Maintenance — intake and grinding
September 1, 2009
However you look at it, the cost of keeping feed mills in running order is becoming increasingly important.
On one hand, there’s the expense of mill maintenance, which can take a healthy bite out of profit margins. There’s also the concern that competing millers have such a tight handle on costs that their production expenses appear to be far lower than your own and you have trouble matching their selling price of finished feed at the farm gate.
When examining the issue of mill maintenance, a logical place to start is at the beginning with intake and grinding. Every feed mill needs to bring in its raw materials, and whether you use flat storage with mobile equipment or intake direct to silos, there will be times when large items of debris will do some serious damage to your plant and equipment, especially if it is not protected adequately.
Make sure grids are always in place and in good order. You often see intake grids lifted up for personnel to clean under and occasionally see drivers trying to lift them up when they are discharging commodities that are not free flowing. Prevention is much better than a cure, and bolting grids down is always good policy.
Cameras at the intake will serve to record what happened in the event of a problem, but at that point it is too late to stop the event from occurring. By the time you are looking at video footage, you have probably already examined the broken conveyor.
Magnets within the intake system are also a useful item, but only if someone checks them and removes the metal objects adhering to them fairly regularly. Install magnets where they can be accessed easily. “Out of sight and out of mind” should be a phrase remembered – place them where they can be seen and cleaned.
Elevators and conveyors are used in all feed mills, and the same rules apply to each mill regarding maintenance. Make sure the drives are in good order and sufficiently tight enough to transfer the horsepower being used to drive them, irrespective of whether they are belt or chain.
Make sure gearboxes are well lubricated with the correct lubricant, and check for leaks. Mark the gearbox clearly to tell the person doing the lubricating which grade they should be using. It is always useful to keep a record on the gearbox of when the last lubricant was applied.
Make sure the elevator belt or conveyor chain is tight enough and well tracked. Using elevator belt tracking devices and bottom pulley rotation sensors is always a good idea, but someone needs to take responsibility for the proper use and monitoring of them. It should be one person’s responsibility to look after all conveying equipment on a site, even if that person does nothing else. Keeping checks on elevators and conveyors can be a full-time job at some of the larger sites, but invariably it will be a self-financing exercise to have someone dedicated to conveying maintenance. With power consumptions under control, an adequate control on spare parts and the risk of downtime being charged on vessels and trucks because of mechanical failure being minimized, you are in good shape to do the thing you do best — making feed.
Conveyors tend to wear out quickest when they do not have stock moving on them and when component parts come into contact with each other. The use of sensors that enable items of equipment to be shut down when not in use is a valuable means of keeping both maintenance and power costs to a minimum.
Grinders can be problematical at times, and it sometimes seems you have a grinder that will not behave itself, a machine that was made on a Friday afternoon in a rush before the weekend. However, this is rarely the case, as more likely it is a problem with the installation. The machine perhaps is not level or does not have strong enough support, leading to movement within the grinder, which can cause problems.
Apart from the routine changing of beaters and screens, which is often a personal preference as to whether this is done according to time or tonnage throughput, there are a few other items which need attention. Lubrication is at the top of the list, checking the wear patterns of kibbling plates and breaker bars within the machine comes next, and then, perhaps most importantly, is air flow. With poor air flow characteristics, the costs of grinding can skyrocket with up to twice the power being consumed per tonne of product being ground. Poor air flow leads to excess retention time in the grinder barrel and that leads to an increase in the rate of wear to beaters and screens. It also makes for heavy power consumption at the fan and high pressure drops across filters when sleeves become blind.
Check the filter cleaning cycles daily and make sure the cleaning air supply is functional and adequate. Use a manometer if you can so untrained personnel can also keep an eye on air conditions. It is very easy for an unskilled operative to observe a reading on a manometer once he or she is told what it should be and how to read it.
There’s a tendency to neglect to train the people who spend the most time in the mill. There are many things that a cleaner can observe during their day with a little training, and it not only saves you time but makes their day more interesting, too. Although you must always remember that a little knowledge can be a dangerous thing, it can also prevent major breakdowns when using the eyes and ears of all your personnel and not just a select few.
Moving on from grinders to the more general aspects of maintenance, the workshop and those who work in it should be equipped for the jobs that will be undertaken at the mill. Don’t try to carry out tasks which you do not have the trained personnel to perform. For example, you don’t have to be a skilled certificated marine welder to simply repair a small hole in an elevator leg, and you do not need the very latest in welding gear for the simple tasks. However, good tools which will make the job easier and less arduous are always welcomed. Hydraulic extraction tools invariably come in handy in the feed mill and a good range of electrical power tools are always useful. A good press is essential if you are to carry out your own press reshelling.
Keep a good record of maintenance costs by performing regular accounting and making sure you have good control on casual expenditures on consumables. If possible, make one person responsible for doing all the buying and give them a budget. It may be best to manage mills with a buddy system in which case that person responsible for purchasing will have a backup employee somewhere on site to cover for them when they are away. It is much easier for one person to control total expenditures than it is to split it up into different factions. People have to “own” the buying decision. You also have the added advantage of that person knowing where everything is, or at least they ought to know where their spare inventory is housed.
Another task for your sole buyer is to monitor and control sub-contractors and service providers. The use of subcontractors for various specialist functions can be useful, but invariably it is more cost-effective to carry out as much work as possible using in-house personnel. Sub-contractors are always eager to do work for you, but they are always keen to charge for it as well, and it is surprising how costs can quickly run above expectations if not kept in check. Small annual percentage increases quickly accumulate.
There are some duties where it pays to bring in specialist contractors. These include work on man lifts, safety equipment, firefighting impedimenta and other items where certificates are required. Items like compressors can easily be dealt with in house, and yet these are often palmed out to third parties when significant savings could be made by doing the work with your own personnel.
Often a small amount of training is worth the expense, as it can save much more than it costs in the long run. Portable appliance testing, for example, is not complicated, and once you have someone trained to do it they can deal with everything that requires testing, and for relatively little expense. It always pays to offer the services of your own staff to assist visiting service personnel since they can learn and observe. Perhaps then you can stretch out the time between external service visits, even if you aren’t able to eliminate them entirely.
Perhaps the best and least expensive investment you can make in terms of mill maintenance is in the time you spend looking around your mill, observing the changes from day to day, listening to the noises that weren’t there yesterday and identifying them, and looking at the debris on magnets to see where it has come from. Looking at raw material samples may also tell you when origins have changed or when a shed of soy, for example, has just been emptied. Small items like this will tell you when a problem has developed at the intake point. Many a disaster has been prevented by the keen eye identifying machine parts on a plate magnet.
Jonathan Bradshaw is a consultant to the agribusiness and food processing industries, specializing in project management and bespoke training programs through his company, J.B. Bradshaw Ltd. He has extensive experience in flour and feed milling in Africa, the Americas, Europe and the Caribbean. He may be contacted at firstname.lastname@example.org .