The revision of this part of ANSI/NACE MR/ISO involves a ANSI/ NACE MR/ISO will be processed in the same way and will lead to. This NACE International standard represents a consensus of those .. Adding New Materials for MR Section 4: Corrosion-Resistant Alloys (CRAs)—All. The document too frequently referred to simply as “NACE”, was first issued in by the National Association of. Corrosion Engineers, now known as NACE .
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NACE MR/ISO standard should be submitted to NACE. . NACE MR/ISO consists of the following parts, under the general title. Details of the software products used to create this PDF file can be pertaining to ANSI/NACE MR/ISO should be submitted to. Details of the software products used to create this PDF file can be .. ASNI/ NACE MR/ISO will be processed in the same way and.
New Projects For this reason, CAPP Pipeline Technical Committee felt it was important to create a supporting document, which could be used by industry as a reference tool to: It was also designed to provide guidance for the selection and specification of SSC-resistant materials when the H2S thresholds were exceeded.
In more recent editions, NACE MR has also provided application limits for some corrosion-resistant alloys, in terms of environmental composition and pH, temperature and H2S partial pressure. This effort introduced fundamental changes to the MR, incorporating industrial practices and testing methodologies previously not addressed by MR As stated above, the new standard addresses issues which were not considered in the previous versions of NACE MR and which may have significant implications for the users of the document.
For example, the new standard: All maintenance issues such as interpretation, amendments or total revisions must be submitted directly to the designate or focal point appointed by the MP. An exception is made for the interpretation of technical content: These ballots are presented to the OSC membership for voting.
This site allows users of the standard to access other information such as: The most substantial change in the document was to stainless steels. Figure 4. The increased emphasis on end user responsibility was established to ensure the correct material was being selected for the intended environment. Part 1: Part 3: Figure 1 of Part 2: Clause 7.
This differs from previous editions where only the partial pressure of the H2S was considered. Hardness requirements for welds Part 2: Other test methods require the agreement of the equipment user. This differs from previous editions where HRC was the primary basis of acceptance. Previous standard versions only considered SSC as the governing cracking mechanism.
Section 6 9. The cracking mechanisms addressed include: For example, austenitic stainless steels e. In previous editions, only sulfide stress cracking SSC was considered; there were no temperature restrictions.
Clause A. In previous editions of MR, several legacy materials had no environmental restrictions, implying they were suitable for any sour service environment. For example, wrought precipitation hardening nickel alloy UNS N had no environmental restrictions in previous editions of MR; in the current standard this alloy has H2S partial pressure limitations based on the maximum operating temperature.
The environmental limits listed in Tables A. For example, austenitic steels such as AISI are limited to a maximum of kPa partial pressure of H2S at a maximum temperature of 60o C for any combination of chloride concentration and in situ pH in the production fluid.
For example, martensitic, precipitation hardening stainless steel was deleted from the general usage section, but remains an acceptable Corrosion Resistant Alloy Categories Part 3: These categories or materials groups austenitic steel, martensitic steels, etc are further split into material types similar compositional limits and individual alloys.
For example, Annex A, Table A.
This table is sectioned into general materials type and individual alloys, e. UNS S The individual alloys tend to have broader environmental limits than those set for the group.
Suitable labeling or documentation is also acceptable. A summary of the content described below is presented in a flowchart diagram in Appendix B, see Appendix B.
This document supplements, but does not replace, the material requirements given in the appropriate design codes, standards or regulations; its intent is to address and apply to: For design using plastic criteria strain—based and limit states use of this standard may not be appropriate. All items in this section are repeated in both Part2 and Part3 of the standard.
Clause 6. December Guide on the Use of International Standard NACE Page 10 experience, and the severity of the intended service ensuring it does not exceed that of the documented service conditions.
Clause 8. The data used to qualify a material based on field service, once submitted to NACE, may be used by the public as reference for identical applications. Testing may be conducted under service conditions similar to the limits applied to pre-qualified materials or under service conditions outside these limits.
