Analysis of centrifugal pump can not pump water
Centrifugal pump with its simple structure, convenient operation and maintenance, high efficiency and become the most widely used in agriculture water pump, but also because sometimes can not pump water to annoyed. Now we will analysis for this fault.
Feed pipe and internal pump body has air
(1) some users before pump start-up not fill enough water; sometimes seemed to infuse water has been overflow from stomatal, but did not turn pump shaft into the air exhausted, causing a little air discharge completely still remain in the feed or pump body.
(2) Contacing with pump feed water pipe horizontal section under flow direction applied 0.5% of slope, connecting pump inlet end is the highest, without completely level. If upward cock, internal feed tube will remain air, reduced the water pipe and the pump vacuum, affecting pumping wtaer.
(3) packing due to long-term use has worn or packing gland too loose, causing a lot of water from the packing and pump shaft sleeves of gaps jet, the result is external air from these clearances into the internal pump, affecting pumping water.
(4) Feed water pipe due to long-term potential underwater, wall corrosion appear hole, after water pump working, continuously falling, when these holes above the water, air from holes entering into the feed water pipe.
(5) feed tube bending place has cracks, feed pipe and pump contacing joint has appeared tiny clearance, may make air entering into the feedwater pipe.
rotating speed is excessive low
(1) human factor. Quite a number of users due to the original motor damage, random match another machine motor driving, it caused flow less and head low even can not pump water consequences.
(2) Driving belt wear. There are many large centrifugal pump uses belt preach, due to long-term use, driving belt is also loosen, appear skid phenomenon, which reduces the pumps rotating speed.
(3) installed incorrectly. Two pulleys centre distance is too small or two shafts are not too parallel, driving belt tight-side installed on the top, causing angle too small, two pulleys diameter calculated errors and pump shaft transmission two axis eccentricity larger etc, all can cause pump rotation speed change.
(4) pump itself mechanical failure. Impeller and pump shaft fastening nut loose or pump shaft bending deformation, causing impeller moving, directly friction with the pump body, or bearing damage, may reduce the pump rotating speed.
(5) power generator maintenance not record. Motors due to winding consumed and the magnetism loss, in maintenance turn ratios, line diameter, wiring method change, or in maintenance, the fault is not completely eliminated factors will also cause the pump rotating speed change.
suction head is too high
Some water is deep, some water peripheral landslowlands flat place, and ignore the pump allowable suction, thus had a little or can not pump water results. You need to know pump suction vacuum is limited and the absolute vacuum suction is about 10 meters high, while water pump is impossible to build the absolute vacuum. Excessive vacuum makes internal pump water gasification easily, harmful to pump working. So each centrifugal pump has its biggest allowed suction, commonly between 3~8.5 metres, when installing pump must not only figure convenience simple.
The excessive resistance losses of in-out water pipe flow
Some users through measurement, although the vertical distance of the impounding reservoir or water tower to the surface is less than pump head, but always small carry water volume or can not pump water. Its reason is pipeline is too long, conduit corners are too many, flow in water pipe resistance loss is too big. Normally 90 degrees elbow resistance is larger than 120 degrees elbow, every 90 degree bend pipe head loss is about 0.5 ~ 1 meter, every 20 meters pipeline resistance can make head loss is about 1 meter. In addition, some users also optional change pump inlet or outlet diameter, which has some influence on the head.
other factors influence
(1) bottom valve can not open. Usually due to pump aside time is too long, bottom valve gasket is sticky die, no gasket bottom valve may rust.
(2) bottom valve filter screen are blocked, or bottom valve submerged in water sludge layer caused filter screen clogging.
(3) impeller badly worn. Impeller blades wear through long-term use, impact the pump performance.
(4) gate valve or check valves have fault or jams would cause flow decrease even can not pump water.
(5) outlet pipe leakage will also affect pump water volume.
