RU2626152C1 - Device for protection of marine stationary construction from drifting ice or ice coating - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: device for protection of the offshore stationary construction 1 from the drifting ice 2 which is located at a distance from the offshore stationary construction 1 is a high-frequency energy radiator connected electrically to a source of converting electric power to ultrahigh-frequency energy. The ultrasonic radiators 6 are used as the radiators of ultrahigh-frequency energy, and the device is equipped with a ring-shaped enclosure of a cylinder-shaped form 3, made of reinforced concrete, which is immersed in seawater for part of its height, which surrounds the marine stationary construction 1. On the outer surface of the side wall of the ring-shaped enclosure 3, the radiators 6, made as ultrasonic, are located. The ring-shaped enclosure 3 is made of interconnected modules, each of which is a part of the wall of the ring-shaped enclosure, which is rotatably mounted around a permanently installed marine construction.

EFFECT: reduction of energy consumption and labour of destruction of ice and increase in productivity when creating the opportunity to defragment the ice cover, while preserving the ice area around the drilling rig.

2 dwg

Description

The invention relates to the field of mining of the continental shelf of the freezing seas and is intended to protect the supports of stationary marine engineering structures from external ice exposure, in particular, drifting ice in the Arctic and subarctic regions where ice is present. The invention allows to solve the problem of protecting the Arctic drilling platform from drifting ice, which ensures year-round drilling of wells mounted directly at sea.

The term “stationary offshore engineering structure” is understood to mean a drilling system for drilling offshore wells and / or performing other work on the platform at numerous consecutive well locations in a “subarctic” climate. The specified system should provide resistance to the load from icing when the system is located at the well location and when ice is present in the subarctic zone.

“Subarctic” marine conditions are characterized by annual seasonal ice occurrences. Climatic conditions in this zone are less severe than in the “upper” Arctic, where ice can be present year-round. However, even the subarctic climate presents challenges when using standard offshore drilling systems. Standard offshore drilling systems are primarily designed with resistance to stress from waves, winds and currents and, where necessary, earthquakes, but not from ice. In a subarctic climate, the total or total load due to the ice compression of the offshore drilling system may be of a higher order than the load associated with waves, winds and currents. Thus, the design of a conventional offshore drilling platform is not able to withstand significantly higher loads in the subarctic climate.

Ice compression can also create high pressures in small, localized areas of any piece of drilling equipment. In a conventional offshore drilling system, such high local loads would damage unprotected elements of frame structures, since these elements are ordinary offshore platforms designed exclusively to resist wind, waves and currents.

The use of mechanical systems for the destruction of sea ice does not give the required effect, since any mechanical system is designed for certain loads and certain conditions in which its effectiveness and the possibility of functioning are manifested. But one can never predict in advance the magnitude of those high local loads that can be exerted by the sea ice cover or drifting ice floes. In this regard, developments have appeared on the use of electricity for the destruction of the ice structure and bringing this structure to a state that is easily destroyed using mechanical means.

So, according to the decision in RU 2231593, ЕОВВ 15/02, publ. 06/27/2004, it is proposed to make holes in the ice sheet for subsequent force impact on the ice sheet. Through the holes under the ice, electrodes are lowered into the water. Power action is created using high-voltage electric discharges supplied alternately between pairs of electrodes. When performing an odd number of holes located at an equal distance from each other, electrical discharges are alternately supplied between the even electrodes and adjacent odd ones.

The disadvantage of this method lies in its complexity, which consists in the need to drill holes in the ice cover with a certain step and order of location, placement of electrodes, which must be connected to the control system and power system. This method of destruction can work well in a small local zone, but with the expansion of the area of the zone, technical problems may arise in wiring, installation of electrodes, etc.

More promising are the development of the destruction of sea ice (or just ice or ice crust) using microwave energy.

For example, in RU 2465399, ЕОВВ 15/00, ЕОВВ 15/02, publ. 07/01/2010 a method for the destruction of sea ice is described, consisting of irradiating its thickness with microwave energy, which acts on a liquid contained in the form of capsules in the thickness of sea ice, while under the influence of this energy the liquid instantly evaporates and the formed liquid vapor, expanding, destroys by its pressure ice crystals. For this, a microwave generator is used to convert electricity to microwave energy, which is fed to the emitter through a waveguide. Microwave energy freely penetrates the ice and, acting on the liquid in capsules, instantly turns it into steam. The resulting high pressure, like an explosion, destroys ice crystals, weakening its structure.

