1、AEROSPACE RECOMMENDED PRACTICEARP4285Issued 2001-03Aerospace - Evaluation of Particulate Contamination in Hydraulic Fluid - Membrane Procedure1. SCOPE:This SAE Aerospace Recommended Practice (ARP) establishes a method for evaluating the particulate matter extracted from the working fluid of a hydrau
2、lic system or component using a membrane. The amount of particulate matter deposited on the membrane due to filtering a given quantity of fluid is visually compared against a standard membrane in order to provide an indication of the cleanliness level of the fluid. A particular feature of this metho
3、d is the membrane preparation to achieve an even particulate distribution on the membrane suitable for other applications.Membrane evaluation using standard membranes, described in this document, is an alternative technique to counting with either an optical microscope (ARP598) or an automatic parti
4、cle counter (ISO 11500). The latter particle counting procedures are considered more precise. This procedure shall not be used as an alternative to particle counting unless agreed to by the customer since the results by this procedure may differ from those by particle counting, even though the stand
5、ard membrane correlates to a specific particle count.2. REFERENCES:2.1 Applicable Documents:The following publications form 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 effec
6、t on the date of the purchase order. In the event of conflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained.SAE Tec
7、hnical 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 therefrom, is
8、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 cancelled. SAE invites your written comments and suggestions. Copyright 2008 SAE International All rights reserved. No part of this publication may be rep
9、roduced, 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: 724-776-4970 (outside USA) Fax: 724
10、-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org Reaffirmed 2008-06SAE ARP4285- 2 -2.1.1 SAE Publications: Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.ARP598 The Determination of Particulate Contamination in Liquids by the Particle Count Method.ARP
11、5376 Aerospace - Fluid Systems and Components - Methods, Location and Criteria for System Sampling and Measuring the Solid Particle Contamination of Hydraulic Fluids.AS4059 Aerospace, Cleanliness Classification of Hydraulic Fluids.AS1241 Fire Resistant Phosphate Ester Hydraulic Fluid for Aircraft.AS
12、8775 Hydraulic Systems Components, Aircraft Aircraft; Missile and Ordnance. Inactive for new design.MIL-PRF-680 Dry Cleaning and Degreasing SolventMIL-PRF-6083 Hydraulic Fluid, Petroleum Base, for Preservation and OperationMIL-PRF-83282 Hydraulic Fluid, Fire Resistant, Synthetic Hydrocarbon Base, Ai
13、rcraft, Metric, NATO Number H-537MIL-PRF-87257 Hydraulic Fluid, Fire Resistant; Low Temperature, Synthetic Hydrocarbon Base, Aircraft and MissileFED-STD-209 Airborne Particulate Cleanliness Classes in Clean Rooms and Clean Zones2.1.3 ISO Publications: Available from ANSI, 11 West 42nd Street, New Yo
14、rk, NY 10036-8002.ISO 11500 Hydraulic Fluid Power - Determination of Particulate Contamination by Automatic Counting using Light Extinction Principle.3. DEFINITIONS:3.1 MEMBRANE (PATCH):A commercially available filter membrane through which a volume of compatible fluid has been filtered using a spec
15、ified procedure to deposit particulate contamination from the fluid onto a controlled area of the membrane surface.3.2 MEMBRANE METHOD:A general term identifying a procedure that produces a membrane used to assess the cleanliness of aerospace fluids such as hydraulic fluid.SAE ARP4285- 3 -3.3 STANDA
16、RD MEMBRANE:A membrane made in an identical manner to other test membranes and specially selected by the contracting parties as representing the contamination limit for that component. It is recommended that the standard membrane correlate to a recognized classification system such as AS4059 or equi
17、valent. It may be an actual single membrane preserved for use between glass slides, or a photograph of an actual membrane and capable of reproduction as agreed by the contracting parties.4. MEMBRANE PREPARATION:4.1. Membrane Preparation Workroom:The workroom shall be in a clean, draft free area remo
18、te from contaminant-generating operations such as testing, grinding, machining, etc. and shared only by similar laboratory-type operations. A clean room or underhood environment of Federal Standard 209 Class 100,000 is recommended.4.1.1 Workstation: The workstation used to prepare the membrane shall
19、 have a hard, continuous surface which can be readily wiped down and may be equipped with compartments and drawers for the various pieces of membrane-making equipment. It may be equipped with a vacuum source capable of 25 in Hg. Alternatively, a manual pump may be used which is vented by detaching t
20、he inlet.4.2 Equipment:4.2.1 General: The Membrane Test Assembly contains components for processing and analyzing hydraulic fluid samples and are described below:4.2.2 Filter Membranes: These filters consist of a cellulose ester material (or other equivalent material) having a mean pore size of 5 m.
