Marine Hatch Cover

 Marine Manhole

Marine Hatch Cover

Definition

In order to prevent the water into ships, installed on the hatch wooden or steel cover, also can be used as supporting structure of cargo deck, called hatch cover .According to the requirements of general tightness, divided into water tight hatch cover, oil tight hatch cover and non tight hatch cover.

Hatch cover main role is to ensure that waves and rain do not invade the cargo hold, some hatch cover also bear weight of cargo on deck.

small hatch cover installed in liquid cargo warehouse, refrigerated cargo warehouse , personnel access hatch and manhole

According to the transmission mode divided into rolling hatchcover l, oblique type, sheathed type, roll shift including lateral displacement type, cascade, roll roll type, hinge type including hinged flap, folding and so on.

With tightness hatch can devide into watertight, oiltight, airtight and nontight hatchcover etc., according to the different tightness that hatch cover plate and the adjacent components are respectively equipped with layering, packing, gasket, pressing device sealing apparatus.

classification

According to the hatch size, divided into large and small hatch cover. The former is used for bulk cargo loading, material or vehicle cargo, cabin hatches; the latter is used for loading liquid cargo, refrigerated cargo and personnel entrance hatch and manhole.

According to hatch cover plate material and type have assembly wooden or metal hatch cover, Box type hatch made by metal or glass. Small hatch cover generally open and close by human, large hatch cover must use electric or hydraulic driven mechanical opening and closing.

According to the transmission mode can be divided into rolling hatch cover ,verrtical type, oblique type, sheathed type, roll shift including lateral displacement type, cascade, roll roll type, hinge type including hinged flap, folding and so on.

According to tightness with water tightness, oil tightness,gas tightness and non tight hatch cover etc., according to the different tightness that hatch cover plate and adjacent components are respectively equipped with composed of layering, packing, gasket, pressing device of sealed cabin device or sealing device.

1.Weathertight cargo hatch cover

Cargo hatch in the freeboard deck must steel weathertight hatch cover.

2.Oil sealing cargo hatch cover

Cargo hatch cover not install in conceal place,should not be less than 600 mm * 600 mm. Measurement hole diameter not less than 150 mm and observation hole hatch. The hole should ensure effective oil tight cover closing device. The opening of cargo hatch usually made of round or oval.

3.Non watertight hatch cover fit cargo and residential

Under cabin deck hatch without coaming, hatch cover parallel with around.

Hatch design requirements

1.The structural strength of all open deck hatch cover should be adjacent to around structure.;

2, Hatch cover closure device should ensure the weathertight;

3,The vehicle deck hatch cover if under vehicle load, hatch cover design pressure should be by vehicle load values of the strength check.

Weathertight hatchcovers installation inspection

Door, window,cover are small weathertight closing devic. Because the number much, the shipyard during installation random checks, include:

1.Look up Small weathertight hatchcovers marine product certificate, and check the real stamp or mark.

2.The opening position according to the approved classification review drawings inspection cover. Particular attention should be given to the freeboard deck Small weathertight hatchcovers, for Small weathertight hatchcovers, focus on examination deck height.

3.The cover is installed, check the structural integrity, durability and performance of headstock.

4.The welding quality check.

5.Check door ,window, cover tightness. General installation quality pigment adhesion method check the seal, then after installation, flush test according to the classification society.

Steel watertight cargo hatch cover test

Steel cargo hatch covers is an important hull outfitting equipment, which is used to hatch cover and protect the cabin and goods from invasion of wind and rain. When the ship loading and unloading of goods, can be easily opened or closed, the cargo hatch covers should have enough strength, to ensure under waves or other set of load not deformation, effect use.

Steel watertight cargo hatch cover generally with shipyard's quality inspection department inspection certificate, should accordance with classification society, apply ship inspection of product ,during manufacturing process to surveyor and ship owner submit acceptance and inspection of steel watertight cargo hatch covers. Classification society give certificate to acceptable covers.

Steel watertight cargo hatch covers installation inspection has two contents: ship hatch coaming installation inspection; hatch cover at coaming installation inspection and test.

Marine Window, Porthole

 Marine Window

 Marine Porthole

Marine Rectangular Window

Location: a rectangular window is arranged in a second level building, as square and rectangular window for light or ventilation.

