ISO 3968 pdf download.Hydraulic fluid power – Filters – Evaluation of differential pressu re vers us flow characteristics
1 Scope
This International Standard specifies a procedure for evaluating differential pressure versus flow characteristics of hydraulic filters and constitutes a basis for agreement between the filter manufacturer and user. It also specifies a method for measurement of the differential pressure generated at different flow rates and viscosities by the relevant parts of a filter assembly, that is the housing, the filter element and any valves contained within the housing that are in the flow stream.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of IEC and IS0 maintain registers of currently valid International Standards. IS0 1 21 9-1 , Fluid power systems and components – Graphic symbols and circuit diagrams – Part 7: Graphic symbols * IS0 3448, Industrial liquid lubricants – IS0 viscosity classification IS0 4021, Hydraulic fluid power – Particulate contamination analysis – Extraction of fluid samples from lines of an operating system IS0 4406, Hydraulic fluid power – Fluids – Method for coding the level of contamination by solid particles I S0 5598, Fluid power systems and components – Vocabulary I S0 1 6889, Hydraulic fluid power filters – Multi-pass method for evaluating filtration performance of a filter element
3 Terms and definitions
For the purposes of this International Standard, the definitions given in IS0 5598 and the following apply. 3.1 filter rated flow rate flow rate recommended by the filter manufacturer for a specified kinematic viscosity 3.2 viscosity index empirical measure of the viscosity/temperature characteristics of a fluid NOTE The smaller the change in viscosity within a given temperature range, the higher the viscosity index.
5 Test equipment
5.1 General indications A suitable test rig consists of a pump, a reservoir, a clean-up filter, the filter under test and, if required, a heat exchanger, together with all the necessary equipment for measuring the pressure, the flow rate, the temperature and the fluid cleanliness level (see 6.5). Figure 1 shows a typical test rig in schematic form. A test rig in accordance with I S0 1 6889 is suitable for this test. The test rig shall be constructed so that it does not contain dead legs or zones or quiescent areas where contaminant can settle out and re-entrain later during the test. When testing return filters to be half-immersed in the reservoir, the test equipment located downstream of the test filter on Figure 1 [flow meter, heat exchanger (counter pressure valve is not necessary)] shall be located upstream of the test filter. 5.2 Pump Use a pump with a flow rate equal to or greater than the maximum flow rate required for the test. The delivery pressure shall be sufficient for pumping the required flow through the filter under test and for supplying simultaneously the clean-up filter and the remainder of the rig. A device shall make it possible to continuously vary the flow rate from zero to maximum. Pressure ripple shall be suppressed, if required, to guarantee pressure readings with the required accuracy.5.4 Temperature control Use a heat exchanger to control the temperature measured upstream of the filter under test to the required value with an accuracy conforming to Table 1. 5.5 Clean-up filter Use a clean-up filter with a filtration ratio (see IS0 1 6889) greater than that of the filter under test, so that no measurable increase in differential pressure of the .filter under test due to partial blocking can occur. 5.6 Sampling valve To verify fluid cleanliness, equip the circuit with a sample valve in accordance with IS0 4021. The sample point shall allow connection of an on-line monitor or extraction of a fluid sample for off-line analysis. 5.7 Mounting of filter Mount the filter on the test rig in the normal orientation. Use the correct sizes of standard unions to connect the filter. Use pipes between the filter and the pressure measuring points with substantially the same internal diameters as the unions.