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1、Reference number ISO/TR 16386:1999(E) ISO 1999 TECHNICAL REPORT ISO/TR 16386 First edition 1999-12-15 Impact of changes in ISO fluid power particle counting Contamination control and filter test standards Consquences des changements survenus dans les normes ISO relatives au comptage des particules C
2、ontrle de la contamination et essais de filtres ISO/TR 16386:1999(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and install
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5、ase inform the Central Secretariat at the address given below. ISO 1999 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writin
6、g from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 ? CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 734 10 79 E-mail copyrightiso.ch Web www.iso.ch Printed in Switzerland ii ISO 1999 All rights reserved ISO/TR 16386:
7、1999(E) ISO 1999 All rights reservediii Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member bo
8、dy interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrot
9、echnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. The main task of technical committees is to prepare International Standards. Draft International Standards adopted b
10、y the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. In exceptional circumstances, when a technical committee has collected data of a different kind from that which
11、is normally published as an International Standard (“state of the art“, for example), it may decide by a simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely informative in nature and does not have to be reviewed until the data it provides a
12、re considered to be no longer valid or useful. Attention is drawn to the possibility that some of the elements of this Technical Report may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO/TR 16386 was prepared by Technical Committ
13、ee ISO/TC 131,Fluid power systems, Subcommittee SC 6, Contamination control and hydraulic fluids. This Technical Report has been prepared as an information document to give users an understanding into the background and implications of a number of new and revised contamination control standards, ISO
14、 11171, ISO 11943, ISO 16889 and ISO 4406:1999. ISO/TR 16386:1999(E) iv ISO 1999 All rights reserved Introduction The adoption of four revised and updated contamination control standards, ISO 11171, ISO 11943, ISO 16889, and ISO 4406:1999, has produced significant changes in terms of how solid conta
15、mination levels and filter performance are reported. With ISO 11171, the AC Fine Test Dust (ACFTD) particle counter calibration method used since the early 1970s has been replaced with a new National Institute of Standards and Technology (NIST) traceable particle counter calibration method. As a res
16、ult, contaminant sizes previously referred to as 2 m, 5 m, 10 m and 15 m, will become approximately 4,6 m(c); 6,4 m(c); 9,8 m(c) and 13,6 m(c), respectively, where (c) refers to calibration per ISO 11171. ISO 11943 is a new standard for calibrating on-line particle counters, primarily used to evalua
17、te filter performance. With the ISO 16889 multi-pass filter test, which replaces the original ISO 4572 method, ISO Medium Test Dust (ISO MTD) replaces ACFTD as the test dust and the new traceable particle counter calibration method is used. In ISO 4406:1999, the new calibration method is used and a
18、new 4 m(c) size class has been added to the solid contamination code for particle counts made with an automatic particle counter. These improvements in particle counting and filter testing have a significant impact on contamination control activities. However, it is important to note that there has
19、been no change in the actual contamination levels nor in the performance of filters, or their effectiveness in protecting the reliability of components. This report discusses what the changes are, why they have been made, how they will impact contamination levels and filter ratings, and how they ben
20、efit the industry. TECHNICAL REPORTISO/TR 16386:1999(E) ISO 1999 All rights reserved1 Impact of changes in ISO fluid power particle counting Contamination control and filter test standards 1Scope Liquid automatic optical particle counters (APCs) are used in monitoring contamination levels in hydraul
21、ic oil, to establish component and assembly cleanliness level specifications, and in determining filter efficiencies and size ratings. As a result of the replacement of ISO 4402 with ISO 11171 (particle counter calibration), the replacement of ISO 4572 with ISO 16889 (multi-pass filter test), and th
22、e new ISO 11943 (on-line particle counter calibration), it is anticipated that the quality and reliability of particle count and filter test data will improve, increasing their usefulness to industry. However, the resultant redefinition of particle sizes and the use of a new test dust affects how co
23、ntamination levels and filter performance are reported and interpreted. The impact of these changes is discussed in this report. 2Historical background 2.1What is ACFTD? ACFTD was originally produced in batches by the AC Spark Plug Division of General Motors Corporation. ACFTD was manufactured by co
24、llecting dust from a certain area in Arizona, then ball milling and classifying it into a consistent particle size distribution, including particle sizes from roughly 0 to 100 m. The average volumetric particle size distribution of each batch of ACFTD, as determined by either the roller analyzer or
25、laser diffraction technique, was supplied with purchased samples. In 1992, production of ACFTD ceased. Because of its relatively consistent particle size distribution, ACFTD has been used to calibrate APCs in ISO 4402 and to evaluate filter performance in ISO 4572 for hydraulic and other application
26、s. With its irregular shape and siliceous nature, ACFTD was believed to be representative of contaminants found in typical hydraulic systems. In ISO 4402, a number size distribution for ACFTD is given that is based on optical microscopy work done in the late 1960s. At that time, there was no statist
27、ical analysis of batch-to-batch variations in ACFTD. Later, it was discovered that differences exist between the published size distribution and actual particle size distributions of subsequent batches of ACFTD. These differences are a significant source of variability in particle count results. 2.2
28、Calibrating particle counters using ACFTD Though often taken for granted, particle counting is the mainstay of contamination control programs. Automatic particle counters are used to monitor contamination levels in the oil of operating equipment, to establish component and assembly cleanliness level
