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1、 Reference number ISO 24490:2005(E) ISO 2005 INTERNATIONAL STANDARD ISO 24490 First edition 2005-04-15 Cryogenic vessels Pumps for cryogenic service Rcipients cryogniques Pompes pour service cryognique Copyright International Organization for Standardization Provided by IHS under license with ISO Li
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5、suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. ISO 2005 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by
6、 any means, electronic or mechanical, 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-ma
7、il copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2005 All rights reserved Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 20:08:53 MDTNo reproduction or networ
8、king permitted without license from IHS -,-,- ISO 24490:2005(E) ISO 2005 All rights reserved iii Contents Page Forewordiv 1 Scope1 2 Normative references .1 3 Terms and definitions.1 4 Requirements for pump2 4.1 General.2 4.2 Materials.2 4.3 Design 3 5 Test procedures 6 5.1 Prototype testing.6 5.2 P
9、roduction testing 7 6 Cleanliness 7 7 Marking.7 Annex A (informative) Guidance on installation design8 Annex B (informative) Acceptable materials for construction of centrifugal pumps for liquid oxygen10 Bibliography .14 Copyright International Organization for Standardization Provided by IHS under
10、license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 20:08:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 24490:2005(E) iv ISO 2005 All rights reserved Foreword ISO (the International Organization for Standardization) is a world
11、wide 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 established has the right to be represented on t
12、hat 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. International Standards are drafted in
13、 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. Publication as an International Standard
14、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 identifying any or all such patent rights. ISO 24490 was prepared by Tec
15、hnical Committee ISO/TC 220, Cryogenic vessels. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 20:08:53 MDTNo reproduction or networking permitted without license from IHS -,-,-
16、 INTERNATIONAL STANDARD ISO 24490:2005(E) ISO 2005 All rights reserved 1 Cryogenic vessels Pumps for cryogenic service 1 Scope This International Standard specifies the minimum requirements for the design, manufacture and testing of pumps for cryogenic service. This International Standard is applica
17、ble to centrifugal pumps. However the principles may be applied to other types of pump (e.g. reciprocating pumps). This International Standard also gives guidance on the design of installations (see Annex A). It does not specify requirements for operation or maintenance. NOTE For cryogenic fluids, s
18、ee ISO 21029-1, ISO 20421-1 and/or ISO 21009-1. 2 Normative references The following 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
19、 amendments) applies. ISO 5198:1987, Centrifugal, mixed flow and axial pumps Code for hydraulic performance tests Precision grade ISO 21010, Cryogenic vessels Gas/materials compatibility ISO 21028-1, Cryogenic vessels Toughness requirements for materials at cryogenic temperature Part 1: Temperatures
20、 below 80 C ISO 21028-2, Cryogenic vessels Toughness requirements for materials at cryogenic temperature Part 2: Toughness requirements for temperatures between 80 C and 20 C ISO 23208, Cryogenic vessels Cleanliness for cryogenic service 3 Terms and definitions For the purposes of this document, the
21、 following terms and definitions apply. 3.1 nominal size DN alphanumeric designation of size for components of a pipework system, which is used for reference purposes. NOTE 1 It comprises the letters DN followed by a dimensionless whole number which is indirectly related to the physical size, in mil
22、limetres, of the bore or outside diameter of the end connections. NOTE 2 The number following the letters DN does not represent a measurable value and should not be used for calculation purposes except where specified in the relevant standard. Copyright International Organization for Standardization
23、 Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 20:08:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 24490:2005(E) 2 ISO 2005 All rights reserved NOTE 3 In those standards which use the DN designation
24、 system, any relationship between DN and component dimensions should be given, e.g. DN/OD or DN/ID. NOTE 4 Adapted from ISO 6708. 3.2 nominal pressure PN alphanumeric designation used for reference purposes related to a combination of mechanical and dimensional characteristics of a component of a pi
25、pework system NOTE 1 It comprises the letters PN followed by a dimensionless number equal to at least the maximum allowable pressure. NOTE 2 For a pump, PN can be different for inlet and outlet. 3.3 specified minimum temperature lowest temperature for which the pump is specified 3.4 duty point perfo
26、rmance point defined by pressure or head and volume or mass flow rate 3.5 net positive suction head NPSH inlet total head increased by the head (in flowing liquid) corresponding to the atmospheric pressure at the test location and decreased by the sum of the head corresponding to the vapour pressure
27、 of the pump liquid at the inlet temperature and the inlet impeller height NOTE See also ISO 5198:1997, Table 1. 4 Requirements for pump 4.1 General It is a requirement of this International Standard that a cryogenic pump shall first comply with appropriate general International Standards. In the ev
28、ent of conflict, the requirements of this International Standard shall take precedence over the general International Standards. 4.2 Materials 4.2.1 General Materials of construction shall be selected taking into consideration that cryogenic pumps operate at low temperature, often in a damp environm