This patent does not specify the type of microwave energy. But, for example, in patent RU 2303097, ЕНН 5/10, Е01Н 5/12, publ. 07/20/2007 describes a device for cleaning ice from road and airfield coatings using microwave energy.

This device according to RU 2303097 is a chassis of a self-propelled scraper on which an electric generator (driven by an internal combustion engine) is installed, to which a microwave energy generator is connected. A microwave emitter mounted on a trolley with four support wheels 10 is mounted behind the driving wheels of the self-propelled scraper chassis. First, the main internal combustion engine of the scraper and then the internal combustion engine with the generator are launched and the microwave energy generator is installed on the chassis together with the microwave energy emitter (with a power of 180 kW). The emitter of microwave energy 6, the energy flow is directed to the ice surface of the road surface in strips with a direction parallel to the movement of the device. The directed energy raises the temperature of the ice mass to the state of melting and loss of adhesion to the road surface. In a weakened state and in case of loss of adhesion with the road surface, ice gets under the spur rollers and is ground.

Microwave as a radiation source is also used in patent RU 2408760, E01H 5/10, publ. 01/10/2011, which describes a method of removing ice and ice from various surfaces based on the application of microwave radiation using a mobile unit including suspension units with a power unit and electrical connections. The method consists in installing a mounted radiator on a mobile installation, connecting microwave power to the power unit, bringing the radiator closer to the surface to be treated, turning on the microwave radiation generator, applying microwave radiation to the adhesion zone of the ice crust and the surface and heating it with directed microwave radiation, the molecular bond between the ice and the treated surface is weakened the most. In this case, warm air from the cooling system of the microwave klystron is supplied to the surface of the microwave radiation to the surface, the weakened crust is destroyed by mechanical action, or ice is transferred to the liquid phase and the liquid is sucked off using a pump.

From the same source, a device for protecting a marine stationary structure from drifting ice or ice cover is known, which is microwave energy emitters located at a distance from the marine stationary structure, which are connected electrically with a source of converting electricity to microwave energy. This decision is made as a prototype.

In the development of mounted microwave units can be used microwave technology used in such sectors of the economy as wood drying, food processing. In wood drying, powerful microwave devices (over 40-60 kW) are used, in the creation and production of which the country is at the forefront. Multi-cavity klystrons are ideally suited for use in equipment to remove ice and ice on roads, sidewalks and building elements. For klystrons, the longitudinal size of the collector is not related to the wavelength, therefore, at powers up to 10 kW, air cooling can be used. The use of air cooling is also preferable due to the fact that hot air is used for additional heating of the product. Widely used continuous klystrons have a power of 25-50 kW with an efficiency of 45-50% in the range of 2450 MHz, and the use of multi-beam klystrons will significantly increase the durability and power output in the short-wave range (12.5 cm) used to remove moisture.

These identified information sources reflect the state of the art today regarding the use of microwave energy such as microwave radiation to destroy ice in order to protect or clean the object.

Electromagnetic field, radiation exposure, ultrasonic waves High intensity electromagnetic fields in the high (HF) and ultrahigh (microwave) ranges (the microwave range includes electromagnetic waves starting from the frequency of 433, 920 MHz and higher) frequencies are quite widely used in many modern technological processes used in industry, medicine, science and technology, when effective volumetric heating of non-metallic materials is required, when conventional contact heating of such materials through thermal conductivity It proves ineffective. In the interaction of radio emission with ice, as with any other dielectric, the main process in the medium is dielectric heating, and when exposed to, as shown by experiments, fresh-water polycrystalline ice of a strong electromagnetic field (E-4 kV / cm, / = 40.68 MHz ) after 1.5–2 s, optical and mechanical homogeneity is violated, bulk water inclusions appear after 3-4 s, and after 7–8 s, the stage of intense cracking of the irradiated sample begins, which ends with complete decay into individual crystals. Energy absorption mainly occurs on the surface and grain boundaries, where there are quasi-liquid film inclusions. Liquid layers grow before the appearance of bulk water, while mechanical strength decreases. A powerful microwave electromagnetic field also has a strong effect on the structure and properties of sea salt ice. When absorbing a power of 0.25 W / cm, the compressive strength of ice is significantly reduced due to a rapid increase in temperature and intensive runoff of brine from the ice volume, resulting in a loose "honeycomb" structure that is easily amenable to mechanical stress. The effect of softening of ice is proportional to its salinity, since with its increase the specific absorption of microwave energy in sea ice increases. But upon melting, a film of water forms on the ice surface, which has a high dielectric constant and thereby “shields” the sample.

