1、_ 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 report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2012 SAE International All rights reserved. No part of this p
3、ublication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-497
4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AS598 AEROSPACE STANDARD AS598 Issued 2012-01 Superseding ARP598C Aerospace Micro
5、scopic Sizing and Counting of Particulate Contamination for Fluid Power Systems RATIONALE There is a need to upgrade this document from a recommended practice to an aerospace standard to reflext its usage in the aerospace industry. This document has been changed to reflect this upgrade. FOREWORD The
6、 purpose of this technique is to provide a means of determining the severity of particulate contamination in fluid power systems. AS598 was prepared by SAE A6C1 panel and supersedes ARP598C. AS598 retained the technical content of ARP598C with more prescriptive requirements for the material used to
7、carry out the analysis. The widely used technique has since been replaced in many instances with automatic particle counters (APC) but remains a proven, accurate and reliable technique. SAE AS598 Page 2 of 12 TABLE OF CONTENTS 1. SCOPE 3 2. APPLICABLE DOCUMENTS 3 2.1 SAE Publications . 3 3. OUTLINE
8、OF METHOD 3 4. MATERIALS 3 5. APPARATUS 4 5.1 Filtration Apparatus . 45.2 Particle Count Apparatus 4 6. REAGENTS 5 6.1 Aqueous 56.2 Alcohols . 56.3 Rinse Liquid 56.4 Cleanliness 5 7. PREPARATION OF APPARATUS . 5 8. LIQUID SAMPLES 6 9. FILTRATION PROCEDURE . 6 9.1 Blank Analysis Filtration 69.2 Sampl
9、e Filtration . 6 10. MICROSCOPE CALIBRATION 7 11. PARTICLE COUNTING PROCEDURE 8 12. PARTICLE COUNT CALCULATION 9 13. COUNTING PROFICIENCY . 10 14. DISPUTE CLAUSE . 10 FIGURE 1 ENLARGED VIEW OF GRID SQUARE, UNIT AREAS AND MICROSCOPE FIELD 8APPENDIX A CALIBRATION OF MICROSCOPE OCULAR SCALE . 11APPENDI
10、X B AS598 FLUID CLEANLINESS DATA SHEET 12SAE AS598 Page 3 of 12 1. SCOPE This SAE Aerospace Standard (AS) defines the materials, apparatus and procedure for sizing and counting of particulate contamination, 5 m or greater, in hydraulic fluid samples by membrane filtration with microscopic counting.
11、The microscopic counting method is capable of counting particulate matter in samples withdrawn from fluid power systems as identified by the 12 classes of AS4059 and projected beyond these for the five standard ranges specified and can thus serve as the primary document to determine acceptability. I
12、t is also capable of revealing but not measuring evidence of abnormal amount of water, other fluids, fine particulate and other materials, especially fibers and metals. It is applicable to all military, civil, space vehicles and test equipment. 2. APPLICABLE DOCUMENTS The following publications form
13、 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
14、, 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 International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (insi
15、de USA and Canada) or 724-776-4970 (outside USA), www.sae.org AS1241 Fire Resistant Phosphate Ester Hydraulic Fluid for Aircraft AS4059 Aerospace Cleanliness Classification for Hydraulic Fluids ARP4285 Aerospace - Evaluation of Particulate Contamination in Hydraulic Fluid - Membrane Procedure ARP537
16、6 Aerospace - Methods, Locations and Criteria for System Sampling and Measuring the Solid Particle Contamination of Hydraulic Fluids 3. OUTLINE OF METHOD A known volume of hydraulic fluid is filtered through a gridded membrane filter to give an even distribution of particulate matter on the membrane
17、. The residual contamination is then sized into five defined size ranges and counted by microscopic analysis. 4. MATERIALS 4.1 Membrane filter, 47 mm in diameter with a pore size less than 1.0 m. The filter shall have imprinted grid of 3.10 mm 0.02 mm centers. The color shall be chosen for maximum c
18、ontrast with the particulate contamination to be observed. As defined in ARP4285, when testing petroleum base hydraulic fluid or synthetic hydrocarbon fluid white cellulose ester membrane is required. Phosphate Ester fluid, (see AS1241) requires the use of polytetrafluoroethylene (PTFE) type membran
