Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1103301
24 | March - April 2019 | www . machinerylubrication.com HYDRAULICS be significantly out of synch after only a small number of machine cycles due to the extreme tightness of the flow divider. is is where adjustments come into play. Crossport Relief Valves Adjustments are made via crossport relief valves. Many people assume the purpose of these valves is to absorb shock. While they will indeed absorb shock, their primary purpose is to allow some slippage to keep the actuators moving in synch. When the actuator that is bypassing the least amount reaches its stroke limit, the actuator that is bypassing somewhat more will not be quite at its limit. With the crossport relief valves in place, pressure can build in the line of the actuator that has reached the end of its stroke until the crossport opens. Flow can then continue to the slower actuator and enable it to reach its limit. A lot of flow dividers come with crossport relief valves built in, but some do not. If the actuators are mechanically connected, it usually is advisable to either purchase a flow divider with built-in crossport relief valves or add a set of crossports to the assembly. While speaking at a conference a few years ago, I met a woman from the Department of Transportation. After I had spoken, she introduced herself and said she had attended the conference in hopes of finding someone who could offer some advice on a ferry ramp that had recently been installed. Since my topic included hydraulic troubleshooting, she thought I might be able to assist. e ferry ramp was a relatively simple hydraulic system but of a rather unique and expensive design. Two enormous cylinders were mounted on the ocean floor to lift and lower the ramp. Since the cylinders had to be installed by divers, each one cost more than $1 million. After installation, the ferry ramp worked very well. e ramp would lift, the ferry would move under it, and then the ramp would lower The ferry ramp cylinder/flow divider configuration Crossports added to the original ferry ramp installation ROTALIGN® touch rocks! O� en Copied, Never Matched! Save �me, effort, and cost with the most accurate laser alignment system on the market: the ROTALIGN® touch Single-laser sensALIGN technology In-situ cardan shaft alignment Real-ti me simultaneous multi coupling measurement intelliSWEEP, verti SWEEP and Live Trend analysis www.rotalign-touch.rocks PRUFTECHNIK Inc. | Philadelphia | Montreal | 1-877-778-3832 | info.na@pru� echnik.com Machinery Lubrication.indd 1 06.02.2019 08:21:55