20 June 1998


Dont neglect the store in the hurly-burly of final machinery preparation for harvest. Michael Bird explains the priorities for avoiding trouble when the grain comes in.

A LOGICAL and planned approach will pay dividends when preparing grain drying, cleaning and storage facilities for harvest.

Ideally, buildings, silos and plant will have been cleaned down thoroughly following removal of the previous crop. However, it is still important to carry out a detailed inspection well ahead of the first trailer load of grain to ensure that all is well with the store and its associated equipment.

"Staying on top of the job will make preparation of a grain store prior to harvest considerably easier and safer," points out Richard Heath, a lecturer in farm mechanisation at Lackham Agricultural College, Lacock, Wiltshire. "Leave the job to the last minute and one is likely to be storing up trouble."

The grain store and its ancillary plant is the biggest and most extensive item of serviceable equipment on most arable farms. Not only does the facility have a vast internal and external surface area but it stands higher and lower than any other building or machine. The top of a silo may be 12 metres or more above ground level while the bottom of an elevator or wet grain pit can be sunk deep into the ground, close to or even below the water table.

Constant challenge

As a result, storage is under continual challenge from the elements, as well as living creatures, demanding close inspection and appropriate action to ensure all components remain in sound condition and function to a high standard when dealing with crops moving in or out, or simply standing still.

The logical way to inspect and prepare a grain store and its associated plant in readiness for harvest is to follow the route the crop will take from the moment it is tipped from the trailer. In virtually all cases, this means starting at the wet grain pit.

"However, before any inspection or remedial work is undertaken, it is vital that a full risk assessment of the plant is carried out and suitable counter measures applied to eliminate or minimise potential hazards," says Mr Heath. "I recommend that protective clothing and a hard hat is worn, plus suitable breathing protection where gas, spores or dust may be present."

At the intake pit, the first job should be to examine the physical condition of the complete structure to ensure it can safely support the weight of tractors, trailers and loading vehicles. Check that the protective grid over the top of the pit is securely located and that any cover fits properly and provides suitable protection against the entry of water, rodents and humans.

As most pits are located within or close to a building, a strong barrier will help guide trailer wheels to aid reversing as well as protecting structures from vehicle damage.

Wet grain pits are notorious for attracting water from above and below. If there is evidence of sub-surface water entry, urgent action will be necessary before harvest to reseal the pit by either tanking or lining. If surface run-off is entering the pit from above, it is usually possible to divert the flow by means of a catchment drain or by laying a concrete bund around the affected sides of the pit.

"However, most pits will have been properly constructed in the first place to prevent entry by all but the heaviest of rain storms," comments Mr Heath. "Therefore, the major job before harvest should be the removal of any stray debris from last years final trailer load. I use a vacuum for this as it draws dust away from the store, unlike a brush or air line which can push it forward."

Having a dry sump at the base of the intake pit is crucial since this is the usual location for the bottom casing of a bucket elevator.

As it may be impossible to totally prevent the entry of water into the sump. Many farms have a stand-by pump which switches on automatically if water reaches a pre-set level, preventing damage to casings, bearings or drive motors. In such installations, keep the pump serviced and make sure that its electrical connections are sound and secure.

"If the bottom of an elevator has been sitting in water, then its lower bearings, shaft and roller may be corroded," says Mr Heath. "A rusted assembly will increase friction, resulting in belt wear and slippage, and can seize completely. A number of inspection covers are normally provided on all elevators to allow its internal condition to be quickly checked."

Damage to elevator cups can be caused by stray metal objects or stones brought in with the grain from the field becoming jammed within the casing. Cups should be repaired or replaced as appropriate to prevent further damage or a reduction in crop throughput. If the connecting belt breaks during actual operation it can be very awkward, expensive and time consuming to retrieve. If its condition is suspect, change it now.

Elevator belt tensions are important no matter whether checking existing installations or replacing a worn or damaged assembly. Belts can stretch during use and will need to be retensioned to prevent excessive free movement causing grain spillage when next working.

"Electric motor drive to the elevator is normally via belts or a gearbox," says Mr Heath. "Regular adjustment and maintenance should be carried out to prevent slippage or failure in use. So far as the elevator itself is concerned, these are virtually self-cleaning. However, the base of the casing should be inspected and cleared of any accumulated debris which can attract vermin and insects."

Most grain storage installations of the past 30 years will include at least one fixed or mobile auger. Check the auger-to-casing clearance which, if too close or too wide, may trap and damage grain. The auger spiral is held in place by a centring bearing which, when worn, will allow eccentric auger movement. Replace any bearing which has excessive free movement or causes the auger to rub against the casing.

Auger drive belts and pulleys should also be checked for wear and adjustment. An auger full of grain is a heavy load and a slipping belt can reduce crop throughput significantly. Belt slip can quickly lead to belt failure.

