Pressure not holding, bubbles in the pipe?


New Member

I'm pumping a pretty heavy mix of sand/lime/clay/wood pulp onto straw bales out in the antipodes in NZ.

I have a Chinese pump that's been modified to fit a 2L6 pump. (This can pump the correct aggregate size in my mix, and is available 3 days away instead of 2 or 3 weeks from china).

Kinda like this,

Cranked her up last week and it ran like a dreeeeam. Pumped about 10 ton of mud in 3 days with 4 dudes onsite.

When we turn it on it runs fine for a while initially, then drops in flow to less than half and the dial starts jumping up and down from zero to about 10 bar.

When I pump it out into a bucket with the air off it seems to be blowing bubbles....????

If we reverse it for a second it goes good for 30 secs then drops back to same pattern.

- the R&S holds water well so we assume it's not worn too much, my supplier says.

I have some theorys but would really appreciate your ideas

Thanks in advance



Well-Known Member
Not sure about the material and i expect its quite warm in NZ. I would try firstly pumping at its slowest to get going and make the mix wetter. Dont fill the hopper too full in case the gear starts firming up creating a tunelling effect and only pulling part of the gear. Check the conveying shaft is also most suitable for the material you are pumping.




New Member
Did a clean out halfway through today and discovered that there is a bit of a logjam of compacted mud around the opening of the pump, we've had all sorts of temps from 35deg 3 days ago to a high of 16 today f**ing mad. When we cleaned that out it cranked up fast again for about 2 hoppers, then packed up again. I reckon that's it, but why is it happening now. I prayed to the pump gods and everything before we started up.. even did a little dance..

I'd wondered about the tunnel thing too, but the mixes are pretty wet and we can leave it for ages with no harm. Really happy with my mix like i said she pumped like a dream for 3 days straight. No set until it starts drying on the wall really. I thought it could be a worn seal on the pump sucking in air but we eliminated that today with.