Structure: inner side open type, outside open type, inside open type, drop type and fixed type, etc., under pressure is less than 5m water column (the larger transparent size the lower pressure resistant .)

The rectangular window is arranged on the wall of the upper deck superstructure. rectangular window of the periphery with a rubber seal, close with the bolt pressed, the requirements to ensure weathertight.

Rectangular window according to the size of the rib spacing with a suitable window, the other to consider is water tight pressure. Transparent size 400mm x 300mm can bear 50Pa pressure, 350mm x 50mm, 400mm x 550mm, 450mm x 600mm can be confined to 20Pa. In the superstructure of the general compartment window, the large size of the (550mm x 600mm, 600mm x 700mm, 800mm x 900mm) window is used to request a wide driving room.

Welded window

1.    Dimension of wall opening:W1*H1*R1

2.    Hose test shall be carried out as follow,hose nozzle diameter: >16 hosing distance from window 2.5-3m, water pressure 0.2Mpa after maintain the pressure fro 3 minutes no water mark could be found on the back of window

3.    Both side of glass to be applied with removable plastic lamina

4.    Half-round head bolts GB67-76 may be used for item

5.    During installing the gap between window frame and wall as wall as the gap in way of bolt hole to be filled with putty.

Fixed window

1.    the steel part shall CB*/Z343 hot-dip processing , leaching layer thickness of not less than 45um, aluminum oxide plate blasting quality

2.    flush test requiment: Nozzle diameter greater than 12.5mm, flushing distance: 1.5m ,nozzle water pressure:0.25 Mpa

3.    In according to all other requirement refer ISO3903: 1993 shipbuilding and marine sturctures, marine ordinary recangluar window standard

4.    After the steel main frame sand-blasting spit twice primer, color is gray

Marine Porthole

Install in the side plates, the superstructure deck and outdoor wall , on the hull of the ship, can ensure the hull tightness, Round window with anti storm performance.

Ship's portholes reason are designed into round, according to the principle of mechanics, circular than other shapes more under pressure, shear stress. The installation position of porthole according to insubmersibility of ship.

Classify into heavy and light type. Heavy porthole inboard hinge cover anti wave porthole. Deadlights side with rubber seals, tightly pressed by the bolt to keep watertight. Light portholes are generally not associated with deadlights. In the spaces below the freeboard deck or enclosed superstructure premises portholes were all severe side scuttle.

Portholes fixed type and movable type, the former can not be opened, which can be opened, at watertight bearing capacity of heavy 20Pa, ordinary type 50~100Pa, light (20Pa below). Heavy movable portholes stone in a watertight region in the window, cap with a riot, such a window in stormy weather cannot keep lighting. For circular porthole, specifications with transparent glass diameter usually & Oslash; 200mm, & Oslash 250mm, 300mm & Oslash;, & Oslash 350mm, & Oslash 400mm several, depending on the vessel size (rib spacing selection. As the exit must be more than 350mm.

1.    side scuttle part surface should level bright and clean,surface its rough degrees of Ra should be greater than 12.5um,mould forging surface can’t have crackle,divide into layer,burn etc and forge the defect,casting surface

2.    there can’t be the defects of sand holes,air vent,crackle,loose and intensity of other influence

3.    The windowpane of side ship must adopt the safety glass that GB11946,there should be certificate of competency.Surface of glass both side should be stuck and can shell the membrance.

4.    side scuttle steel part should soak the zinc to deal with according to GB/TZ343 heat it is not smaller than 45um to soak one layer of thickness,the aluminium part should oxidize dealing with according to GB/TZ92,the surface is unglazed and silivery white

Marine Doors

D

Marine Doors

1.Marine Watertightdoors

The watertight door form have hinge and sliding type.

Use on ships watertight door has the following three grade:

Grade 1 - hinged door; Grade 2- manual sliding door; Grade 3-dynamic and manual sliding door.

(1) hinged watertight doors: requirements can quickly open and close of door on both sides.

(2) sliding watertight doors: made of steel plate. According to the sliding direction, horizontal type and vertical type; according to the operation mode of manual operation and dynamic control. (manual closing time less than 90 seconds, power closing time less than 60 seconds.)

