I used to swear by 6-inch dredge pipe until a guy in Mobile set me straight

I ran 6-inch for 3 years thinking bigger pipe meant faster work. Then a old timer at the dock said I was just moving more water not more solids. He told me to drop to 4-inch and bump the pump speed by 200 RPM. First day on the job in Mobile Bay I pulled 30% more sand per hour. Now I only use 6-inch for thin slurry jobs. Anyone else get a size recommendation that changed their production numbers this much?

3 comments

3 Comments

wesley_adams11d agoMost Upvoted

That old timer telling you to drop to 4-inch is the same conversation I had with a guy dredging up near Brunswick. He pointed out that pump suction and discharge size is only half the story. What nobody talks about enough is how pipe diameter changes the velocity and that directly affects how well you keep solids suspended. I ran tests with a flow meter on a 6-inch versus 4-inch setup with the same pump and RPM, and the 4-inch actually kept the sand moving at a higher critical velocity so it didn't settle out in the pipe. You probably already know this but that RPM bump is doing just as much work as the pipe swap.

smith.anna11d ago

You changed my mind @wesley_adams, I was all about bigger pipe before reading this.

milesbailey11d ago

Buddy of mine runs a small dredge outfit down in Louisiana and he said the same thing after swapping from 6 to 4-inch pipe on a shell bed job. That velocity jump made a noticeable difference keeping the grit from dropping out mid-line.