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Don’t be fooled by their apparent simplicity
One item of kit that is seldom left unsold on the auction field is an OPICO GT drier. Simple, reliable and well proven, these units have been a familiar sight in the UK since the early 1970’s. Despite this, these popular tools can make a tricky used buy.
Just because an item of equipment is familiar it does not follow that buying a used example is straightforward. The performance and reliability of any portable driers is directly related to its maintenance and level of wear. So a superficially good looking example can actually be in need of considerable attention.
Of course overall condition is important, but with portable batch driers in general this can also be misleading. Scruffy looking screens on an otherwise sound machine may look dreadful, but in service a coating of rust is not an issue. Screens only need replacing if physically damaged.
Selecting the right used machine calls for some inside knowledge, and goes well beyond the tyres, pto shaft and general condition.
Augers
Portable batch driers comprise a feed auger, main central auger, outer and inner screens, burner and unloading system. There are then the attendant drives and belts. What is not often realised is just how ‘hard’ the main auger works, the job of keeping grain on the move as it dries and cools taking its toll in terms of wear. Although it will vary, the auger will typically last for 2,000 hours in cereals but half this when drying beans.
As an aside, the drier should be supplied with three types of cleaning screen: cereal, rape and blank. These fit on the side of the main auger inside the centre chamber or plenum and are designed to take out weed seeds or small broken grains, an optional extra Pea and bean screen may also have been supplied with the Drier.
Some models (80S’s, 90’s, and 95’s) have a ‘DCM’ Digital Control Monitor operating system as standard which records units total drying hours. This can be a guide to how much wear to expect. In all the cases, the central auger should always be inspected for wear from the top. When stored, the standard discharge head unloading system is normally removed, so it should be easy enough to climb up and take a look at the condition of the auger flights.
A horizontal discharge head, or ‘hydraulic top’, may have been fitted. This option allows the drier to be transported between sites and stored without first removing the unloading system. To check the auger with this type of unloading system or a standard head which is still fitted to the dryer, loosen and then slide up the collar at the bottom of the discharge head tube.
IMPORTANT: The bottom flights of the central auger are made from considerably heavier gauge steel than the flights that operate within the main auger tube. They do not provide a guide to overall auger wear.
The auger tube also wears, but at a slower rate than the auger flights. Tube wear can again be checked from the top, the metal tube thickness at the discharge top clamp ring giving an indication of how much life is left in the tube. Also look for splits and bulges in the tube.
A 12 tonne OPICO batch drier should remove around 5% moisture from 6 tonnes of wheat in an hour. In practice, a drier in good condition should better this, particularly when the ambient air is dry. Typical drying times of a 12 tonne load will be nearer 13/4 hours. A worn drier will take perhaps double the time to do the same job, due to slow recirculation of the grain .
The main auger runs in a bottom well which should last the life of the drier. If it has been left stored full of wet grain, this well will rust out and need replacing. Always open up the well flap and check everything is clean and no rust present.
The main auger running up through the centre of the drier is a wear item. It should be inspected from the top with the discharge top removed.
 With the cleaner screen removed, it is easy to spot the wear both to the auger and tube. This scrap item would have doubled the drying time to perhaps 3 hours.
 The main auger bottom bearing needs a pump of grease every 20 hours – no more and no less. It is easy to renew. Note the corrosion starting on the bottom well. This is a costly item to replace.
Agitators
Inside the drier, the four agitator cam rollers are adjusted via an eccentric bolt to keep them in contact with the cam race. When really worn, the rollers will run in the bottom of the race and not operate correctly. The roller’s sealed bearings also work hard and need to be checked for play and replaced as soon as any movement is detected.
The ‘skirts’ of the plenum chamber mesh can get battered, and this will need correcting if throughput is not to be compromised. In extreme cases, bent screen skirts can catch the agitator ‘star paddles’.
The agitator arms are driven via a chain powered by a gearbox mounted within the plenum chamber. This gearbox MUST be oil tight as it will quickly self destruct if it loses even a small amount of oil. Power from this ‘box is transmitted via a pair of coupler sprockets and chain. If the sprockets are allowed to wear excessively, the drive to the agitator can stop. Crop can then build up in the plenum chamber and block the cast agitator cam race, causing it to shatter expensively! (CHECK CHECK)
The agitator system works hard. Check the star paddle bearings, cam rollers, gearbox, chains and plenum chamber skirts.
Intake auger and driveline
Running in either a short or long loading hopper, wear on the intake auger is less likely to be an issue, but damage to the hopper trough and auger tube is quite common. So check everything is ‘square’ and look for splits, cracks and welded repairs on any of the tin work. The phosphor bronze bearing can seize causing its ‘V’ shaped support to shear. The auger is then free to drop down and run in the bottom of the hopper, wearing the latter through. Any play in the bearing should be repaired promptly.
The belt and pulley driveline is either tractor pto or electric motor driven. A pto drier can be converted to three-phase electric motor drive using a £1,500 Opico conversion kit. On average, electric drive driers carry a £500 to £1000 premium.
The main auger drive belt has to twist through 90 degrees to transmit power to the intake auger driveshaft. To pull off this trick without tying itself into knots, the belt has a special Kevlar and polypropylene construction to allow it to twist. A drive belt of standard construction will fail if purchased to do the same job.