21、 The filter membranes are 47 mm in diameter and are used to filter hydraulic fluid samples. Phosphate Ester fluid, (see AS1241) requires the use of polytetrafluoroethylene (PTFE) type membranes material (or other equivalent material). Filter membranes having a 3 m pore size and 25 mm diameter are us
22、ed to filter the solvent.WARNING: Filter membranes are highly flammable. Personnel are to take every precaution to preclude flames and sparks from coming in contact with the membranes.4.2.3 Filter Holder (47 mm): To effect vacuum filtration of a test sample, a filter base and funnel assembly is used
23、 which consists of a 300 mL Pyrex receiving funnel and a base with a coarse fretted glass support for the filter, a spring clamp and neoprene stopper (see Figure 1).4.2.4 Vacuum Filtering Flask: A 1 L filtering flask is used to mount the filter base and funnel assembly. Vacuum is applied to the flas
24、k to draw the sample fluid through the filter (see Figure 1).4.2.5 Graduate Cylinder: A 100 mL graduate is used to measure the volume of sample fluid and solvent to be filtered.SAE ARP4285- 4 -FIGURE 1 - Membrane Holder and Vacuum Filtering Flask Assembly4.2.6 Wash Bottle: A solvent filtering dispen
25、ser (wash bottle), fitted with a dispensing tube and spout, is used to dispense solvent required in the membrane making process. The wash bottle is fitted with a 25 mm filter holder, to accept a 25 mm (or 24 mm) filter (3 m), to ensure proper cleanliness of the solvent used during membrane making.4.
26、2.7 Filter Mounts: Transparent Petri slides with covers hold the 47 mm membranes flat for examination and offer protection from additional contamination during storage.4.2.8 Forceps: Smooth tipped stainless steel forceps are provided for handling filter membranes.SAE ARP4285- 5 -4.2.9 Lint-Free Labo
27、ratory Coats.4.2.10 Petri Dishes.4.2.11 Waste Funnel and Drum: The waste funnel and drum are not parts of the basic Membrane Test Assembly but are associated items required in the laboratory set up. A 20 L (5 gal) drum fitted with a funnel and standpipe to bring the funnel to bench top height is req
28、uired. This serves as a receptacle for used solvent and hydraulic fluid. Wash down of kit parts can be carried out directly over the funnel.4.2.12 Solvent Supply Drum and Stand: The dry cleaning solvent is supplied in 205 L (45 gal) drums. The drum should be fitted with a suitable valve and be mount
29、ed on a stand to facilitate refilling of the wash bottle.4.2.13 Reading Card: A card containing some sentences in standard Jaegar 1 (J1) size type is used to aid the operator in establishing the distance from the inspection lens at which the membrane and standards should be viewed.4.2.14 Inspection
30、Lens: (Optional) An illuminated inspection lens is used for viewing the membranes and standards (suggested magnification 2X).4.3 Consumable Materials:4.3.1 Solvent: Federal Specification MIL-PRF-680 Type 2 (or as recommended by the contracting agency and as specified by local environmental requireme
31、nts).NOTE: Minimum flash point is 60 C (140 F). Proper safe handling precautions for dry cleaning solvent shall always prevail.4.3.2 Filtering disc for wash bottle, 25 mm with 3 m pore size.4.3.3 Lint-Free rags.4.3.4 Filter membranes, as defined in 4.2.2, suitable for use with petroleum base oils su
32、ch as MIL-H-5606 (INACTIVE FOR NEW DESIGN) and MIL-PRF-6083; and synthetic hydrocarbon oils such as MIL-PRF-83282 and MIL-PRF-87257. This procedure can be utilized with other fluid types as agreed by the contacting parties. Membranes shall be white, ungridded, 47 mm in diameter with a 5 m pore size
33、or as specified by contracting agencies.4.3.5 Filter membranes, as defined in 4.2.2, suitable for use with phosphate ester base oil, AS1241.4.3.6 Detergent - general purpose.4.3.7 Distilled water4.3.8 Lens tissue.SAE ARP4285- 6 -4.3.9 Bottles, narrow mouth, flint glass, round, 500 mL (16 oz) with Po
34、lyseal closures, 28 mm cap size (or as recommended by the contracting agency).4.4 Pressure Tank and Spray Gun:4.4.1 As an alternative to the wash bottle, these components, when assembled, provide a system to obtain and deliver filtered solvent for bottle cleaning purposes and preparation of the memb
35、rane (see Figure 2).FIGURE 2 - Pressurized System for Bottle Cleaning and Membrane-PreparationSAE ARP4285- 7 -4.4.2 Utilize a pressure tank at approximately 690 kPa (100 psi) maximum pressure with a pressure relief valve. Before opening the tank for refilling, the air pressure shall be released thro
