We were sent to troubleshoot a Liftavator LULA, it has a CEMCO controller and CEMCO tank unit with an RV100 valve. The jack and car frame are made or subcontracted by Liftavator. This unit is an inverted hydraulic unit.
The problem we’re having is when the car runs up it will randomly and abruptly stop mid-flight, the pump will stay running and the valve coil will stay energized, until the controller either goes into low oil or trips an overload, whichever it decides to do is random also.
On cartop inspection it will act the same way, stop abruptly, randomly, and will also allow the pump to keep running, let off the inspection buttons and try running up again, the pump will still respond and the car will stay stationary, leading us to believe it is not an electrical circuit cutting out. If we bump the car down on inspection, not even long enough to move the car, just enough to relieve pressure, then try running up it will move up again. Then randomly and abruptly stop the same way. This doesn’t happen at the same spots in the hoistway, or have any equal distances between when/where it decides to stop. Also, it doesn’t do it on every trip, you could have 5 runs of the hoist way with no incident, and then it does it. Or you could have it happen repeatedly on every run, then all of a sudden you’ll get 2 runs without issue again. There is random scraping/clunking noises coming from the jack, but they are intermittent. There is no scoring on the piston, the packing is not leaking. And there is nothing covering the intake of the pump. We’re left thinking this might be a valve issue, or it may have something stuck inside the jack. Do these inverted units have roller skates on the top of the piston that could be deteriorating and getting wedged? (Similar to the TK/Dover inverted units?) or could this be a valve issue? Any insight would be appreciated, this thing has us scratching our heads.
