Lubrication of the kitchen exhaust fan bearings during the course of the job is one definite way to provide a genuine service to our customers – and it is a task which involves very little time and effort to accomplish.
Since our work regularly takes us onto the roof or into the mechanical penthouse, it makes good sense to provide the essential services such as bearing lubrication to kitchen exhaust fan while we are conducting operations.
Equally important to providing this type of service to our customers for their kitchen exhaust fan to realize a full life is the application of the correct medium of lubricant, in an amount sufficient to do the job right.
Manufacturers of kitchen exhaust fan type provide either lifetime lubricated (sealed), or lube-able type bearings on their equipment. Due to the higher rotation speeds and elevated temperatures with which this equipment is known to operate, chances are you will encounter the lube-able type more often than not.
The pre-lubricated type of kitchen exhaust fan will generally require no service under normal operating condition for seven to ten years, and then they will require replacement. The greaseable type of bearings will generally not require re-lubrication for the first six months of operation because they are most often lubricated at the factory.
Kitchen exhaust fan shaft bearings are best served by lubricating them with a blue lithium type grease applied with a manual grease gun. Excepting safety hazards, the shaft bearings are best lubricated with the shaft rotating, and the grease gun should be slowly pumped until a slight discharge of grease is observed at the lip of the grease seal.
Because bearings are precision made, the grease fitting nipple should always be wiped off prior to applying the grease gun to prevent forcible contamination of the unit.
Over lubrication will inevitably lead to premature failure of the bearings due to both the excessive volume of grease unseating the grease seals, allowing foreign matter to collect and contaminate the bearings, and elevated operating temperatures caused by friction as the overfilled bearings rotate at high speed.
Certain considerations should be made concerning the frequency of lubrication of shaft bearings. Generally speaking, an exhaust fan operating 12 hours per day would be best served by lubricating two to four times annually, provided the establishment is opened year round, and the above procedures are followed.
Decreasing the schedule should be considered if the establishment is seasonal, or operates fewer hours per day; increasing the schedule may be warranted if the fan is serving a high temperature system such as solid fuel cooking, or operating 24 hours per day.
Prevent accidental over-lubrication, and mixing of different types of greases, and know if the establishment maintenance staff are providing preventative maintenance of the fans regularly prior to your service commencing.
Electrical motors employing ball type bearings may as well be equipped with either sealed bearings or grease able bearings, however, motor bearings are considerably more sensitive and should be maintained only by staff familiar with the application.
Motors with lube able type ball bearings will either be equipped with a grease fitting, or a removable screw for applying grease. Similarly, most will also use grease relief screws which need removal to ease drainage of excessive grease during a 20 minute operating period after lubrication, and then the drain screw requires replacement.
As a general guide only, your average motor sizes 1 /8 to 7.5 horsepower will only need re-lubrication once every 5 years if operated 5,000 hours annually and equipped with lubrication points.
On units with grease nipples, only I to 2 strokes with a grease gun are required on NEMA frame sizes 215 and smaller, 2 to 3 strokes on NEMA 254 through NEMA 365.
If equipped with a screw type fitting, a 2 to 3 inch grease string should be applied to each bearing on NEMA size 215 and smaller, and a 3 to 5 inch string on larger motors. Again, drain plugs should be removed and the motor operated 20 minutes before replacement.
Motors should always be lubricated at a standstill. Their grease fittings must be cleaned before lubing. Also, only use clean grease obtained from a sealed container.
When possible, manufacturers’ recommendations should be followed when selecting the brand of lubricant to use on a motor, and extreme care should be used to ensure petroleum and silicone greases are not mixed.
Because most lubricants will deteriorate motor winding’s, they should never be over lubed!
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