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Self- unloading bulk carriers pocket elevator & the loop belt elevator


Self unloader bucket elevator
Fig: Self unloader bucket elevator

Bucket (Or pocket) Elevator lift belt
: The pocket elevator positioned at the top of the self unloading bulk carriers cargo transfer system to assist in emptying of cargo from pockets.The lift belts are housed inside the lift belt casing, which is located just forward of the accommodation block.

The lift belt is reinforced with steel cables running longitudinally throughout its entire length. Corrugated side walls are attached, also running longitudinally for the entire length. Pockets are formed by rubber “cleats” which are bolted onto the belt, using side bars, through the side walls. The cleats are secured to intermediate blocks of rubber, and inside each are embedded stainless steel “U” bolts whose ends protrude from the rubber. Each block is attached to the belt by a cold adhesive process. The cleats are secured to the “U” bolts using stainless steel cap nuts.

The lift belt therefore has pockets on its carrying side and is smooth on the other. The lagged pulley drives on the smooth side of the belt, and there is no hydraulic take-up arrangement. Belt tension is set by the tail pulley position using jacking screws.

The tension of this type of belt is not to be adjusted by ships staff. It is only to be adjusted by “flexowell” approved technicians.



The belt is driven by two Hagglunds hydraulic motors which are attached to each end of the drive pulley shaft located at the top of the lift belt casing. The ratchet type backstops are located adjacent to the drive motors and are attached to the upper aft deflection wheel shaft of each belt, which allows the belt to rotate in one direction only. Any change of direction of this belt is effected by ‘deflection wheels’ which are on the carrying side edges of the belt when change of direction is desired. The loading of this belt is transferred via chutes on the carrying pocket side at the bottom just aft of the take-up pulley. The underside of the belt, along its loading area is supported by load rollers, which are rubber lagged to absorb the impact of the cargo.

self unloader installation
Fig:self unloader boom installation

The advantages of the Lift Belt System are:
The disadvantages of the Lift Belt System are:
The loop belt elevator

The loop-belt arrangement is housed in the ‘Loop-Belt Casing’ of the self unloading bulk carriers cargo transfer system and found normally just in front of the ships bridgefront bulkhead. The loop belt elevates cargo material using two belts arranged in a ‘C’ form, with one driven outer belt, and one non-driven inner belt. These belts turn on “trough” section rollers the outer edges of which contain the cargo material within the belts.

The cargo material is lifted in the sandwich formed between the two belts the tension of which creates the clamping force and resultant friction necessary to lift the material.

The system is driven by electric motors at each end of the outer belt using fluid couplings and reduction gearboxes. Speed sensing ensures that the speed of the inner belt which is driven by the friction between the two belts, does not fall below a pre-set level. This is to avoid a reduction in the transfer of cargo material and resultant build up of cargo material at the bottom of the loop elevator. If slippage does occur to the extent that the pre-set level is exceeded then the tunnel and transfer belts will automatically stop.

In the event of a stoppage, the loop belt system is prevented from running backwards under the forces of gravity, by two backstops fitted inside each reduction gearbox.

The hydraulic tensioning of the loop belt system is critical, and the design specifications must be complied with.

The advantages of a Loop Belt Elevating System are as follows:



Related information

  1. Self unloader components

  2. Self unloaders various cargo handling gears

  3. Various type boom conveyor belts - How the belt sytem practically works ?

  4. Dealing with self unloaders stalled lift belt

  5. Conveyor belt construction & troubleshoot guide

  6. Conveyor belt installation guide

  7. Conveyor belt repair & maintenence guide

  8. Safe working practice onboard self unloading bulk carriers

  9. Preventing conveyor belt fire onboard self unloading bulk carriers

  10. Cargo work safety precautions

  11. Various bulk cargoes - free flow ability

  12. Various bulk cargoes & dealing with cargo hang ups

  13. Navigation in Ice & safety precautions

  14. Dust suppression procedure & environment protection

  15. Preparations for cargo planning, handling & stowage

  16. Maintaining safe stability onboard self-unloading bulk carriers

  17. Procedure for bulk cargo handling prior to and during loading

  18. Loading operations - voyage orders, draft restrictions, various grades and rates

  19. Loading sequence and other related considerations

  20. Preparations for discharging & related guideline

  21. self-unloaders-discharging-operation

  22. Safety precautions for boom operation

  23. Directing gate operation, gate problems & crew duties

  24. Cargo holds/ tunnels cleaning, maintenance and check items

  25. Procedure for transporting coal on self- unloading bulk carriers





Related information

Cargo holds bulk flow gate, basket gate & non - consolidated feeder

Instructions for dealing with a stalled lift belt

Our detail pages illustrated many safety aspects of Bulk carrier

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