The ship all watertight doors on the voyage shall be kept closed, due to work needs during the voyage must be opened, and it can be closed at any time. On bulkhead watertight doors, whether power controlled or manually operated, where voyage in use, daily operation. During voyage the sliding watertight doors should be inspected regularly, at least once a week.

2.Marine Weathertightdoors

The entrance of above freeboard deck enclosed superstructure wall of both ends require install weathertight doors.

(1) steel weathertight

Similar to its structure of steel hinged watertight door, but the door is thin, the handle of door number fewer, tightness poorer, only to ensure that the weathertight.

(2) wooden weathertight doors

The door with oak and teak material, divided into hinged and sliding type, tightness is poor. The wall on both sides of cab, all horizontal sliding type.

steel weathertight door structure Similar to steel watertight door, but the door weight is slightly lighter, less wedge handle and close packing press in shallow, which need to meet the corresponding density test requirements to ensure in any storm impermeable; the use of wooden door should also ensure its resistance to water wave impact. Generally used as a freeboard deck room leading to open the cabin door and the furnace door, storage room door, the pantry door and so on. That leads to the open air kitchen, can be used to double leaf type door. When considering the appearance of decoration, can use wooden door.

1.    Close doors and door frames,door entry pressure plate rubber mat depth should be not more than 4mm,indentation should be uniform

2.    Rolling deduction and other activities annex hinge flexibility should be able to rotate,turn off the light

3.    The airtight six experiment pressure 0.01Mpa

3, Marine Light steel door

The structure of door is light, installed in the storage room, no tightness require place at entrance.

4, Marine Fireproof door

1, set up in the fire resistance separation bulkhead, can achieve the same level of fire separation requirements of the door.

2, installed in the fire bulkhead on the ship, can be closed after the fire spread of the door.

Fireproof door is a kind of steel plate made of door and door frame, and mosaic asbestos and other refractory materials of fire prevention. Installed on the fire control area of the bulkhead, normally open; when the fire occurs, the temperature rises to a certain value the door can be closed automatically, or gate is arranged on the pinned magnetic device, off the power door will automatically close. Fire doors in the channel are required to be self closed, when the temperature exceeds 90 degrees can be automatically shut down to prevent the spread of fire.

Fireproof doors are provided with fire protection equipment on fire resistant doors. It has an equivalent fire separation effect with the bulkhead. Ship construction codes are classified into Grade A, grade B and grade C. Fire resistance of class a fire door is the highest

Fishing Float ,Fishing Buoy

Fishing float, Fishing Buoy, Fishing floater as named, it is important equipment of fishing industry.

Materail of finshing float

PVC（Polyvinyl chloride)

Is not flammable, high strength, excellent resistance to climate variability and geometric stability. PVC material is very wide, with good working performance, corrosion resistance, insulation, etc..

PVC had strong resistance to oxidant, reluctant and acid.

EVA: ethylene-vinyl acetate copolymer

1.Water resistance: closed cell structure, no water absorption, moisture, good water resistance.

2.Corrosion resistance: seawater, grease, acid, alkali and other chemical corrosion, antibacterial, non-toxic, tasteless, no pollution.

3.Anti vibration: high resilience and tension, toughness, with good buffer performance.

4.Insulation: thermal insulation and low temperature resistance, resistant to cold and exposure.

EPS: Expandable Polystyrene

Good shock absorption, high compression strength, very light weight and moisture resistance, anti-aging and waterproof. The products made of the expandable polystyrene resin have the function of ant vibration, anti shock, and moisture insulation.

The place to storage the expandable polystyrene resin should be good.Ventilation, away from fire and heat, avoid direct sunlight

PE(Polymerization ethylene)

A thermoplastic resin prepared by polymerization of ethylene

Polyethylene no odor, non-toxic, it feels like wax, has excellent resistance to low temperature performance, good chemical stability, ability of most acid-base erosion.Under normal temperature, insoluble in general solvent, small water absorption, good electrical insulation.

Polyethylene in atmosphere, sunlight and oxygen, occurs with aging, discoloration, crack, brittle or powder, loss of mechanical properties. So it need keep good.

Marine Cable Breif Introduce

Marine cable is for all kinds of ships and marine petroleum platform construction on water power, lighting and general control wire and cable.

