1、 AEROSPACE RECOMMENDED PRACTICE Aerospace Fluid Power - Hydraulic Filter Elements - Method for Evaluating Dynamic Efficiency with Cyclic Flow SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this
2、 report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cance
3、lled. SAE invites your written comments and suggestions. Copyright 2005 SAE International All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, witho
4、ut the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-0790 Email: custsvcsae.org SAE WEB ADDRESS: http:/www.sae.org Issued 2005-12 ARP4205 RATIONALE Flow variations that occur in aircraft hydraulic sy
5、stems are know to have a significant impact on filter performance. Current filter test procedures evaluate filter performance under steady flow conditions, and therefore, do not provide a measure of dynamic filter performance. ARP 4205 was developed to impose dynamic test conditions while measuring
6、filter performance, to more closely simulate how a filter might perform on an operating aircraft. FOREWORD It is important for a laboratory test to simulate conditions of actual operation as closely as feasible. Most aircraft hydraulic systems are subjected to unsteady flow with flow cycles caused b
7、y such conditions as actuator movement. Such flow variations can have a significant impact on filter performance. Most previous filter efficiency tests utilize steady flow, which does not represent such cyclic flow conditions. This standard test method measures filter performance under cyclic flow c
8、onditions. The influence of other stressful operating conditions, such as heat, cold and vibration, are not measured with this procedure. The stabilized contamination level measured while testing with cyclic flow gives an indication of the average contamination level maintained by the filter in a dy
9、namic operating system. The average system contamination level is important in establishing wear rates. The measurements are made with precise control over the operating conditions to ensure repeatability and reproducibility, and the results will more closely represent actual performance than previo
10、us test methods. However, because the test parameters and test contaminant do not exactly replicate actual operating conditions, the measurements cannot be expected to duplicate actual performance in an operating system. SAE ARP4205 - 2 - 1. SCOPE: This SAE Aerospace Recommended Practice (ARP) descr
11、ibes a method for evaluating the performance of filter elements designed for Aerospace hydraulic systems. The performance is measured and reported in terms of filtration ratios and stabilized contamination level while testing with cyclic flow. 2. APPLICABLE DOCUMENTS: The following publications form
12、 a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflict between the text of this document and references cited herein
13、, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. 2.1 SAE Publications: Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Ca
14、nada) or 724-776-4970 (outside USA), www.sae.org ARP24 Determination of Hydraulic Pressure Drop ARP785 Procedure for the Determination of Particulate Contamination in Hydraulic Fluids by the Control Filter Gravimetric Procedure 2.2 ISO Publications: Available from International Organization for Stan
15、dardization, 1, rue de Varembe, Case postale 56, CH-1211 Geneva 20, Switzerland, Tel: +41 22 749 01 11, www.iso.org ISO 4021 Hydraulic fluid power - Particulate contamination analysis - Extraction of fluid samples from lines of an operating system ISO 4402 Hydraulic fluid power - Calibration of liqu
16、id automatic particle-count instruments - Method using air cleaner fine test dust contaminant (Obsolete) ISO 11171 Hydraulic fluid power - Calibration of automatic particle counters for liquids ISO 11943 Hydraulic fluid power - On-line automatic particle-counting systems for liquids - Methods of cal
17、ibration and validation SAE ARP4205 - 3 - ISO 12103-1 Road vehicles - Test dust for filter evaluation; Part I: Arizona test dust ISO 16889 Hydraulic fluid power filters - Multi-pass method for evaluating filtration performance of a filter element 2.3 Military Specifications: Available from the Docum
18、ent Automation and Production Service (DAPS), Building 4/D, 700 Robbins Avenue, Philadelphia, PA 19111-5094, Tel: 215-697-6257, http:/assist.daps.dla.mil/quicksearch MIL-F-8815 Filter and Filter Elements, Fluid Pressure, Hydraulic Line, 15 Micron Absolute and 5 Micron Absolute, Type II Systems Gener
19、al Specification for MIL-PRF-5606 Hydraulic Fluid, Petroleum Base, Aircraft, Missile and Ordnance (Inactive for new design) MIL-PRF-81836 Filter and Disposable Element, Fluid Pressure, Hydraulic, 3 Micron Absolute MIL-PRF-83282 Hydraulic Fluid, Fire Resistant, Synthetic Hydrocarbon Base, Metric, NAT
20、O Code Number H-537 MIL-PRF-87257 Hydraulic Fluid, Fire Resistant; Low Temperature, Synthetic Hydrocarbon Base, Aircraft and Missile 2.4 NIST Publications: Available from National Institute of Standards and Technology, 100 Bureau Drive, Stop 1070, Gaithersburg, MD 20899-1070, Tel: 301-975-6478, www.
