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Given the past few months’ challenging business climate for owners and operators in the dry bulk segment, even more focus should be paid to cost-efficient and safe operations. This article gives an overview of some important operational aspects in this context, along with practical guidance.

Bulk carriers are ships designed primarily for the cost efficient large scale transport of dry bulk commodities such as iron[ds_preview], coals, bauxite/alumina and grain. They have to fit perfectly into the overall logistic chain and consequently this is the scale they are measured to.

Following the typical trading routes as well as the typical bulk commodities to be carried, bulk carries are optimised in sizes and configurations to allow most economical use.

As a general rule, due to the economy of scale, the bigger the cargo parcels, and the faster the loading and discharging operations, the bigger the vessel transporting the cargo would generate greater profit. The market will therefore always seek to use larger vessels when the trade permits.

However, there are general limitations in the average ship size serving the different routes due to factors such as

• port restrictions: berth limitations (e.g. draft limitations, air draft limitations, length of pier, etc.) and lock limitations (e.g. Panama Canal, St. Lawrence Seaway, etc.).

• infrastructure restrictions: Less advanced port- and / or inland infrastructure hinders a quick distribution of large quantities of cargoes to and from the port areas.

• trade restriction: demand for individual cargoes at various destinations is limited.

Consequently, bulk carriers have developed into well known size categories as given in the table above.

Of course overlapping for the given segments can not be avoided and different descriptions are often found.

Design and operational considerations

Where in the past competition between the different bulk carrier designs was mainly on steel weight today it is the competition on operational flexibility.

Advanced ship technology and the introduction of direct strength assessments using Finite Element Method (FEM) in the beginning of the 1980s led to reduced lightship weights and therefore to a rise of deadweight capacities. Also an increasing ratio of high tensile steel to mild steel was a contribution towards lighter ships noting that fatigue became an important issue.

Competition on steel weight with the aim to maximize cargo intake was one reason for the many casualties end of the eighties beginning of the nineties.

A number of measures have been taken by IMO, IACS and the industry to enhance the safety of bulk carriers since then. Latest with the introduction of the IACS Common Structural Rules for bulk carrier all bulk carrier newbuildings are to be constructed towards uniform acceptance criteria.

Operational flexibility is a key issue in bulk carrier designs and acceptance in the shipping market. The operational aspects laid down in today’s Rules and regulations are providing an increased safety compared to the old days. Anyhow, the challenge is to combine the improved safety with improved efficiency.

Beside the optimum size of a bulk carrier also other aspects are of even similar importance. The overall performance of a bulk carrier is subject to its operational flexibility and efficiency and therefore its economic success in the shipping market, in particular where a large number of ships is competing on a given transport volume.

From the operational point of view the following aspects are to be reflected with regard to improved efficiency:

• ship Handling

• cargo Handling

• maintenance and inspection

Ship handling

Handling of a ship is to be understood as covering all aspects related to sailing on route, manoeuvring and berthing in an always navigational safe manner. The primary obligation of the master is to ensure that the ship, the crew and the cargo is not put into unsafe situation. Also training and competence of crew are essential to fulfil this obligation, for which the STCW convention was introduced.

Load and discharge planning is one of the most essential tasks to be performed by ships crew. It is to be ensured that during loading and discharge processes strength and stability of the ship is not compromised at any time. Planning of efficient loading and discharging by minimizing berth time can be only performed within the ship’s strengths and stability envelope it was designed to.

For the Lakesize bulk carrier it is of great importance to have a high loading flexibility to cope with the draft restriction then sailing on St. Lawrence Seaway and the ­Great Lakes. Grain stability, permissible still water values and hold mass curves adjusted to the Great Lake conditions can improve flexibility. Further on, including hull girder deformation in loading computer will give master better reliability for planning loading.

Beside the capability of a ship being loaded at a specific loading rate which is to be time wise synchronised with ships’ de-ballasting rate considered in the planning the discrepancy between actually loaded and planned quantity of cargo is increasing with loading rate and number of loaders.

Although new designs, constructed according to IACS UR S25, have incorporated a 10 % overshot margin for high dense cargoes based on maximum cargo hold mass this is in general not the case for ships constructed prior 1 July 2003, the application date for UR S25. Most sensitive with regard to strength envelope are the outermost holds in alternate loading conditions.

