1、 A Working Guide for Carbon Steel Equipment in Wet H2S Service PUBLICATION 179 Edition 1 RELEASED BY IHS. NOT FOR RESALE THE ENGINEERING EQUIPMENT AND MATERIALS USERS ASSOCIATION A WORKING GUIDE FOR CARBON STEEL EQUIPMENT IN WET H2S SERVICE (DEVELOPED LARGELY FROM OIL REFINERY EXPERIENCE) PUBLICATIO
2、N No. 179: 1996 Copyright 1997 The Engineering Equipment and Materials Users Association ISBN 0 85931 085 X ARTILLERY HOUSE, 3rd Floor South ARTILLERY ROW LONDON SW1P 1RT Tel: 0171 222 3822 Fax: 0171 222 3922 EEMUA THE ENGINEERING EQIDPMENT AND MATERIALS USERS ASSOCIATION The Engineering Equipment a
3、nd Materials Users Association - EEMUA - is an organisation of substantial purchasers and users of engineering products. Its members include leading representatives from the energy, process and oil industries. EEMUA is concerned with the design, installation, operation and maintenance of the enginee
4、ring plant used in members business operations. The Association aims to reduce members costs by providing the opportunity for them to share resources and expertise in influencing the environment within which their engineering activities are carried out. EEMUA supports the British Standards Instituti
5、on, works with other institutions, associations, government departments, regulatory authorities and the Confederation of British Industry, and is also actively involved with other standards-making bodies, both national and international, such as the American Petroleum Institute. Work, which is carri
6、ed out in-house by members alone or with the help of other organisations, may lead to the production of Association publications. These are prepared primarily for members use, but are often offered for sale and thus for more general use. Such publications may also be submitted to the British Standar
7、ds Institution as bases for appropriate Standards. A list of EEMUA publications is given at the end of this document. ii ABOUT TillS PUBLICATION: LEGAL ASPECTS In order to ensure that nothing in this publication can in any manner offend against or be affected by the provisions of the Restrictive Tra
8、de Practices Act 1976, the recommendations which it contains will not take effect until the day following that on which its particulars are furnished to the Office of Fair Trading. As the subject dealt with seems likely to be of wide interest, this publication is also being made available for sale t
9、o non-members of the Association. Any person who encounters an inaccuracy or ambiguity when making use of this publication is asked to notify EEMUA without delay so that the matter may be investigated and appropriate action taken. It has been assumed in the preparation of this publication that the u
10、ser will ensure selection of those parts of its contents appropriate to the intended application and that such selection and application are correctly carried out by appropriately qualified and experienced people for whose guidance the publication has been prepared. EEMUA does not, and indeed cannot
11、, make any representation or give any warranty or guarantee in connection with material contained in its publications, and expressly disclaims any liability or responsibility for damage or loss resulting from their use. Any recommendations contained herein are based on the most authoritative informa
12、tion available at the time of writing and on good engineering practice, but it is essential for the user to take account of , pertinent subsequent developments or legislation. All rights are reserved. No part of this Publication may be reproduced, stored in a retrieval system, or transmitted in any
13、form or by any means, electronic, mechanical, photocopying, recording, or other. Infringing the copyright is not only breaking the law, but also, through reduction in the Associations income, jeopardising future publications. ill IV TABLE OF CONTENTS Page FOREWORD . . . . . . . . . . . . . . . . . .
14、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1. SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. INTRO
15、DUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 Damage Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Process Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3
16、 Materials Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.4 Welding and Post-Weld Heat Treatment (PWHT) . . . . . . . . . . . . . . . . . . 6 2.5 Classification of Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.6 In-Service I
17、nspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. PROCESS CONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1 Conditions for SSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2 Conditi
18、ons for HIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4. ASSESSMENT OF RISK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.1 Probability of Wet H2S Attack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.2 Cons
19、equences of Wet H2S Attack . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.3 Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4.4 Re-Evaluation of Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5. NEW CONSTRUCTIO
20、N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.1 General Materials Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.1.1 Established Requirements for Sour Service . . . . . . . . . . . . . . . . . 15 5.1.2 Improvements in Materials
21、15 5.1.3 Different Product Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.1.4 Microstructural Homogeneity . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.1.5 Material Test Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.2 Plate for Improved Resista
22、nce to HIC . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.2.2 Material Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.2.3 Chemical Composition . . . . . . . . . . .
23、 . . . . . . . . . . . . . . . . . . . 17 5.2.4 Ultrasonic Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.2.5 HIC Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.2.6 HIC Acceptance Limits . . . . . . . . . . . . . . . . . . . . . . . .
24、 . . . . . 18 5.3 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.4 Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5.4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25、 . . . . . . 19 5.4.2 Post Weld Heat Treatment (PWHT) . . . . . . . . . . . . . . . . . . . . . 20 5.5 Welding Procedure Qualification (WPQ) . . . . . . . . . . . . . . . . . . . . . . . 20 5.5 .1 Steels for Qualification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5.5.2 Hardness Te
26、sting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5.5.3 Welding Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5.6 Production Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5.6.1 Welding Procedure Variables .
27、. . . . . . . . . . . . . . . . . . . . . . . . . 21 v 5.6.2 Production Hardness Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5.6.3 Production Test Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5.6.4 Non-Destructive Examination of Welds . . . . . . . . . . .
28、 . . . . . . . . 22 6. WELDING OF IN-SERVICE EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 6. 1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 6.2 Damage Caused by Prior Service . . . . . . . . . . . . . . . . . . . . . . .
