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TANKER SHORTAGE CLAIMS : CARGO REMAINING ON BOARD (ROB)
Published: 1 August 2015
This article continues our series highlighting good practices that can be shared with Members and looks at shortage claims due to cargo residues remaining on board (ROB).
Claims for short-landed cargo arise if an excessive residue of the cargo loaded remains on board after completion of the discharge. To assist in defending such claims, the ship must show that all ’pumpable’ cargo was discharged. In order to do this, the ship’s crew must carefully record all details of the loading and discharge operations and must show that they acted in accordance with the ship’s procedures. They must also show that they were complying with the industry standards for the carriage of the particular cargo.
Our analysis of recent shortage claims against Members shows that there are three main factors which contribute to ROB claims:
- Nature of the cargo.
- Heating of the cargo during carriage and at discharge.
- Unpumpable cargo : sediment / sludge)
We will discuss these factors in detail below and provide examples of claims handled by the Club. In all cases, and always prior to loading, it is essential that Members receive clear instructions from charterers (and shippers, as appropriate) on the cargo, including any specific handling requirements eg when, for how long and to what temperature to heat cargo. In turn, those instructions should be provided to the master and crew.
1. NATURE OF THE CARGO
It is often the case that the inherent nature of the cargo is not properly considered when fixing the ship, especially when looking at the pumping capabilities and the heating system of the ship.
Molasses
Molasses is a dark, viscous by-product of the sugar refining process. Molasses may have a viscosity of several hundred centistokes (as a comparison, a very heavy lubricating oil may be in the region of 100 centistokes). The viscosity of molasses is affected both by dry matter content and temperature. For example, a rise in temperature of 10º C may reduce the viscosity to half (or even less) and a reduction in the dry matter content will also decrease viscosity. Due to high viscosity and dry matter in the cargo, it can be difficult to handle the cargo with traditional centrifugal pumps and, therefore, screw pumps are best suited for handling molasses cargo. Sometimes steam is required to help with the removal of ROB. Chartering and commercial departments should be aware of these issues when fixing a molasses cargo.
Further observations:
- Heating instructions must be followed precisely and a heating log must be maintained.
- The temperature should be measured at several positions and levels in the tank as different temperatures can be experienced within the cargo.
- At a temperature of 40ºC molasses is relatively stable but as the temperature is raised, sugar may be lost by thermal decomposition and the cargo could be found to be off-spec. Where temperatures over 60ºC are recorded there is a heightened possibility of thermal decomposition that could result in the complete destruction of the cargo. The crew should be vigilant in monitoring the temperature of the cargo to ensure that it does not exceed 40o
Crude oil
Over the past few years there has been an increase in the number of variations in both the types and quality of crude oil. Traditionally, crude oil is heated when it is carried and a crude oil wash (COW) is carried out at the completion of discharge. However, two notable exceptions were apparent from our analysis of shortage claims where it will not be appropriate to carry out a COW:
- Viscous /waxy cargoes – COW may lead to high ROB; and
- Volatile cargoes – COW causes excessive gas evolution.
Crude palm oil
In order to maximise outturn, it is usually necessary to sweep any residue of crude palm oil manually from the cargo tanks at the final stage of discharge. The Club has handled a shortage claim where the shortage was due, in part at least, to the fact that the terminal restricted this sweeping of the cargo tanks.
2. HEATING OF THE CARGO DURING CARRIAGE AND AT DISCHARGE
Many cargoes need to be maintained at specific temperatures during the voyage and at the discharge port. The Federation of Oils, Seeds and Fats Associations (FOSFA) provides heating instructions for vegetable oil cargoes during the sea voyage and discharge operations.
In a recent case, a Member’s ship loaded 2,555.942 mt of Indonesian RBD palm stearin in bulk destined for Europe. The cargo was loaded into ship’s tank no. 3 starboard. In this case, the ship’s temperature records, obtained from the chief officer, indicated that the FOSFA recommended temperatures were maintained throughout the sea passage.
The cargo tanks were equipped with framo cargo heaters. In order to heat the cargo, the cargo pumps are used to re-circulate the cargo through the heater until the required temperature is achieved. Cargo cannot be discharged and heated at the same time and so when cargo is being heated, discharge must stop.
The cargo discharge was stopped twice in order for the ship to conduct heating and re-circulation of the cargo. Despite this, the cargo temperature during discharge was below the required level.
When the ROB was 50mt, the hose was disconnected by the terminal due to a misunderstanding between the chief mate and the terminal staff. The chief officer immediately requested that the hose be reconnected with the intention to reload a small quantity of the cargo from the terminal in order to warm up the remaining cargo.
However, on instructions from the cargo receivers, the terminal rejected the chief officer’s request. The ship was then instructed by the local agent to shift to another terminal in order to discharge further parcels and to avoid both delay and expense.
The master and chief officer issued protests but the ship had to change berths while the crew heated the ROB cargo. After completing discharge of the other parcels, the master informed the agents that more time was required to heat the ROB cargo from the first parcel. As a result the ship was moved to anchorage.
The remaining 50mt of palm stearin cargo was discharged after several hours of heating, re-circulation, sweeping and also squeezing of the dense/solidified product in the tank bottom, by the ship’s crew.
The delay to the ship and additional costs could have been prevented by better preparation of the cargo plan, including consideration of the nature the ship’s cargo heating system. In addition, the discharge should have been carried out with more care as follows :
- As soon as the chief officer noticed a reduction in the discharge rate (due to low temperature) discharge should have been suspended. The cargo lines should then have been cleared and the heating system re-started, with the discharge resuming as soon as the temperature reached the minimum level required.
- This operation should have continued until the minimum amount of cargo remained in order to maintain sufficient heat transfer throughout the cargo (typically 1 metre of sounding). This would ensure that the remaining cargo could be pumped, despite the absence of heating. Discharge could then be completed with final stripping.
- The crew should also have considered internal stripping of cargo ROB into one tank.
In similar cases, the Club has noted that there has been a high ROB due to heat loss caused by cold ballast water reaching the tank top. When ballasting, the tanks should be kept slack if possible to avoid the tank top cooling down too quickly during discharge.
3. UNPUMPABLE CARGO: SEDIMENT/SLUDGE
ROB claims can arise from cargo sediments remaining in the tank. The Club recently handled a claim in respect of a cargo of waxy paraffinic crude oil where the total wax content and pour point values were not declared in the cargo documents issued by the load port terminal. As a consequence, the crew were under a misapprehension as to the nature of the cargo and they treated this cargo as if it were a waxy crude oil, heating all the cargo tanks and the slop tank in order to carry out a COW. If the correct cargo documentation had been available and had been read properly then the crew would have realised that the properties of this waxy paraffinic crude oil meant that they did not need to carry out a COW.
CONCLUSION
Members should always ensure that they receive clear and understandable instructions from the charterers, which should include tank cleaning requirements and tank heating instructions. The instructions may also include references to particular trade requirements, such as FOSFA. The instructions should be communicated to the master and crew and if there is any doubt about the exact nature of the cargo to be carried or about the voyage instructions, then immediate clarification should be sought from the charterers. In addition, before loading and discharging the master and crew must have full knowledge of the intended loading/ discharge plan.