Thus, the use of microwave radiation is energy-consuming and requires appropriate equipment, which should function autonomously on the platform and power the emitters. This energetically overloads the functional equipment of the platform and leads to the energy inefficiency of using microwave systems to weaken the ice cover.

In addition, the use of such high-frequency radiation as microwave leads to a weakening of the structure of the ice cover due to dielectric heating, leading to a violation of optical and mechanical uniformity with the appearance of inclusions of bulk water, which should lead to cracking of ice. But energy absorption mainly occurs on the surface and grain boundaries, where there are quasi-liquid film inclusions. This is what causes the increased energy consumption to create a rapid increase in temperature at a radiation power cost of 0.25 W / cm. But at the same time, the effect of ice cracking directly depends on the heating rate, since the water (water film) that appears on the surface of the ice coating begins to work for such a type of radiation as a protective shield.

The considered analogues show that the use of high-frequency energy makes it possible to weaken the structural bonds in the ice paste, but these solutions do not address issues directly related to the mechanical destruction of the ice cover, which should be present in these methods as part of the process. The issue of ice cover destruction becomes important when it comes to stationary offshore engineering structures such as drilling systems or drilling platforms mounted in the sea on columns or rack-mount engineering systems; for such supporting elements of the platform, even small ice floes are undesirable. Therefore, the issue of weakening bonds in ice is directly related to the destruction of this weakened ice to a state of dimensions that are not dangerous for supporting structures. Moreover, it is generally desirable to divert these pieces or ice from the zone of location of stationary marine engineering structures.

The present invention is aimed at achieving a technical result, which consists in reducing the energy consumption and the complexity of the destruction of ice and increasing productivity while creating the possibility of guaranteed defragmentation of the ice cover while maintaining around the drilling rig water areas that are not covered with ice.

The specified technical result is achieved by the fact that in the device for protecting a marine stationary structure from drifting ice or ice cover, which is located at a distance from the marine stationary structure, microwave energy emitters, connected electrically to a source of converting electricity into microwave energy, as microwave energy emitters ultrasonic emitters are used, and the device is equipped with a marine stationary enclosure surrounding the cylindrical shape of the ring of concrete, immersed to part of its height in sea water, on the outer surface of the side wall of which are made in a checkerboard pattern made by ultrasonic emitters, while the specified annular fence is made of interconnected modules, each of which is a part of the wall an annular fence, which is installed with the possibility of rotation around a stationary marine installed structure.

These features are significant and are interconnected with the formation of a stable set of essential features sufficient to obtain the desired technical result.

The present invention is illustrated by a specific example of execution, which, however, is not the only possible, but clearly demonstrates the possibility of achieving the desired technical result.

In FIG. 1 shows a device for protecting a marine stationary structure from drifting ice or ice cover, side view;

In FIG. 2 is a plan view of a ring fence.

According to the present invention, a novel design of a device for protecting an offshore stationary structure from drifting ice or ice cover during the whole year of operation in the Arctic and subarctic regions where ice cover is present constantly or seasonally is contemplated. The device allows for offshore drilling operations and at the same time to withstand the general or local ice load, which is present during the annual seasonal occurrence of ice (including drifting ice). The protection device increases the efficiency of ice destruction, thereby ensuring year-round drilling of wells.

The effectiveness of the fight against ice is carried out by means of an ultrasonic dynamic ring, which is a concrete ring on which there are sources of ultrasonic radiation (ultrasound). An ultrasonic wave, passing through ultrasound transducers, crushes ice and at the same time releases heat. Since the ring is dynamic (that is, it can rotate or reverse), and the ultrasound sources are staggered, all layers of ice will be crushed. UZDK consists of modules, which simplifies its installation and transportation. The ultrasonic unit is designed on the basis of the already existing ultrasonic homogenizer company Bandelin Sonopuls HD.

