Oils from different suppliers should not be mixed. The oil must be well-refined, good grade, straight cut, and filtered mineral oil. It must be free from water, sediment, resin, soaps, acid, and fillers of any kind. It should also be nonfoaming with a viscosity of about 150 to 200 SSU at 100F (approximately SAE-20).
In installations with moderate temperature changes, humidity, and dirt, the oil should be changed after approximately 160 hours of operation. The oil should be inspected at this time to determine the operating period before the next oil change. Oil change periods may be increased from 2,000 to 4,000 hours based on an 8,000-hour year. Check the oil frequently for moisture, dirt, or signs of "breakdown."
DO NOT OVER OIL; THIS CAUSES THE BEARINGS TO RUN HOT. THE MAXIMUM DESIRABLE OPERATING TEMPERATURE FOR BEARINGS IS 180F. SHOULD THE TEMPERATURE OF THE BEARING FRAME EXCEED 180F, SHUT DOWN THE PUMP TO DETERMINE THE CAUSE!
The standard stuffing box consists of rings of packing, a seal cage, and a gland. A shaft sleeve that extends through the box and under the gland is normally provided to protect the shaft.
A tapped hole is supplied in the stuffing box directly over the seal cage to introduce a clean, clear sealing medium. The stuffing box must be supplied at all times with sealing liquid at a high enough pressure to keep the box free from foreign matter, which would quickly destroy the packing and score the shaft sleeve.
Only a sufficient volume of sealing liquid to create a definite direction of flow from the stuffing box inward to the pump casing is required, but the pressure is important. Apply sealing water at a rate of 0.5 to 1.0 gpm and at 5 to 10 psi above the stuffing box operating pressure.
Piping that supplies sealing liquid to the stuffing box must be sized to supply a sufficient volume of water at the required pressure, based on the location of the pump (or pumps) with respect to the liquid source. A small pipe can be used for the connection to the stuffing box. A valve should be installed to adjust and regulate sealing liquid, and a gauge should be installed to check the pressure to the box.
External sealing liquid should be adjusted to the point where the packing runs only slightly warm with a slow drip from the stuffing box. Excessive pressure from an external source can be destructive to packing. More pressure is required, however, for abrasive slurries than for clear liquids. Examination of the leakage will indicate whether it is necessary to increase external pressure. If slurry is present in the leakage, increase the pressure until only clear liquid drips from the box. If the drippage is corrosive or may be harmful to personnel, it should be collected and piped away.
A common error is to open the external piping valve wide and then control the drippage by tightening the packing gland. Actually, a combination of both adjustments is essential to arrive at the optimum condition. The life of the packing and the sleeve depends on this careful control more than any other factor.
GREASE LUBRICATION. - Pump stuffing boxes are also suitable for grease lubrication. Several types of grease lubricators are available. When you use a grease lubricator, grease pressure to the stuffing box should be equal to the pump discharge pressure.
PACKING. - All pumps are packed before shipment, unless otherwise requested. The packing used is of the highest grade material. Before the pump is put into operation, check the condition of the packing. If the pump is installed within 60 days after shipment, the packing should be in good condition with a sufficient supply of lubrication. If the pump is stored for a longer period, it may become necessary to repack the stuffing box. In all cases, inspect the packing before starting the pump.
The standard packing is made of a soft, square asbestos material that is impregnated with oil and graphite. A soft, well-lubricated packing reduces stuffing box resistance and prevents excessive wear on the shaft, or shaft sleeve. Many brands of packing on the market have the desired qualities. For specific recommendations, consult the manufacturer's manual.
When a pump with fiber packing is first started, it is advisable to have the packing slightly loose withoutContinue Reading