Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1080534
14 | January - February 2019 | www . machinerylubrication.com Conta mination is the cause of approximately 90 percent of all hydraulic system failures. If the systems are maintained at the desired cleanliness level and the oil tempera- ture is controlled, then downtime can be kept to a minimum. e ideal oil temperature for an industrial hydraulic system is 120 degrees F. If the temperature reaches 140 degrees F, oil begins to break down. e life of the hydraulic oil will be cut in half for every rise in temperature of 15 degrees F above 140 degrees F. Mobile hydraulic systems gener- ally are designed to operate at higher temperatures due to their smaller reservoir size, which limits the amount of heat that can be dissipated to the atmosphere through reservoir walls. A higher viscosity oil is often used in mobile systems in order to operate at higher temperatures. C ont a m i n a nt pa r t ic le s i n hydraulic systems are measured in microns. One micron is one- millionth of a meter. e clearances inside most pumps and valves are approximately 0.0004 inch. How small is this? Consider that a grain of salt is 0.0039 inch or 100 microns. e lower visibility of the human eye is 40 microns (0.00158 inch). A red blood cell is 0.0003 inch or 8 microns. A particle much smaller than what the human eye can see is capable of causing a hydraulic system failure. Hydraulic f ilters should be selected to protect the most critical component in the hydraulic system. In the "old days," a 10-micron filter was used to protect a system without servo valves, but there was no measurement for how efficient the 10-micron filter was. Did it remove all particles that were 10 microns and above, some of the particles or 25 percent? Today, filters are assigned a beta rating to determine their effi- ciency. e beta rating represents the number of particles that enter the filter relative to the number of particles that are flowing out. System filters should have a beta rating of 75 or higher. For a 10-micron filter, this is expressed as B 10 =75. is means that for every 75 solid, spherical particles entering the filter which are 10 microns and above, only one particle will exit the outlet port. Beta ratings of 200 are common for many filters in use today. Contamination levels in hydraulic systems are measured by the ISO 4406 cleanliness code. e desired target level is dependent on the most critical hydraulic component and the pressure in the system. is is expressed in three numbers, which represent the number of contami- nants that are 4, 6 and 14 microns and above in a 1-milliliter oil sample. For example, if a variable Minimizing Hydraulic Downtime with Proper Filtration HYDRAULICS Al Smiley | GPM Hydraulic Consulting "If one or more systems in your plant are not meeting the recommended ISO cleanliness level, examine the system to ensure the filters are in the proper locations." Some hydraulic units have an in- expensive breather that doubles as a fill cap. A desiccant breather can be used to remove moisture from the air before it enters the tank.