Unfortunately I have not took a part in disassembling and have not seen neither impellers nor check valve peculiarly, only photo's. Moreover the customer harried to repair the check valve in presence of service center representative. I do not know for what. They even did not make a photo.
I do...
This is another kind of water hammer. This is a wellknown centrifugal pump backflow prevention problem. Please read my this thread messages and references, particularly the Lawrence Pumps Inc. newsletter "Preventing reverse rotation"...
I do understand the pumps have been working out of zone and it is clear that the manufacturer has a ground to void the warranty. It is not the question.
The question is if it could cause the damages like these.
The probability of this is unknown and this can not be proved while the...
Poppeye,
You are writing about an insufficient flow again. I do understand this case.
Let us take a concrete example. Grundfos CR 90-4 50 Hz is working in conditions as follows(hope you have diagrams or can find them easily):
1. inlet pressure is 2 bar
2. discharge pressure is 5 bar
If to...
Poppeye, Have you seen the photo's of the impellers at
http://new.photos.yahoo.com/totemcruise/
I would appreciate if you as very experienced service and repair manager look at them and share your opinion. Do these damages similar to that that you wrote about.
I do not see erosion there on the...
Thank you for discussion.
The extreme right point of NPSH curve is only 7m. I would like to remind that as I wrote the pump station input pressure has never been less then 2,5-3 bar. Do you think it is an appropriate to cavitation condition.
I would suggest to read all my messages more carefully.
"According to service protocol the parameters were as follows:
Pin= 2,5 bar
Pout=5,2 bar
Q= 430 m3/hr"
It's a reverse osmosis booster pump station so the flow could never be unstable and less then above mentioned. The pump station...
I found some corroborations of my assumption.
1. First corroboration is indirect. It's Goulds AquaForce Pumping Station Typical Specification
http://www.goulds.com/pdf/AQFSPEC.pdf
Page 6, Pump Check Valves, last paragraph.
The quotation:
"When pump is retired, valve shall function to close...
These pictures are all I have. If I was there I made some more. The customer said the check valve parts are too big to recirculate but the debris of the impeller are just right. You can see them at the photo's. Nothing else was found there. In conditions of check valve mulfunction it was enough...
When the pump is switched off there is not any flow through the pump(if certainly the check valve is in working condition).
When the pump starts, first period of time it simply works in reciculation conditions, the check valve is closed until the pump head slightly exceeds the pressure in output...
Thank you for help.
I am not sure if I can mention the model number and the name of manufacturer at this forum. It may be considered as false advertising.
At the end the operation of station became unstable so they decided to increase the inlet pressure. This helped.
According to service...
The damages are absolutely typical for all the pumps. I surmise the small impeller debris could recirculate for a long time through the broken check valve and pump#2 when it was switched off. It was swiched on for only 1/5 of total pump station operation time. If the total time is 90 days only...
I have placed some photo’s of damaged impellers to the Web. Anyone can find them at
http://new.photos.yahoo.com/totemcruise/
I have not done any simulations. Is there any software that can help. Can you advise. I am afraid all of them simulate only normal operation mode.
I would like you to...
I forgot to write that
1. the pumps are multistage centrifugal pumps with 304SS impellers.
2. the total pump station flow was right and stable, about 400m3/hr. If the discharge pressure would 7.8 bar the pump station worked in right operation point.
3. the first stage of each impellers were...
Hello!
Before 300 m3/hr RO system 6 pump booster pump station used to work round the clock for three months. At the end of this period the customer informed us about periodical alarm disconnections of pump station. The message informed about the frequency converter fault and pump #2 short...
