FISHING: First Ammonia RSW In SA
Recent Western Cape Business News
PAM Refrigeration recently completed a new installation onboard the Ruwekus. The vessel’s owners are Pioneer Fishing, based in St Helena Bay on the west coast.
The new refrigerated sea water (RSW) system is capable of chilling the total catch of 200 ton sardine from +18°C down to -1°C in less than 5 hours. In the past, the vessel required ice to cool the fish and then reduce the temperature down to about +10°C, whereafter the RSW system will chill the fish further. “With the new system there is no ice required and the chilling time is still less that what they achieved before with ice,” says PAM’s Evert Potgieter.
The Ruwekus RSW system was out-dated with two freon compressors, with a total capacity of about 350kW, and a chiller and condenser under capacity with tubes from the heat exchangers often leaking due to corrosion. PAM delivered an ammonia system with a total refrigeration capacity of 480kW. The increased capacity of the system was about 40%. The heat exchangers are from titanium and the tubes will not corrode, Potgieter says.
Sardine need very fast cooling rates which need to be maintained at a temperature of -1°C until offloaded and processed for canning. This ensures the best quality and yield.
PAM delivered the system with a large titanium chiller and a condenser suitably sized for sea water condition over +25°C. The system comprises two new Grasso screw compressors, ‘model E’ each with 75kW electrical motors. The starting gear for the compressors motors are soft starters with PAM designing the system to minimize the start-up load. The challenge was to design the system in such a way to ensure the increase in refrigeration capacity does not impact on the power requirements. “We had to ensure that the larger refrigeration system could still be driven with the same power supply generator onboard,” Potgieter explains.
“The refrigeration capacity of the compressors increased with 40% and the power supply requirements are still the same thanks to the efficiency improvement with ammonia compared to Freon systems. A further reason for the improved power requirements was the larger condenser we installed, reducing the absorbed power of the screw compressors.”
“After our initial test we measured the cooling time. The actual time to cool the same water compared to the old system was less than half the time. This improved system performance is proof of our complete approach to our system design philosophy of best performance with maximum efficiency, robust, and service friendly,” he says.
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