Variance in specific gravity – cargo not discharged

Problem

The variance in the permissible specific gravity on a bulk shipment of limestone cargo resulted in the cargo not being discharged with the ship’s grabs, at the discharge port.

Analysis

The vessel needed by the charterers needed to have the minimum cargo gear requirements of 4 x 25 mt. cranes and 4 x 10 cu. mt. grabs. The age of the vessel should also be less than 20 years. The owners had declared the maximum allowable density of cargo at a specified 1.28 mt/cbm.

While the age of the vessel and the weight of the total scoop of the grab was well within the permissible capacity, the specific gravity showed a variance in comparison to the permissible limit, and the ship owners refused to discharge the cargo with ship’s grabs. This required  the hiring of shore grabs for discharge, which not only delayed but increased the cost of the discharge operation.

Goodrich Maritime solution

Goodrich made alternate arrangements to hire shore grabs in the eventuality that they may be needed to be used, alerted the ship owners and headquarters about the delay, the cost involved and also sought technical clarifications from two IACS Classification Societies, on the ability of the ship’s grabs to safely lift the cargo.

Both societies concurred with the computations of Goodrich. The original makers of the grabs (located in Europe), were contacted by Goodrich, and suggestions for adjustment of the grabs spill plates to reduce the grab capacity was agreed to by the manufacturers.

A joint survey for assessing the performance and capacity of the grabs was conducted and the ship owners agreed and discharged the cargo.

Process integration initiated

At the time of negotiating the vessel to be chartered, the cargo details (MSDS / stowage factor / density) are obtained from the head charterers and shared with the ship owners, to ensure cargo load / discharge be effected by ship’s grabs.

A confirmation of acceptance of TC specifications is to be obtained from the Head Charterers. Goodrich will carry out a self-assessment of cargo gear specifications, against the weight and volume of cargo to be loaded.