Impeller damage
Impeller damage
(OP)
Hi Buddies, we visited a water &sewage water co. The factory includes an inlet pump station and an out pump station. There are 6 split case pumps in each pump station.
The customer told us that the first 4 pumps of each pump station were all damaged at the shroud of the lead edge, They had noticed that the pressure of the discharge of the first 4 pumps in inlet pump station was 13.8 meters and that of the suction was 4 m. there should be no cavitation damage. Who knows what have happened to these pumps ? The pics please see the link below. http://photo.163.com/photos/sunloco/69422874/
The customer told us that the first 4 pumps of each pump station were all damaged at the shroud of the lead edge, They had noticed that the pressure of the discharge of the first 4 pumps in inlet pump station was 13.8 meters and that of the suction was 4 m. there should be no cavitation damage. Who knows what have happened to these pumps ? The pics please see the link below. http://photo.163.com/photos/sunloco/69422874/





RE: Impeller damage
I2I
RE: Impeller damage
The photo's certainly seem to show classic cavitation -however, the damage is on underside of the blade (the side you can readily see) which indicates that the pumps are operating at over-capacity.
You need need to establish what the operating point is for each unit in relational to the original selection / selection and where the pumps are operating on their performance curves. You may find the pumps are way out on their curve.
I would also involve the supplier / manufacturer as you might neeed to make some changes to the pump once the duty has beeen established.
Naresuan University
Phitsanulok
Thailand
RE: Impeller damage
I have seen similar damage in a water recirculation pump in our coker. In that installation, I found that the operators had pinched down on the minimum flow spill-back line in order to try and get more flow at high demand conditions. However, at another time in the cycle, the destination tank would fill up and the control valve would go closed. The pumps were running at very low flow rate for part of the cycle. In those pumps, the cavitation damage looked like what you are seeing but extended into the impeller hub where it had almost eaten the impeller in two pieces.
If you have a spill-back line, check to make sure it is in operation. If the flow is measured and can be trended, look at the variation in flow rate over time. If the flow cannot be measured, estimate it based on the head produced and the motor amps.
RE: Impeller damage
What is the water quality and material of construction?
By the way, nice photo posting.
There may be a lot of inlet head, but is the flow nice and smooth? There may be too much inlet resriction to run all pumps at once.
When you run tests measure the intake/discharge pressures right at the pump.
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RE: Impeller damage
RE: Impeller damage
The damage on the underside (low pressure)side of the blade is typical of under-capacity NOT over-capacity. This is a mismatch of flow onto the blade where it impinges on the low pressure side as the flow into the impeller does enter into the high pressure side of the impeller as it should.
However, it is still necessary to establish flow rates, head etc so as to compare what is actually happening to what should be happening - without this information everything else becomes guess work.
Naresuan University
Phitsanulok
Thailand
RE: Impeller damage
It happens - CI impellers are very susceptible to the damage.
RE: Impeller damage
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RE: Impeller damage