The reefer container capacity on board container carriers has been increasing for the past few years. These installations give rise to new technical problems with respect to ventilation, electrical power supply and control systems that are not currently covered by DNV rules.
Based on the above, DNV is currently developing rules for the carriage of reefer containers. A brief description of these tentative rules is given below.
The rules will have three different notations covering various trading patterns, from 100% chilled cargo to 100% frozen cargo as illustrated in table 1. In addition, a notation will be given to show the number of reefer containers that may be carried on deck and in holds.
The DNV rules will state explicit requirements for both water-cooled containers and systems using supply air cooling. Other systems with a novel design may also be given the notations described above after special consideration and testing.
In the following you will find a list of some of the key items of the rules:
Ventilation
Air distribution systems are to be provided to supply air directed at each container refrigeration unit. The air supply is to be adjustable in order to cope with different stowage patterns for high cube and standard height containers.
The positions of supply air inlets and exhaust air outlets are to be such as to reduce the possibility of short circuiting, i.e. hot exhaust air should not be sucked back into the holds.
Electrical and Control System
Under sea-going conditions, the number and rating of service generators must be sufficient to supply all container socket outlets and the hold space ventilation system in addition to the ship’s essential services when any one generator set is out of service.
The number and rating of all service generators must be sufficient to supply all container sockets and the hold space ventilation system in addition to the consumers needed under manoeuvring conditions.
Ships designed for the carriage of more than 150 reefer containers are to be equipped with a remote reefer container monitoring system of the power cable transmission type.
Access
Suitable accesses are to be provided to allow the removal of each refrigerated container’s compressor or electrical motor, taking into account that the vast majority of reefer containers are a high cube type.
Access is to be provided for the maintenance and replacement of the cargo hold fans in all loading conditions.
These rules have been developed based on input from both yards and owners, thus incorporating an already established industry standard into the DNV rules.