A Rolling Steel Mill Had Trouble With the Roll Removal Circuit Trying To Eject a Roll
By Robert Sheaf, CFPAI/AJPP, CFPE, CFPS, CFPECS, CFPMT, CFPMIP, CFPMMH, CFPMIH, CFPMM, CFC Industrial Training.
The circuit attached shows the hydraulic system used for roll removal at the end of the line. They could remove small rolls with no problems, but the larger rolls would move very slowly or not at all. This required the operator to use an overhead crane that slowed down the production cycle time.
The main system pressure was set at 13.8 MPa (2,000 psi) and the pressure reducing valve output was still reading 3.9 MPa (572 psi).
Any idea what could be causing the problem?
See Solution
The circuit for the roll removal system is commonly called a part time Regen (regeneration) allowing the rod flow to join the pump flow moving the cylinder at a fast rate and when encountering a load, the speed would drop to a steady slow rate as the cap end pressure increased. The 1.3 mm (0.050”) orifice prevented the rod side pressure from intensifying and reducing the total extension force. The drawing showed a 0.5 mm (0.020”) orifice that was blocked causing this problem. Just another note, when they found the blocked orifice in a fitting, they also discovered it was a 0.5 mm (0.050”) size, and not as shown on the drawing. The builder must have changed it to a larger size to acquire the slower speed and the high force they needed.
Robert Sheaf has more than 45 years troubleshooting, training, and consulting in the fluid power field. Email rjsheaf@cfc-solar.com or visit his website at www.cfcindustrialtraining.com. Visit fluidpowerjournal.com/figure-it-out to view previous problems.
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