According to the invention, the claimed device for protecting a marine stationary structure 1 from drifting ice 2 or ice cover is a cylinder-shaped reinforced concrete fence 3 surrounding the marine stationary structure 1 (Figs. 1 and 2). Under the stationary stationary structure 1 is understood, for example, an Arctic drilling platform year-round for drilling offshore wells. The specific design of such a platform is not considered, since it is not an essential part of the claimed invention.

This fence 3 is submerged in sea water to a part of its height, and part of the fence is located above sea level 4. The parameters of the depth of immersion or height of elevation in relation to the level of sea water are determined by the average statistical data on the thickness of the ice cover in a given area and the parameters of its part located in the dive and the part rising above the water level.

Since the fence is a power structure that must withstand a given pressure from the ice load, it is preferable to make this fence from those materials that can withstand such a load. The developers focused on the use of reinforced concrete, as a material well developed by industry, from which a power structure can be made. The fence is assembled from separate interconnected modules, each of which is a part of the fence wall. The module in the fencing assembly can be rigidly interconnected to form a loop structure or have some mobility (each module is connected to adjacent modules by, for example, chains). The mobility of the bonds allows you to redistribute the excess load on one of the modules due to its movement and displacement of adjacent modules. It is possible to use other materials or schemes for solving the fence, the main thing is that this fence should be a solid wall. The salinity of the oceans varies insignificantly and amounts to 34-35 g / l. The pH value is usually 7.8-8.3. The Atlantic Ocean, for example, contains about 11 g of Na +, 20 g of Cl-, 2.9 g of SO42- and 1.4 g of Mg2 + per liter, as well as in smaller amounts of K +, Ca2 +, Br-, НСО3- (0.08 g / l). To reduce the processes destroying concrete from the effects of salt water and the environment as a whole, the outer surface of the concrete fence is covered with a protective material. The aggressive processes that destroy concrete in sea water are: corrosion caused by magnesium sulfate, corrosion caused by carbon dioxide, corrosion caused by the action of bacteria, corrosion of concrete above the upper water level. For many years, additional materials have been successfully used for additional surface treatment of concrete, such as: MC-DUR 1277 WV and Emcephob SX, which is applied 3-4 weeks after applying MC-DUR 1277 WV. MC-DUR 1277 WV consists of a two-component epoxy resin containing a solvent. The material has a low viscosity and significantly improves the chemical and mechanical resistance of concrete. A Emcephob SX is a low viscosity, siloxane based material. Thanks to the hydrophobization effect, the wear resistance and protective properties of concrete are significantly improved. Additional frost resistance and resistance to salts contained in melt water is achieved by closing the pores of the concrete surface. The need to obtain closed pores is determined by the evaporation of water from the concrete surface through open pores. The presented protective system was used in the water area of the port of Hamburg (Germany), and its effectiveness is confirmed in the course of many years of monitoring the condition of the concrete structures of the port ("Technology for the protection of reinforced concrete structures from the effects of sea water", http://bitumplus.net/cats/ 11004676/11004679 / 11004679-0.pdf).

As a protective coating for concrete, bituminous emulsions can be used, sprayed or manually cold applied, and other materials: polyurethane, polyuria, polyurethane \ polyuria, epoxy and based on cements that are resistant to sea water (sulfate-resistant, slag cements).

To keep the enclosed fence 3 on the water with partial immersion in height in sea water, pontoons 5 or floats made, for example, of GGHV-1 tile foam plastic chemically resistant to hydrocarbons, attached to the inner wall of the fence, can be used. This simple solution allows you to adjust the depth of the dive by changing the volume of displacement.

For the guaranteed location of the fence at a distance from the offshore stationary structure, any means can be used to keep the fence from approaching the structure. In the framework of the present invention, the fence is made with the possibility of its rotation reciprocating in a certain angular range or with the possibility of rotation around a marine stationary structure. Technically, this is possible, for example, through the use of a water-jet propulsion connected with the fence or with one of the pontoons. Rotary or rotational movement of the fence is necessary to expand the zone of influence of the emitters 6 high-frequency waves mounted on the outer wall of the fence. This movement of the fence is periodic and the drive is switched on only in the mode of increasing the activation of the action of the emitters. This drive allows for each radiator to expand the zone of its impact on the adjacent ice cover. The rotatability of the fence also solves the problem of eliminating the influence of a radiator that is broken or has ceased to work for some reason, since when turning it, the adjacent radiator will cover its coverage area.

