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

Fig:self unloader boom installation

The advantages of the Lift Belt System are:

It occupies less space in the vessel than any other elevator belt system, as the angle of the elevation is vertical.
It requires a smaller number of rollers to support the belt.

The disadvantages of the Lift Belt System are:

High Cost
Long belt change-out time required i.e. three to four weeks and this can only be performed in a shipyard with sufficient crane height, and capacity.
The belts are prone to damage from cargo falling from the upper part of the system.
The belts are prone to damage if the side guide wheels become
seized. The resultant edge damage lays open the steel cables to corrosion which will eventually result in the belt being scrapped.

Important note: the side guide wheels must be inspected during and after each discharge. Any seized guide wheels must be repaired immediately. Any edge damages on the lift belt must be repaired using cold cure procedures immediately.
Hotwork in the lift belt casing is extremely hazardous as hot material can lodge in the pockets.
Lift belts are susceptible to stalling, if the system is shut down during high rates of discharge.

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:

High cargo handling capacity
A relatively small volume of the vessel is occupied by the Loop System with its near vertical lift.
Belts can be completely changed out in a short period of time i.e. three to five days.
Easy to maintain.
Belting material is available from several manufacturers at competitive prices.
Simple and robust drive system.
A minimum of automation is required.

Related information

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

Home page |||Bulk carrier types ||| Handling of bulk coal |||Cargo planning ||| Carriage of grain |||Risk of iron ores |||Self unloading bulk carriers |||Care of cargo & vessel |||Cargoes that may liquefy |||Suitability of ships |||Terminal guideline |||Hold cleaning |||Cargo cranes |||Ballast handling procedure |||Bulk carrier safety |||Fire fighting systems |||Bulk carrier General arrangement

Operation of sea going bulk carriers involved numerous hazards . Careful planning and exercising due caution for all critical shipboard matters are important . This site is a quick reference to international shipping community with guidance and information on the loading and discharging of modern bulk carriers so as to remain within the limitations as specified by the classification society.
It is vital to reduce the likelihood of over-stressing the ship's structure and also complying with all essential safety measures for a safe passage at sea. Our detail pages contain various bulk carrier related topics that might be useful for people working on board and those who working ashore in the terminal. For any remarks please Contact us

Copyright © 2010 bulkcarrierguide.com All rights reserved.

Although every effort have been taken to improve the accuracy of content provided the publisher of this website cannot take responsibility for errors. Disclaimer Privacy policy Home page