FISH FARMING TECHNOLOGY
RAS
Feeding systems for fish farms and RAS by Fish Farm Feeder, Spain
Let’s do a little history. The concept of automatic feeding was born and developed in Norway in the early 1980s. The first equipment was developed for sea cage feeding and was very basic. This equipment consisted of a hopper with a capacity of less than 200kg of processing power, a blower to send the feed to the cages and an auger screw to drive the feed from the silo. Over the years, the evolution of technology and the demand for equipment with greater performance led to new solutions appearing on the market such as revolver type feed distributors and software that allowed for greater control over feeding. These centralised systems consist of a central station where the silos and all the (automatic) dosing, distribution and control elements are located. The distribution of the feed to the different tanks is done by means of a fluid (typically air in the pneumatic systems) that flows through pipes. Early in this decade, with the evolution of robotics and artificial intelligence, new power feeding systems have been fully designed and optimised for land-based and RAS systems to emerge from.
Silos
Silos, as necessary tools for safe feed storage, vary in number and capacity according to the needs of the aquaculture company using them. They can be manufactured in various types of material (stainless/galvanised steel, fiberglass, polyethylene, etc) and must be certified for food purposes. They can also be standard or custom-made to cater to the clients needs. An angle at the bottom of the silo ensuring that the feed falls easily is recommended.
has to dose in a defined period of time. When feed and batch are changed calibration should be carried out. Depending on the manufacturer, different types of volumetric dosing units can be found. The most common ones are dosers and auger screws. The auger screw-based system is the most widely adopted to achieve accurate dosing of feed from the hopper. The very thrust of the auger is what makes the precise amount fall into an intermediate hopper, and it is in such a compartment where the various mixtures from several hoppers (up to four) converge to achieve the feed mixture defined by the fish farmer. This functionality allows different sizes of pellets and/or types of feed to be included in one dosage at the same time in a certain proportion. A rotary valve or shutoff located downstream of the intermediate hopper allows the already dosed feed to be regularly introduced into the feed line, avoiding clogging.
Selector
The selector is the device that aims to distribute the feed to the different tanks by selecting an outlet, which is linked to the tank by means of an HDPE pipe. Here we find two types of selectors: • The ‘revolver’, a system wherein the outlets are placed in a circle and the selection of the mouth is done by a motor with a reducer • The ‘matrix’, where the outputs are placed in a matrixial way and the selection of the port is done by two servomotors, one
Doser
Two dosing systems are usually used for feed dosage: Gravimetric and volumetric. Gravimetric systems are based on weighing the doses by means of one or more electronic load cells. The only unit of measurement is weight In volumetric systems the dosage is made according to the volume. In such systems, it is essential to calibrate the dosing element according to the type and size of feed to be used. It is necessary to establish what quantity of mass the dosing element 48 | June 2020 - International Aquafeed