Implementation criteria: marine power cable execution standard: IEC60092-350, IEC60092-353 or GB9331-88

The main parameters of marine power cable are model, number of cores, combustion characteristics, rated voltage, temperature, nominal section area and so on.

Marine Power Cable

For all kinds of ship, offshore oil platforms on water buildings lighting and general control purposes. Power cable is used for transmission and distribution of high power cable electrical energy in the main line of power system, including 1-500KV and above voltage level, all kinds of insulated power cable.

The basic structure of power cable is composed of four parts, which are the core, the insulation layer, the shield layer and the protective layer.

Core of electric cable, used to transport electrical energy, and is a major part of power cable.

Insulation layer: Isolate cable more with earth and other phase cable core, to ensure the power transmission, is an indispensable part of power cable structure.

Shielding layer: 15KV and above power cable generally have a conductor shield and insulation shielding layer.

Protective layer: the role is to protect power cable from external impurities and moisture intrusion, as well as to prevent external force direct damage to power cable external.

Marine control cable

For all kinds of ships and offshore oil platforms and other on water buildings general control purposes. PVC insulated, PVC sheathed control cables ,AC rated voltage 450/750 volts for control and protection circuits, etc.

Performance characteristics

1 DC resistance: 20℃, 0.4mm copper wire, less than or equal to 148Ω/km, 0.5mm copper wire, less than or equal to 95Ω/km.

2 Insulation electrical strength: 1kV 1min between the conductor does not breakdown ,3KV 1min between the shield does not breakdown

3 Insulation resistance: each core wire and the rest wire grounding, control cable is greater than 10000 MΩ, HYAT cable is greater than 3000 MΩ.

4 Working capacity: average value is 52 + 2nF/km

5. Distal crosstalk ratio: the specified 150kHZ combination of average power value is greater than 69dB/km.

Marinecommunication cable

used in all kinds of communication, electronic computer, information processing equipment signal transmission and control system. It has the advantages of high communication capacity, high transmission stability, good secrecy, less natural conditions and external interference.

Communication cable is classified as follows:

1, single wire: refers to the most primitive communication cable, single wire loop, to the earth as a return line.

2, Symmetrical cable: two same wire in the ideal condition make a loop.

3, Coaxial cable: in the same axis of inner and outer two conductor loop, outer conductor surround inner conductor, and both insulation.

What's the Marine Hydrophore ?

Marine Hydrophore is for ship drinking water, washing water, rinse with water and outboard water supply system (Marine Auxiliary Equipment).

Marine Electric Heating Hydrophore Tank

Application: suitable for heating water on the ship or platform, heated fresh water for crew use.

Principle Description

Hot water tank can be combined to use with fresh water pressure tank on board, namely use fresh water to renew the stock of hot water tank, and then heated by electric for usage of entire vessel.

Working procedure and structure:

The heater shall be connected with fresh water pressure tank. Supply fresh water to the heater, after the fresh water is heated it can use. The temperature in the heater is controlled by pressure temperature controller. When the temperature is lower than 45℃, the power will be switched on, the electric heater becomes to heat. When the temperature rises to 65℃, the power will be switched off. When the water is reduced to lower than control range of the level relay, the power will be switched off automatically, to ensure the electric heater coil safety. On the tank there also has a safety valve, to protect the tank works safety.

Marine Pressure Hydrophore Tank

Application: pressure water tank can be used to provide fresh water for living and cleaning of ship and drilling platforms.

Model Significance

A：Wall-hanging type, Repair entrance: barrel flange，

B：Wall-hanging type ,Repair entrance: barrel manhole，

C：Vertical type, Repair entrance: barrel manhole.

Principle Description

The device use gas pressured by pump to compressed air in order to maintain the water in cabinet body under a suitable air pressure. To provide fresh water to crews.

Marine Steam Electric Heating Hydrophore Tank

Application: steam-electric hot water tank is suitable for all kinds of ship which have steam  source or power to produce hot water which is for crewmen。

With electric/steam as the heating recourse，this series of heater is applicable for life use fresh water pipe system in vessel and well-drilling platform，it can be work independent，water temperature in a certain scale，provided safety relief device.

