Banner Finding balance between cost and performance in dripline selection

Finding balance between cost and performance in dripline selection

A successful farming endeavour is one of the most complex economic activities, as success depends on a list of factors so vast that a complete list cannot even be attempted by putting pen to paper. This list includes everything from soil preparation to harvesting practices, it will depend on important decisions the farmer and the experts he consults will make, but it will also depend on many factors beyond the farmer’s control.

One of the many decisions to be made, is selecting the irrigation method and approach, and consequently selecting the products to be installed in the orchard, vineyard, greenhouse, or field. After the long list of variables has been considered and drip irrigation was selected as the optimal irrigation system for the circumstances, another long list of choices must be made regarding the configuration of the system.

Throughout all of this it is crucial to rely on experts to guide informed decision-making, but also to keep yourself informed to a level sufficient to guide you through the process.

Understanding Dripper Data

When technical dripper data is shared, we are confronted by terms that describe certain engineering features. These features determine how well a dripper does its job. On the farm, success depends on the dripper’s ability to deliver a supply of water that never varies. This in turn depends on the dripper’s ability to stay clean. Dripper clogging must be prevented at all costs, as it is very difficult to return flow once a dripper has clogged. Clogging prevention depends on dripper design and quality, as well on efficient maintenance once it is in action.

The dripper’s ability to stay clean, depends on turbulence. In fact, one of the most important additions to drippers as dripper design evolved, was the addition of teeth to the flow path to create turbulent flow.

This made a massive contribution to clogging resistance as particles are kept in suspension through the turbulence created.

What you need to know

A typical dripper needs to reduce its inlet pressure from 1 bar to 0 bar and get 1 ℓ/h through it. A complicated mathematical equation explains the pressure difference from the inlet of the dripper flow path to the outlet. All we however need to understand is that the pressure difference comprises two aspects: Turbulence (Measured as a Turbulence Coefficient) and friction loss (Measured by Filtration Area).

Pressure loss = turbulence + friction loss

It is important to understand the interaction between these two aspects. The less turbulence the dripper can create, the more it must resort to friction loss to create the necessary pressure loss. Friction loss does not contribute to keeping a dripper clean, but the more turbulence, and the higher the turbulence coefficient, the better the dripper is at keeping clean.

K: Turbulence coefficient - The higher the better

A higher turbulence coefficient translates to a more turbulent flow path in the dripper. This in turn translates to lower clogging risk. The dripper will be better at keeping itself clean. This value depends on labyrinth depth, width, length (number of teeth), as well as design and manufacturing excellence.

A few engineering features contribute to a higher turbulence coefficient:

Number of teeth – Less is better

Flow path length – Shorter is better

Flow path depth – Deeper is better

Flow path width – Wider is better

Filtration area: The bigger the better

The other important contributing factor to a dripper’s ability to stay clean, is the size of the effective filtration area. The larger the area of a dripper’s filter, the more area is available for contaminants to accumulate on and the longer it will take for contaminants to completely cover the filtration area. Therefore, the dripper with the larger filtration area will last longer.

Cost-performance Ratio

Beyond what is discussed here, a variety of factors must be considered in dripper and dripline selection. The designer and/or farmer must determine which attributes are necessary for the crop and circumstances.

The important purpose being to maintain a balance between dripper cost and performance. Equipment cost is a sliding scale determined by a host of factors. A comprehensive portfolio of drippers and driplines is available that cover a wide range of crops and applications.

Consider a dripline selection graph where the y axis is cost, and the x axis is a composite of application, durability, clogging resistance and other factors considered in dripper comparison. Movement along the x axis will result in movement along the y axis, that is an increase or decrease in price. The higher the values discussed above, for example, the longer the dripper will last, but the higher the cost. The thicker the pipe wall, the longer the dripline will last, but the higher the cost.

Take note, that quality is not one of the items listed on the virtual x axis. Whether selecting thin wall or heavy wall drip, the most advanced dripper or dripper with fewer features, quality cannot be compromised on. Although it might not seem so, it is possible to not veer from selecting quality products, while still maintaining the optimal balance between drip irrigation performance and your budgetary restrictions.

Consider the necessary specifications to truly determine which dripline can be relied on in the field. Look for a product that offers guaranteed longevity and is designed and manufactured with the explicit goal to decrease clogging risk and deliver water uniformly and efficiently.

It all boils down to what your crop needs. The experts would, for example, not recommend the same equipment for irrigation with hard, murky water for a single season, as for irrigation with the same water where the equipment needs to last many seasons. Similarly, the same equipment will not be used for irrigation with much better water quality.

Dripline selection boils down to selecting the correct product for the crop and circumstances, selecting a quality product that can do the job at hand in difficult conditions and selecting the product that will offer the best return on investment.