1、 Reference number ISO 28521:2009(E) ISO 2009INTERNATIONAL STANDARD ISO 28521 First edition 2009-06-01 Ships and marine technology Hydraulic oil systems Guidance for grades of cleanliness and flushing Navires et technologie maritime Circuits dhuile hydrauliques Guide relatif aux degrs de propret et d
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7、9 All rights reserved iiiContents Page Foreword iv 1 Scope 1 2 Normative references1 3 Symbols2 4 Recommended pipe cleaning levels2 4.1 Pipe cleaning levels during/after prefabrication 2 4.2 Surface treatment 3 4.3 Storage of prefabricated pipes and fittings 3 5 Level of cleanliness.3 6 Assembly and
8、 installation of pipe system3 7 Blow-through/pull-through of the system.3 8 Description of coupling 4 8.1 Design phase .4 8.2 Other considerations 4 9 Leakage test.4 10 Filling with oil.5 11 Shock testing/pressure testing5 12 Flushing of yard-installed pipe system.5 12.1 Connection.5 12.2 Special pu
9、mp units5 12.3 Flushing filters.5 12.4 Flushing oil.9 12.5 Flushing times .11 12.6 Methods for checking the cleanliness level .12 12.7 Leakage testing13 13 Start-up of system .13 Annex A (informative) Example of particle counting.14 Bibliography15 ISO 28521:2009(E) iv ISO 2009 All rights reservedFor
10、eword 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 body interested in a subject for which a tech
11、nical 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 Electrotechnical Commission (IEC) on all matters of
12、 electrotechnical standardization. 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 t
13、o the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for
14、 identifying any or all such patent rights. ISO 28521 was prepared by Technical Committee ISO/TC 8, Ships and marine technology, Subcommittee SC 3, Piping and machinery. INTERNATIONAL STANDARD ISO 28521:2009(E) ISO 2009 All rights reserved 1Ships and marine technology Hydraulic oil systems Guidance
15、for grades of cleanliness and flushing 1 Scope This International Standard specifies pipe cleaning and cleaning levels of hydraulic oil pipe systems. The cleaning of pipes and components in hydraulic oil pipe systems is essential for the trouble-free operation of hydraulic systems. It indicates meth
16、ods and equipment for the practical execution of the cleaning of specific parts of hydraulic systems with appurtenant components. The purpose of the cleaning process is to remove installation dirt and to check that the piping and hydraulic system have been adequately cleaned. The cleaning process of
17、 a system is considered a “washing through” process when the Reynolds number, R e , u 3 000, and a flushing process when R eW 3 000. The Reynolds number is an indicator of whether a fluid flow is considered laminar or turbulent. This International Standard presupposes that the pipe sections of the h
18、ydraulic system have been cleaned partly by pickling and partly by mechanical cleaning. It is furthermore assumed that both dynamic and static components from system suppliers are adequately clean when delivered (see Clause 5). The specifications given in this International Standard are supplementar
19、y to, and not a replacement for, the guidelines specified by the various manufacturers. The manufacturers guidelines, where available, take precedence. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edi
20、tion cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 3448, Industrial liquid lubricants ISO viscosity classification ISO 4406, Hydraulic fluid power Fluids Method for coding the level of contamination by solid particles ISO
21、 28523, Ships and marine technology Lubricating and hydraulic oil systems Guidance for sampling to determine cleanliness and particle contamination ISO 28521:2009(E) 2 ISO 2009 All rights reserved3 Symbols The following symbols are used throughout this International Standard. A (mm 2 ) pipe cross-se
22、ctional area x () particle filtration ratio d (mm) pipe diameter p (bar) pressure drop K 1() flushing-filter factor R e() Reynolds number Q 1(l/min) flow rate of filter Q 2(l/min) flow rate of system v (cSt) viscocity W (m/s) flow velocity 4 Recommended pipe cleaning levels 4.1 Pipe cleaning levels
23、during/after prefabrication 4.1.1 Black-steel pipes and pipes of other material qualities showing oxide scale as a result of heating or welding These should be cleaned internally after welding together of prefabricated pipes and fittings using either chemical cleaning (alkaline cleaning and pickling
24、) or mechanical blow cleaning to achieve a cleanliness corresponding to Sa 2 as specified in ISO 8501-1. Steel shot should not be used because of the risk of adhesion by magnetism and subsequent rust seizure; copper (Cu) slag should be used instead. Sealing faces should be protected during the blow
25、cleaning. 4.1.2 Precision-steel pipes and pipes of other material qualities, which are delivered, and remain, free of oxide scale (no heating or welding) After cutting and careful deburring, pipes and fittings that are joined without being subjected to prior heating or welding processes, for example
26、 by means of clamping rings, should be cleaned by one of the following methods: chemically (using an alkaline cleaning process); blown through with pressurized air; by pulling through lint-free cloths. ISO 28521:2009(E) ISO 2009 All rights reserved 34.2 Surface treatment In order to maintain the afo
27、re-mentioned cleanliness of pipes and fittings until their mounting onboard, it is recommended to treat internal and external surfaces at the ends of the pipes and fittings with a suitable oil product. To prevent dust and sand entering the pipes and sticking to the surfaces, the pipe ends should be
28、blanked off. The applied oil product should not change the properties of the flushing or system oil. 4.3 Storage of prefabricated pipes and fittings Cleaned and surface-treated prefabricated pipes and fittings should be blanked off and stored in dry, preferably controlled, conditions. If this is not
29、 possible, the pipes shall be protected against rain and venting should be secured on all surfaces. Inadequate storage conditions might necessitate additional cleaning and surface treatment. 5 Level of cleanliness For pretested components and oils forming part of the system: Component suppliers shal
