1. metallic piston rings Petroleum-base and synthetic fluids, phosphate esters - for high
pressure and severe conditions low to 500° F (260° c)
2. leather Petroleum-base and some
synthetics, phosphate esters - for medium to high pressure
-65° F to 225° F -54° c to 107° c
3. neoprene rubber General purpose industrial use, Freon 12; weather and salt water
resistant
-65° F to 300° F -54° c to 149° c
4. nitrile rubber (Buna n) Petroleum-base fluids and mineral oils - used for some rotating seals,
extrusion resistant
7. Polyurethane Petroleum-base fluids - high resistance to ozone, sunlight and weathering; low water resistance.
-65° F to 200° F -40° c to 93° c
table 5-1: common sealing materials and their applications
Review 5.2.1.1: Referring to table 5-1, which seal material has the widest temperature range?
5 - • Hydraulic Specialist • Study Guide HS Manual # 401 - 07/10/0
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Task 5.3: Match the filter specifications to the requirements of a machine.
Outcome 5.3.1: Match filter specifications to a machine.
the type of fluid to be used in a particular machine is determined by the manufacturer of the hydraulic components to match service related conditions. the manufacturer of a machine, such as a hydraulic press, may or may not manufacture the hydraulic pump and components used on the machine. therefore, in order to back up the guarantee on the machine, the machine manufacturer generally uses the fluid specification published by the component manufacturer. not using the specified fluid will usually void the machine warranty.
most hydraulic component wear is caused by contaminants in the system. contamination present in the system from the construction stage is termed built-in contamination. contaminants generated by components in the system, such as pumps and motors, are called system generated contaminants. contaminants added with the hydraulic fluid, or during service of the system, are called induced contamination. other contaminants, such as moisture, are ingested during operation. ingested contaminants typically enter the system through the reservoir breather or on the cylinder rod as the rod retracts past the rod seals.
many main system hydraulic pumps are damaged or destroyed because of poor inlet flow conditions. it is for this reason that many major pump manufacturers discourage the use of suction (inlet) line filters or strainers. if a customer insists on the installation of such a filter or strainer the manufacturer will often write an addendum to their warranty. manufacturers of hydraulic systems recommend good pressure, return and off line filtration so that quality clean fluids reach the pumping units.
one micron (micrometer) = 1 millionth of a meter. this equals 39/1,000,000 = 0.000,039 inches. By comparison, the smallest particle visible to the unaided human eye is approximately 40 microns.
Filter performance is measured by the extent to which silt and particulate matter can be removed from the fluid. as fluid passes through the filter, filtration is proportional, which means that only a portion of the particles above a certain micron size are removed from the fluid.
the Beta Ratio is a comparison of the number of particles in the fluid greater than the micron rating of the filter on the upstream side of the filter, to the number of particles in the fluid greater than the micron rating on the downstream side of the filter. the Beta Ratio is derived from the iso standard 16889 (1999) multipass Filter test.
in typical contamination reports, the contamination level is measured by range numbers which give the actual number of contaminants above a specified micron size per milliliter of hydraulic fluid. When two range numbers are given the micron sizes are 6 and 14 microns. When three range numbers are given the micron sizes are 4, 6 and 14 microns.
the Beta Ratio compares the number of particles, of a certain size, upstream of the filter to the number of particles of the same size downstream of the filter. efficiency represents the percentage of particles removed from the fluid as it passes through the filter. a rating of ß10 = 12 means that 92% of the particles larger than 10 microns were captured by the filter when the test was conducted. the multipass Filter test is ended when the pressure drop across the filter reaches a predetermined pressure differential, for example 20 psi, indicating the filter has become saturated with contamination. Particle counts are taken at one minute intervals during the test. after the completion of the test, the results are divided into ten equal time increments and the upstream and downstream particle counts for the three standard particle sizes are analyzed and ratios are calculated. then, a final ratio is produced by averaging the ten calculated ratios.
9/7/07
Hydraulic Specialist • Study Guide • 5 - 7 HS Manual # 401 - 07/10/0
Recommend Fluid, Fluid conduc toRs, and Fluid FiltR at ion
(eq. 5-1)
Beta Ratio = (# of particles introduced / # of particles passed) ß10 = (100/25) = 4
(eq. 5-2)
efficiency = R-1/Rx100 = % element efficiency efficiency = 75-1/75x100 = %
the efficiency of any ßeta ratio rated element is to subtract 1 from the rating and divide by the rating.
example: ß10 = 50 would be 50-1/50 = 49/50 = .98 x 100 = 98% efficient in removing 10 μ particles and larger. note: Bx =200 is highly recommended.
table 5-2 gives the number of particles for range numbers 6 through 24. For a range number of 24, the number of particles will be between 80,000 and 160,000. the range number does not give the particle size, just the number of particles.
the range numbers in table 5-2 are part of a coherent system in that as the range number decreases from 24 to 6, the number of particles is half the preceding number. For example, a range number of 24 shows that the number of particles is between 80,000 and 160,000, whereas a range number of 23 shows the number of particles to be between 40,000 and 80,000. this means that if the particle count for one range number is known, the particle count for the remainder of the range numbers between 24 and 6 in table 5-2 can be figured out.
cleanliness levels for hydraulic fluid can now be specified by the iso code number which identifies the micron size of the particles, and the actual count of the number of particles equal to or greater than the micron size given by the range number in 1 ml of hydraulic fluid. For example, an iso code number of 13 means that the number of particles equal to or greater than the micron size given in a sample of 1 ml of hydraulic fluid will be between 40 and 80 particles. of course, the sample size taken from the machine is larger than 1 ml, but the count is given per ml of hydraulic fluid. also, the number of particles smaller than Review 5.3.1.1: assume that a hydraulic fluid
being analyzed for 5 micron sized particles contains 100 particles of contaminant upstream of the filter and 50 particles of contaminant downstream after passing through the filter. What is the Beta Ratio of the filter?
5 - • Hydraulic Specialist • Study Guide HS Manual # 401 - 07/10/0
Recommend Fluid, Fluid conduc toRs, and Fluid FiltR at ion
the micron size given by the range code cannot be determined. For example, in the range number 19/18/14, the number of particles greater than 14 microns in size is between 80 and 160 particles per milliliter (ml).
the number of particles greater than 6 microns is size is between 1300 and 2500 particles per ml. the number of particles greater than 4 microns in size is between 2500 and 5000 particles per ml.
the current standard for the number of particles lists the count for three sizes of contaminants. the three sizes are given on the left side of table 5-3. Prior to 1999, the iso tables listed only two micron sizes: >6μ and >14μ. the classification code gives the >4μ size particle range number on the left, the >6μ particle size range number in the center, and the >14μ size particle range number on the right. For example, a classification 18/16/13 indicates that the particle size is measured at three levels (>4μ / >6μ / >14μ).
the maximum number of particles equal to or greater than 14 microns (>14μ) will lie between 40 and 80 particles. the maximum number of particles equal to or greater than 6 microns (>6μ) will be between 320 and 640. the maximum number of particles equal to or greater than 4 microns (>4μ) will be between 1300 and 2500. the quantities are given for a sample size of 1 ml of hydraulic fluid.
the iso classification code is used to specify fluid cleanliness for various components in the hydraulic system, as well as for the entire system. the cleanliness of new fluid (right from the drum or bulk storage) is rarely sufficiently clean for use in hydraulic systems. all new oil should be filtered as it is added to
(number of Particles per milliliter of hydraulic fluid)
Range Number More than Up to and including
24 80,000 160,000
table 5-2: Range numbers and Particle counts
09/07/07