier to see that the "main signals" S 1 and S2 indicated here in the same example embodiment as in Fig.
  • the "burr" signal which in this example lasts for 0.5 seconds, consists also in this scale of quite short spikes, and in order to show more clearly how these spikes actually appear, an enlargement has been entered below the two curve diagrams. It appears from the enlargement that the "burr” signal, which as previously stated is synchronous and equal for the two transducers of the pair, is a square pulse signal also, however with a low duty cycle. During the half second at disposal, 16 such double pulses are accommodated, see the indication between the S 1 and the S2 curves. At a time of about 4.5 seconds, the "main signal" is started again, and a sweep
  • Fig. 1 it appears in the lower part of the figure how the "burr" signal affects a swimming larva.
  • this signal starts, the larva is stunned, and it stops swimming.
  • the swimming pattern of the larva is interrupted repeatedly, and this is an effect in addition to the effect of the "main signal” which is adapted to provide a strong particle movement in the water just outside the hull, and which by means of the sweep arrangement constantly shifts the areas where pressure, respectively particle velocity, are at a maximum.
  • Fig. 3 is shown a diagram of the pressure conditions in the water outside the ship's hull near two transducers A and B in a pair, in a case where the two transducers are driven in phase, i.e. like in a "burr" period.
  • the ship's hull is represented in the figure as the elongated line through A and B, and the water is situated above this line.
  • Midway between A and B there is a perpendicular line, along which in the case shown there is no phase difference between signals from A and B, and along which maximum pressure is found.
  • Corresponding maximum pressures are found along the other curved, emphasised lines on both sides of the perpendicular mid-line.
  • a phase different of 1.4° is found between every such pressure maximum line, and this- means that a gliding phase shift introduced between signals from A and B will shift the pattern successively laterally in one or the other direction in such a manner that when a phase difference of 1.4° is achieved, that pattern will overlap the original pattern.
  • the maximum pressure lines will so to speak sweep the whole water area outside the hull, and adjacent to the hull.
  • FIG. 4 An "opposite" case is shown in Fig. 4.
  • the starting point is an inverse phase operation of the two transducers A and B, and the emphasized lines then indicate surfaces with minimum pressure.
  • This means of course then that both maximum and minimum pressures, as well as maximum and minimum particle velocities in the water can be swept and moved in the area outside and adjacent to the ship's hull, by means of an operation as discussed above.
  • the arrows indicated in the water in Fig. 4 state particle motion in the case of opposing phases.
  • a phase difference of 1.4° provides a repetition of the pattern, and thus such a phase difference is the minimum usable phase difference for making a desired movement of the pattern in the water.
  • a phase sweep may be much larger than this, compare the example of Figs. 1 and 2, where a sweep is made through a range of 180°. It should also be noted that in Fig. 1 it is stated in the upper left circle, just that 1.4° is added or subtracted for each cycle of the S2 signal, in order to change from 90° phase difference to 270° phase difference.
  • the sweep during the "main signal" period must not necessarily be made in a gliding and regular manner, the sweep can also be introduced in a stepwise fashion, so that a constant phase difference is held through a lower number of cycles for S2, but so that a desired sweep from the beginning to the end of the "main signal" period is achieved anyway.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • Ocean & Marine Engineering (AREA)
  • Catching Or Destruction (AREA)

Abstract

On empêche le dépôt de larves sur la coque d'un navire en mettant en oeuvre des transducteurs basse fréquence montés par paires sur la partie interne de la coque et émettant des vibrations dans l'eau adjacente à ladite coque. Deux types de signal alterné peuvent être utilisés pour réaliser le procédé. Dans un type de signal, la phase d'un transducteur dans chaque paire est balayée par rapport au signal de la phase constante de l'autre transducteur, en vue de créer des positions maximales de pression progressive dans l'eau, le long de la coque. Dans l'autre type de signal, les deux transducteurs dans chaque paire sont actionnés de manière synchrone et égale par des pulsions à faible cycle de travail.
PCT/GB1998/000535 1997-02-28 1998-02-20 Procede permettant d'empecher le depot de salissures larvaires sur la coque d'un navire Ceased WO1998038082A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU62997/98A AU6299798A (en) 1997-02-28 1998-02-20 Preventing deposition of fouling larvae on a ship's hull

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NO970947A NO304506B1 (no) 1997-02-28 1997-02-28 FremgangsmÕte og anordning for Õ forhindre avsetning av begroingslarver pÕ skipsskrog
NO970947 1997-02-28

Publications (1)

