Machinery checklist: Top tips for spreader accuracy
Keeping a fertiliser spreader running at optimum performance is vital for application accuracy, as ever-frequent checks and maintenance should ensure the spreader is working correctly.
With some expert advice, Alex Heath compiles a checklist...
Ensuring your fertiliser spreader is firing on all cylinders is imperative to accurate application, particularly topical with environmental issues surrounding nitrate leaching in water courses and the agronomic cost of over- and under-applying product.
Keen to get some top tips on how to keep a spreader in tip top condition, we spoke to Alex Birchall, product specialist at Kuhn, who says maintenance of your prill chucker should start as soon as it has finished being used each day.
Washing the spreader off will limit the amount of corrosive residue left on the machine, which he says causes unsightly rusting and damage to the disc bearings.
While Kuhn, along with most other manufacturers, does not recommend blasting the paint work with a pressure-washer, a good misting with plenty of water will remove most of the destructive dust.
Removing mud guards and discs will aid in getting plenty of access to the spreader, taking care not to drown the delicate electrical parts.
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VANE CONDITION
CONDITION of the vanes has the biggest impact on direction and distance prills are thrown, and these need to be in top condition.
If any pitting can be felt, or the vanes take on a fish scale appearance, these need replacing.
Likewise, the length of the vanes is a vital factor to spreading accuracy, with most vanes showing their length on the side. These should be periodically measured, and replaced if the length becomes lower than the figure given.
When replacing vanes, ensure the correct disc and vane combination are used, and tighten with a torque wrench as per the manufacturer’s guidelines, in this case 20Nm.
It is also advisable to replace the locking nuts and bolts at this time as well.
Any border control vanes should also be inspected for defects, often seen after getting to friendly with hedgerows.
OBSERVATIONAL CHECKS
TO see what needs checking and adjusting, we walked around the company’s Axis 40.2 M-EMC-W.
This mechanically driven spreader is fitted with the firm’s Electronic Mass Control technology, which uses torque sensors to adjust the drop point, said to maintain spreading rate, width and accuracy. Weigh cells were also fitted.
However, many of our checks apply to most makes of spreader.
When going out with the fert spinner, observational checks should be carried out on a daily basis.
Mr Birchall says rust which can be prevented will inevitably rear its head from time to time.
If it is caught early, it can be remedied and patches can be repainted. Checking for play in the discs ensures accurate application and early detection of bearing failure.
While uncommon, it can be a nuisance during busy times, so the advice is if a bearing looks suspect, replace it as soon as possible.
POSITION OF SPREADING DISC HUB
THE next area to measure and check is possibly the most critical and overlooked, says Mr Birchall.
With the spreading disc removed, the spreading disc hub should be positioned exactly under the agitator, with just a 2mm tolerance for misalignment on this model. These should also be checked for cracks.
The distance between the upper edge of the spreading disc hub and the edge of the agitator is often less than it should be, due to the spreader being filled while resting on the floor, says Mr Birchall.
Stresses
Instead of putting the spreader on the floor, he says the spreader should actually be raised 20-25cm off the floor while filling, to prevent putting stresses on the structure between the gearbox and disc assembly and the hopper.
The weight of the fertiliser in the hopper will compress the gap that is needed to maintain an even spread, which on this spreader should be 136.5mm, again with just a 2mm tolerance. If the distance is less than this, it is a task for the dealership to reconfigure.
When reapplying the disc, a line of grease should be put on the threads of the holder to reduce the risk of stripping the threads from the plastic retaining cap, which should be done up hand tight then tweaked further by a quarter turn with a bar.
AGITATOR ATTENTION
AGITATORS in the bottom of the hopper should be given regular attention for signs of wear, and should always cover the furthest point of the aperture from the centre of the agitator.
They should also move freely in one direction, but lock when turned the other way.
Failure to lock is likely to be down to a problem with the con rods which power the agitators off the gearbox.
Grid
On our example machine these were plastic and can be subject to cracking and bending from time to time, so should also be checked regularly.
The grid inside the hopper should also be checked for even squares and replaced if any large holes appear.
ADJUSTMENTS OF APERTURE AND DROP POINT
CALIBRATION of the drop point should ideally be carried out at the start of each season by a tray test.
If trays are unevenly filled, the calibration has likely been lost.
The actuator for the drop point must be disengaged from the yokes, before adjusting the length of the rods that hold the yokes.
A thin piece of string should then be put between the drop point indicators and tensioned.
In this case, each side needs to be in the same position of number six, but the taut string should also be in line with the marker in the centre between the two discs.
Grease
Once this is complete, the yokes on the rods can be adjusted and re-engaged with the actuators to ensure the drop point is the same each side.
Drop point sliders should always have a thin layer of grease on them to assist in opening and closing under pressure.
The calibration test for the metering opening on our example machine involved setting the opening to 85, then inserting a category two pin into the gap, which should be snug.
If it is not, the opening should be closed or opened to accommodate the pin, then the scale should be adjusted to align with the scale value 85.
GEARBOXES AND STORAGE
GEARBOXES are generally hassle-free, however, regular inspection of the oil level is needed.
Kuhn recommends the oil in its gearboxes is changed every 10 years. On hydraulically driven models, the filter should be periodically checked for debris, and changed when an accumulation of gunge has built up, or spreading performance drops.
When storing the spreader, Mr Birchall recommends removing the discs, and ensuring no fertiliser has accumulated around the bearings, before thoroughly washing it off.
The openings in the bottom of the hopper should be left completely open for two reasons.
The first being the actuators will be fully closed up, preventing deterioration of the chrome rods, and secondly it will make less of a pleasant space for rodents to make their homes.
A light spray of biodegradable oil should be applied all over to stop the onset of rot, with particular attention paid to stainless steel parts and hydraulic control blocks.
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