19、es material (or other equivalent material). 4.2 Membrane filter 25 mm as filtering disc for rinse dispenser 1 m or smaller. 4.3 Plastic film, 0.05 mm (0.002 in) minimum thickness. The film shall be compatible with sample and rinse liquids (pressure dispenser) or 3 m (manual dispenser). SAE AS598 Pag
20、e 4 of 12 5. APPARATUS 5.1 Filtration Apparatus 5.1.1 Petri dishes, plastic or glass. If plastic, it shall be compatible with sample and rinse liquids. 5.1.2 Sample bottles, shall preferably be made from glass, small mouth, screw cap, permanently marked to indicate sample volume. The bottle shall ha
21、ve a nominal capacity of 250 mL and a minimum capacity of 150 mL and shall be sealed by means of caps ( of phenolic resin), which will not cause contamination. Alternatively, a non-flaking plastic film compatible with the hydraulic fluid may be used. 5.1.3 Funnel, Filtration The lower hole shall hav
22、e a diameter of approximately 35 mm ID. The effective filtering area shall be calibrated by filtering a contrasting particulate pigment through a membrane filter. The diameter of the residual pigment shall be measured at quadrature diameters with resulting area 960 mm2 25 mm2. If the receiving funne
23、l is to be used for measuring the sample volume, the funnel shall be calibrated within 2% of the required volume. 5.1.4 Membrane Filter Support Either a fritted glass, sintered metal or stainless steel screen may be used. The support shall be so designed as to enable attachment to a vacuum source. 5
24、.1.5 Vacuum Flask A 1 L filtering flask is used to mount the membrane filter support and funnel assembly. Vacuum is applied to the flask to draw the sample fluid through the filter. 5.1.6 Funnel holding device, with a provision to dissipate static electricity from the funnel. 5.1.7 Funnel cover, to
25、prevent extraneous contamination. 5.1.8 Vacuum source with a minimum vacuum of 457 mm (18 in Hg). 5.1.9 Forceps with unserrated tips. 5.1.10 Rinse Dispenser A pressurized container equipped to pass rinse liquid through a membrane filter with a pore size of 1 m or finer. 5.1.11 Pressurized container,
26、 manual dispenser can use 3 m membrane filter. 5.2 Particle Count Apparatus 5.2.1 Microscope Binocular or monocular (stereo microscopes shall not be employed with this procedure). 5.2.2 Objectives and oculars (eyepieces) in combinations to give magnifications of 50x 10x and 100x 10x. The higher powe
27、r objective shall have a minimum Numerical Aperture of 0.15. The ocular shall not be greater than 15x. 5.2.3 Ocular Micrometer Linear scale installed in one eyepiece. The smallest division shall not subtend a distance larger than the smallest particle to be counted at a particular magnification. SAE
28、 AS598 Page 5 of 12 5.2.4 Mechanical Stage Capable of traversing the entire area of the membrane filter. It shall have provisions for holding a membrane container. 5.2.5 Stage Micrometer Divisions of 0.1 mm and 0.01 mm (0.004 to 0.0004 in). 5.2.6 Microscope Light - External, Focusing It shall be equ
29、ipped with an external adjustable arm to give oblique incident light. It shall provide an illumination of 54 to 65 kilolumens per square meter (5000 to 6000 ft-c) at the counting surface. 6. REAGENTS 6.1 Aqueous Liquid detergent solution that leaves no solid residue. 6.2 Alcohols Isopropyl alcohol,
30、acetone free. 6.3 Rinse Liquid Petroleum naphta - CAUTION: EXTREMELY FLAMMABLE. DO NOT USE NEAR ANY IGNITION SOURCE. - minimum initial boiling point of 29.4 C (85 F) and a maximum end point of 104.4 C (220 F). Alternate rinse liquids which are compatible with the test fluid may be used if they leave
31、 no residue on drying. Ozone depleting solvents must meet local, federal and international regulations. 6.4 Cleanliness The filtration of reagents shall be performed with the apparatus described in 5.1.10. The term “filtered” shall herein refer to 1 m filtered reagent. 7. PREPARATION OF APPARATUS 7.