Marine Steam Heating Hydrophore Tank

Application : This series of hot water tank is suitable for fresh water system which is heated by steam。

steam hot water tank and vessel fresh water pressure tank in series, namely the use of fresh water pressure tank in the freshwater of the cabinet, after steam heating heating components for use in the whole ship.

1. Temperature control valve: according to the set temperature control range open and close.

2. Pressure gauge: the pressure in the cabinet.

3. Thermometer: display cabinet temperature.

4. Safety valve: when the pressure inside the cabinet exceeds 0.63MPa, the safety valve open, releasing the pressure in the cabinet.

Marine Combined Hydrophore Tank

Application

This series of pressure water tank is suitable for ship fresh water pipes and sea water pipes, pumps; pressure switch, electric control box and hydrophone are installed together. It is compact and good look appearance, easy to install and maintain, and it is an ideal unit for water supply system.

1. Temperature control valve: according to the set temperature control range open and close.

2. Pressure gauge: the pressure in the cabinet.

3. Thermometer: display cabinet temperature.

4. Safety valve: when the pressure inside the cabinet exceeds 0.63MPa, the safety valve open, releasing the pressure in the cabinet.

Do you know Marine Life Jacket ?

On ship can be configured separately in the sea of floating or running a variety of life-saving tools. Commonly used lifesaving equipment with a lifeboat, life raft, life cycle and life jackets, etc.. The International Convention for the safety of life at sea has specific requirements for life saving equipment.

Personal life saving equipment can support a single person floating in the water of life appliances, generally refers to the life buoy, life jacket, warm life jacket, anti-immersion suit and thermal insulation bag.

Marine Adult Lifejacket

Suitable for all kinds of coastal and inland water use, the buoyancy of the life jacket is greater than the 113N. The life vest in the water for 24 hours, the buoyancy lose should be less than 5%.. Life jacket buoyancy material: polyethylene foam. The new type of life jacket is designed and manufactured according to the requirements of MSC207 IMO (81) and MSC200 (80)

Marine Child Lifejacket

Suitable for all kinds of coastal and inland water use, the buoyancy of the life jacket is greater than the 113N. The life vest in the water for 24 hours, the buoyancy lose should be less than 5%.. Life jacket buoyancy material: polyethylene foam. The new type of life jacket is designed and manufactured according to the requirements of MSC207 IMO (81) and MSC200 (80)

Marine Screw Lifejacket

Suitable for coastal and inland water use of all kinds of personnel. The buoyancy of the life vest is more than 75N, and the loss of the life vest is less than 5%  after 24 hours of immersion in water.

Marine Inflatable Lifejacket

Usually use it to when fishing, the internal use of the double high strength chemical material, in case of drowning, press the button on the right side and left side automatic air suction air, reflecting plate will air storage until it is full. Such lifejackets buoyancy larger is 10 kg / 24 hours, but it should be as far as possible to prevent contact with the reef to prevent damaged.

Requirement:

1 the life vest should choose red, yellow and other bright colors, because once the wearer accidentally fell into the water, you can make the rescue more easily find you.

2 in the vest there should be a life-saving whistle, to help the drowning of whistler.

3 in order to find the water in the sea easy, In general life jackets of the fabric are more bright colors, and the life jacket on the two shoulder with a reflective board, should pay attention when buy.

Marine Pump Introduce

Marine Pump

Pump is a ship widely used hydraulic machinery, it consists of a prime mover drive, and the mechanical energy into fluid pressure energy, potential energy and kinetic energy. Pump medium liquid is water and oil.

In order to pump water, fresh water, fuel, oil and other liquids, the need for a certain amount and different type of pumps. Generally in the engine room must be set bilge pump, fuel pump and oil pump, boiler feed pump, cooling pump, ballast pump, sanitary pump and other major pumps.

In the marine machinery and equipment, marine pump is a large number, variety and important ship matching products. It is widely used in ship power system, fire protection system, cooling system, pressure loading system, stripping system, life security services and other special system, but also be equipped in certain auxiliary devices. In recent years, the domestic ship large, ship type diversification, the trend of the whole ship automation is increasingly obvious.

In general, the number of various types, different uses pump total number accounted for 20-30%, the total power of ship's equipment 5-15%. In addition, marine pumps have been widely used in marine engineering equipment, docks, port terminals, etc.

