Industrial flow-ice generators for Russian trawler

The vessel Desert Diamond discharges its cargo either in Port Elizabeth or Cape Town, depending on the fishing.

Each of the packages, designed and built by South African-headquartered PAM Refrigeration in Killarney Gardens, produces six tonnes of flow ice of 20% concentration per hour, to pre-chill and hold the freshly landed fish before being frozen in on-board plate freezers.

The trawler has the capacity to freeze 170 tonnes of fresh fish every 24 hours and previously used a refrigerated sea water (RSW) system to pre-chill the fresh fish, but this proved inadequate and the owners opted to install the Pam Flow Ice Generators to increase production.

The packages are fitted with Grasso G series screw compressors, directly coupled to 75kw motors, operating at 2800 rpm and have a sea water shell and tube condenser. The screw compressor is done with thermo siphon oil cooling, adding to reliability and low maintenance.

The refrigeration capacity of each screw package is 225kW at -10/+35°C.

Liquid ammonia is fed through a low pressure receiver system (LPR), specifically designed by PAM for the application, to pre-cool sea water to -1°C before entering the six Flow Ice generators. The internal scrappers of the horizontally mounted ice generators are each driven by a 0.5kw motor.

A single pump on each package, driven by a 2.2kw motor, sucks sea water from a header which also supplies the condenser and pumps the flow ice slurry to the pre-chilling tanks, which are located on the rear end of the trawler.

The compact package measures 2.4 x 2.4 x 2.4m and has a small charge of only 60kg of ammonia. The packages are installed in an enclosure at mid ship on deck.

Over the past 24 months, PAM claims to have delivered about 10 similar design systems to different Russian trawlers operation in Mauritania, Namibia and South Africa.