Ok guys question, I think I know the answer but would like to know for sure. Yesterday morning I started out fixing to do 500 yards of panels. I primed out and proceded to pumping my first panal. After pumping out about 9 yards the boom started shaking violently as if plugged but concrete continued flowing. I shut off pump back stroked and walked to back mixer drivers said back end was shaking violent and pump seemed to be surging instead of smooth stroking. I moved boon safely away from every one and tried pumping a lil more through it while staying by pump listening for clues to hydraulic problems. Heard none , called my boss he said check u joints, I shut it down checked ujoints with a bar and they were tight. So called my bos back he told me to pull a songe and he would try to get a back up out asap. So I pulled a sponge and was getting rdy to wash her out when contractor handed me the phone and my boss was on it instructing me to go ahead and pump out the trucks that were there and be prepared to blow the boom if pump went down. So I pumped the sponge back out and proceeded to slowly pumping out the trucks on location, pump ran smooth as silk with no more vibrations. My question is , was this maybe a partial blockage due to something out of the first mixer that may have caused this that maybe pulling the sponge and restarting may have corrected? Pumped out 340 yards no problem afterwards

Anybody had this happen before?

I have seen something similar before and I would bet that load #2 had dropped an initial hopper full of separated, crappy, unmixed material (maybe dislodged from behind his fins) into your hopper and upon realizing that, he mixed up his load while you struggled to push that unmixed crap through your system. once you got through the crap, she pumped fine the rest of the day.

Could maybe pockets of air working through your hydraulic system? Maybe? Is that even possible? seems legit to me.

That's a theory I had not thought about, we did replace 2 hose the day before, coming off of the accumulator, had not thought about the possibility of air in the system. Not sure is that possible . Anyone?

Was the pump short stroking? As in not taking a full stroke and maybe chattering. Could have been a bad proximity signal.