Summary

Pump is to increase the liquid and liquid material pressure or flow. Deliver liquid to a higher location, distance, higher pressure must use the pump, the pump can also be used to produce high pressure liquid for hydraulic transmission. Motor driven by electric or other.according to the working principle can divided into vane pump, (such as centrifugal pump, mixed flow pump, axial flow pump, vortex pump), displacement pump (reciprocating pump, rotary pump) and other types of pumps, (such as jet pump, electromagnetic pump, etc.); according to the structure is divided into vertical pump horizontal pump, self- priming pump and non self- priming pump; according to use can be divided into dynamic pumps (such as boiler pump, condensate pump, circulating pump, fuel pump, lubricating oil pump and cooling water pump, etc.) and ship system pump( ballast pump, bilge pump, water pump, sanitary pump, fire pump, cargo oil pump, vacuum pump, mud pump and fishing pump, etc.) Flow rate and head are the two main parameters of pump.

Marine pump features: requirements pump when ship sway and incline, not due to inhalation of level fluctuation have cavitation occurs; in order to reduce the occupied area of pump and convenient maintenance, general use vertical structure; through flow components are made of bronze, made of stainless steel and other materials, to as much as possible to reduce corrosion.

classification

Marine pump has a very wide range of applications in ships, according to different purposes, can be divided into:

1, marine power plant pump

With fuel pump, lubricating oil pump, seawater pump, fresh water pump, steering gear or other hydraulic deck machinery hydraulic pump, boiler device water feed pump, cooling water pump, sea water desalination device of water pump and condensate pump.

2, marine general pump

Bilge pump, ballast pumps, fire pumps, daily fresh water pump, daily water pump, hot water circulation, and doubles as a pressure load, fire protection, bilge general pump.

3, special ship pump

Some special purpose ship, also has special operation requirements and special pump provided, such as oil tanker cargo oil pump, hopper dredger mud pump, salvage ship salvage pump, spray propulsion ship water boost pump, no net fishingship fishing pump.

According to the working principle, the marine pump mainly has following categories:

1, volume type pump

Positive displacement pump is by the movement of working parts caused by volume of work periodically changes and liquid smoke platoon. When working volume increases, and the pressure is dropped inhalation liquid, when working volume decreases and pressure discharging liquid, by crushing the pressure of liquid can increase. According to the way of moving parts, it can be divided into reciprocating pump and rotary pump. The former has a piston pump and cylinder pump, the latter has a gear pump, screw pump, vane pump, etc..

2, vane pump

Impeller pump mainly by increasing the liquid kinetic energy to increase the liquid energy. It relies on the impeller to drive liquid for high-speed rotary motion, continuous production of suction and discharge, the mechanical energy can be transferred to the liquid delivery, so that the liquid pressure can be increased, and to achieve conveying liquid. According to different characteristics of pump impeller and flow channel, it can be divided into centrifugal pump and vortex pump.

3, jet pump

Jet pump is a working fluid with a certain pressure to produce high speed jet injection fluid in the nozzle, and then through the momentum exchange, the energy of injection fluid is increased. According to different working fluid, it can be divided into water jet pump, steam ejector and air ejector.

Pump in addition to classification according to the working principle, can also according to position of pump shaft is divided into horizontal pump and vertical pump; according to number of suction inlet is divided into single suction pump and double suction pump; divided by prime mover driven into electric pump, steam pump and diesel pumps, marine pump most electric pump and emergency fire pump is directly driven by a diesel engine, cargo oil pump often consists of a steam turbine drive.

Performance parameter

In order to explain the basic working performance of pump , convenient select and compare the performance of pump , usually expressed in the following parameters.

1, displacement

Pump displacement refers to the amount of liquid discharged or transported by pump in the unit time, often expressed in volume displacement, and its unit is m3/h.

2, pressure head

Pump pressure head is used to overcome the resistance of suction and exhaust pipe and the suction and discharge of liquid level of the pressure difference, pressure liquid to a certain height of the energy. the pressure difference between the suction and discharge ports can be approximately measured by the pressure difference between suction and discharge ports. It is expressed as a unit of liquid in the flow through pump the pressure can be obtained.

