FERTILISERS AND FUMIGANTS. METERING OR FLOW REGULATION - ORIFICE PLATES

FERTILISERS AND FUMIGANTS.   METERING OR FLOW REGULATION - ORIFICE PLATES - TREATED HECTARES AND WATCH OUT FOR PRODUCT SG (SPECIFIC GRAVITY.)

Here are a few examples of orifice plates which are placed in-line to accurately meter or regulate the flow of soil fumigants or fertilisers.

This tractor with a five-tine implement is applying a sub-surface fumigant as an overall application.

A single or double tine setup could be used per row.

This will have a dramatic impact on the usage per field hectare. 

Also note, in this case the fumigant must be applied as supplied i.e. in its concentrated form.    Remember the specific gravity for water is 1 (1litre weighs 1 kilogram) and the SG for this product is 1.2.       20% heavier than water.

A beautiful image of the orifice plate showing how it should be mounted in the nozzle assembly. Inlet on the left and outlet on the right.

NOTE THAT THE NUMBERED SIDE OF THE ORIFICE PLATE MUST FACE THE OUTLET.

IF  NOT TOO SURE ABOUT TREATED HECTARES AND FIELD HECTARES PLEASE REFER TO THE POSTS COVERING CALIBRATION AND AREA.

PRACTICAL EXAMPLE:

Overall fumigant application using the 5-tine setup. The fumigant is to be applied at 60 litres per hectare. The tines are spaced at 50 cm or 0.5 metre centres on the drawbar. Speed is 5 kilometres per hour. We need to calculate the flow rate in litres per minute.

l/min = (60 litres / ha x 5 km per hour x swath or spacing of tine 0.5 metres) ÷ 600

= 0.25 litres per minute

Oh dear! Where does the 600 come from?  It's a constant which pops up as there are 60 seconds in a minute and 60 minutes in an hour, 1'000 metres in a kilometre and the swath is used in metres instead of centimetres.

So we need to find an orifice plate that matches the flow rate of 0.25 l/min or 250 ml per minute. Refer to page 44 of the TeeJet 51M catalogue. The CP4916-25 will do the trick at 2 bar or 200 kPa.

BUT!! Watch out for the SG of the product. In this case the SG is 1.2 (1 LITRE WEIGHS 1.2 KG) and the conversion factor is 1.1 so merely multiply 0.25 l/min x 1.1 = 0.28 l/min. Check the table again and you'll see that you have merely to increase the pressure to 2.5 bar or 250 kPa.

Ok! So you could have multiplied the product rate of 60 l/ha by 1.1 and come out with the same result. Six of one half dozen of another.

Next post I'll look at row application in Sugarcane.

REAL WORLD.  WHAT ABOUT THE TEMPERATURE OF THE PRODUCT AND WHAT ABOUT WHEEL SLIPPAGE?  THE WORLD ISN'T FLAT.  

Tel Intl : +27 83 289 0327

Tel Natl : 083 289 0327

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