November 2004
Full contents
Introduction to NACE standard MR0103
U the materials to reduce sulfide stress cracking in corrosive refinery environments
Many process streams in petroleum refineries contain enough H 2S to cau sulfide stress cracking (SSC) in susceptible materials. Until recently, however, no industry standard was available that covered material requirements for sour refinery rvice. In April 2003, NACE International relead MR0103, “Materials Resistant to Sulfide Stress Cracking in Corrosive Petroleum Refining Environments.”1 Several motivating factors led to the development:
Although refineries sometimes specify materials compliant with NACE MR0175,2
application practices varied widely among engineering contractors and urs.
Refinery “sour” environments are quite different from the sour environment definitions provided in MR0175.
MR0175 was being revid to address chloride stress corrosion cracking, resulting in unnecessary environmental restrictions on some materials commonly ud in refinery applications.
The MR0103 document us borrowed concepts and requirements from various versions of MR0175 with modifications and additions as needed to create a new standard that meets
industry needs. For example, MR0103 utilizes the alloy grouping philosophy that is ud in what is now NACE MR0175/ISO 15156, but did not implement environmental limits such as H 2S partial pressures, temperature limits, pH restrictions, etc. Materials and material condition requirements are bad on a mix of MR0175 requirements and refinery-specific experience. There are veral major differences between MR0103 and MR0175/ISO 15156:
The refinery standard guidelines for determining whether an environment is “sour” are quite different from the sour environment definitions provided in previous and current versions of MR0175.
The refinery standard does not include environmental restrictions on materials.
Materials and/or material conditions are included in MR0103 that are not listed in MR0175/ISO 15156.
夸夸我的老师Materials and/or material conditions are included in previous and/or current versions of MR0175/ISO 15156 that are not listed in MR0103.
Becau welding is prevalent in refinery piping and equipment, MR0103 places extra emphasis on welding controls in veral material groups, most notably the carbon steels. Applicability of MR0103. Both MR0175 and MR0103 include ctions that describe applicability of each of the standards. Both describe material factors and environmental factors, and provide guidelines to the ur on how the standard should be applied. Note that both standards require the ur to specify whether the environmental conditions are such that the material requirements of the standard should be applied.
D. R. BUSH, Emerson Process Management / Fisher Controls Intl. LLC, Marshalltown, Iowa, J.
C. BROWN, Motiva Enterpris, Convent, Louisiana, and K. R. LEWIS, Shell Global Solutions Intl., BV, Amsterdam, The Netherlands.
Comments? Write:
One of the key differences between the MR0175 and MR0103 standards lies in the guidelines addressing the environmental conditions under which SSC is likely to occur. MR0103 covers a broad
er range of sour environment conditions experienced in downstream process units. The guidelines are bad on:
Ur's plant experience and practices
Existing NACE and industry recommended practices and reports (i.e., NACE RP0296,3 8X194,4 8X294,5 API Publication 5816)
A fundamental understanding of atomic hydrogen generation in the sour rvice corrosion
reaction and the subquent rate of hydrogen flux into the process-contacted steel, i.e.,
S and HCN.
combined effects of pH, H
2
A significant difference between upstream and downstream sour environments is that, in many refinery sour water environments, dissolved ammonia is prent. This increas the pH, thereby increasing the solubility of H
S, which in turn increas the bisulfide ion concentration and
2
corrosivity. Ammonium bisulfide corrosion in the high-pH environments generates a relatively high rate of hydrogen flux.
Furthermore, the prence of cyanides at an elevated pH further aggravates the degree of atomic charging and hydrogen flux into the steel by poisoning the surface reaction that results in a stable and protective iron sulfide scale from forming.
The outcome of the connsus approach has resulted in the following guidelines on what constitutes a sour rvice in downstream units.
钟楼怪人动画片The fluid must contain a free water pha and:
毕业证认证>50 ppmw dissolved H2S in the free water (in recognition that significant levels of
S can result in SSC even in low-pressure systems), or
dissolved H
2
A free water pH <4 and some dissolved H2S prent (in recognition that in low-pH
environments, significant charging of materials with atomic hydrogen can take place
S level), or
irrespective of H
2
A free-water pH >7.6 and >20 ppmw hydrogen cyanide ion (HCN) and some H2S
dissolved in the free water (in recognition that at high pH, the HCN ion is stable and
results in significant charging of ferritic materials by poisoning the formation of a protective iron sulfide scale), or
>0.0003 MPa abs (0.05 psia) partial pressure H2S in a process with a gas pha (bad on the historical MR0175 definition of sour rvice, without the 0.4 MPa abs [65 psia]
minimum pressure requirement).
Another key difference between MR0175 and MR0103 is that MR0103 allows the ur to supplement the environmental guidelines in the standard with actual plant experience and risk-bad analysis to determine whether the material requirements of the standard need to be applied. When making this determination, the ur is expected to consider all plant operating scenarios, including operational upts, startup/ shutdown conditions, etc.
Materials of construction.
Carbon steels. For the most part, refineries u carbon steels classified as P-No. 1 Group 1 or 2 in Section IX of the ASME Boiler and Pressure Vesl Code for piping and vesls.7
MR0103 impos no ba metal hardness requirements on the materials becau the grades have maximum tensile strength requirements that effectively limit their bulk hardness. Other carbon steels must meet a 22 HRC maximum requirement.
MR0103 shares the following requirements with MR0175:
Carbon steels must be in one of the following heat treatment conditions:
a.Hot-rolled
arxb.Annealed
c.Normalized
d.Normalized and tempered
e.Normalized, austenitized, quenched and tempered
f.Austenitized, quenched and tempered.