36、ugh the pressure relief valve, or by other means.4.4.3 The spray gun is a normal trigger operated unit equipped with a membrane filter unit and nozzle. The membrane filter shall be replaced weekly or more frequently if flow becomes restricted.4.5 Bottle Cleaning Procedure:4.5.1 The approved sampling
37、 bottles are cleaned prior to performing the cleanliness evaluation of hydraulic fluid.4.5.2 The bottle cleaning procedure for the recommended sampling bottle requires the use of an air pressurized dispensing system with a filterjet solvent dispenser. The air supply can be a central system or a dedi
38、cated pump. As an alternative, the wash bottle having the on-line filter can be used to clean sampling bottles.4.5.3 Upon completion of the Membrane Test evaluation, drain all remaining hydraulic fluid from the 500 mL glass bottle into a waste container. Thoroughly rinse bottle and bottle cap three
39、times with MIL-PRF-680 Type 2 solvent to ensure cleanliness. After the three consecutive flushings of the bottles, invert bottle and cap to drain as much solvent as possible into waste container. The recapped bottle is then ready for sample taking.The film of clean solvent (MIL-PRF-680 Type 2) remai
40、ning in the bottle will not interfere with subsequent evaluations in regard to particle counting.NOTE: Proper safe handling precautions for dry cleaning solvent (MIL-PRF-680 Type 2) shall always prevail.4.6 Standard Membranes:4.6.1 Contamination standards, to which membranes are compared, are used f
41、or determination of fluid sample acceptability.5. MEMBRANE MAKING PROCEDURE:5.1 Precaution:This standard may involve hazardous material operations and equipment. This standard does not purport to address all the safety problems associated with their use. It is the responsibility of whomever uses thi
42、s standard to consult and establish appropriate safety and health practices and determine the application of regulatory limitations prior to use.5.2 This part provides a description of the procedures necessary for obtaining representative fluid samples, preparing the Membrane Test Kit for use, makin
43、g membranes using fluid samples and evaluating sample membranes.SAE ARP4285- 8 -5.3 The various steps in producing a successful membrane from a hydraulic fluid sample are relatively simple and use standard laboratory procedures requiring a period of familiarization of the operator. All steps in the
44、procedure must be carried out each time in a careful unhurried manner without diversions. A successful membrane is one where a minimum of extraneous contaminant is present. This can only be assured by adhering to proper procedures and by careful attention to cleanliness throughout the membrane makin
45、g process.NOTE: Proper safe handling precautions for dry cleaning solvent (MIL-PRF-680 Type 2) shall always prevail.5.4 Sample Taking:5.4.1 A representative hydraulic fluid sample taken from a hydraulic component undergoing evaluation shall be taken in accordance with ARP5376.5.5 Solvent Dispenser:5
46、.5.1 The most important tool used in the membrane making process is the solvent dispenser (wash bottle/pressurized solvent dispenser). It is essential that the solvent wash coming from the dispensing system be as clean as possible to preclude adding outside contaminants during the membrane making pr
47、ocess. Filtering the solvent through a 3 m filter is required prior to use.5.5.2 Operation: A steady jet of solvent must be delivered from the solvent dispenser.5.5.3 Filter Change: The filter in the top of the wash bottle assembly must be changed whenever there is evidence of damage or plugging, an
48、d on a routine basis as a preventive measure. Plugging of the filter is indicated by difficulty in obtaining a stream of solvent when the wash bottle is operated, or a decrease in pressure when using a pressurized solvent dispenser. Filter damage is indicated by contaminant showing up on a blank mem
49、brane.5.6 Making A Blank Membrane:5.6.1 Blank membranes should be made each day that the Membrane Test Kit is to be used, to ensure cleanliness of the solvent being delivered from the wash bottle or the pressurized dispensing system. Additionally, a blank membrane must be made after changing the dispensing system filter.5.6.2 The procedure for making a blank membrane simulates the normal membrane making procedure in respect to the amount of solvent used and time span (see 5.7). The only exception is that a fluid sample is not introduced when preparing a blank membrane.5