Cracking-Resistant Carbon and Low Alloy Steels Part 2 outlines the requirements and recommendations for the selection and qualification of carbon steels, low alloy steels and cast irons for service in equipment used in H2S-containing environments of oil and natural gas production and natural gas treatment plants. The parameters affecting the behavior of carbon and low alloy steels in H2S environments are explicitly listed metallurgy, H2S partial pressure, pH, chloride content, etc.
The user must evaluate the severity of the service environment based on a combination of H2S partial pressure and in service pH. Three hardness testing methods are specified: Any other test method requires explicit user approval.
Hardness testing shall be specified as part of the qualification for fabrication methods such as burning and cutting if any HAZ remains in the final product. To address this prospect, additional testing and specific acceptance criteria may be required. Cracking-Resistant CRAs and Other Alloys Part 3 gives the requirements and recommendations for the selection and qualification of CRAs corrosion-resistant alloys and other alloys for service in equipment used in H2S-containing environments of oil and natural gas production and natural gas treatment plants.
For example, when selecting any austenitic stainless steel for a general application, the service environment limits and material requirements are listed in Table A. However, if the austenitic stainless steel is UNS S, then the specific limits listed for this particular austenitic grade must be used.
The hardness limits for material types or individual alloys are listed in Annex A. The use of the HRC method requires specific user approval. This includes qualification testing for fabrication methods such as burning and cutting if any HAZ remains in the final product. Some environmental restrictions are placed on certain alloys based on the PREN number 5.
Examples of the downloading information Clause 7.
Each group of alloys are identified by materials type within compositional limits or as individual alloys. Acceptable metallurgical conditions and environmental limits are given, for which alloys are expected to resist cracking.
End User decision flow charts are included in Appendix C and must be used in conjunction with section.
Each of the paragraph numbers below have been recorded on the corresponding Appendix C charts for easier cross-reference. The applicability of the Standard can be determined in two steps: Determine the level of H2S in the environment by calculating the partial pressure of H2S. New Projects Once it is established that the document applies, the user has to define the type of application involved. Even though similar options are available for all application types, there are different considerations when selecting materials for existing facilities such as replacement in kind or small projects on existing installations.
For this reason, it may be more advantageous to investigate all methods of material qualifications available to ensure the most economical solution. Situation Examples: A sample form for material selection is presented in Appendix E. If the existing material complies with the requirements of the pre-qualified material, the same material can be used.
If the existing material does not comply, proceed to step 6. If the designs for a new facility are modeled after an existing facility and intended for the same service, the materials requirements can be documented based on the existing facility. For new facilities operating in the same service conditions, refer to 6. As a result of laboratory testing and field experience NACE MR details the parameters of acceptable chemical composition physical properties manufacturing processes and fabrication processes that will yield a material acceptable for processes and fabrication processes that will yield a material acceptable for use in a NACE defined sour environment.
These parameters as they pertain to carbon steel materials will be detailed in a later section of this paper. However for the environment to be defined as NACE sour it must exhibit characteristics that are favorable for the initiation of sulfide it must exhibit characteristics that are favorable for the initiation of sulfide stress cracking.
It is important to understand that the environments which can result in the SSC of materials are very specific in their compositions. SSC does not occur under all operating conditions. Several factors affect whether or not SSC will occur to a particular metallic structure.
How each of these impacts the SSC potential is discussed below. Generally speaking iron based materials or ferrous metals are more susceptible to SSC than nickel based alloys or non-ferrous materials. Therefore each material should be reviewed prior to use to ensure it is acceptable for the intended use ensure it is acceptable for the intended use. Yield Strength and Hardness Properties Ilthhihthtthf llthhdth tildth In general the higher the strength of an alloy the harder the material and the more susceptible it is to sulfide stress cracking.
Although yield strength is a true material property hardness is not. Generally the higher the yield strength the higher the hardness value. This is often quoted for ferrous steels used in a NACE sour service.
However through controlling steel chemistry and using special mill processing this li it b i d T ti d lifi ti f t i l b upper limit can be increased. Testing and qualification of materials can be performed to determine its suitability for use in sour systems. Hardness values can be utilized by manufacturers and procurement agents as a quality control method during the manufacturers and procurement agents as a quality control method during the 1 fabrication process or 2 by the field personnel as a field inspection technique.
