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Heavy Lift Cargoes

Before beginning a heavy lift operation the officer in charge should make sure that the lift can be carried out in a safe and successful manner. Depending on the load to be lifted, the vessel can be expected to heel over once the lift moves off the fore and aft line. Therefore, heads of departments should be given ample warning of an expected list, before the operation begins.

The ship’s gangway should be lifted clear of the quayside, and all fore and aft moorings tended, to ensure no damage is incurred by the heeling angle of the vessel. The critical times are when the load is over side and the vessel is at maximum angle of heel, and once the load is landed and the vessel returns to the upright position.

The vessel’s stability should be thoroughly checked before starting the operation, with particular regard to free surface in tanks. When the lift is taken up by the derrick, the rise in the ship’s centre of gravity should be such that she is not rendered unstable. (The effective C of G of the load acts from the derrick head position, above the centre of gravity of the ship, once the load is lifted.)

All rigging must be examined by the officer in charge, and any preventer backstays to the supporting mast structure should be secured in position prior to lifting the load. Correct slings should be used on the load, together with beam spreaders if required. Steadying lines should be secured to all four corners of the load, and these should be substantial enough to control oscillations when lifting from ship to quay and vice-versa.

Steam guys or power guys should be rigged and tested to ensure correct leads. The lifting purchase should be seen to be overhauling, and winches should all be in double gear.

The lugs on the load itself should be checked before securing slings to ensure that they are adequate to handle the load stress. Extreme care should be taken with crated heavy objects. Shippers are known to crate loads without reinforcing the crate itself, and the possibility of having the load fall from the bottom of the crate is a real one.

Landing the load on to a truck or flat top rail car may cause lateral drag on the vehicle as the weight comes off the derrick; and the vessel may return sharply to the upright position, accentuating this effect. To alleviate the situation, the offshore guy could be eased out as the load lands and the lifting purchase with the topping lift should be veered smartly. It is essential that competent winch drivers are operating the lifting purchase and the guys, and that throughout the operation they are under the control of a single person.

 

Read More: GENERAL CARGO

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