Machinery Lubrication magazine published by Noria Corporation
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actuators, while an acid-remediation and 1-micron polishing filter skid runs in kidney loop off the reservoir. Two 2,400-watt heaters in the filter skid sustain the fluid temperature when the system is offline. Super-dry air is supplied to the reservoir headspace for maintaining the moisture level in the fluid. Tube and shell coolers keep the fluid temperature at the desired level. System Flushing and Cleaning Due to the complexity and size of the system, an outside company was contracted to perform the flushing and cleaning. A large 300-gallon-per-minute pump/filtration unit would provide the circulation. A large quantity of fittings, flanges, jumper hoses and valves was required to flush the system. For a true high-velocity flush, the fluid was circulated at five times the normal flow rate to achieve turbulent flow through the piping and components. This was accomplished by running sections or circuits rather than the entire system during the oil flush. To help with the cleaning process, the oil was heated and temperature cycling was performed. No filtration was done during the cleaning process. Particle counts were taken in the beginning for a baseline and after the completion of each system process. The particle counts usually spiked rapidly and then began to level out as the process proceeded. Once three consecutive particle counts remained level or dropped slightly, the flush/cleaning was stopped. All fluid was drained from the system, air was blown through the piping to help remove any trapped fluid, and the vessels that could be opened were cleaned and wiped out, including the reser voir. Time was of the essence, as the fluid would begin gelling as it cooled, making it harder to remove and clean. The Rinse Cycle and the New Fluid After the entire system was drained and wiped down, the reservoir was filled with a lesser value phosphate-ester fluid, which was used to rinse and clean out the system. Approximately three-fourths of the tank volume or 1,600 gallons were used for the rinse. This was completed in the same manner as the flush, utilizing different system sections or circuits. This time the fluid was filtered as it ran through the system. Particle counts were taken at the end of each complete system cycle. Once the desired particle count was reached for three consecutive cycles, the rinse was completed. The rinse fluid was then drained and saved in large totes for use on the second unit's flush. Piping was blown out, and the reservoir and all vessels were opened and wiped down. New filters and acid-remediation media were also installed. The system was now ready for the new fluid . Of the new EHC fluid, 1,600 gallons had been transferred to large totes from the drums and flowed through a polishing filter for several days. The remaining 800 gallons were pumped through the filter skid when it was installed in the reservoir. Since the unit was not able to be run when the project was completed, a filter skid was kept onsite and used on the reservoir through the commissioning of the system and valve setting. Once particle count levels were acceptable, the filter skid was removed and the system filtration was resumed. When the system was returned to service, a few minor leaks and loose flanges were reported. Of the hundreds of fittings and flanges that had been opened, bypassed and reassembled, a few leaks were expected. The Aftermath The second unit's flush was completed first. The fluid manufacturer, oil analysis lab and others were contacted to determine which tests could be conducted to confirm that the cleaning agent had been thor- A large pump/filtration unit provided the circulation for the system flush. What Is EHC Fluid? Electrohydraulic control (EHC) fluids are typically fire-resistant lubricants, which are important in applications where hydraulic fluids can be exposed to high temperatures or sources of ignition, such as power generation, furnaces, foundries, and military and aeronau- tical applications. What is a fire-resistant fluid? According to Exxon- Mobil, "fire-resistant hydraulic fluids are specially formulated lubricants that are more difficult to ignite and do not propagate a flame from an igni- tion source. Fire resistant should not be confused with fireproof, as fire-resistant fluids will still ignite and burn given specific conditions." Fire resistance is defined by ISO 12922, rev. 2 (2013), which evaluates fluids based on three tests selected to represent three different fire scenarios: spray flammability (ISO 15029-2), wick flame (ISO 14935) and hot manifold igni- tion (ISO 20823). The difference between some of the fluids as tested, based on ISO 12922 rev. 2, is whether they will self-extinguish once the heat source is removed. 8 | January - February 2017 | www.machinerylubrication.com COVER STORY