3, power and efficiency

Power is usually expressed as power and output power is expressed in kilowatts. Pump efficiency is the ratio of the output power to the shaft power, and it is the index of pump work economy.

4, speed

Refers to the pump shaft rotation per minute, unit is R / min. Reciprocating speed can also be used in the double stroke piston number per minute completed said.

Bow Thruster also know as Tunnel Thruster

Bow Thruster

Bow thruster allow the vessel turn to port or starboard side, without using the main propulsion mechanism which requires some forward motion for turning。Bow thruster is a transversal propulsion device built into or mounted, either the bow or stern, of a ship or boat, to make it more maneuverable. Bow thruster is primarily used for docking, slow speed maneuvering, emergency steering and station keeping at zero or slow forward speed. Bow thrusters make docking easier, since they allow the captain to turn the vessel to port or starboard side, without using the main propulsion mechanism which requires some forward motion for turning.

Tunnel thruster

1.Marine vessels usually have one or more tunnels built into the bow, below the waterline order to improve manoeuvrability.An impeller in the tunnel can create thrust in either direction which makes the ship turn. Most tunnel thrusters are driven by electric motors, but some are hydraulically powered. These bow thrusters, also known as tunnel thrusters, may allow the ship to dock without the assistance of tugboats, saving the costs of such service. Ships equipped with tunnel thrusters typically have a sign marked above the waterline over each thruster on both sides

Depending on the type of vessel, the range of application for bow thrusters extends from brief docking and casting-off in ports with a limited number of operating hours every year up to continuous operation under extreme load conditions in demanding offshore applications with dynamic positioning. Allow the ship to dock without the assistance of tugboats, saving the costs of such service

Bow Thrusters can be powered by diesel engines, electric motors or hydraulic motors.

Electric motors are included optionally in the scope of supply. The prime mover can be connected either horizontally or vertically and thus incorporated optimally into the naval architectural design.

When fixed-pitch propellers are used, electric and hydraulic motors allow the direction of thrust to be reversed. An additional reversing gearbox is required if the thruster is powered by a diesel engine.

Thrust is the decisive criterion of a bow thruster. Therefore attaches great importance to an optimum propeller design that is individually adapted to the vessel geometry in each case. At the same time, the propeller design takes into account any special requirements in terms of noise level that are relevant for the application. A major parameter for the effectiveness of a bow thruster is the size of the gap between the tunnel and the propeller, which has reduced to a minimum on all models.

Advantages

•For extreme load conditions, e.g. in the offshore sector

•For continuous and short-time service

•Low noise emission

•Available with either fixed or controllable-pitch propellers

•Compact design due to horizontal, vertical or inclined arrangement of the power input flange

•Combinable with diesel, hydraulic or electric drive

Mark as a big cross in a red circle: (x).

Tunnel thrusters increase the vessel's resistance to forward motion through the water, but this can be mitigated through proper fairing aft of the tunnel aperture (see below photo). Ship operators should take care to prevent fouling of the tunnel and impeller, either through use of a protective grate or by cleaning. During vessel design, it is important to determine whether tunnel emergence above the water surface is commonplace in heavy seas. Tunnel emergence hurts thruster performance, and may damage the thruster and the hull around it.

Externally mounted bow thrusters Instead of a tunnel thruster, boats from 30 to 80 feet (9 to 24 m) in length may have an externally mounted bow thruster. As its name suggests, an external bow thruster is attached to the bow, making it suitable for boats where it is impossible or undesirable to install a tunnel thruster, due to hull shape or outfitting. Externally mounted bow thrusters have one or more propellers driven by a small reversible electric motor which provides thrust in either direction. The added control provided by a bow thruster helps the captain to avoid accidents while docking.

Waterjet bow thrustersA Waterjet thruster is a special type of bow thruster that utilizes a pumping device instead of a conventional propeller. The water is discharged through specially designed nozzles which increase the velocity of the exiting jet. Waterjets generally have the advantage of smaller hull penetrations for an equivalent size thruster. Additionally, the higher exit velocity of the discharged water increases the relative efficiency as speeds of advance, or currents, increase, as compared to standard tunnel thrusters. Some waterjet bow thrusters can be configured to provide forward and aft auxiliary propulsion, or even full 360 degree thrust.