30、l be able to specify the level of cleanliness of the components delivered. This applies to suppliers of dynamic as well as static components. ISO/TR 10949 and ISO 18413 indicate methods according to which evaluation and documentation of the level of cleanliness can be carried out. In addition to inf
31、ormation regarding the level of cleanliness at the time of delivery, the yard and the system supplier should agree in advance on the necessary level of cleanliness of the system oil and the cleaned system to achieve a long and reliable operation. 6 Assembly and installation of pipe system It is impo
32、rtant to avoid any welding, brazing, soldering or heating of the pipes (and production of oxide scales) when assembling and installing pipes. If this cannot be avoided, then the pipes in question shall be cleaned and protected again (repaired). In particular, it is important to remove soldering mate
33、rials. Protection covers should be removed as late in the installation process as possible. Preventing dirt (from the installation process) from entering the pipe system is crucial. PTFE sealing fluids and tape should be applied with great care. 7 Blow-through/pull-through of the system Before conne
34、cting the pipe system to machines, panels, pump stations, etc., all pipes should be blown through with dry pressurized air and/or nitrogen. If this is not possible (because of the pipe dimension) then pulling through clean, lint-free cloths should clean the pipes. The purpose of this is to remove lo
35、ose dirt in the most efficient way and, at the same time, ensure that the pipes are dry internally (nitrogen helps eliminate water that has condensed in the pipes). ISO 28521:2009(E) 4 ISO 2009 All rights reserved8 Description of coupling 8.1 Design phase During the design phase, i.e. at the structu
36、ring of the hydraulic diagram, it is important to consider carefully how the complete system can be flushed in practical terms (including grouping). When grouping off the pipe system, the following should be observed. a) “Dead” areas are unacceptable during flushing (these can be avoided by changing
37、 the coupling points). b) Circuits should always be connected in series. c) Relevant coupling options should be considered (the objective being connection of uniform pipe diameters in order to avoid large pressure losses). 8.2 Other considerations The following shall also be taken into account. a) C
38、omponents that might hinder a high flow velocity, or which might be destroyed by a high flow velocity, should be bypassed. b) Built-in filter elements shall be removed before flushing. c) Pump stations, assembled units and subcomponents that have not been pre-tested shall be flushed separately in ca
39、se they are not delivered in a cleaned condition. NOTE This also applies to pipe systems where space conditions on board do not allow flushing of the pipe systems installed. d) It is important that sampling of oil during the actual flushing be carried out in a way that ensures a representative sampl
40、e. Reference should be made to ISO 28523 and ISO 4021, which describe sampling from a dynamic system. 9 Leakage test Before filling with flushing oil, the leak-tightness of the system can be checked in the following ways: a) Connect the pipe system (bypass/blank off components), then pressurize in a
41、ccordance with the directions of national standards, using clean, dry air or nitrogen, and perform external testing with soapy water or monitoring for pressure drop during a certain time. b) After filling with the flushing oil, the leak-tightness of the system can be tested by means of shock or pres
42、sure testing (see Clause 11). ISO 28521:2009(E) ISO 2009 All rights reserved 510 Filling with oil For the choice of oil type and quality, see 12.3. The filling procedure is as follows. a) Connect the pipe system (bypass components). b) Clean the tank in the portable pump-station and the power pack t
43、o a cleanliness level corresponding to the cleaning level of the components supplied to the system (see Clause 5). c) Fill the system by pumping the oil through a filter until the tank is full. The filter shall be capable of filtering the oil to a minimum of two ISO-codes below the cleanliness speci
44、fied for the system, in accordance with ISO 4406. Care should be taken that air bubbles do not enter the system during the filling operation; if necessary, the system should be topped up and vented. 11 Shock testing/pressure testing a) Connect the pipe system (bypass components). Ensure that it is c
45、ompletely filled. b) Pressurize the pipe system up to the relevant testing pressure and relieve it again by opening the relief valve on the pump station. Repeat this procedure a minimum of 25 times, unless otherwise specified. 12 Flushing of yard-installed pipe system 12.1 Connection Connect the pip
46、e system (bypass/blank off components). Ideally, the use of a vibrating unit will be over a broad frequency range. It is appropriate to change the flow direction more than once during the flushing period. 12.2 Special pump units Experience shows that very good results can be achieved when cleaning p
47、ipes using a hydraulic accumulator and a pulsation valve sending pressure/flow pulsations through the pipes. In a pipe system with a small internal diameter, in which a turbulent flow can be difficult to achieve because of a large pressure drop, special gas/oil units can be used that fill the entire
48、 pipe system with gas and oil loads which are subsequently compressed; when these loads are released, the gas pockets expand, resulting in a turbulent oil flow. 12.3 Flushing filters 12.3.1 Filter capacity The permanent filters of the systems should not be used for cleaning of flushing oil; instead,
49、 special flushing filters designed to increase the filter capacity to a predetermined extent during flushing may be used together with the portable pump station. It is advisable to place filters on both the pressure line and the return line in order to reduce the total flushing time. The choice of filter capacity should be made with the aim of achieving an acceptable service life for the filter element. ISO 28521:2009(E) 6 ISO 2009 All rights reservedThe service life is, all other things being equal, determ
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