Traditional irrigation systems use a multitude of pilot operated, self actuated, control valves for in-field pressure reduction, and flow control. However, there is much simpler equipment available, which is less expensive to set up, and provides long lasting maintenance-free irrigation operation.
Pressure Reducing Valves
PRVs are used wherever the distribution pressure is too high for the irrigation equipment, i.e. in sprinklers, drippers, and any other water-using equipment. One of the problems with pilot operated PRVs is that they can be easily tampered with; they are also very susceptible to dirt due to the small passages in the control pilots and piping. Although blockages are prevented by installing small strainers on the control piping, these become high maintenance items, and detract from the actual activity of farming (growing product).
Ratio reducing valves can do the function of most of these applications. A ratio reducing valve reduces pressure in a fixed ratio, which cannot be adjusted or tampered with. Ratio reducing valves are also not susceptible to dirt, as there are no small passages on any part of the valve.
Flow Control Valves
Flow control valves are used to control the flow into any section of the system. They ensure that the amount of water supplied is optimal, and that certain sections do not starve others due to differences in elevation, or resistance to flow. Traditional flow control valves are also pilot operated, and suffer from the same problem as pressure reducing valves, in that they are easily tampered with and vulnerable to dirt. They also require a great deal of ongoing maintenance to function effectively.
Maric flow control valves can do the function of most of these applications. These valves are very simple, tamper-proof, and are not vulnerable to dirt. The average expected service life is 20 years. Maric flow control valves control the flow rate chosen, irrespective of pressure fluctuations.
In many applications, flow control valves can be used instead of pressure reducing valves. For instance, in a normal sprinkler, you can adjust the amount of water used by controlling the pressure to the sprinkler. If, on the other hand, you use a flow control valve instead of a PRV, you will essentially achieve the same thing. A Maric flow control valve is a lot simpler, and cheaper, than a pilot operated pressure reducing valve.
Centre-pivot sprinkler systems are a typical application where the Maric flow control valve can be used instead of pressure reducing valves. Let me explain: pressure reducing valves are normally installed on center pivots, so that the sprinklers can be protected from over-pressure, and the flow rate can be set to the ideal setting. A Maric flow control valve will achieve exactly the same end result! If you know the number of sprinkler heads on a centre pivot, and you know the ideal flow rate for each one of them, you know the total flow required. By simply installing a Maric valve in front of the centre pivot, the ideal volume of water will be supplied to the centre pivot.
Pressure will also be automatically reduced to that which is ideal for the centre pivot.
This will ensure even distribution of water to all the centre pivots.
In very large centre pivots, one may find that the sprinkler at the beginning, first from the pivot, will spray a larger amount of water than the ones closer to the end. It may, then, be a good solution to install a Maric flow control valve on a few sections of the centre pivot… or even on each sprinkler.
In the context of irrigation, the purpose of any development in equipment used, has mostly resulted in simpler, and less expensive, options. This stands to reason when one considers the environment in which the equipment has to operate, the level of education of staff, and the tendency to adjust things for the wrong reasons. These factors are particularly true in the African continent.
The use of the ratio reducing valve, and the Maric flow control valve, provide options around simplicity, tamper proof operation, long life and lower initial cost.
Please click here for a video of the Maric Flow Control Valve.