29、 . . . . . 23 6.3 Hydrogen Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 6.4 Hydrogen Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 6.4.1 General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
30、 6.4.2 Heat Treatment Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 6.5 Testing and Inspection after Welding . . . . . . . . . . . . . . . . . . . . . . . . . . 25 7. INSPECTION OF IN-SERVICE EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 7.1 General . . .
31、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 7.2 Establishment and Review of Inspection Frequency and Extent . . . . . . . . . . 27 7.3 Inspection methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7. 3 .1 Visual . . . . . . .
32、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7.3.2 WFMPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7.3.2.1 Surface Preparation . 7.3.2.2 Technique . . 7.3.3 Ultrasonic Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33、. . 7.3.3.1 Detection and Sizing . 7.3.3.2 UT Attenuation . 29 29 30 30 31 FIGURES. . . . . . . . . . . . . . . . . . . 33 Fig. 1 Typical Forms of Wet H2S Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Fig. 2 Vickers Hardness Testing for Welding Procedure Qualification . 34 Fig. 3 E
34、xamples of Blistering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Fig. 4 Trans-weld and HAZ Cracking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Fig. 5 Cracking in HAZ and Parent Materials . . . . . . . . . . . . . . . . . . . . . . . . . 37 Fig. 6 Step
35、wise Cracking Induced by Welding Stresses . . . . . . . . . . . . . . . . . . . 38 LIST OF ABBREVIATIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 LIST OF REFERENCED DOCUMENTS. 41 EEMUA PUBLICATIONS- SUMMARY LIST . . . . . . . . . . . . . . . . . . . . . . .
36、 . . . . . 43 vi FOREWORD This EEMUA Working Guide has been prepared by a joint working group of members of the Associations Materials this can result in hydrogen blistering, step wise cracking (SWC) and stress-oriented hydrogen induced cracking (SOHIC). Typical forms of damage are illustrated in Fi
37、g 1. The severity of hydrogen damage depends on a combination of factors. These include process conditions, materials, methods of construction and operating history. 2.2 Process Conditions The process conditions leading to cracking involve the presence of an aqueous environment , containing dissolve
38、d hydrogen sulphide. Sour service with respect to sse is defined as set out in 3.1 below. Liquid only systems are not addressed but a figure of 50 ppmw H2S in the water phase is often used, irrespective of system pressure, as a definition of wet H2S service. Potential for attack is greatest under th
39、e following conditions: increasing acidity in the presence of cyanides or other species promoting hydrogen permeation a combination of high pH and high H2S concentration. 2.3 Materials Factors The material quality and condition have an effect on resistance to hydrogen damage: for sse, the material c
40、omposition, level of hardness and imposed stress (applied and residual) are all factors which affect the likelihood of cracking; for Hie and SOHie, steel chemistry, cleanliness and homogeneity affect the likelihood of cracking. To improve the resistance to hydrogen damage in general, it is preferabl
41、e to select good quality lower strength grades of carbon steel and to minimise micro-alloying elements and other elements which promote hardenability. This should help avoid undesirable weld and heat affected zone hardness and reduce residual stresses. For resistance to Hie special low sulphur steel
42、s are available to enhance performance, and have been used with success in many applications. Ultrasonic examination and Hie testing are carried out to give an assessment of material resistance to hydrogen damage. It should be recognised, however, that manufacturing vessels from these materials and
43、employing controlled methods of construction do not guarantee resistance to wet H2S damage. 5 In some circumstances, internal cladding or coating has been used to improve resistance to damage. 2.4 Welding and Post-Weld Heat Treatment (PWHT) Weld procedure qualification should be subject to special a
44、ttention to avoid high hardnesses. Hardness testing of weldments is necessary. A hydrogen removal treatment may need to be carried out before welding on equipment that has been in wet H2S service. PWHT is beneficial in reducing the likelihood of SSe, and possibly SOHie, because it reduces residual s
45、tresses to a general level of 20-30% of yield and tempers the weld zone microstructure. However, additional stresses from nozzle loadings, internal pressure etc. may locally increase the overall stresses, and under these conditions sse or SOHie might still be possible. 2.5 Classification of Risk Ris
46、k can be assessed by taking account of: i) materials as installed and their susceptibility to sse and Hie, and hydrogen loading, leading to a prediction of the probability of cracking ii) an evaluation of the consequences of failure. 2.6 In-Service Inspection It is important to carry out inspection
47、to confirm the integrity of steels operating in wet H2S service. An inspection schedule should be established based upon risk and operational factors. This should be regularly reviewed in the light of inspection evidence. It should be noted that since wet fluorescent magnetic particle inspection (WF
48、MPI) of in service vessels has become more common, the detection and reporting of cracking in pressure vessels in wet H2S has increased due to the sensitive nature of the test. However, one consequence of this during subsequent operation is believed to be an increase in hydrogen charging rates on pr
49、epared surfaces. It may be necessary therefore to apply some means of protecting such surfaces after WFMPI during start up, or to use some alternative inspection method, e.g. external ultrasonics, which does not disturb the partially protective sulphide scale. 6 3. PROCESS CONDITIONS The range of process conditions which are relevant to any of the various forms of wet H2S attack are those which permit a liquid water phase to occur at some stage, including normal operation, start-up, shutdown, and during special operations such as catalyst pre-sulphiding and regeneration. 3.1 Co
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