Consequently, efficient means to control amount of cargo loaded to the individual holds are necessary to avoid overstressing and unfavourable trim.

Another important aspect to be considered then talking about ship handling is the exchange of ballast water. The efficiency of ballast water exchange is mainly dictated by the design of the ballast piping system including pumps, valves and arrangement of ballast tank.

Although an approved ballast water management plan guaranties that the exchange process does not put the ship in an unsafe situation in principal it is recognized that time needed to conclude one step might take a very long time, time in which weather condition can impair. This is particular the case for Capesize vessel where double bottom and top side tanks are generally connected and extending over two cargo holds in the midship area. Serving smaller tanks would definitely make this operation more efficient.

Cargo handling

Cargo handling covers all activities in connection with safe transferring, stowing, lashing and securing considering the typical behaviour and characteristics of the different cargoes to be transported.

Driven by a fast turn around time in port cargo handling is an important design aspect. In general design requirements are to be linked to the harbour conditions such as optimum hatch openings to providing easy access to the hold and shipboard cargo handling gear.

Lashing equipment in cargo holds and on deck as well as appropriate cargo hold ventilation and humidity control are further design aspects in this connection.

Cargo variety is a typical feature of the smaller bulk carrier segments up to Handymax, carrying all kinds of dry bulk as well as break bulks, such as steel products, forest products or project cargoes.

In general handling of dry bulk cargoes is done by port side equipment and fitted ship board cranes are used for handling break bulk and project cargoes. Anyhow, if used for handling of dry bulk cargoes as well design of the cranes should account for and grabs may be stowed on board.

Cleanliness of cargo holds prior loading is an important issue particular for bulk carriers changing type of bulk cargo very often, such as Handysize and Handymax. Operational efficiency is improved by the ability to perform fast cleaning of the cargo spaces. Providing appropriate cleaning tools and furnishing necessary water and air supply are necessary preconditions. Sufficient pump capacity and a dedicated wash water holding tank are supplementing the arrangement.

Maintenance and inspection

It is sufficiently known that lack of maintenance will lead to rapid structural deterioration and in the worst case to loss of life and properties. Lack of maintenance and improper inspection scheme by ships’ crew were contribution factors to the massive losses of bulk carriers in the past.

To avoid un-necessary off-hire situation or costly repairs a regular inspection and maintenance plan should be drawn up focusing on critical areas typical for bulk carriers enabling the owner to better control the condition of his ships.

Although, with the introduction of the enhanced survey program (ESP) for bulk carriers in 1992 surveys are carried out much more thoroughly, it can not replace continuous maintenance. It is to be noted that the ESP through the resolution A.744(18) requires the ship owner to maintain on board documentation relating to inspection carried out by ship’s personnel with respect to structural deterioration and the condition of the coating, if any.

Further on, to assist owner in doing so, IMO has developed »Guidance to Ships’ Crew and Terminal Personnel for Bulk Carrier Inspections« (A.866(20)) to provide guidance to ship’s crew and terminal personnel with respect to the principal areas on bulk carriers that are likely to be susceptible to corrosion or damage. This guidance is supplemented by the IACS recommendation No. 76 on »Guidelines for Surveys, Assessment and Repair of Hull Structure – Bulk Carriers«.

Maintenance of cargo hatch covers of bulk carriers became mandatory with the introduction of regulation 7 of revised SOLAS Chapter XII entered into force 1 July 2006 and forms part of the ISM scheme.

Never the less, today charterers are getting concerned about the condition of the bulk carrier they are going to charter in and a rating scheme similar to those used for tanker is becoming more and more popular.

With respect to the operational efficiency a structured inspection and maintenance plan combined with crew training will keep availability and reliability of the ship through

• detection of deficiencies at an early stage

• dealing with problems while they are small

• being able to document the ship condition

• maintaining a uniform standard across the fleet

In DNV, we have the expertise and experience needed to help owners ensure their bulk carriers are operated efficiently. Our philosophy is that a safe and reliable bulk carrier is more easily obtained if it is properly designed, constructed, maintained and inspected.

A safe and reliable bulk carrier is only obtained if it is proper design, constructed, maintained and inspected.

Sönke Pohl