29、 specifications, and to provide a basis for determining filter beta ratios, efficiencies and size ratings. Calibration consists of establishing the relationship between APC threshold voltage setting and particle size. This was done by comparing observed particle concentrations at known threshold set
30、tings to the published ACFTD size distribution. Calibration accuracy is dependent on the accuracy of the published size distribution. In the absence of a more controlled contaminant, ACFTD has been used for APC calibration for fluid power and many other applications. The ACFTD particle size distribu
31、tion used for calibration in ISO 4402 is based on the longest chord dimension of particles as measured by optical microscopy in the late 1960s. At the time, optical microscopy was the most common method used to obtain particle counts. The goal of the APC calibration -,-,- ISO/TR 16386:1999(E) 2 ISO
32、1999 All rights reserved procedure was to ensure that particle counts obtained with an APC agreed as closely as possible with counts obtained by optical microscopy. The accuracy of the published ACFTD size distribution, and the corresponding APC particle counter calibration, has been questioned sinc
33、e the late 1970s. Since the original microscopy work was done on specific batches of ACFTD, the effects of batch to batch variability on the size distribution and APC calibration were not considered. Despite this, ISO 4402:1991 requires laboratories to calibrate to the original published size distri
34、bution, even though the particular batch of ACFTD being used may differ. 2.3The original multi-pass filter test While the ACFTD method of particle counter calibration was being developed, the hydraulic filter multi-pass test method was developed to measure filter performance, primarily efficiency an
35、d dirt capacity. In 1981, the multi-pass test was adopted as an International Standard, ISO 4572:1981, and is still widely used. The characteristics of ACFTD that made it valuable for APC calibration also make it ideal for filter testing. In a multi-pass test, oil is recirculated through a test filt
36、er while a slurry of ACFTD is continually added to a reservoir located upstream of the filter. Particle counts are taken, both upstream and downstream of the filter, throughout the test. These are used to calculate particle removal efficiency as a function of particle size. The results, expressed as
37、 filtration or beta ratios, are obviously dependent on the APC calibration, but also on the particle size distribution of the test dust. The retained dirt capacity of the test filter is also reported, as the amount of ACFTD needed to cause the filter to reach its terminal differential pressure. The
38、particle size distribution and morphology of the test dust also have a significant impact on filter efficiency and retained dirt capacity. 3New test dusts In 1992, efforts to revise particle counter calibration and filter test standards took on new urgency when the AC Rochester (formerly AC Spark Pl
39、ug) Division of General Motors Corporation discontinued production of ACFTD. ISO Technical Committee TC 22 responded by adopting ISO 12103-1, a filter test dust standard that specifies the physical, chemical, and particle size distribution characteristics of four silica test dusts. The new test dust
40、s are manufactured using jet milling, instead of the ball milling process used for ACFTD. As a result, their particle size distribution and the shape of individual particles differ from ACFTD. Further, ISO 12103-1 specifies electrozone techniques, instead of the roller analyzer or laser diffraction
41、methods used in the production of ACFTD, to specify the particle size distribution of the new dusts. As a result of ISO 12103-1, the new test dusts are better controlled and batch-to-batch variability is less than with the old ACFTD. One of the dusts described in ISO 12103-1, ISO Medium Test Dust (g
42、rade A3) , was chosen by ISO/TC 131/SC 6 to replace ACFTD for particle counter calibration and multi-pass filter testing. ISO MTD is physically and chemically identical to ACFTD, but contains fewer particles smaller than 5 m and is easier to disperse in oil. The high concentration of fine particles
43、in ACFTD can result in coincidence errors when particle counting. Thus, the use of ISO MTD reduces this source of error while retaining the desirable characteristics of ACFTD. 4New APC calibration procedure Due to concerns about the accuracy of the ACFTD particle size distribution, the National Flui
44、d Power Association (USA) began a project in 1980 to develop a traceable APC calibration method. The first attempt at a traceable method resulted in a new method, USA standard ANSI/(NFPA) T2.9.6R1 (1990), that used mono-sized latex particles suspended in MIL-H-5606 mineral oil with sizes traceable t
45、o NIST. Usage of this method has been discouraged, however, because shortly after its introduction, it was found that poor agreement was obtained between different types of APCs calibrated with latex. APCs made by different manufacturers and APCs utilizing different light sources (such as laser diod
46、e or white light) or different measurement principles (light scattering or light extinction) yielded different particle count results when analyzing ACFTD or similar samples. This is due to differences in the optical properties of latex and silica. It was concluded that the APC calibration contamina
47、nt should be optically similar to the contaminants typically used in filter testing. In order to develop a traceable particle counter calibration method, NIST was asked in 1993 to certify the particle size distribution of suspensions of ISO MTD. The certified suspensions, NIST Standard Reference Mat
48、erial (SRM) 2806, consist of 2,8 mg/L suspensions of ISO MTD in Mil-H-5606 hydraulic fluid. Scanning electron microscopy and -,-,- ISO/TR 16386:1999(E) ISO 1999 All rights reserved3 statistical analysis techniques were used to measure the projected area equivalent diameters of ISO MTD particles and
49、to determine the particle size distribution of the SRM. The projected area equivalent diameter is used as the basis for determining particle size because it more closely approximates the dimension actually measured by liquid automatic optical particle counters than the longest chord dimension used to define the ACFTD size distribution. A particle sensor measures the change in light intensity caused by the presence of a particle in its sensing zone. In a sense, a
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