Self Trimming Bulk Carriers

Self Trimming Bulk Carriers

An operation that we experience rarely these days is the requirement to bag bulk cargoes on loading or at discharge. The need to bag cargoes on loading goes back to the time when dry cargo ships were not purpose built or specialized.

When loading grain the cargo will fill the hold but once at sea with the vibration and movement in the seaway the cargo will settle and leave an empty space at the top. When the ship heels, due to wind or sea, the grain will shift to the low side causing a list to the ship which can be a safety hazard.

In the old days, it would be necessary to secure the top of the cargo with at least two tiers of bags filled with the cargo and perhaps even secure those bags with lashings over the top. Modern Bulk Carriers which will carry such bulk cargoes are designed and built as Self Trimming Bulk Carriers which, among other things, removes the requirement to bag any of the cargo for safety and trimming.

If a cargo is to be bagged at the discharge port this is usually to facilitate the discharge of the cargo and its subsequent distribution by road or rail in areas where the port facilities are undeveloped. In either of the above cases, thought must be given to ensuring the charterparty will clearly set out who will pay and be responsible for the operation and how time will count for laytime and demurrage purposes.

Where the load or discharge operation involves, or may involve, lightering there needs to be a clear understanding as to who will pay for and be liable for the lightering. There are certain areas of the world, for example the shallow waters off Bangladesh, where a deep sea ship may have to discharge her entire cargo, or some of her cargo, due to draft restrictions alongside.

The fact that the operations are likely to be in open waters means that poor weather conditions will have a detrimental effect on the speed and efficiency of the operation.

Lighterage may take place with other ships or lighters or barges that is not fitted with their own power and will require a tug to move them, the likelihood being that the deep sea ship and the other ships will be different sizes bringing with it operational risks to the safety of the cargo and indeed the ships themselves. There will be the logistical problem of how many ships will be available and how many trips will be needed to complete the operation. Under circumstances that time is lost it is important to ensure it is clear how laytime be calculated.

An important difference between the tanker and dry cargo ships’ cargo operations is that all tankers are loaded utilizing shore pumps. Thus, depending on charterparty, dry cargo ships’ cargo operation is under Charterers’ Responsibility.

Whereas tankers are designed to discharge their own cargoes, using ships’ pumps in 24 hours, thus tankers’ cargo operation is under Shipowners’ Responsibility, If the tanker is allowed to use her full pump and pipeline capability. Thus, typically a Very Large Crude Carrier (VLCC) 300,000 deadweight will be fitted with 3 cargo pumps and pipeline systems, so that if all three are fully utilized the tanker will complete discharge in 24 hours. A smaller tanker will be fitted with smaller pumps and pipelines in order to achieve the 24 hour discharge requirement. However, at some discharge terminals where, perhaps, only 1 pipeline is available the tanker will not be able to discharge the entire cargo in 24 hours.