There is a range of accessories that we can use to complement our fertigation system in order to make it easier to install and maintain and to reduce the risk of accidents.
FILTER
Vital for preventing damage to the collars, pistons and valves. When solids (normally precipitated) pass through a dosing pump, it increases the wear of the collars, scratches the pistons and prevents the valves from closing correctly, which results in reduced performance and increased pressure loss. Minimum 120 mesh.
The filter must be placed between the tank and the dosing pump. If a dosing pump can suck products from numerous tanks, the filter must be placed downstream from the collection point. It must be made from a material that is resistant to the chemical products being dosed, normally with a polypropylene body and a stainless steel or polyester mesh, or preferably it can be a plastic ring filter. Valves must be installed before and after it to prevent excess spillage of the product when testing or cleaning it.
The dimensions must be suitable for the flow rate and the expected impurities of the product being injected. If it is properly maintained, a 3/4” filter is enough for flow rates of up to 400 l/h and a 1 ¼” one for flow rates up to 1200 l/h.
INJECTION VALVE
This is a check valve that protects against fluid backflow and prevents irrigation water from entering the dosing circuit. This type of valve has several advantages:
- Diffuser: They keep the product away from the walls of the pipe, thus preventing it from corroding, and place the product in the area with the greatest velocity, allowing it to diffuse properly to ensure it dissolves and reacts quickly, guaranteeing correct meter readings (EC and pH).
- Spring-loaded: The spring stops the product from passing through the valve, unless it is propelled by the dosing pump, thus preventing the tank from accidentally discharging. In this case it replaces the anti-siphon valve, without the disadvantage of air entering the system and possible splashing when closing it. The sensitivity of the spring – made from AISI 316 stainless steel – to the chemical products being injected must be taken into consideration and its condition must be periodically checked, replacing it if appropriate to prevent the product from being accidentally discharged. Ensure that there is no overpressure beyond the levels permitted by the dosing pump.
ANTI-SIPHON VALVE
This device, located in the impulsion above the maximum water line, opens when there is very low or no pressure or a depression, allowing air to enter the system and preventing the product stored in the tank from accidentally discharging into the irrigation pipes when the dosing pump is not running. It does not generate a head loss , so it must only be used in systems where the maximum pressure of the dosing pump is very close (< 1 bar) to the maximum irrigation pressure.
A common issue when using this device with saline solutions, such as fertilisers, is that air enters the pipes and crystallises the product, affecting the watertightness when it closes. In this case, some of the product is lost and the closure seal can be damaged.
Combining an anti-siphon valve with a spring-loaded check valve offers the guarantee that the anti-siphon valve will not open unless the check valve loses its watertightness.
PURGE OR PRIMING VALVE
The purge or priming valve is installed on the pump’s cylinder and it allows the dosing pump to work without the counterpressure of the network, quickly purging it. It is particularly useful when working with spring-loaded check valves, long or deep suction tubes or with high pressures.
This valve is opened manually and it can be closed when the liquid being injected reaches the drainage bypass.
RELIEF VALVE
This valve allows excess pressure to be released from the system, which may be caused by a blockage, a manual valve being closed during pumping or an injection valve being blocked. When the maximum allowed pressure is exceeded, it acts as a path of least resistance, allowing the product to return to its original tank.
If a dosing pump is pumping a product that doesn’t have an outlet, or if it has an insufficient outlet, in the delivery pipeline, as the dosing pump is a volumetric pump, it will continue to pump fluid into the circuit until the valves, channels or even the pump itself break.
