This practice causes the pump to cavitate . Throttling the discharge is just as easy and is not harmful.
Liquid is necessary to lubricate and cool the internal clearances . A pump running dry will generally overheat and seize . This means - NEVER START A PUMP WITH THE SUCTION VALVE CLOSED.
First, unless reduced capacity operation is normal for the service the pump design may be one which results in a high radial reaction and shaft failure . Second , the hydraulic design may be such that actual impeller failure will result . Third, part of the power consumed by the pump goes into heating the liquid and if insufficient flow is available , the pump will overheat and seize . As a rule of thumb, the minimum flow to protect against overheating is about 30 gallons per minute for every 100 horsepower at shut-off .
Watch for irregularities in performance . Investigate changes in the sound of a running pump immediately . Observe bearing temperatures and stuffing box operation hourly . Check pressure gauges and the flow indicator hourly to see whether pressure and flow correspond to normal operating conditions
Some leakage is necessary to provide lubrication and cooling of the packing.
If using grease , the bearing , should be about one third packed with grease . If oil lubricated , the level should not exceed that marked on the oil gauge
Do not add one or two rings to the old packing . This may displace the seal-cage , if used , and plug the sealing liquid opening.
Check for free movement of stuffing box glands, clean and oil the gland bolts and nuts, and inspect the packing . Check the pump and driver alignment and correct it , if necessary . Drain and refill oil lubrication bearings . Check grease- lubricated bearings for suitable consistency and correct amount of grease
Thoroughly inspect a pump annually . Remove bearings to clean and examine them for flaws . Remove the packing and examine the sleeves for wear . Disconnect the coupling and check alignment . Check and flush the drain , sealing water and cooling water pumping . Recalibrate all instructions and run full tests of pump performance
SAM designs, manufactures, and services pumps for the essential industries in India and abroad. Since 1972, SAM has built a reputation of blending craftsmanship with mass production, techniques with innovation, quality, and quantity