21、nist.gov NIST SRM 2806 National Institute of Standards and Technology - Standard Reference Material 2806 - Medium Test Dust (MTD) in Hydraulic Fluid SAE ARP4205 - 4 - 3. GLOSSARY OF TERMS: DX = the total number of particles per unit volume greater than a given particle size x downstream of the filte
22、r element GB = the required base upstream gravimetric level (mg/L) of contaminant in the filter element test system. GBA = the actual, average base upstream gravimetric level (mg/L) of contaminant in the filter element test system. GI = the required gravimetric level (mg/L) of contaminant in the con
23、taminant injection system fluid. GIA = the calculated average base upstream gravimetric level (mg/L) of contaminant in the contaminant injection fluid. ME = the estimated mass (g) of contaminant required for the test filter element to reach the terminal filter element differential pressure. M = the
24、required amount of contaminant (grams) to be added to the contaminant injection system to achieve the desired base upstream gravimetric level, GB, in the filter element test system. MI = the total mass of contaminant injected at the terminal differential pressure. MV= the required amount of contamin
25、ant (grams) to be added to the filter element test system to achieve the target base upstream gravimetric level required to validate the filter element test system. PH= differential pressure of housing and free flow dummy element at rated flow, QF. PF= differential pressure of housing and clean test
26、 filter element at rated flow, QF. PCE = Clean filter element differential pressure at rated flow, QF. PT= terminal filter element differential pressure at rated flow, QF, for test termination. NOTE: The terminal filter element differential pressure for test purposes should be set at the maximum dif
27、ferential pressure the element is expected to see in service. This is normally higher than the setting of the filter change indicator. SAE ARP4205 - 5 - PN = net element differential pressure, equals PTminus PCE. P2.5A = assembly differential pressure at increase of 2.5% of net element differential
28、pressure. P80A = assembly differential pressure at increase of 80% of net element differential pressure. QA = Average flow rate (L/min) through the filter element, during cyclic flow. For flow cycling from 0.25 QFto QF, QA= 0.63 QF. QF= Rated filter flow rate (L/min) through the filter element; maxi
29、mum value during cyclic flow. QI= the required rate (L/min) of injection flow from the contaminant injection system to the filter element test system. QIA = the calculated average rate of injection flow from the contaminant injection system to the filter element test system. UX = the total number of
30、 particles per unit volume greater than a given particle size X upstream of the filter element. VF = the filter element test system fluid volume (L). VI = the contaminant injection system fluid volume (L). VIF = the contaminant injection system fluid volume (L) at the conclusion of the test. VIU = t
31、he unusable fluid volume (L) in the contaminant injection system. X = contaminant particle size, m(c), per ISO 11171 calibration. = the filtration ratio, omega, obtained using ISO Fine Test Dust (ISO 12103-A2) under cyclic flow test conditions. T = the predicted test time (minutes) of the cyclic flo
32、w portion of the test. TT = the timer value at the end of the test (minutes). SAE ARP4205 - 6 - 4. TEST EQUIPMENT AND CONDITIONS: 4.1 Utilize and maintain instrument accuracy and test conditions within the limits in Table 1. TABLE 1 - Instrument Accuracy and Test Condition Variation Test Parameter S
33、I Unit Instrument Accuracy () of Reading Allowed Test Condition Variation () Differential pressure Pa, kPa or bar 5% - Base upstream gravimetric mg/L - 10% Flow: Injection flow mL/min 2% 5% Test flow L/min 2% 5% APC sensor flow L/min 1.5% 3% (1) Kinematic viscosity (2) mm2/s 2% 1 mm2/s Mass g 0.1 mg
34、 - Temperature C 1 C 2 C (3) Time s 1 s - Volume: Injection system L 2% - Filter test system L 2% 5% (1) - Sensor flow variation to be included in the overall 10% allowed between sensors (2) - 1 mm2/s = 1 centistoke (cSt) (3) - Or as required to guarantee the viscosity tolerance 4.2 Test Fluids: The
35、 test fluid used shall conform to MIL-PRF-5606 specification, or alternatively to MIL-PRF-83282 or MIL-PRF-87257, or shall be as specified by the procuring agency. 4.3 Test Fluid Temperature: The temperature of the test fluid, during the test, shall be controlled at a temperature to result in a test
