1、Hydraulic fluid power contamination control General principles and guidelines for selection and application of hydraulic filters Vrification de la contamination des transmissions hydrauliques Principes gnraux et lignes directrices pour lapplication et la slection des filtres hydrauliques ISO 2011 Re
2、ference number ISO/TR 15640:2011(E) First edition 2011-12-15 ISO/TR 15640 TECHNICAL REPORTISO/TR 15640:2011(E)COPYRIGHT PROTECTED DOCUMENT ISO 2011 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 me
3、chanical, including photocopying and microfilm, without permission in writing 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 22 749 09 47 E-mail copyrightiso.org Web www.
4、iso.org Published in Switzerland ii ISO 2011 All rights reservedISO/TR 15640:2011(E) ISO 2011 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope 1 2 Normative references . 1 3 Terms and definitions . 1 4 Types and sources of contamination . 1 4.1 General . 1 4.2 Solid contamina
5、nts . 2 4.3 Liquid contaminants . 3 4.4 Gaseous contaminants 3 5 Effects of particulate contamination and the benefits of its removal . 3 5.1 General . 3 5.2 Failures caused by particulate contamination 4 5.3 Benefits of filtration to reduce solid particulate contamination . 4 6 Evaluation of cleanl
6、iness 4 6.1 General . 4 6.2 Particle size range of interest 5 6.3 Methods of measuring and monitoring solid particulate contaminants 5 7 Coding systems for expressing level of solid particulate contamination . 6 7.1 General . 6 7.2 ISO 4406 coding system 6 7.3 NAS 1638, SAE AS4059 and ISO 11218 codi
7、ng systems 7 8 Setting required cleanliness levels (RCLs) for a hydraulic system . 7 9 Cleanliness management concepts . 9 9.1 System design considerations 9 9.2 Monitoring system cleanliness 9 9.3 System maintenance for cleanliness management .10 10 Filters 11 10.1 Mechanisms of filtration 11 10.2
8、General filter concepts .12 10.3 Types of filters and filter elements .14 10.4 Filter accessories 15 11 Filter evaluation .16 11.1 General .16 11.2 Laboratory filter test methods .16 12 Filter selection process .18 12.1 General .18 12.2 System definition and setting of the RCL .18 12.3 Selecting the
9、 minimum recommended filter rating 19 12.4 Filter location 20 12.5 Filter sizing 23 12.6 Assessment of candidate filters 24 12.7 Verification of correct filter selection .24 13 Summary 25 Annex A (informative) Types of filters and separators .26 Bibliography .28Foreword ISO (the International Organi
10、zation 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 body interested in a subject for which a technical committee has been establishe
11、d 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 Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
12、International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Pub
13、lication 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 is normally published as an International Standard (“state of the art”, for ex
14、ample), 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 are considered to be no longer valid or useful. Attention is drawn to the possi
15、bility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO/TR 15640 was prepared by Technical Committee ISO/TC 131, Fluid power systems, Subcommittee SC 6, Contamination control. ISO/TR 1
16、5640:2011(E)iv ISO 2011 All rights reservedIntroduction Hydraulic systems transmit power by means of a pressurized liquid in a closed circuit. Foreign materials or contaminants present in the fluid can circulate around the system, cause damage to the component surfaces, and reduce the efficiency, re
17、liability and useful life of the system. Hydraulic filters are provided to control the number of particles circulating within the system to a level that is commensurate with the degree of sensitivity of the components to the contaminant, and the reliability and durability objectives of the hydraulic
18、 system. The selection and application of filters takes into account the filter design and performance, the system design and function, the required cleanliness level (RCL), the severity of the system operation and the standard of maintenance. The only way to confirm whether the correct filter has b
19、een selected is to monitor the cleanliness level in the fluid, and the reliability and durability of the system. These guidelines are intended to introduce the concepts of cleanliness management and filter selection and application to both system designers and users. Although this guide cannot make
20、one an expert on filter selection and use, it does seek to educate and thereby assist the reader in making informed decisions about filtration, and to improve the communication process. ISO/TR 15640:2011(E) ISO 2011 All rights reserved vTECHNICAL REPORT ISO/TR 15640:2011(E) Hydraulic fluid power con
21、tamination control General principles and guidelines for selection and application of hydraulic filters 1 Scope This Technical Report is applicable to contamination control principles for hydraulic fluid power systems and includes guidelines for the selection and application of hydraulic filters. Al
22、though control of non-particulate contamination, e.g. air, water and chemicals, is important, and is briefly discussed, the primary focus of this Technical Report is the control of particulate contamination and the selection and application of filters for that function. 2 Normative references The fo
23、llowing referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 5598, Fluid power systems and components Vocabulary
24、 NOTE The other documents mentioned and referenced in this document in a non-normative way are listed in the Bibliography. 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 5598 and the following apply. 3.1 contaminant any material or combination of ma
25、terials (solid, liquid or gaseous) that can adversely affect the system 3.2 ingression introduction of environmental contamination into the system NOTE Contamination introduced through ingression is referred to as ingressed contamination. 3.3 filter medium part of the filter structure that removes a
26、nd retains contaminant 3.4 filter media collective layers that make up a filter element 4 Types and sources of contamination 4.1 General Contaminants in a hydraulic fluid are any material or combination of materials (solid, liquid or gaseous) that can adversely affect the system. ISO 2011 All rights
27、 reserved 14.2 Solid contaminants 4.2.1 General Solid contaminant particles come from four main sources as shown in Table 1 and can vary considerably in material, hardness, shape and size from sub-micrometre to millimetres. Contaminant shape varies widely and debris can appear as granular (cube-shap
