1、 API PUBL*939 94 0732270 0539Z07 bTT Research Report on Characterization and Monitoring of Cracking in Wet H2S Service API PUBLICATION 939 OCTOBER 1994 American Petroleum Institute 1220 L Street, Northwest Washington, D.C. 20005 SPECIAL NOTES (1) API publications necessarily address problems of a ge
2、neral nature. With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed. (2) API is not undertaking to meet the duties of employers, manufacturers, or suppliers to warn and properly train and equip their employees, and others exposed, concerning heal
3、th and safety risks and precautions, nor undertaking their obligations under local, state, or federal laws. (3) Information concerning safety and health risks and proper precautions with respect to particular materials and conditions should be obtained from the employer, the manufacturer or supplier
4、 of that material, or the material safety data sheet. (4) Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anything con- tai
5、ned in the publication be construed as insuring anyone against liability for infringement of letters patent. (5) Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years. Sometimes a one-time extension of up to two years will be added to this review cycle
6、 This publication will no longer be in effect five years after its publication date as an operative API standard or, where an extension has been granted, upon republication. Status of the publication can be ascertained from the API Authoring Department telephone (202) 682-8000. A catalog of API pub
7、lications and materials is published annually and updated quarterly by API, 1220 L Street, N.W., Washington, D.C. 20005. Copyrighe 1994 Welding Research Council Inc. API PUBL*939 94 0732290 0539209 472 Research Report on Characterization and Monitoring of Cracking in Wet H2S Service FOREWORD In 1990
8、 cracking of refinery process equipment in wet H2S service was being widely reported. As a result, committees and task groups of industry organiza- tions, including API, NACE and the Materials Properties Council, were actively seeking improved understanding of the phenomenon. Of particular concern w
9、ere conditions leading to cracking and blistering, the incidence of cracking, the consequences of such damage, and the efficacy of NDE methods for detection and monitoring. The Program reported herein was one of several significant industry-wide efforts on this subject. It was intended to supplement
10、 other activities by examining, in a large-scale test vessel, issues which could not be addressed satisfactorily either with conventional small-scale laboratory specimens or with in-situ exposures in refineries. The construction of a welded steel pressure vessel with a replaceable “window” for test
11、purposes was proposed by MPC to the API Subcommittee on Corrosion and Materials. Its Task Group on Materials and Corrosion Research developed the program to study the effect of variables on cracking and the capabilities of certain NDE monitoring methods. At that time, it was realized that the result
12、s would not be directly translatable to field application because the environment to be used would be extremely severe, and the thickness of the steel studied was limited to 0.5 inch. Nevertheless the guidance to be obtained would be valuable. The results of the program have helped to provide valida
13、tion of observations of conventional laboratory test specimens and clarify the roles of the variables considered. The work on acoustic emission monitoring was particularly enlight- ening. However, it must be realized that the information obtained is to be viewed in the context of specific service de
14、mands before application in the plant should be attempted. For example, pressure vessels usually have thicker shells than used in the test which will affect NDE capabilities, hydrogen permeation and material behavior. A large measure of the credit for the success of this program goes to the members
15、of the API Subcommittee and Task Group and the MPC Sponsor Committees who contributed their ideas and vast experience. M. Prager E? - API PUBLr939 94 E O732290 0537230 174 Research Report on Characterization and Monitoring of Cracking in Wet H2S Service M. S. Cayard, R. D. Kane, L. Kaley, andM. Prag
16、er CONTENTS 1.0 Executive Summary . 1 2.0 Introduction . 2 2.1 Background . 2 2.2 Goal . 3 2.3 Technical Approach . 3 2.4 Terminology. 3 2.4.1 Wet H2S Cracking Mechanisms . 3 2.4.1.1 Hydrogen Blistering .3 2.4.1.2 Hydrogen Induced Cracking (HIC) . .3 2.4.1.3 Stress Oriented Hydrogen Induced Cracking
17、 (SOHIC) . .4 2.4.1.4 Sulfide Stress Cracking (SSC) . .4 2.4.2 Steels 4 2.4.2.1 Conventional Steel .4 2.4.2.2 Low Sulfur Conventional Steel .4 2.4.2.3 “HIC Resistant” Steel 4 2.4.2.4 Ultra-Low Sulfur Advanced Steels . .4 2.4.3 General Terminology . .4 2.4.3.1 Crack Length Ratio (CLR) .4 2.4.3.2 Crac
