Dosing cabinet for oxygen
Fish grow better with a constant oxygen level in the tank, but the consumption of the fish varies according to what they eat and how active they are. To maintain as constant oxygen level as possible in the fish tank, different amounts of oxygen have to be dosed at different times.
The dosing cabinet is designed to do just that. Emphasis is placed on its simple and flexible construction, with the option to expand the cabinet changed.
Function
Based on information from the PLC of the fish farm, the dosing cabinet distributes oxygen to each individual fish basin. The dosing cabinet is divided into two separate sections, one for normal operation and one for emergency operation. The oxygen used for the normal operation is dosed via two flowmeters.
One of the flowmeters doses for normal consumption and remains constant 24 hours a day. The other flowmeter is installed in series with a solenoid valve (NC). This valve is controlled by the PLC measuring the oxygen saturation in the fish tank, opening to allow increased oxygen flow when the oxygen consumption of the fish is elevated, closing again once the output saturation is at a desired level.
Constant oxygen level
In this way the oxygen level for the fish can be kept relatively constant and optimal round the clock, while at the same time keeping oxygen usage at a minimum. Both circuits are adjusted manually by the valve at the flowmeter outlet.
Emergency oxygen
If there is any water blockage or the oxygen level of the water is particularly low, the emergency solenoid valve (NO) opens. This distributes oxygen to the water by means of – for example – perforated hoses on the bottom of the tank. The amount of oxygen is pre-set by a needle valve. This cabinet can either be connected to the customer’s PLC, which again controls the solenoid valves, or the solenoid valves are connected directly to a power supply and open automatically in case of a power cut.
The illustration shows a cabinet for three tanks, with operating oxygen and emergency oxygen. This cabinet is shown with a separate pressure regulator for emergency oxygen.