32、1 The apparatus shall be thoroughly washed in a solution of liquid detergent and hot water. 7.2 Rinse with hot distilled or-de-mineralized water. 7.3 Rinse with filtered isopropyl alcohol to remove water. 7.4 Rinse with filtered solvent. 7.5 Sample Bottle Preparation Repeat 7.1 through 7.4, then all
33、ow the bottles to drip dry. Place a piece of plastic film, which has been rinsed with filtered liquid, over the mouth of the bottle. Hold the film while, screwing on the cap to prevent the film from rotating. SAE AS598 Page 6 of 12 8. LIQUID SAMPLES 8.1 The standard sample should be 100 ml 1 ml exce
34、pt in the following cases: When the particle count from this volume is greater than 100 000 or less than 500 particles total, the sample volume may be altered. For counts less than 500 particles, the volume should be a minimum of 200 ml. For counts greater than 100 000 particles, the volume may be d
35、ecreased to allow proper particle differentiation. Caution: In all cases, the sample volume shall be recorded. 8.2 Samples shall be as representative of the system as possible. Procedures for sampling shall be established by individual plants or laboratories. To assure reproducibility, the sampling
36、program should be checked by testing replicate samples from the sample port. Where samples are required from remote facilities two samples should be supplied, taken concurrently in the same operation. 9. FILTRATION PROCEDURE 9.1 Blank Analysis Filtration 9.1.1 Remove a membrane filter using forceps
37、from the container and rinse with filtered rinse liquid. 9.1.2 Place the filter on the support, lower the funnel, and secure with the holding device. Cover the funnel 9.1.3 Place equivalent to the volume to be tested of filtered rinse liquid into a sample bottle and agitate. 9.1.4 Remove the cover a
38、nd pour the contents of the bottle into the funnel. 9.1.5 Turn on the vacuum and allow the sample to filter until approximately 50 ml remain. 9.1.6 Pour an additional 50 ml of filtered rinse liquid into the bottle and agitate. 9.1.7 Pour the contents of the bottle into the funnel, rinsing the funnel
39、 walls, and replace the funnel cover. When the fluid filtration rate is excessive, causing a vortex, the vacuum should be released to allow adequate rinsing of the funnel walls and to eliminate the possibility of upsetting the particle distribution by the rinse liquid. 9.1.8 Allow the sample to filt
40、er until dry. 9.1.9 Remove the cover, holding device and immediately turn off the vacuum. 9.1.10 Remove the membrane filter using the forceps and place in a petri dish and label. 9.1.11 Perform a particle count as specified in Section 11. 9.1.12 If the blank count exceeds 10% of the acceptable sampl
41、e count, the apparatus shall be re-cleaned and the procedure rerun. 9.2 Sample Filtration 9.2.1 Repeat steps 9.1.1 and 9.1.2 9.2.2 Thoroughly agitate the sample and then remove the cap. 9.2.3 Remove the funnel cover and pour the contents into the funnel. 9.2.4 Pour approximately 50 ml of filtered ri
42、nse liquid in the sample bottle and agitate. 9.2.5 Pour the filtered rinsed liquid into the funnel and cover. 9.2.6 Turn on the vacuum and allow the sample to filter until approximately 50 ml remain. SAE AS598 Page 7 of 12 9.2.7 Lift the cover and carefully wash down the funnel walls with rinse liqu
43、id. When the fluid filtration rate is excessive, causing a vortex, the vacuum should be released to allow adequate rinsing of the funnel walls and to eliminate the possibility of upsetting the particle distribution by the rinse liquid (see ARP4285). 9.2.8 Replace the cover and filter until the membr
44、ane is dry. 9.2.9 Remove the cover, clamp and funnel and then release the vacuum immediately. 9.2.10 Using the forceps, transfer the membrane filter to the petri dish. 9.2.11 Label the petri dish giving the sample volume and identification. 9.2.12 The filter is now ready for microscopic examination.
45、 10. MICROSCOPE CALIBRATION 10.1 Place the stage micrometer on the mechanical stage and adjust the light. 10.2 Place the required objective and oculars in the microscope and focus on the micrometer. 10.3 Calibrate the ocular micrometer, as detailed in Appendix A, located in one eyepiece at each magn
46、ification to be used. Do not place the eyepiece containing the ocular micrometer in an adjustable draw tube eyepiece because the calibration will change as the ocular is adjusted. Each operator shall perform this calibration when using a the latter microscope. When a binocular is used, the focal len
47、gth and calibration will change when the interpupillary distance changes. The calibration method requires that the length of the entire linear scale be measured rather than only a portion. 10.4 The operator shall calculate the number of linear divisions required to measure each range at all magnific
48、ations. For example: If an ocular micrometer with 100 divisions measures 250 m at 50x, then each division would equal 2.5 m. By calculating the ranges as specified in AS4059, measure as follows: over 100 m equal 40 division, 50 to 100 m equals 20 to 40 divisions, 25 to 50 m equals 10 to 20 divisions
49、. 10.5 Figure 1 shows two possible unit areas within a grid square for statistical counting. The calibration factor is defined as the effective filter area divided by the total area counted and may be calculated from the following formula: NL312orNL08.3960Fuuu (Eq. 1) where: F = Calibration factor (effective filtration area) see 5.1 N = Number of basic
