Mud pump pressure spike after switching to a smaller liner
Ran a 10x8 pump on a river job outside Baton Rouge for two weeks, steady at 38 psi. Swapped to a smaller liner last Tuesday because the cutterhead was bogging down in clay. Pressure jumped to 61 psi and we blew a fitting off the discharge line, sent mud everywhere. The liner gave us more velocity but our suction hose couldn't keep up, so we were pulling a partial vacuum. I thought smaller liner meant more cutting power, but it just stressed the whole system. Now I'm wondering if anyone else has seen this and whether you drop pump speed or change the suction setup when you go down in liner size. What's your move when that pressure spike hits? Has anyone else blown a line doing the same thing?
Did the guys on the crew try dropping the pump speed first? My buddy went through this exact deal on a job over in LaPlace, dropped from a 10 to an 8 liner and figured he'd just run it wide open. Pressure went crazy and his suction line started dancing, you could hear it starving for mud. He backed the throttle down about 200 rpm and that got the vacuum under control without losing his cut. Turns out the smaller liner needs less flow coming in, not more, so running it hard just chokes the suction side. Might be worth checking your hose size and length too, a long run with a small hose will bite you every time.