36、 fluid viscosity of 15 cSt 1 cSt. 4.4 Test Contaminant: 4.4.1 The test contaminant used shall be ISO Fine Test Dust per ISO 12103-A2. 4.4.2 Test Contaminant Concentration: The target base upstream gravimetric level, GB(mg/L), is defined as the desired test contaminant mass per unit fluid volume ingr
37、essed into the filter element test system, upstream of the test filter element. The target base upstream gravimetric level shall not normally be less than 3 mg/L nor more than 10 mg/L in order to achieve a sufficient number of particles challenging the filter while minimizing saturation errors for t
38、he automatic particle counters. SAE ARP4205 - 7 - The target base upstream gravimetric level shall be selected as either 3 or 10 mg/L to obtain (if possible) a test time of 30 to 120 minutes, excluding the total stabilization time (6.1.3.8). The predicted test time, T, can be calculated from the est
39、imated mass of test contaminant, ME, required to achieve the terminal filter element differential pressure, the base upstream gravimetric level, GI, selected, and the average test element flow rate, QA, per the following equation: T = (1000 ME)/(GB QA) (Eq. 1) 4.5 Test Circuit: 4.5.1 Use a filter pe
40、rformance test circuit comprised of a “filter test system“ and a “contaminant injection system“. NOTE 1: A schematic diagram of the typical cyclic flow filter performance test system is shown in Figure A1, Appendix A. NOTE 2: A Multi-pass test circuit per the guidelines in ISO 16889 can be modified
41、for use with this procedure by addition of valves for creating flow cycles. 4.6 General Considerations: 4.6.1 Conduits, reservoirs and fittings shall be selected with smooth contours, no pockets, and shall be properly oriented to prevent contaminant entrapment. 4.6.2 All lines should be sized to pro
42、vide turbulent mixing flow conditions within the line to ensure that the system can be validated at the lowest flow rates. However, validation, not line sizes, shall be the criteria for the suitability of the test stand. 4.6.3 Reservoirs shall be constructed with smooth conical bottoms that have an
43、included angle of not more than 90 degrees. Reservoir outlet shall be located at the bottom of the cone. 4.6.4 Fluids entering the reservoir shall be diffused. Diffusion should take place below the reservoir fluid surface in order to eliminate the formation of air bubbles. These air bubbles could ad
44、versely affect automatic particle counter readings. Reservoir diffusion will also aide contaminant dispersion. 4.6.5 Pressure Measurements: Pressure measurements are to be performed in accordance with ARP24. SAE ARP4205 - 8 - 4.6.6 Cleanup Filter: It is recommended that cleanup filter elements used
45、for cleaning of test fluids meet or exceed the efficiency requirements of MIL-PRF-81836 specification. Filters with a filtration ratio of 2(c)200 should be adequate. Filter elements meeting this efficiency will control particles in the 4 m(c) size range, which can affect both the particle counts and
46、 the dirt loading characteristics of fine aerospace filters. 4.7 Contaminant Injection System: 4.7.1 A turbulent means should be provided for transferring fluid from the contaminant injection system to the filter test system to yield a flow rate, QI, in the range of 0.1 to 0.25 L/min. NOTE 1: The in
47、jection flow should be set as low as possible to minimize any influence of contaminant removed by the downstream fluid discarded (see 4.8.2). The injection system must be validated at the minimum flow rate (see 5.1). NOTE 2: Turbulence may not always be possible or guaranteed by calculation. Long st
48、raight lines should not be used. Validation will assure that system is satisfactory. 4.7.2 The total fluid volume, VI, of the contaminant injection system may be adjusted by varying the level of the fluid in the reservoir and shall be sufficient to contain the fluid volume required by the following
49、equation: VI (1200 QI ME)/(GB QA) + VIU (Eq. 2) NOTE 1: The volume calculated above will assure a sufficient quantity of contaminated fluid to load the test element plus 20% for adequate circulation throughout the test. The injection fluid volume may be increased as needed by increasing the amount of test dust proportionately. Since during the test, the flow is cycled from 0.25 QFto QF, the average flow, QA= 0.63 x QF, is used in the equation. NOTE 2: The minimum usable volume, VIU, is measured as the minimum volume