Chain condition

The same advice on drive belt tension applies to overhead chain and flight conveyors used to fill grain silos. Also, inspect the condition of drive chains and flights, particularly those fitted with rubber or canvas strips which both move the grain and help keep the base of the casing clean. Missing strips must be replaced, bent ones straightened and the chain tension checked.

"Such conveyors are often positioned above outdoor bins where it is difficult to prevent water entry," Mr Heath points out. "A loose or damaged chain can soon wear the base of the casing leading to rusting and holes being opened up by sprouting grains pushing their way through the casing, joints or overlaps.

"Many conveyors have been damaged when levers or hammers are used to force open jammed delivery slide openings. Valuable time and cost savings can be made by ensuring that all slides are operating freely prior to harvest."

Cleaners and driers come in a wide variety of makes, types and sizes and Mr Heath says any specific pre-harvest servicing requirements must be carried out in accordance with the manufacturers recommendations.

"Store operators need to make sure that crop cleaning and drying equipment is thoroughly cleaned out prior to harvest and between different crop varieties," he says. "Inspect screens for damage and wear and make sure that air intakes and outlets are clear of crop residues. The movement of moisture-laden air makes outlets particularly susceptible to blockage.

"And dont forget electric cabling and switchgear controlling plant and machinery," stresses Mr Heath. "The working environment is fairly hostile in and around most grain stores, and dust, moisture, vermin and vibration can attack connections and cause shorting and sparking. Exposed installations should be thoroughly cleaned and checked, but the job can be made easier and safer by housing controls and cables within sealed casings. Always switch off the power before removing safety guarding from equipment."

Mr Heath believes it is worthwhile firing up an oil-fired drier prior to harvest to check flame and exhaust quality which can reveal problems with injection nozzles and incomplete combustion. Fuel and air pressure can also be checked and the compressor serviced.

In bins and silos inspect the seals between panels for leakage both from the inside and outside. Mastic can set rock hard and crack or fall out after a number of years exposure to extremes of heat and cold. Renewing seals is not difficult using modern flexible mastics through plunger-type cartridge applicators.

Clean the mesh floor of ventilated bins with a brush and then vacuum away any remaining debris, checking that air ducts are clear and not damaged.

Although the quickest and most convenient to fill, on-floor wooden and concrete ventilated floors are easily damaged by vehicles and equipment being driving onto and over them, especially when the building is used as a machinery store when the grain has been removed.

It can be a major problem to maintain a good seal between the mesh and the surrounding floor to prevent the accumulation of dust and grains in the gaps and below the floor.

With the building completely empty, inspect the floor and repair any damaged vents, cleaning all cracks and gaps thoroughly with a small trowel, brush and vacuum.

Dust and cobwebs on the roof, eaves and walls of a floor store must also be removed. A pressure washer will be much faster and easier than a brush or vacuum provided the building has time to dry out completely before filling begins.

Overhead belt conveyors within buildings are virtually self-cleaning and are normally equipped with self-tensioning devices. However, problems can be caused by accumulated dust which should be removed with the help of a securely-guarded access platform.

Repair or replace damaged wall or roof panels and renew any broken floodlight bulbs. Position a container beneath the light to catch broken glass should the bulb shatter when removed. Stray glass within a grain store is a major hazard.

If there is a gap or hole in the building, its a sure bet that vermin will find it. Sealing the building and making sure that the doors fit properly is a good start. Another line of defence is laying bait on rat and mice runs on approaches to the farmyard or a silo pad. Dont forget to replenish the bait regularly and remove and destroy any dead animals.

Richard Heath, who runs the HND course in farm mechanisation at Lackham College.

Dirt and debris accumulate quickly within a worn auger. Always empty an auger completely after use and replace bearings to prevent wear.

There are still a few non-sealed bearings to be found on farm machines. Greasing will prolong life and force out abrasive material.

Check all guards and safety rails. The weld has failed completely on this rail on top of a grain silo. Growing it could have fatal consequences.

Air vents within a drying floor can block easily. They should be cleaned with a brush and vacuum, lifting the vent for a thorough job.

Motor drive belt tensions must be checked on all conveyors and elevators. A slipping belt will reduce throughput and will soon fail.

Grain store checklist

&#8226 Carry out full risk assessment and apply appropriate counter measures

&#8226 Equip all personnel working on or within a store with suitable protective clothing and equipment

&#8226 Regular inspection and maintenance is better than a last minute rush

&#8226 Cleanliness and hygiene must be a top priority

&#8226 Ensure that all building and plant structures are safe, sound and secure

&#8226 Check that guards, railings and protective covers are in place and secure

&#8226 Never work on a machine when it is running. If practicable, switch off mains electric supply before removing guards or covers

&#8226 Look for leaks, cracks, signs of water entry and damaged or worn components, repairing or replacing as appropriate

&#8226 Make a checklist of essential mechanical and electrical spares which need to be ordered ahead of the busy harvest period

&#8226 Ensure that everyone working within or close to the store is trained in safety procedures and understands how to operate the plant and machinery.

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