18、k Thickness Ratio (CTR) . .5 2.4.3.3 Crack Sensitivity Ratio (CSR) . .5 2.4.3.4 Longitudinal-Transverse (LT) Section . .5 2.4.3.5 Transverse-Longitudinal (TL) Section . .5 3.0 Experimental Procedures . 5 3.1 Materials Evaluated .5 3.2 Specimen Configurations 5 3.3 Experimental Overview . 7 3.3.1 Eva
19、luation of Plate Containing Pre-existing HIC Damage . .9 Hard Welds (HRC 22-30). . .9 3.3.2 Evaluation of Plate Containing M. S. Cayard and R. D. Kane are with CLI International; L. Kaley is with Det Norske Veritas Industry; and M. Prager is with The Materials Pro erties Council. TKis WRC Bulletin c
20、ontains a Report of Research funded cooperatively by The Materials Properties Council, Inc. and the American Petroleum Insti- tute under the direction of the Task Group on Materials and Corrosion %search of the API Subcommittee on Corrosion and Materials. 3.3.3 Evaluation of the Repair of 3.3.4 Simu
21、lation of the Cracking Behavior of Thick Plate 10 3.3.5 Evaluation of HIC Resistant Plate/I.D. Surface Cleaning/ Severe Hydrogen Charging Conditions . 10 3.3.6 Evaluation of Nozzle Attachments/Effect of PWHT . 11 3.3.7 Verification of AE Signature for Hydrogen Blistering and SSC . 11 4.0 Results and
22、 Discussion . 12 4.1 Materials Selection. 12 4.2 Fabrication . 13 4.3 Inspection 17 4.4 Vessel Design and Integrity .28 5.0 References .31 Appendix I-Serviceability of HIC Damaged Steel .33 Appendix II-Serviceability of Hard Welds .45 Appendix III-Evaluation of Weld Repair/PWHT 57 Appendix IV-Simula
23、tion of Thick Plate Behavior . 75 Appendix V-Environment al Staging/ Effect of Cleaning .93 Appendix VI-Serviceability of Nozzle Attachments and PWHT . 121 a HIC Damaged Vessel. . 10 1.0 Executive Summary This report presents the experimental methods and findings of a research program of MPC entitle
24、d “Characterization and Monitoring of Cracking in Wet H,S Service.” The program was supported by the Refining Division of the American Petroleum Insti- tute (MI) and by The Materials Properties Council (MPC) and its Fitness-for-Service group-sponsored program. The two main objectives of the program
25、were to study the performance in wet H2S of welded steel plate of various qualities and microstructures, and evaluate the effectiveness of NDE techniques to characterize and monitor the cracking. To accomplish these objectives, a series of large scale exposure tests were conducted with steel panels
26、referred to herein as “windows”) containing welds and attachments welded into a fabricated steel vessel filled with a Cracking in Wet H2S Service 1 API PUBL*39 94 0732290 0539211 O20 2 WRC Bulletin 396 pressurized H2S containing solution prepared in accor- dance with NACE Standard TM0177-90, Method
27、 A. Experiments were performed using windows com- prised of conventional, low sulfur, ultra-low sulfur and advanced thermo-mechanically controlled pro- cessed (TMCP) steels per the ASTM A516-70 and A841 specifications using various weld fabrication methods. Characterization and monitoring of interna
28、l cracks resulting from Hydrogen Induced Cracking (HIC), Stress Oriented Hydrogen Induced Cracking (SOHIC) and Sulfide Stress Cracking (SSC) was accomplished at various pressures, solution pH, H2S content, and time. Methods utilized included: (1) manual and automated ultrasonic testing (UT), (2) wet
29、 fluorescent magnetic particle testing (WFMPT), and (3) acoustic emission (AE). The results of these nondestructive techniques were confirmed using metallographic sectioning following exposure. It was found that resistance to blister-type HIC was greater in lower sulfur steels than in the higher sul
30、fur conventional steels. Maximum resistance to HIC was found in ultra-low sulfur advanced steels produced by thermo-mechanically controlled process- ing (TMCP) with ultra-low sulfur contents ( I 0.001 wt. percent) and processed to produce controlled homogeneous microstructures free from ferrite/ pea
31、rlite banding. Based on all materials evaluated in this program, the resistance to through-wall crack propagation also increased with decreasing sulfur content and decreas- ing microstructural banding. However, under very severe hydrogen charging conditions, i.e., two to three times the NACE TM0177
32、solution charging levels, all steels evaluated exhibited through-wall cracking to depths ranging from approximately 30- 50% of the plate thickness irrespective of either the sulfur content or degree of banding. These data suggest that there is a threshold level of hydrogen charging above which the r
33、esistance of these materi- als, even those processed to optimize resistance to HIC, breaks down. At such severe hydrogen charging conditions, the use of stainless steel clad vessels may be more appropriate. One of the most notable findings of this program was the significant impact of surface cleani
34、ng and removal of protective sulfide films on the subsequent cracking behavior of carbon steel equipment. It was found that removal of surface films on the internal surface of carbon steel equipment, using techniques typically used prior to WFMPT, increased the hydro- gen flux and likelihood of wet
