A manufacturer’s production of railroad “frogs” (switches that allow trains to move from one track to another) had dropped. Production was running 15 to 20% slower than normal. This company takes straight lengths of railroad rails and bends them to different shapes for uses where curves and switching tracks are needed. An example would be part of the turnout where the main gauge line intersects to determine which rail it needs to be on.
The hydraulics for clamping the rail had a separate power unit and it worked fine. They determined that the rail bending cylinder was running slower than normal. They checked the program that controls the proportional directional valve and all seemed correct. They felt it was either because the cylinder was bypassing, the main relief was opening too soon or the pump had gone bad.
Rail frog bending machine running slow troubleshooting challenge
They knew to check the case drain on the pump when it was fully loaded and it showed that it was a little less than 1 gpm. The safety relief looked to be in good condition and its setting was higher than 2,700 psi. When the cylinder bottomed out, the pressure was close to 2,700 psi. The system idled a little higher than 300 psi. They took the cylinder to a repair shop, where they were told it was in decent shape.
What would you do next? Can you identify what was the problem? We welcome responses of all kinds directly to Robert Sheaf at [email protected] or to [email protected]. The solution will be provided in conjunction with next edition of Fluid Power World and will be published online next month.
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