28、ed), acicular (rod-shaped), platelets (very thin, nearly two dimensional), irregular fragments and fibres. Shape affects the way that particles are aligned in the moving fluid and thus the likelihood of the particles becoming lodged in a small clearance or trapped within the filter medium. Although
29、quite important, particle shape is rarely reported because of the difficulties involved in its determination. Table 1 Primary sources of particulate contamination Built-in (manufacturing debris) Ingressed Generated Maintenance (service debris) Process Atmosphere Surfaces Fluid burrs machining swarf
30、weld spatter abrasives drill turnings filings dust contaminated components dust from grinding incompatible fluids paint chips initial fluid fill addition of incorrect fluid compressed air or gas pulp pulverized coal ore dust aggregates cement catalysts clays process chemicals ingestion via reservoir
31、 breather ingestion via seals reservoir opening rock dust mill scale quarry dust foundry dust slag particles dust from welding and grinding mechanical wear corrosive wear cavitation exfoliation hose materials filter fibres break-in debris elastomers re- entrainment filter desorption additive precipi
32、tation sludge insoluble oxides carbonisation coke aeration varnishes repairs preventive maintenance new filter new fluid dirty hose, connector, components top-up containers incorrect fluid cleaning rags dust from welding and grinding dust from atmosphere and workplace 4.2.2 Built-in contaminant All
33、new systems contain some contaminant left during manufacture and assembly. This can consist of fibres (from rags, etc.), casting sand, pipe scale, cast iron or other metal particles, jointing material or loose paint. When a system is operated at an unusual load or if there are high pulsations in the
34、 flow, it is likely that built-in contaminant becomes dislodged. 4.2.3 Ingressed contaminant Systems can also be contaminated during normal operation, through openings in the reservoir, inadequate air breather filters, through worn seals in vacuum conditions and by intrusion through the fluid film o
35、n piston rods. Worn seals increase the likelihood of ingression. These ingressed contaminants can be highly abrasive. 4.2.4 Generated contaminant When a normal system has been run for a reasonable period of time, a quantity of solid contaminant can be present in the form of small metallic platelets,
36、 created by the normal wear process. For correctly designed ISO/TR 15640:2011(E)2 ISO 2011 All rights reservedsystems, which are provided with suitable filtration, the majority of these particles are smaller than 15 m. If a filter blockage indicator is ignored, previously retained contaminant can be
37、 dislodged from the filter element (see 10.4.1). However, if abnormal wear occurs, both the size and quantity of particles increase and, if not detected by monitoring, wear rates can accelerate and the wear mode can change from benign fatigue wear to abrasive wear. With abrasive wear, substantial am
38、ounts of surface material can be removed. 4.2.5 Maintenance-induced contaminant Contaminants can easily be introduced during routine system maintenance unless the maintenance is performed in a clean environment, and precautions are taken to prevent contaminant from getting on serviced items. For exa
39、mple, topping up the system with new fluid can add contaminants unless the fluid is filtered upon addition. 4.3 Liquid contaminants After damage caused by solid particulate contamination, damage caused by the presence of liquid contamination is the next highest cause of contamination-related problem
40、s. This damage is caused either directly through corrosion or indirectly through the interaction of the liquid contamination with the hydraulic fluid. This either reduces the fluids effectiveness and thereby increases component wear rates, or reacts with it to produce insoluble products that can blo
41、ck filters, clearances, etc. Blockage under these circumstances is often rapid and unless it is detected and rectified, filtration ceases. Water is the most common liquid contaminant in systems using mineral or synthetic fluids. Water can enter the system from the atmosphere, leaking coolers and con
42、densation. Although most hydraulic fluids are formulated to cause water to separate so that it can settle in the reservoir and be drawn off, it is essential that the water content is maintained at levels well below the solubility or saturation level of the fluid used, at the minimum operating temper
43、ature. Contamination by even small amounts of water in the fluid significantly lowers the load-sustaining capabilities of the fluid. This deterioration of lubrication ability is of great importance to many components in hydraulic systems. One example is that of rolling-element bearings, in which ver
44、y high pressures are generated. If water is present in the hydraulic fluid, even in dissolved form, the viscosity increase required for the form of lubrication required in the bearing might not be achieved, and wear can result. 4.4 Gaseous contaminants Nearly all fluids contain some dissolved gases.
45、 At atmospheric pressure, hydraulic fluids normally contain about 8 % of their volume as dissolved air, which, at this pressure, causes no problem. Increasing the pressure in the hydraulic fluid causes an increase in the amount of air that can be dissolved, and in low-pressure parts of the system, s
46、ome of this dissolved air can be liberated in the form of bubbles, a situation frequently found downstream of pressure relief valves. The presence of air bubbles in a system almost always causes erratic operation of the system, as it affects the stiffness (bulk modulus) of the fluid and thereby syst
47、em response. Air bubbles in an inlet (suction) line of a pump reduce the volumetric efficiency and cause damage to most kinds of pumps through cavitation. Another effect often seen in high performance systems is the sudden compression of the fluid in the high pressure section of the pump, which caus
48、es the air bubbles to implode, and causing the vapour to ignite momentarily. The very high temperatures generated cause thermal stress on the fluid, leading to oxidation and nitration. A similar condition can exist downstream of metering valves; the process is known as “dieseling” and leads to the f
49、ormation of gums, varnishes and even microscopic “coke” particles. These in turn can lead to lacquering of valves and plugging of filters. 5 Effects of particulate contamination and the benefits of its removal 5.1 General It has been demonstrated that, in the majority of hydraulic systems, the presence of solid contaminant particles is the main cause of failure and reduced reliability. The sensitivity of components to these particles
