Plant Services - July 2008 - (Page 39)

Power Transmission Reliability from the reservoir, they’ll be drawn into the pump and cause premature failure of the system components. And, of course, be sure to use lint-free cloths when cleaning out the reservoir. It all begins at the sump 12 8 5 High Clean and flush 7 When you clean the sump, you don’t necessarily need to replace the hydraulic fluid. Unless the oil is severely degraded, all you need to do is run it through a 1-micron filter into a storage tank to remove solid contaminants and water. Then, run the oil through a clean 1-micron filter when refilling the sump. 4 9 3 Low 10 2 6 11 Depending on the location, the breather cap might need to be changed a couple of times per year. The next step is flushing the lines to the valves and actuators with clean oil. Figure 2 shows the flushing unit we use for this process. Connect the inlet and outlet lines of the cylinders and motors together. If possible, electrically or manually actuate the directional valves to allow the fluid to circulate through the piping. If this isn’t possible, bypass the directional valves by connecting the pressure and tank lines to the actuator’s outlet lines. Use the pump on the machine to circulate the oil through the lines. Connect the flushing unit so it circulates the oil in the reservoir through 1-micron filters. Allow the system to run for as long as possible. Figure 3 shows the purity of the oil for a system before it was flushed, then after one, four and 16 hours of flushing. Key: 1. Reservoir 2. Reservoir heater thermostat 3. Manhole 4. Level indicator 5. Suction line 6. Foot valve/filter screen 7. Level switch 8. Breather cap 9. Temperature indicator 10. High-temperature switch 11. Manual drain valve 12. Water-type cooler Figure 1. The reliable hydraulic system reservoir needs to be outfitted with specific components. Portable flush Other reservoir tasks An important variable is the reservoir heater setting. Check the reservoir heater thermostat (item 2 in Figure 1) to verify that it toggles on at a minimum temperature of 70°F. A pump mounted on top of the reservoir can cavitate if the oil temperature drops below about 60°F. Insufficient oil depth can cause problems, so most reservoirs feature two switch settings (item 7 in Figure 1) – a warning and a shutdown. The problem with this configuration is that the difference between the two levels might represent several hundred gallons of oil. Eliminating the warning switch and setting the shutdown at a higher level minimizes the oil loss should a hose rupture. Next, verify that the breather cap (item 8 in Figure 1) has a rating of about 10 microns. This is the first line of defense against airborne contaminants entering the tank. Depending on the location, the breather cap might need to be changed a couple of times per year. Other options include pressurizing the reservoir with an internal bladJuly 2008 Figure 2. Circulate filtered oil from the refilled sump through the system to flush contamination out of the other components. der or using a moisture-removal-type breather. High temperature can undo your efforts. Oil starts breaking down at 140°F, but many systems won’t initiate system shutdown until the oil temperature reaches 160°F. If your hydraulic system is operating above 140°F, there’s a problem in the system that might be traced to a cooler malfunction or excessive bypassing at the pump, valves, cylinders and hydraulic motors. Set your high-temperature switch (item 10 in Figure 1) at 140°F to shut the pump off and prevent Headline oil breakdown. 39 www.PLANTSERVICES.com http://www.PLANTSERVICES.com

Table of Contents Feed for the Digital Edition of Plant Services - July 2008

Plant Services - July 2008 Contents From the Editor Letters The PS Files Up and Running Crisis Corner Asset Manager Technology Toolbox Cover Story Compressors Power Transmission Flooring Web Hunter In the Trenches Product Picks Classifieds Energy Expert

Plant Services - July 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.