TECHNOLOGY: PAM First With Ammonia Cooling
Recent Western Cape Business News
PAM Refrigeration recently completed a new installation onboard the Ruwekus. The vessel owner is Pioneer Fishing based in St Helena Bay.
The new refrigerated seawater system (RSW) is capable of chilling the total catch of 200 ton sardine from +18°C down to -1°C in less than five hours.
In the past, the vessel required ice to take the initial heat out of the fish, and 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 than what was achieved before with ice.
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 of 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.
Sardine need very fast cooling rates and need to stay 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. Two new Grasso screw compressors, ‘model E each with 75kW electrical motors were incorporated.
The starting gear for the compressor motors are soft starters and the system was designed to minimize the start-up load. The challenge was to design the system in such a way to ensure that the increase in refrigeration capacity did not impact on the power requirements.
PAM also had to ensure that the larger refrigeration system could still be driven with the same power supply generator onboard.
The refrigeration capacity of the compressors increased with 40%, and the power supply requirements are still the same.
The reason for this is the efficiency improvement with ammonia compared to Freon systems.
Another reason for the improved power requirements was the larger condenser PAM installed, reducing the absorbed power of the screw compressors.
After the initial test, PAM measured the cooling time.
The actual time to cool the same water compared to the old system was less than half.
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