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OR: make sure drippers don't get clogged up

"Don't mash the marble track"

A watering system is actually a chain with different parts: water pump, pipes, and so on. A crucial part in that chain is the filter. "This part should actually not break down, and if it does break down, you need to be able to repair it very quickly. The SAF filter is so robust that it can't actually break," says Stefan Bakker, product manager at Netafim. The originally Israeli company recently introduced a new, improved version of the SAF-XN filter.

The SAF-XN filter is a typical product for the Dutch market: the country places high demands on water systems, which, like the greenhouse, they are part of, are often high-tech. But Stefan now also sees a hefty market for export. "Dutch greenhouse builders often take the filter with them when they carry out projects abroad. In that respect, the SAF-XN filter is like the engine block of a car being exported."

From industry to horticulture
The SAF-XN filter is an industrial filter based on a filter that is also used in cooling towers and in shipping, among others - where processes absolutely cannot fail. When applied in horticulture, Netafim ran into specific challenges.

"We are the only sector to build the filter on PVC piping instead of steel. If you put it on steel pipes, you don't need to support the filter. PVC is not strong enough to support the filter, so supports had to be placed underneath. Amiad, the manufacturer of the filter, was not familiar with that principle of building on PVC pipes, so that took some doing, but in the end, it worked out perfectly."

'Beyond expectations'
We are now six months on since the introduction of the new filter. "Both the number of customers and the number of units we put away is above expectations," he says. The new filter's popularity is down to small things. "It's not rocket science, but it all works a lot better. For instance, we have built a hatch into the new model to make maintenance much easier."

Another important update is that the series of SAF-XN filters no longer consists of four different models but now has one model, of which only the size is slightly different: there is one with 1500 cm2, 3000 cm2, and 4500 cm2 screen area. "You can also continue production while using the filter because those screens are automatically cleaned by a kind of small hoover."

Continuous learning
In the 26 years since the SAF filter first appeared on the market, a lot has changed. "And we are constantly learning. An example: we recently found out that the filter can handle more water than we always thought. The advice was always to flush every 10 cubic meters, for example, but in shipping, they rush 40 cubic meters through it in no time, they flush it continuously - so apparently, the filter can handle that without immediately breaking down. That may not be the intention, but it is good to know that overload situations do not immediately lead to major problems."

Mashing the marble track
Stefan then names the 'highlight' of the product, which he believes is what it is all about in the end. "Parts you don't need, you have to leave out. You can't remove a filter to prevent drippers and nozzles from clogging up even a little bit."

Stefan talks about two factors here: the size of the contamination and the 'marble track effect.' "A filter is nothing but the colander in your kitchen cupboard. When you drain your food, there's some that stay behind, and some that get through anyway - if you then mash it, more gets through."

Then comes the marble track. There is a funnel at the bottom, and if the marbles go in one by one, all is well. But if you throw a whole handful of marbles in at once, the whole thing clogs up. "You have the same thing with drippers: a few dirt particles pass through, but if too many particles come in at once, even if they are small enough, the dripper still clogs up. If you go wrong with your filter, you start 'mashing' the soft biological pollution, and so you get these clogging situations."

In the SAF-XN filter, the screen is 'woven' in such a way that only a quarter of a hair fits through the holes of, say, a 30-micron screen. "Since the first SAF filter, those weaving techniques have also advanced another 30 years. So they filter much better - we can make the screens more precise in terms of passage, but we can also make the screens so that the pollution stays on them better, mashing as little as possible."

Water footprint
Finally, Stefan illustrates the steps made in another way, using the water footprint of a tomato. "Only 1 percent of the water on earth is fresh and usable. So water use has to be looked at critically. In Italy, in growing tomatoes for cans of puree, you are talking about a footprint of 600 liters per kilo. In the foil greenhouses in Almeria, you're talking about 150 liters per kilo. In the Netherlands, we make do with about 10 liters of water per kilo."

So the more high-tech, the lower the water footprint. "That's what we're doing in the Netherlands: the difference between open fields and greenhouses, especially high-tech greenhouses. I don't know of any country where food production is at such a high level as the Netherlands, both in the greenhouse and outdoors."

For more information:
Stefan Bakker
Aartsdijkweg 22, 2676 LE
Maasdijk, the Netherlands
Tel.: +31 174 525444
Mob.: +31 6 13237160
Email: [email protected]

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