Ammonia packs replace old central plant

By John Ackermann
When the time came for Gansbaai Marine to upgrade their flake ice-making system in 2018, they approached Everflo, who subsequently designed and manufactured a unique ammonia cooling system comprising four packaged refrigeration units piped to four flake ice makers.

Gansbaai Marine in the Western Cape was founded in 1962 and requires 100 tonnes of ice daily to cool sardines caught at sea. The sardines are then brought back, pumped off the boat, and canned in their factory.

Although some fishing boats have an ice maker on-board or refrigerated seawater (RSW) systems, at Gansbaai Marine, because of the short duration at sea, the ice is made onshore. Before leaving for sea, flake ice is conveyed from a bunker about 50m from the quayside and mixed with seawater in the hold to create slurry ice to cool the freshly caught sardines.

Old dimple plates

Their existing flake ice maker was of the ‘falling film’ design with vertical dimpled plates. The harvested ice dropped into a vertical 8m bunker with raking system and conveyor to the quayside.

Gansbaai Marine was an ideal application for Everflo’s packaged ammonia units. To meet the maximum daily requirement, Everflo proposed four packaged units piped to four vertical flake ice makers.

The new system was installed during the months when no fishing took place and was ready for the new season in August 2018.

Images by Everflo

Standard packs add flexibility

Evert Potgieter, managing director of Everflo, gave insight to the design of the plant.

“Instead of going for a more conventional central plant, we selected four of our packaged ammonia packs and these were piped to four imported Geneglace flake ice makers designed for pumped ammonia circulation,” he explains.

Each package has a cooling capacity of 145kW at -25°C evaporation and +30°C condensing temperatures. The absorbed power is 56kW for each unit with a 75kW motor.

Each package incorporates a compressor, marine shell and titanium tube condenser, and suction accumulator designed with a heat exchanger to sub-cool high-pressure liquid and evaporate the liquid overfeed from the ice maker.

The entire package is manufactured by Everflo and includes all valves and controls. They only require a liquid and a suction line connection on site.
Everflo’s standard package comes with the marine shell and tube condenser and could be used with cooling tower or seawater. In this case, they used seawater for the condensers due to the proximity of cold seawater. “The advantage is water saving and improved coefficient of performance (COP) with lower absorbed power,” said Potgieter.

How do these ice makers work, though? The ice maker has a double-walled vertical steel drum, and low-temperature ammonia is circulated through the wall of the drum without the use of an ammonia pump. Freshwater is sprayed on the inside of the drum and forms ice, which is scraped off by a rotating scraper. The ice falls into an insulated bunker below. The bunker has a raking system to rake the ice into a conveyor, which takes the ice about 50m to the boats.
Gansbaai Marine built the original ice bunker and racking system and duplicated the same to accommodate the increased capacity of the four new ice makers.
The use of Everflo packaged units reduced the installation time of the complete system on site to only four weeks.

Quality control in factory assembly

Everflo has been designing and manufacturing refrigeration systems for industrial applications since 2003, fine-tuning the design over the years until finally coming up with their new range of packaged ammonia packs. Except for the imported compressors, valves, and motors, the manufacture and fabrication are all done in-house at the Everflo plant in Killarney Gardens, Cape Town. The packs have a small footprint and can be transported on conventional road vehicles or in standard shipping containers for export. The packs for Gansbaai Marine each had a mass of only four tonnes.

Benefits of independent systems

There are seven models available in the range of Everflo ammonia packs and it can, with the least amount of site labour, be piped to ice makers, evaporators in cold stores, blast freezers, or plate freezers. The packs are complete with control panel and require the least amount of site wiring.
A very distinct advantage of the packs is flexibility and Gansbaai Marine is a typical example. Previously, if something went wrong with the system, the entire plant would shut down and the operation would stand still. Now, because the four packs are independent systems, if one shuts down, the rest can still operate as normal, preventing any loss of production.

The Everflo package design also negates the need for ammonia pumps, simplifying the system design to make things easier for the client. It is a stop-and-start operation without all the unnecessary complex functions. It also requires a much lower ammonia charge than a central plant and much shorter pipe runs — all adding up to great cost savings and easier maintenance in future.

The performance of the system, which has a lifespan of 15–20 years, can be viewed remotely by Everflo via the mobile network, and they can provide advice on any faults or assess the remedial action needed before travelling to site.

Within months, the performance of the plant has clearly indicated that the replacement of the old plant was long overdue.

The future is packaged equipment

When it comes to the marine industry, Potgieter is an expert. Coming from a fishing background, he has the unique skill set of understanding both the world of the client and the engineering side of things. This has allowed him to come up with engineered systems over the years that really address the need of the marine world.

Potgieter elaborates, “There is a global shortage of specialised skills to install, service, and maintain industrial refrigeration systems and more so where plants are to operate in remote areas.” At Everflo, their focus has been to design and develop modular package units that are simple to operate, easy to transport by normal transportation, and of the highest quality. They have developed three packages each for a specific range of applications: the compact flow-ice unit complete with its own ice generator, the ammonia freezing package, and the RSW water chilling package for on-board refrigeration.
To meet the required cooling duty or volume of flow ice, a single package or multiples of one of the standard packages are selected. When more capacity is required in the future, further packages can easily be added.

“Building the packages under controlled conditions in our factory provides a guarantee of quality and standardisation,” says Potgieter. This is also of particular importance for clients who have multiple packages on a single site. “Only one set of spares is required.”

Although the packages were originally developed to meet the refrigeration demands of the marine industry, the packaged solutions are very much suitable for any industry where cooling would be required. The flow-ice pack and the ammonia pack can be used in processing plants, for cold stores, desalination, blast freezing, and on any type of fishing vessel, such as tuna, purse-seiners, or whitefish trawlers.

“Wherever possible, we opt for ammonia as the refrigerant in our packs because of its zero global warming potential and excellent thermodynamic properties,” explains Potgieter.

Gansbaai Marine has now proudly been added to a long list of Everflo projects, not only in southern Africa but across the globe in South America, Australia, and Russia.

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