35、H2S cracking during operation prior to the reformation of a protective sulfide scale. Nondestructive evaluation techniques (Le., WFMPT, UT and AE) were useful to varying degrees in identifying and monitoring HIC, SOHIC and SSC. Automated ultrasonic testing (AUT) T-scan ad- equately identified in-pla
36、ne, blister type cracking caused by HIC in a semi-quantitative manner which correlated reasonably well with metallographic sec- tioning. AUT P-scan was only able to qualitatively identify through-wall SOHIC. This may have, in part, been due to the relatively thin section size of the plate used in th
37、is study. Manual UT was required to size through-wall flaws in plate specimens resulting from SOHIC and sulfide stress cracking (SSC). However, manual UT crack sizing measurements in the regions around nozzle attachment welds and surface crack indications ob- tained using WFMPT typically did not acc
38、urately identify areas of significant through-wall cracking from SOHIC as confirmed by metallographic section- ing. Many of the indications obtained from WFMPT were limited to surface cracks and imperfections. AE monitoring was able to detect and characterize damage during periods of active cracking
39、 resulting from HIC, SOHIC and SSC. Al3 also differentiated cracking related to in-plane (blister-type) HIC growth from through-wall crack growth resulting from SOHIC and SSC. AE conducted during hydrotesting of HICSOHIC damaged material required relatively high levels of internal pressure, beyond t
40、he normal operating levels for the vessel, to produce a significant AE response. In general, the observations of material behavior found in this study were consistent with the findings of the previously conducted laboratory testing con- ducted in the MPC group-sponsored Wet H2S Re- search Program. T
41、he results of the present study validated the wet HIS test methods developed previ- ously in that work and showed their applicability to refinery wet H2S service conditions. 2.0 Introduction Presented herein is the final report for a research program conducted at CLI International as contrac- tor to
42、 The Materials Properties Council, Inc. (MPC). The program was jointly funded by MPC, its Fitness- for-Service sponsor group and the Refining Division of the American Petroleum Institute (MI). DNV Industry Inc. provided nondestructive services for WFMPT, UT and AE inspection as well as nondestruc- t
43、ive test data analysis. Chicago Bridge and Iron fabricated the wet H2S full-scale test vessel. This report contains a comprehensive summary of the test facilities and experimental methods, pertinent find- ings and analysis of the test results. 2.1 Background Refinery equipment in wet H2S service is
44、character- ized by exposure to aqueous process environments containing hydrogen sulfide. Systematic inspection programs conducted by petroleum companies have shown that wet H2S refinery processes can provide conditions for hydrogen charging of steel and wide- spread cracking of carbon steel The resu
45、lts of operating experience surveys and technical investigations have described situations where car- bon steel equipment exposed to wet H2S environ- API PUBL*939 94 O732290 0539232 Tb7 ments may be susceptible to cracking via hydrogen induced cracking (HIC), stress oriented hydrogen induced crackin
46、g (SOHIC) andior sulfide stress crack- ing (SSC).3-6 In some cases, cracking has been found to be minimal, resulting in no significant effect on equipment integrity or serviceability. In other cases, widespread cracking initiates andlor cracks propa- gate to a substantial degree thus limiting the re
47、sidual load and pressure capabilities of the affected equip- ment. Prior to the initiation of this program, MPC orga- nized a research program on wet H2S cracking of steels sponsored by more than twenty major petro- leum companies, steel manufacturers and equipment fabricators. This program was aime
48、d at (1) the devel- opment of screening procedures for evaluation of steels, (2) the determination of the influence of metallurgical processing and welding variables, and (3) the better understanding of the roles of stress, environment composition and temperature. It has provided valuable fundamenta
49、l information which has improved both the awareness of the causes of wet H2S cracking and potential solutions in terms of both new construction and repair and remediation of existing equipment. However, there was a desire to validate the findings and conclusions of that program and to explore the complex interrelations of variables that can affect the actual behavior of large scale equipment used in wet H2S service. The present study was conducted to provide impor- tant information regarding the serviceability of welded steel equipment in wet H2S service. Specifically, situations ex
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