June 1, 2010
by Jim Kline
Optimizing equipment maintenance is an area of engineering and management that schools build curriculums around, texts are written about and companies create for their expertise. But in the end, maintenance is about knowing your equipment, caring about the equipment, doing the right things at the right time and the skills of the caretakers. Properly performed maintenance assures equipment reliability and extends the useful life of machines well beyond any standard depreciation period.
Where does knowing your equipment fit into a maintenance program? For management, it is as an overview and for mechanics, a tool. Sound is one of the best indicators of equipment condition. When you walk around the bakery, listen and learn the sounds of productivity, and listen when there are problems. Eventually, a simple tour of the bakery will expose a piece of equipment that doesn’t sound right — when a compressor or vacuum pump changes pitch; when a mixer has a chain, belt or bearing noise; or when a drive is operating at a different speed. The immediate questions are what is different, how to correct it and was it preventable.
When you are walking around, also take the time to look. Is the slack in the conveyor chain correct? Is it less or more then you are accustomed to seeing? Is it rubbing on its frame? Is it starting to jump on the drive? Are conveyors running smoothly without hesitation, jumping or chatter? What about the oven belt or hearth plates, are they traveling smoothly without hesitation? Is the chain engaging the sprockets and seating as it should, or is it riding on the tooth? What is the tension like in the spiral cooler chain? (Each manufacturer provides guidelines on how to tell if the cooler chain is properly tensioned; go ahead and give it a pull to see for yourself.) Are those trays, peel boards or pans traveling square on the belt, or are they canted or crabbing?
Finally, use your sense of touch. Is a depositor, mixer or bagger frame vibrating excessively? Does an AC motor feel hot? All these things you can observe by simply walking around, with no need for fancy monitoring equipment or devices. Use your senses and keep notes on what you learn. Once you are in tune with your equipment, you can educate your maintenance team on what to watch for. Observation and monitoring should be key parts of your preventive maintenance program.
Does caring belong in the maintenance department? You bet! When you’re taking that tour, include the maintenance shop, boiler and compressor rooms. A precursor of how your equipment will operate can be found by looking at these areas. The quality of workmanship that goes into your maintenance effort can be directly related to the performance, reliability and life of your bakery’s equipment.
Besides poor lubrication, the greatest cause of mechanical equipment failure is dirt. Assemble a pump, blower or motor on a workbench loaded with steel drillings, fillings and other debris. Think about the impact on a bearing or an elastomer seal. Have you ever wondered why the next breakdown came so quickly? That’s not to take away from the importance of the mechanics’ skills, but even the best skilled mechanic, working quickly in a dirty environment, will achieve less-than-ideal results.
Care enough to look at the failed part. There is a story there, and with some detective work you can learn it. Failed components will show signs of wear. Does the wear pattern show that it happened over time or instantaneously? Was there adequate lubrication? Did it overheat? Did it become loose? Each answer will take you a different direction in making the repair and correction a permanent one.
You do not encounter these problems every day, but if you make it a practice to learn from the failures, you will quickly develop your methods of analysis and sources of information. It will make a positive difference in your maintenance program and your bakeries performance.
Not familiar with the wear patterns? You will find all the information you need in vendor literature, texts and online research. The following are examples where a little research went a long way.
A few years back, eight ¾-in. bolts that held a drive sprocket to a tunnel oven main shaft sheared off in a catastrophic failure. After repairing the oven and getting it back into service, we examined the failed bolts. There were two distinctive patterns at the shear points. Through a little research we were able to identify that four of the bolts showed wear rings at the point of shear; they had been loose and moving around for awhile. The other four showed an instantaneous failure had occurred. The information enabled us to identify the cause (procedural) and to work with the manufacturer to eliminate the possibility of another failure in the future.
In another instance, a baker was experiencing bearing failures in a dry ingredients material blending and handling system. Examinations of the failed bearings showed electric currents were present. Using some problemsolving steps we indentified that a electrical short and a high-resistance ground existed. After correcting both issues, the bearing failures went away.
With maintenance, timing may not be “everything,” but it is important. It is safe to say that every maintenance department has limited resources and faces ongoing cost constraints. Establishing an effective schedule for preventive and predictive maintenance is a great way to control these costs. Certainly the starting place for any preventive maintenance program is equipment manufacturers’ recommendations, although these are for a typical installation and will be conservative in their approach.
The hours the equipment runs, the way it is operated and maintained, the environment it is in and the quality of the power source all impact the manufacturers’ recommendations. The best way to optimize your program is to base it on your experience in your bakery. Modify scheduled work based on the equipment’s performance history, and don’t be afraid to adjust the frequency or the content of the scheduled maintenance over time. If a facility is experiencing breakdowns or seeing a requirement for more frequent adjustments, increase the maintenance frequency; on the other hand, a plant may be able to extend the maintenance schedule for those items that are used intermittently or that run lightly loaded.
Beyond traditional methods of preventive and predictive maintenance, some great tools and services are available to help your maintenance efforts.
Thermographic scans remain one of the best tools available to the maintenance department. Using infrared technology, a thermographic scan gives you thermal profiles of your motors, electrical cabinets, switchgear, transformers, the building and even the roof. The scans quickly identify hot spots in equipment, electrical distribution systems and steam systems as well as points of heat loss when looking at exterior walls and roofs.
Typical hot spots picked up by a thermographic scan include motors — bearings that are failing, motors that are overloaded; electrical circuits — loose connections, under- rated breakers, bad contacts or transformer connections that have loosened; ovens — insulation voids or unevenness of the band temperature; steam distribution systems — steam traps that have failed or valves that are leaking; roofs — areas with saturated insulation can be identified.
Vibration analysisis an excellent diagnostic tool for larger horsepower motors and the equipment they power. This can be used to identify problems such as outof-balance, misalignment or bad bearings within a piece of rotating equipment that is exhibiting vibration when in operation. Using either handheld meters on a periodic basis or continuously monitoring using permanently affixed sensors, vibration analysis can be used as a component of a preventive or predictive maintenance program.
Transformer oil analysis can provide information on the condition of your transformer and identify problems with the oil, internal wiring and insulation; any of which can lead to a failure of the transformer.
Switchgear should be inspected, lubricated, calibrated and tested every three to five years. Establishing a routine program is the best way to assure the switchgear will function properly when it is needed to protect people and your equipment.
Power monitoring is not only a useful part of a bakery’s energy conservation program but also a significant tool in monitoring the health of the electrical supply and distribution system. Use it to monitor the incoming voltage, track frequency of dips and spikes and as an alarm if a phase be lost.
Knowing, caringand doing require a dedicated and skilled maintenance organization. Optimizing equipment maintenance requires a team effort by the maintenance organization, and certainly one that has to be coordinated with operations and sanitation. For those seeking to improve their maintenance skills, some great resources are available in the baking and snack industry — not only the capabilities of equipment suppliers but also the American Institute of Baking and the American Society of Baking have supporting programs; and the archives of Baking & Snack provides a great resource as well.
Maintenance optimization is attainable within any organization: It takes a commitment, requires consistency and a realization of the importance of knowing, caring and doing. •