Structure of Single Arm Davit

Single-arm davit main components: davit arm, pedestal, slewing bearing, slewing tray, hydraulic slewing unit, hoisting mechanism, guide tackle, boat fall and its accessory, remote control unit, limit unit, hydraulic system and electrical parts, and so on. (See drawing as follows).

1—— Davit arm                           7——Guide tackle

                     2——Pedestal                               8——Boat fall and its accessory

3——Slewing bearing                     9——Limit switch unit  

                    4——Slewing tray                           10——Remote control rope unit         

5——Hydraulic slewing unit             11---Hydraulic system   

6——Hoisting mechanism           12---Electrical system

1. Davit arm: It is a main active structure member of the appliance, and can be used for slewing the davit arm.

2. Pedestal: It is the base of the appliance to bear force, welded on deck. Using bolts to connect single davit arm and slewing tray and slewing bearing.

3. Slewing bearing: A special bearing used to support slewing tray and slew.

4. The slewing tray: An assembly part connecting the davit arm and slewing bearings. It can effectively slew the davit arm to outboard position or to stowed position through the hydraulic slewing device.

5. Hydraulic slewing unit: a drive device used to slew davit, consist of hydraulic motor, wet sheet hydraulic brakes, planetary reducer, small gear, and other components.

6. Hoisting mechanism: used for lifting rescue boat or life raft, consist of electrical motor, reducer box, one-way clutch gear, speed limit clutch unit, handle unit, and so on.

A——Hoisting handle socket        F——Electric motor

B——Lowing handle socket           G——Box body

C—— Limit speed clutch                H——Drum

D——One-way clutch                       I——Remote drum

E——Brake lever                               K——Handle  

1) Reducer box: A wholly closed oil bath lubricating box consists of gears, gear shafts, shafts, and so on. It is used to reduce speed and transfer moment.

2) One-way clutch gear: Installed in reducer box. It mainly consists of the outer ring, star body, roller, and so on. It can transfer moment unilaterally and reverse brake. When hoisting a rescue boat or life raft, the electric motor can be used to drive the drum, and it won’t be driven by the electric motor when gravity launching.

3) Speed limit clutch unit: It mainly consists of a speed-limiting brake and a counterweight operating clutch.

① Speed limit brake: It mainly consists of shell, speed limiting block, speed limiting spring, and so on. It limits gravity lowering the speed of the winch by friction which is caused by centrifugal force.

② Counterweight operating clutch: It consists of a screw rod, press sleeve, sleeve, friction plate, counterweight, and so on. combined with the one-way clutch mentioned above to produce a manual brake be in close in common, it brakes when hoisting and lowering. so it is an operation unit controlling gravity launching.

4) Handle unit: It is laying on the reducer box in common. Takes down when working, then insert socket A or B on the reducer box (seeing a drawing of the winch) for manual hoisting or manual fast lowering non-loaded hook.

5) Drum: It consists of a drum and a remote control drum in the same shaft. The main drums are used to wind on and wind off boat fall. The remote control drum is used to wind on and wind off the remote rope.

7. Guide tackle unit: installed on davit arm, it is used for support and guide of boat falls.

8. Boat fall is galvanization, non-twist, fiber core wire, its size is 18×19+Fc (its dia. refer to technique document enclosed with the appliance).

The rigging is consists of a manual release hook (for rescue boats not with its own release mechanism) (or manual and automatic dual-release hook), ring, shackle, and so on.

9. Remote control unit: Two steel rope droops from a davit arm. one is used to remote control the boat or life raft launching. The other one is used to remote control davit arm slewing.

10. Limit unit: Its main component is a limit switch (seeing electric section), used to limit the hoisting travel of a boat or life raft to avoid overload.

11. Hydraulic system: It is used to slew davit. The hydraulic system mainly consists of the pump station, control valve, hydraulic motor, hand pump, accumulator, and so on (see attached hydraulic schematic drawing).

① Pump station: offered power for the hydraulic system.

② Integrated valve provides the function of charging pressure and turning left or right for system.

③ Hydraulic motors: when turning, drive small gear on slewing unit to make the davit slewing.

④ Hand pump: use manpower to provide power for the system when loss of power.

⑤ Accumulator: provide slewing power for lowering boat/life raft.

12. Electric part: It mainly consists of an electric motor, control box, remote button box, limit switch, and so on. (See electric principle drawing in the attached technical documents enclosed with the delivered equipment).

① Electric motor: three-phase marine induction motor, the squirrel-cage type. Its shell protection grade is IP56. The insulation class is F grade, and there is a space heater in it. There are three electrical motors on this appliance. One is for the hoisting mechanism, one is for the hydraulic pump station.

② Remote button box: there is a hoisting button on it and the protection grad IP 56(according to customer’s request).

③ Electrical control box: it is set to ensure regular operation, its protection grade is IP56.

④ Limit switch: It is designed for limiting the hoisting travel of the boat or life raft. The protection grade is IP56.

13. Head tackle: Located on the top of the davit arm, is used for supporting and guiding lifting rope.

14. Lifting rope and hook: lifting rope is galvanized, anti-rotation, fiber core wire rope, its specifications are Φ16-18×19+Fc.

New Marine is China famous lifeboat davit manufacturers, providing high-quality single arm davit. If you have any needs, please contact us.