An Australian fishing fleet with more than 50 vessels is reviewing options to replace its ageing R22 equipment.
The vessels are licensed to operate in one of the best managed fisheries in the world, the Northern Prawn Fishery (NPF), which covers an enormous area from the tip of Cape York to the Kimberley.
The vessels must rapidly freeze the prawns they catch and maintain them frozen and dry at minus 35 degrees Celsius.
Because they have to snap freeze their catch, it can involve reducing the temperature of thousands of kilograms of prawns a day from around 28o to 18o degrees in a six to 16 hour period, and then store as much as 30 tonnes of frozen product at 35oC for weeks before unloading.
Expert Group managing director, Peter Brodribb, said this is a huge task for a land based system, let alone one installed in a confined space and on a constantly moving fishing vessel.
“Nearly every vessel in the fishing fleet is delivering the goods using R22 in hard working low temperature refrigeration systems, some of which are well past design life,” he said.
Brodribb has just completed a study commissioned by the NPF, to find the best technological and refrigerant gas options for the fleet. The report found that the fishing fleet really only had one option.
“There is only one other gas besides R22 that is suitable for the task and that is HFC 507A,” Brodribb said.
“However given the focus of international discussions about the future of high GWP HFCs we cannot be sure it won’t suffer the same fate as R22 in the next decade.”
Another factor is the carbon tax which is scheduled for removal later this year.
Brodribb said the report recommends a two stage process to ready the fleet for a change over to HFC 507A.
Firstly, the NPF industry will commission the design and construction of a high performance reference design, built to work on 507A.
“All vessel owners can them provide the specifications and performance parameters of this system to their preferred contractors when preparing to change over,” Brodribb said.
“This should reduce the cost for the fleet owners as many of the important design and sizing decisions will be made for refrigeration contractors who can size for individual vessels against a design with demonstrated performance.
“By the time the reference design is done, the timing for the removal of the carbon tax should be understood and fleet owners can start planning their capital replacement programs and ordering systems.”