In the framework of the present invention, a specific solution to drive rotation or rotation of the fence is not considered, since it does not relate to the topic of ice destruction.

Microwave emitters located at a distance from the offshore stationary structure are electrically connected to a source for converting electricity to microwave energy. As the emitters 6 of microwave energy used ultrasonic emitters (piezoceramic), which are mounted on the outer surface of the side wall of the fence with the direction of the ice cover. On this wall, the ultrasonic emitters 6 are located with an offset relative to each other in height and along the outer perimeter of this structure (for example, in a checkerboard pattern) (Fig. 1). With this arrangement, the maximum possible expansion zone is provided, that is, with a narrow radiation beam, a point field of points of influence on ice is created. And when turning or during rotation, the point action passes into the linear movement of the point.

The choice of ultrasonic waves as high-frequency radiation is determined by the nature of their effect on the liquid medium.

Ultrasound - sound waves having a frequency higher than those perceived by the human ear, usually, by ultrasound they mean frequencies above 20,000 Hertz. The frequency of ultrasonic vibrations used in industry and biology lies in the range from several tens of KHz to units of MHz. High-frequency oscillations are usually created using piezoelectric transducers, for example, of barium titanite. In the framework of the present invention we are talking about emitters - electro-acoustic transducers that convert already specified fluctuations in the voltage or current into mechanical vibrations of a solid, which emits acoustic waves into the environment. The use of ultrasound for mechanical cleaning is based on the appearance of various nonlinear effects in a liquid under its influence. These include cavitation, acoustic currents, sound pressure. The main role is played by cavitation. Its bubbles, arising and collapsing near contaminants, destroy them. This effect is known as cavitation erosion. The ultrasound used for these purposes has a low frequency and increased power. The propagation of ultrasound is the process of moving in space and in time the disturbances that occur in a sound wave.

A sound wave propagates in a substance in a gaseous, liquid, or solid state in the same direction in which the displacement of particles of this substance occurs, that is, it causes a deformation of the medium. The deformation consists in the sequential discharge and compression of certain volumes of the medium, and the distance between two adjacent regions corresponds to the length of the ultrasonic wave. The greater the specific acoustic resistance of the medium, the greater the degree of compression and discharge of the medium at a given vibration amplitude. Particles of the medium involved in the transfer of wave energy oscillate around their equilibrium position. The speed at which particles oscillate around the middle equilibrium position is called the vibrational velocity.

Important nonlinear phenomena that occur during the propagation of intense ultrasound in liquids include acoustic cavitation - the growth of bubbles in an ultrasonic field from existing submicroscopic nuclei of gas or vapor in liquids to sizes in fractions of mm, which begin to pulsate with the frequency of ultrasound and collapse in the positive pressure phase . When gas bubbles collapse, large local pressures of the order of thousands of atmospheres arise, spherical shock waves form. Acoustic microflows form near pulsating bubbles. Ultrasound, which uses ultrasonic cavitation for technological purposes, lies in the field of ULF.

Acoustic cavitation occurs when sound waves of high intensity and amplitude exceed the threshold value. For water and aqueous solutions, the cavitation threshold increases as the gas content in the liquid decreases, with an increase in hydrostatic pressure, after the gas "compresses" in the liquid (~ 10 Pa) by hydrostatic pressure, or with an increase in the sound frequency. With pulsed ultrasonic exposure, the cavitation threshold depends on the pulse duration and reaches a maximum at 0.06-0.6 μs.

The physical process of cavitation is close to the process of boiling a liquid. The liquid boils, and microscopic-sized cavitation vapor-gas bubbles form. Cavitation bubbles form in places where the pressure in the liquid becomes lower. The accumulation of gas in the bubble, causing the average size of the bubble to grow in the field of variable pressure, is called straightened, or directed, diffusion. The diffusion mechanism provides a relatively slow growth of bubbles, and at a high frequency of ultrasound they make a significant number of pulsations before they reach the resonant sizes. The amplitude of the pulsation of a bubble with resonant dimensions (for a given ultrasound frequency) is maximum. An increase in the intensity of ultrasound leads to unstable cavitation: the bubbles quickly (over several periods) reach a resonant size, expand rapidly, and then collapse sharply, creating short-term (~ 10 ^-6 s) powerful pressure pulses (up to 10 ⁸ Pa and above) and shock waves that can destroy even durable materials. The collapse of the bubbles is accompanied by a significant impact. When collapsing, the vapor-gas mixture contained in the bubble adiabatically (not having time to exchange heat with the environment) is compressed to a pressure of 105 Pa (300 atm) and heated to temperatures of the order of several thousand degrees (8000-12000 K). The entire process of increasing and collapsing bubbles occurs within a few milliseconds. The pressure inside the bubbles and in the water reaches hundreds of MPa, and the temperature reaches several thousand degrees, which causes the decomposition of water molecules and the formation of radicals with high chemical activity (station "Cavitation". OV Mosin, Ph.D., Assoc. ., 05/05/2015).

