Can we talk about how fast a cutterhead can wear down in rocky ground?

I was reading through some old dredge logs from a job we did up in Portland last year and found a stat that blew my mind. We ran a 14 inch cutterhead through a stretch of mixed cobble and clay, and after just 28 hours of run time, the teeth were worn down by nearly 40 percent. That's way faster than I expected, and I started wondering if the hardness of the rock or the angle of attack matters more. On one hand, you could argue it's just the material and you can't do much about it, just swap teeth more often. On the other hand, maybe changing your swing speed or using a different tooth profile could save you hours of downtime. I've got a buddy who swears by running slower in rock, but my old foreman always said to keep the rpms up and let the cutter do the work. What's your take, do you baby the cutterhead or push through and deal with the wear later?

3 comments

3 Comments

laura_chen411mo ago

Wait, are you saying it was only 40% after 28 hours? That actually sounds pretty good to me for mixed cobble, honestly. We had a job in the Sacramento River delta a couple years back where we hit a patch of rhyolite gravel with some clay binder, and we were swapping teeth every 12 to 15 hours. I think the angle of attack matters more than most guys give it credit for. On that job, we started running the cutter at a lower swing speed, maybe 2/3 of what we normally did, and the teeth lasted almost twice as long before they started rounding off.

the_tessa1mo ago

@laura_chen41 Are you saying the lower swing speed was the key change or did you also adjust the crowd pressure like Sean mentioned? I ask because we had a job in decomposed granite that felt similar - dropping the rotation rate helped a ton but only after we backed off the down pressure too. Running it slow and gentle kept the carbide from fracturing on the embedded quartz chunks. Did you ever try playing with the tooth pattern or just the speed adjustments?

sean_green441mo ago

Rhyolite gravel with clay binder sounds like a nightmare. We were digging up in the Pacific Northwest once, working on a stormwater pond, and hit a seam of what the geotech report just called "weathered basalt." Turned out that was code for "you'll be changing teeth every coffee break." I dropped the rotation speed and actually slowed down the crowd pressure too, not just the swing, and we got almost 30 hours out of a set. There's something about letting the cutter sort of nibble instead of bite that keeps the carbide from chipping out.