inspection period can be lengthened somewhat. This system can be followed until a maximum period of operation is reached which should be considered the operating schedule between inspections.
Grease-lubricated bearings are packed with grease at the factory and ordinarily require no attention before starting, provided the pump has been stored in a clean, dry place before its operation. The bearings should be watched the first hour or so after the pump has been started to see that they are operating properly.
The importance of proper lubrication cannot be overemphasized. It is difficult to say how often a bearing should be greased, since that depends on the conditions of operation. It is important to add 1 ounce of grease at regular intervals, but it is equally important to avoid adding too much grease. For average operating conditions, it is recommended that 1 ounce of grease be added at intervals of 3 to 6 months, and only clean grease should be used. It is always best if the unit can be stopped while the grease is added to avoid overloading.
Excess grease is the most common cause of overheating.
The bearing frame should be kept clean, since contamination of foreign matter that may get into the housing can destroy the bearings within a short period of time. When cleaning bearings, use a bearing or an industrial cleaning solvent. Do not use gasoline. Use a lint-free cloth. Do not use waste rags.
A regular bearing grease should be used, but a standard commercial vaseline can be substituted if necessary. Do not use graphite. A No. 1 or a No. 2 grease is generally satisfactory for operation at ordinary temperatures; the lighter grease should be used for operation at high speed or at low room temperature.
Mineral grease with a soda soap base is recommended. Grease, made from animal or vegetable oils, is not recommended because of the danger of deterioration and the forming of acid. Most of the leading oil companies have special types of bearing grease that are satisfactory. For specific recommendations, consult the manufacturer's manual.
The maximum desirable operating temperature for bearings is 180F. Should the temperature of the bearing frame rise above 180F, the pump should be shut down to determine the cause. Grease-lubricated bearings should not be used where temperature of the pumped liquid exceeds 350F.
A bearing frame that feels hot to the touch is not necessarily running hot. Check the temperature with an accurate measuring device to be sure.
An oil-lubricated pump normally has an oiling ring. In these, the oil is picked up from the reservoir by a rotating oil ring and deposited on the shaft and the bearings inside the bearing housing. Some may have an oil slinger that creates a shower of fine droplets of oil over the entire interior of the bearing cavity.
After the pump has been installed, flush the bearing housing to remove dirt, grit, and other impurities that may have entered the bearing housing during shipment or erection. Then refill the bearing housing with proper lubricant. The oil level to be maintained is shown by a line in the sight glass or oil level indicator.
Lubricating oils can be furnished by any of the major oil companies, and it is the respon- sibility of the oil vendor to supply suitable lubricants. Experience has shown that oils meeting the following specifications provide satisfactory lubrication.
|Saybolt viscosity at 100F||150 SSU-200 SSU|
|Saybolt viscosity at 210F||43 SSU|
|Viscosity index, minimum||95|
|Pour point, maximum||20F|
|Flash point, minimum||390F|
|Additives||Rust and oxidation inhibitors|