29、ent, and at times with liquid oxygen or flammable fluids. The minimum requirements given in 4.2.2, 4.2.3 and 4.2.4 shall apply. 4.2.2 Mechanical properties at low temperature Metallic materials which are under stress at low temperature and which exhibit a ductile/brittle transition (such as ferritic
30、 steels) shall have minimum toughness values in accordance with ISO 21028-1 or ISO 21028-2 as appropriate. Metallic materials which can be shown to have no ductile/brittle transition do not require impact testing. Copyright International Organization for Standardization Provided by IHS under license
31、 with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 20:08:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 24490:2005(E) ISO 2005 All rights reserved 3 Non-metallic materials are generally used only for seals or heat barriers. If such m
32、aterials are to be used for structural parts, the stress levels and material impact values shall be shown to be acceptable for the intended use. 4.2.3 Corrosion resistance Materials should be resistant to, or protected from, atmospheric corrosion. Where this is not achievable, a suitable corrosion a
33、llowance shall be considered. 4.2.4 Oxygen compatibility If the specified minimum service temperature is equal to or less than the boiling point of air, or the pump is intended for oxygen service, the materials which are, or are likely to come, in contact with oxygen or oxygen- enriched air shall be
34、 oxygen-compatible in accordance with ISO 21010. If the pump is employed for oxidising cryogenic fluids, e.g. nitrous oxide, the requirements for oxygen compatibility should be taken into consideration. Materials should be selected that minimise the potential for ignition and inhibit sustained combu
35、stion. Suitable material properties are high ignition temperature, high thermal conductivity, low heat of combustion. Table B.1 lists materials found through testing and operating experience to be particularly suitable for centrifugal cryogenic pumps in oxygen service. Materials other than those ide
36、ntified in Table B.1 may be used, but their selection shall be justified by specific testing or long-term experience in this application. For (any) parts of the pump which are, or are likely to come, in contact with oxygen and which could be exposed to energy sources such as friction, aluminium or a
37、luminium alloy including aluminium bronzes shall not be used. The use of aluminium or aluminium alloy for any other parts shall only be adopted after careful consideration. Stainless steel shall not be used for exposed thin components. Exceptions allowed are seal bellows, trapped shims or gaskets an
38、d screw-locking devices of stationary parts where knowledge of past satisfactory performance is available. However, suitable alternative materials, e.g. nickel or nickel alloy, Monel and Inconel, should be considered. NOTE Tin bronze has been found to be most suitable for the main “wetted” pump comp
39、onents. The most common aluminium bronzes, which typically contain between 6 % and 11 % aluminium, have relatively high heats of combustion and, if combustion occurs, are practically impossible to extinguish in an oxygen environment. 4.3 Design 4.3.1 General Pumps for cryogenic service shall met the
40、 requirements of ISO 5198. 4.3.2 Pressure-containing parts The high-pressure side of the pump shall be designed to withstand at least the nominal outlet pressure. The low-pressure side shall be designed to withstand at least the nominal inlet pressure. Copyright International Organization for Standa
41、rdization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 20:08:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 24490:2005(E) 4 ISO 2005 All rights reserved The material stress level from pressure may n
42、ot be the dominant factor in pump design. The allowable stress level may be calculated at the pressure rating, using ISO 21009-1 for guidance. For any parts subject to fatigue, material stress levels should not exceed one-half of the infinite fatigue life for the part in question. 4.3.3 Performance
43、The pump design and installation shall meet the performance requirements specified on a data sheet (or similar document). Examples of a data sheet can be found in ISO 5199 and ISO 9908. 4.3.4 Clearances Clearances between moving and stationary parts within the pump shall be as large as practical, co
44、nsistent with good hydraulic performance and sealing. Material selection for components should take into account the often large differences in expansion coefficients to ensure satisfactory clearances and interferences at the operating temperatures and during cool-down. 4.3.5 Prevention of rubbing T
45、he consequences of bearing failure or the consumption of parts by wear shall be considered, particularly in pumps designed for liquid oxygen duty. 4.3.6 Fastenings All internal fasteners shall be secured to prevent them loosening in service (e.g. friction nuts, tab washers). Consideration shall be g
46、iven to more adequately securing items which might normally be held in place by an interference fit only (e.g. wear rings). These components can cool down more quickly than others and become temporarily loose. 4.3.7 Warm bearings Rolling-element bearings designed to run warm shall be located or prot
47、ected such that freezing of the lubricating grease or oil is avoided. The effect of ice build-up over a period shall be considered. This can result in overcooling of the bearing and can allow shaft-seal leakage to be forced directly into the driver bearing. Motor-bearing heaters may be considered fo
48、r cold standby pumps. 4.3.8 Cold bearings For bearings designed to run cold, lubricated by the cryogenic fluid, the use of materials and design arrangements that can safely withstand short-term dry running shall be considered. 4.3.9 Bearing lubrication For direct-coupled cryogenic pumps, grease and oils shall be suitable for all oxidising and predictable offset conditions. The lubricants should typically be suitable down to 40 C. Sealed bearings are preferred. Where bearing re-greasing in situ is requir