Thus, the use of ultrasonic waves to act on the ice cover makes it possible to destroy the ice structure due to the formation of cracks due to the cavitation process in a minimum amount of time. In this process, an increase in pressure in the region of the liquid or quasi-liquid phase leads to the appearance of tensile forces without heating or heating the ice. The use of this type of radiation allows us to simultaneously solve two problems: weakening the bonds in the ice structure and defragmenting the ice into separate pieces. At the same time, it is important that the process of ice destruction takes place within a few milliseconds, which allows, given the speed of movement of ice or ice or the rate of rise of the ice cover, it is guaranteed to destroy the ice before it physically reaches the fence (meaning contact with the fence ) Unlike microwave radiation, the appearance of a water film will lead to a spontaneous intensification of the cavitation process in the zone in front of the fence. Thus, in front of the fence during the ultrasonic radiation session there will always be a zone free of monolithic ice. Pieces of ice will be picked up by the sea current and, passing around the fence, pass by. If some pieces of ice nevertheless come into contact with the fence, then due to the streamlined shape of the fence, they will slip along the perimeter of the fence and will be carried away by the flow. In any case, those pieces of ice that will not be subjected to complete destruction will not adversely affect the fence and the marine stationary structure protected by it.

At present, ultrasonic wave emitters are widely used in industry, for example, in the field of cleaning and cleaning (in the field of force acting on the verge of cavitation). For example, studies by O.G. Pavlenko, working in the field of creating ultrasonic emitters, allowed to create efficient small-sized emitters of a simple design (RU 110302, 60791, 3704).

The small-sized half-wave piezoelectric ultrasonic transducer developed by OG Pavlenko contains a passive steel plate in series, piezoelectric elements connected electrically to the generator for generating the frequency of ultrasonic vibrations, and a radiating plate made of aluminum or aluminum alloy or duralumin, made in the form of a truncated cone, smaller the base attached to the piezoelectric element, while the radiating and passive plates are made of different heights, and the ratio of the height pa sivivnogo pads to the height of the radiating pads made equal to or greater than one when the number of piezoelectric elements equal to two or more pairs. For the operation of the piezoelectric device, an ultrasonic generator is used, the design of which is described in RU No. 3704. Electrical signals generated by the generator in the form of packs of radio pulses (or in continuous mode) of ultrasonic frequency are fed through the overload protection units to the corresponding power amplifiers and then through hermetic cables to the ultrasonic piezoelectric emitters. Using the blocks of automatic frequency adjustment introduced into the feedback circuit of each channel, the necessary adjustment of the output frequencies of the radio pulses (or continuous oscillations) of the ultrasonic generators is performed until the developed cavitation mode appears.

Ultrasonic emitters are small-sized and are attached to the outer wall of a reinforced concrete fence. For this, nests can be formed in the wall for the recessed arrangement of the emitters and for the purpose of protecting them from external force, for example, from pieces of ice.

The present invention is industrially applicable and can be manufactured using modern technologies of concrete construction and ultrasonic technology.

Claims (1)

A device for protecting a marine stationary structure from drifting ice or ice cover, which is microwave energy emitters located at a distance from the marine stationary structure and connected electrically to a source of converting electricity to microwave energy, characterized in that ultrasonic radiators are used as microwave radiation sources, and the device is equipped with the surrounding marine stationary structure of a cylindrical ogre waiting from reinforced concrete, immersed to part of its height in sea water, on the outer surface of the side wall of which are placed ultrasonic emitters located offset from each other in height and along the outer perimeter of this structure, while the said fence is made of interconnected modules, each of which is a part of the wall of the fence, which is installed with the possibility of rotation or angular rotation around a stationary marine structure I am.

Images