Publication Number Publication Date
WO1998038082A1 true WO1998038082A1 (fr) 1998-09-03

Family

ID=19900441

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1998/000535 Ceased WO1998038082A1 (fr) 1997-02-28 1998-02-20 Procede permettant d'empecher le depot de salissures larvaires sur la coque d'un navire

Country Status (4)

Country Link
AU (1) AU6299798A (fr)
GB (1) GB2327211A (fr)
NO (1) NO304506B1 (fr)
WO (1) WO1998038082A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006045161A1 (fr) * 2004-10-29 2006-05-04 Watertech Holdings Ltd Systeme antisalissure marin utilisant des ultrasons
WO2009150437A3 (fr) * 2008-06-14 2010-08-26 Blue & Green Marine Limited Dispositif antisalissure
EP2527050A1 (fr) 2011-05-26 2012-11-28 Skånemejerier AB Nouveau procédé

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO82676C (fr) 1950-03-01
US4058075A (en) * 1975-03-21 1977-11-15 Ralph M. Guito, Jr. Marine life growth inhibitor device
GB2040314A (en) * 1978-12-20 1980-08-28 Soyuzny Z Mekh Khim Ochistke K Protecting objects immersed in aqueous medium against fouling with microorganisms
FR2603016A1 (fr) * 1986-08-25 1988-02-26 Treboz Michel Dispositif tres basse frequence pour l'inhibition de la souillure des coques de navires par les mollusques marins
WO1990013474A1 (fr) * 1989-05-12 1990-11-15 Infrawave Technology A.S Procede et systeme de protection contre la salissure biologique marine d'une carene ou autre edifice immerge
NO168513C (no) 1987-08-07 1992-03-04 Infrawave Tech As Fremgangsmaate og en anordning for aa hindre begroing paa flater som er utsatt for innvirkning fra sjoevann.
US5143011A (en) * 1991-02-05 1992-09-01 Stephen Rabbette Method and apparatus for inhibiting barnacle growth on boats
JPH08196163A (ja) * 1995-01-24 1996-08-06 Hitachi Zosen Corp 海生生物付着防止装置

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO82676C (fr) 1950-03-01
US4058075A (en) * 1975-03-21 1977-11-15 Ralph M. Guito, Jr. Marine life growth inhibitor device
GB2040314A (en) * 1978-12-20 1980-08-28 Soyuzny Z Mekh Khim Ochistke K Protecting objects immersed in aqueous medium against fouling with microorganisms
FR2603016A1 (fr) * 1986-08-25 1988-02-26 Treboz Michel Dispositif tres basse frequence pour l'inhibition de la souillure des coques de navires par les mollusques marins
NO168513C (no) 1987-08-07 1992-03-04 Infrawave Tech As Fremgangsmaate og en anordning for aa hindre begroing paa flater som er utsatt for innvirkning fra sjoevann.
WO1990013474A1 (fr) * 1989-05-12 1990-11-15 Infrawave Technology A.S Procede et systeme de protection contre la salissure biologique marine d'une carene ou autre edifice immerge
NO170320C (no) 1989-05-12 1992-10-07 Infrawave Tech As Fremgangsmaate og system for motvirking av marinbiologisk begroing paa skipsskrog eller andre neddykkede konstruksjoner
US5143011A (en) * 1991-02-05 1992-09-01 Stephen Rabbette Method and apparatus for inhibiting barnacle growth on boats
JPH08196163A (ja) * 1995-01-24 1996-08-06 Hitachi Zosen Corp 海生生物付着防止装置

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 96, no. 12 26 December 1996 (1996-12-26) *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006045161A1 (fr) * 2004-10-29 2006-05-04 Watertech Holdings Ltd Systeme antisalissure marin utilisant des ultrasons
WO2009150437A3 (fr) * 2008-06-14 2010-08-26 Blue & Green Marine Limited Dispositif antisalissure
WO2009150436A3 (fr) * 2008-06-14 2010-08-26 Blue & Green Marine Limited Dispositif antisalissure
EP2527050A1 (fr) 2011-05-26 2012-11-28 Skånemejerier AB Nouveau procédé
WO2012160185A2 (fr) 2011-05-26 2012-11-29 Skånemejerier Ab Nouveau procédé

Also Published As

Publication number Publication date
GB9803499D0 (en) 1998-04-15
AU6299798A (en) 1998-09-18
GB2327211A (en) 1999-01-20
NO970947D0 (no) 1997-02-28
NO970947L (no) 1998-08-31
NO304506B1 (no) 1999-01-04

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