Additional discussions on hardness determinations are discussed in the next section section. Testing and qualification of materials can be performed to determine its suitability for use in sour systems systems. A microstructure comprised of tempered martensite with fine grains will result in materials of superior resistance to SSC.
Anneal Usually refers heating a cold-worked metal to soften it by allowing it to recrystallize. Austenitic or Normalize Heating a ferrous alloy above its upper critical temperature — to the austenite phase on the phase diagram.
Cold-work Plastic deformation of metal usually at room temperature to increase hardness. Solid solution Single crystalline phase containing two or more elements 7.
Solution-annealing 7. Solution annealing Heating a material to and holding it at temperature for long enough to dissolve any carbides followed by rapid cooling to ensure carbides cannot re-precipitate and reduce corrosion resistance. Stress relieved Heating a metal to a suitable temperature and holding for long enough to reduce residual stresses and then cooling slowly enough to minimize the development of new residual stresses 9.
As stated above the tempered martensite is more resistant to SSC than the tempered bainite or mixed structures of the same hardness. Additionally the degree of segregation and the type size shape and distribution of inclusions are other microstructural variables that can influence the resistance to sulfide stress cracking.
This t d bl d illi ti t tili hi h t th t i l i tendency enables drilling operations to utilize high strength materials in zones known to produce H 2 S. Although pH control is acceptable and manageable in drilling operations it is not readily utilized in production scenarios. Maintaining gp y p g a constant pH in production would prove troublesome and impractical. The partial pressure of H2S is defined as the portion of the total pressure associated with the specific component of interest in this case total pressure associated with the specific component of interest in this case H2S.
The partial pressure is calculated by multiplying the total system pressure by the mole fraction of H2S in the gas phase. If the calculated partial pressure of H2S is above 0. Figures 1 and 2 show the relationship to H2S system pressure and partial pressure for gas and multiphase systems as illustrated by NACE pressure for gas and multiphase systems as illustrated by NACE MR edition. Therefore care should be taken to review all factors involved in the material selection.
Understanding this threshold level will enable the designer to ensure that the stresses applied to a material will not result in cracking It needs to be stresses applied to a material will not result in cracking. It needs to be understood that the total stresses working on a material are the combination of both the applied stress i.
The higher the applied stress on a material the more susceptible to SSC it becomes. Cold working will 1 alter the microstructure d 2 i th id l f t il t and 2 increase the residual surface tensile stresses. For this reason heat treatment is recommended for cold worked or cold formed low alloy steels before they are used in a sour environment.
An annealing or normalizing heat treatment will return the material to its original SSC resistance following cold working SSC resistance following cold working.
Therefore additional high strength tubing and casing materials can be utilized above threshold temperatures However if a well is to be completed or operated in threshold temperatures. However if a well is to be completed or operated in a sour zone with a temperature above a threshold temperature for a particular material the engineer must confirm that the environment in contact with the material does not drop below that critical temperature.
Below this temperature these high strength materials are susceptible to SSC and cannot be utilized. Under laboratory controlled conditions it is possible to determine the time to failure laboratory controlled conditions it is possible to determine the time to failure of a given alloy under a particular set of conditions.
However in actual field conditions projecting a time to failure is extremely difficult. The time it takes for a material to fail due to SSC is dependent on the aggressiveness of the environment and the degree of susceptibility of the material.
SSC can happen quickly or may take years to develop Therefore it is critical that a review of quickly or may take years to develop. Therefore it is critical that a review of the materials and environment be conducted prior to specifying the completion equipment.
SSC resistant materials should be utilized.
Hardness by definition is the resistance of a metal to plastic deformation Hardness by definition is the resistance of a metal to plastic deformation usually by an indention. Hardness testers utilize an indenter which is forced into the metal surface by a known loading.
The relationship to the area or yg p depth of the indentions to the load applied is known as the hardness of the material. Controlling hardness is an acceptable method for preventing SSC.
However if hardness control is to be utilized for approving a welding However if hardness control is to be utilized for approving a welding procedure for use in sour services specific locations and numbers of tests must be performed.
These illustrations must be followed for weld procedure qualifications These illustrations must be followed for weld procedure qualifications.