I keep seeing guys run the cutterhead too fast in pure sand

At my last job on the Mississippi near Baton Rouge, we had this new operator burning through pump seals every 2 weeks because he was spinning at 28 RPM in loose sand instead of dropping down to 18-20. Has anyone else noticed that running slower in sand actually moves more material and saves your gear, or am I the only one who got taught that the hard way?

2 comments

2 Comments

rosew3727d agoMost Upvoted

Wait are you sure about 28 RPM? I thought 28 was on the low end for a standard 14 inch cutterhead on most hydraulic dredges, not the high end. At that speed you're barely churning the material, which could explain why he was burning seals - not because it was too fast but because the pump was cavitating from not getting enough flow into the intake. You need around 30-32 RPM in pure sand to actually keep the material suspended and moving through the pump without deadheading the impeller. Running slower in sand just lets the heavier particles settle back out and clog everything up, which creates more suction problems and seal damage.

umaprice27d ago

Wait is this like when my buddy ran his truck engine at idle thinking he was saving gas but actually cooked the transmission because the pump wasn't spinning fast enough to lube anything? Sounds like he was trying to be gentle and just made everything worse.