Multistage pump failure?

[julianf]

Ive just had my pump fail mid-batch. 

It still pumps, but more like a pour, rather than a gush.

Its too late now to investigate (i swapped in an identical spare) but what should i be looking for?

notes -

Pump has been getting slightly more noisy for some time.
Motor is certainly still spinning fine
Looking in the input port, i could see some blackened stuff, like bits of straw, or sawdust, around the first visible plate (this leads me to suspect more further inside)

The pump is a Grunfoss multistage.  I forget the model, but ill look it up.

Is there anything to watch out for before i start taking it apart? 

Thank you,
julian

[Tony]

They don't like pumping fibrous debris - it sticks in the impeller eyes and on the diffuser edges.  I bet it's clogged with gunk - nothing a quick clean shouldn't sort.  I use a length of copper wire from an electrical cable to poke clean the impellers and diffusers.

[julianf]

Do i just take the front off it, and all will be on display, or will i need to look at diagrams etc?

You have to clean yours often?

[Tony]

I'm not sure on the Grundfos ones as I've not got one, but the Calpeda ones the case comes off, then a locking nut on the motor shaft, and then all the impellers and diffusers easily slide off the shaft (which is splined).  Have to pay attention to the order for re-assembly purposes.

No I don't have to clean mine often at all, but I do course filter and settle my WVO before it goes in the processor, so usually very little in the way of contaminants.

[willbuild]

pretty straightforward just remove the 4 screws. easy access to impeller.
tried to buy a new impeller for a 80 grufos pump that i found but was told that they don't sell parts for them as they never go wrong

[Tony]

I have spare impellers for my multistagers (from a three phase pump of the same type) but they never fail in any way.  The only problem I've seen is worn bearings on the pump motors and expanded sealing o-ring between the pump housing and body (now replaced with Viton) - very little else to go wrong really!

[therecklessengineer]

Yes, I've had this problem too. Thankfully no more since I fitted a 100 micron filter to the processor inlet.

As above. Take it apart and be methodical - lay everything out in the order in which it came off. Take photos if you need to.

[Tony]

Take photos if you need to.

Definitely take photos.  For the wiki