The easiest check for pulley wear is to look at how a new belt sits within its respective pulley. The deeper the belt runs into the groove, the greater the wear on that pulley.
When severely worn (right), the agitator cam roller will run in the bottom of the cam track and can no longer be adjusted on its eccentric bolt. The cam roller’s bearings are also wear items that need to be routinely checked.
The agitator gearbox transmission sprockets wear quickly. The worn item on the right failed in service.
 The support at the tube end of the intake auger will shear if the bearing seizes. The auger will then drop, and will wear itself and the bottom if the hopper if not repaired promptly.
 Worn or damaged flights can be replaced on the intake auger, but this is not recommended on the main central auger because it can upset the unit’s balance.
Burner
There are essentially two types LPG burner fan – standard and ‘Quiet Fan’. The latter are genuinely quieter in operation, and are well worth seeking out if the drier is to be used near dwellings. The welds at the base of the blades on all-metal fans need to be checked for fractures. More recent driers have a plastic fan which should be problem free. Look out for play in the fan bearings.
The now common ring type burner used in Opico driers is extremely simple, with only the gas outlet holes needing a periodic clean and the spark plug igniter the occasional check. Early driers produced up until the early 1980’s have a barrel burner which also works well, but if damaged or worn it can no longer be repaired.
If the burner refuses to fire up, a common cause is a blocked feed pipe to the air switch. The spark plug electrodes can also ‘whisker’ over, particularly if the air stream does not blow through the electrode gap.
This pipe links to the burner air switch. If it gets blocked, the burner will not fire. This is the main cause of starting problems when the drier is first used from storage.
Gauges and controls
There are two gauges on the drier, indicating the plenum chamber and grain temperature respectively. The latter should always indicate the ambient temperature, so if the needle is resting on its stop the chances are it is not working. The plenum gauge can only be checked in service. If either dial is faulty, a new replacement is around £190.
Most driers sold in the UK will have the manual burner control system, and it pays to understand how to operate it. The procedure is often forgotten by users, and this can lead to the settings being incorrectly adjusted. This is particularly the case on earlier driers fitted with two gas regulators. These need to be set to balance the flow of gas to the burner. Once set, they can be left, but if tampered with they can lead to increased gas consumption and/or a dirty flame.
A DCM operating unit is fitted to most Quiet Fan models. Before it can be checked, it needs to be connected up to a tractor and its battery. It will list pto speed, auger speeds, operating hours and other information.
The grain temp thermostat adjuster can be checked for correct operation if the ambient temperature is over 10C. As the thermostat adjuster is turned, the unit should trip with a quiet click if it is in good order. The plenum dial and thermostat cannot be realistically checked until the unit is in service.
One final point; always check the wiring. Loose connections, corrosion and rodent damage can cause real problems in service.
  The grain temperature gauge should read the ambient temperature…
…if the needle is on its stop, it will probably need replacing.
Summary: A well used Opico batch drier is likely to be worn and yet can still look in really good nick when offered for sale. This makes detailed basic checks important as the buying price needs to reflect how worn the machine is and the cost of putting it back into shape.
Properly refurbished driers, on the other hand, can represent excellent value. When key components have been replaced, the drier can be as good as new. So the usual advice to buy the latest model possible does not apply as a sound 10 to 15 year old example is a better used bet than a well worn juvenile.
When choosing between a 9 and 12 tonne capacity unit, the latter are now proving to be considerably more popular and they are about 25% more expensive as a result. Specification tends not to have too great an influence on used prices, but Quiet Fan QF models are more sought after and can carry a 10% premium. Other choices are:
- Standard discharge head. This needs dismantling to get the drier inside a shed for storage and for transport. The horizontal discharge head is more compact
- DCM operating unit – see table
- A short feed hopper suits units to be filled from a trailer spout. Long hopper can be filled from a standard grain bucket
- 3-phase electric drive models worth an extra £1000
- Central greasing system
- Adjustable jacks
Gas or oil?
Most portable batch driers use LPG fuelled burners, the output on current Opico units developing a whopping 3.9 million BTU, some 400,000 units up on the type fitted to models made until 1981. By comparison, a typical workshop space heater will develop perhaps 26,000 BTU. To have enough fuel to feed a drier calls for ample on farm storage of LPG, and the cost of setting this up should not be overlooked. The supply also needs to be sited close to where the drier is to be used, so consider this if space is at a premium.
Oil fired Opico driers were available up until 1990, legislation at the time indicating that oil fired driers should be phased out. It was for this reason that Opico stopped importing oil fired units. As is so often the case with regulations, oil firing is now accepted again, with Opico now reintroducing oil burner driers for this season.
Oil fired burners are not covered in this article because they are relatively rare. The same general checks apply, but the burner itself will need to be thoroughly inspected by a specialist. If worn or incorrectly set, oil fired units can taint the crop being dried.
 A bulk LPG propane supply also needs to be considered. It will cost XX to hire two 1 tonne tanks a year, with bulk gas costing around 16p per litre. Typical fuel costs to dry wheat down from 21% to 16% will be £1.50 per tonne.
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