Carbon steel materials that are cold worked to produce outer fiber deformation greater than 5% must be stress relieved to ensure that the material is below 22 HRC.
Welding carbon steels. Welding introduces the potential for creating hard regions in carbon steels. As such, controls must be impod to ensure that weldments will be soft enough to resist SSC in rvice.
MR0103 requires that welds in P-No. 1 carbon steel materials be performed per the methods outline
d in NACE Standard RP0472.8 RP0472 requires that the weld deposit meet a hardness limit of 200 HBW maximum. It requires control of heat-affected zone (HAZ) hardness by one of the following methods:
Post-weld heat treatment
out of sightaudience复数Ba metal chemistry controls, usually via a specified maximum carbon equivalent and limits on elements such as niobium, vanadium and boron. Carbon equivalent is defined as: Array
cork
Custom welding procedure utilizing a combination of welding process controls, ba metal chemistry controls (usually less restrictive than method 2 above) and a hardness traver conducted on the procedure qualification specimen demonstrating that the hardness does not exceed 248 HV in the HAZ.
Alloy steels. MR0103 defines alloy steels as tho with a chromium content of less than 10%. Total alloying element content can exceed 10%. In practical terms, alloy steels in MR0103 are tho steels that contain alloying elements greater than the amounts allowed in carbon steels, but which do not contain enough chromium to be considered stainless steels.
Alloy steels with assigned P-Numbers in Section IX of the ASME Boiler and Pressure Vesl
Code are required to meet the hardness requirements shown in Table 1.
Alloy steels without P-Number assignments must meet a 22 HRC maximum hardness requirement, the same as in the various MR0175 revisions.
程度英语Welding alloy steels. MR0103 includes very specific information about welding alloy steels. It allows welding P-Number 3 and 4 materials without PWHT in cas where the practice is allowed per ANSI/NB-23.9 In other cas, PWHT is required. In all cas, with or without PWHT, a hardness traver is required on the PQR specimen to demonstrate that the procedure will produce weldments with hardness values below 248 HV.
Martensitic stainless steels. Only specific alloys are listed as acceptable, with specific heat treatment and maximum hardness requirements. The martensitic stainless steel alloys most commonly ud in sour applications are S41000, its cast equivalent, CA15 and CA6NM. The alloys are required to be double-tempered and meet maximum hardness requirements of 22 HRC, 22 HRC and 23 HRC, respectively.
Welding martensitic stainless steels. For S41000, CA15, and CA6NM, the ba material is required to be in the double-tempered condition prior to welding. Weldments in S41000 or CA15 must be PWHT at 1,150°F (620°C) minimum to produce a maximum weldment hardness of 22 HRC. Weldme
nts in CA6NM must be double-tempered per the same requirements as the ba metal to produce a maximum weldment hardness of 23 HRC.
Precipitation-hardenable martensitic stainless steels. MR0103 includes wrought S17400, S15500, and cast CB7Cu-1 and CB7Cu-2 in the general ction. The materials are all acceptable in either the double-H1150 or H1150M conditions. The maximum hardness requirements are the same as tho specified in the MR0175 documents – 33 HRC maximum for the wrought grades, and 310 HBW (30 HRC) for the castings. S17400 or S15500 pressure-retaining bolting is required to be in the H1150M condition with a maximum hardness limit of 29 HRC. S45000 is allowed with a single-step precipitation-hardening treatment and a maximum hardness limit of 31 HRC.
Austenitic stainless steels. The acceptable austenitic stainless steel alloys are defined by a general composition requirement as shown in Table 2.
General composition requirements allow u of many grades of stainless steel that are covered
under non-US standards and, as such, were technically unacceptable under MR0175-2002 and previous versions. Austenitic stainless steel materials are required to be in the solution-annealed or solution-annealed and thermally stabilized condition, must be free from cold work intended to enhance mechanical properties and must meet a maximum hardness requirement of 22 HRC. Free-machining alloys containing lead or lenium are not acceptable.
Specific austenitic stainless steel grades. MR0103 contains only one specific grade of austenitic stainless steel that doesn't fit into the standard austenitic stainless steel definition –
S20910. This material is `allowed in the solution-annealed, hot-rolled or cold-worked condition at 35 HRC maximum hardness. All of the conditions are listed in the general ction, indicating that all are acceptable for general u.
Highly alloyed austenitic (superaustenitic) stainless steels. The highly alloyed austenitic stainless steels (commonly called superaustenitic stainless steels) are defined in MR0103 and MR0175-2003 as follows:
%Ni + (2 × %Mo) >30 and Mo >2%
不给力英文or
Pitting resistance equivalent number (PREN) >40%
where PREN is determined as:
PREN = %Cr + 3.3 × (%Mo + 0.5 × %W) + 16 × %N
The materials are acceptable per MR0103 in the solution-annealed or solution-annealed and cold-worked conditions with a hardness requirement of 35 HRC maximum.
ancient是什么意思Duplex stainless steels. MR0103 allows wrought and cast duplex stainless steels in the solution-annealed and liquid-quenched condition to 28 HRC maximum. The material must have a ferrite content of 35 – 65%, and heat treatments to increa strength or hardness are not allowed.
Welding duplex stainless steel. To ensure that production welds in duplex stainless steels posss the correct microstructure and hardness, MR0103 requires that the PQR and resulting WPS include the following:
The PQR must include a Vickers hardness traver demonstrating an average value of 310 HV maximum with no individual reading exceeding 320 HV.
The PQR must include examination of the weld deposit and HAZ conducted in accordance with ASTM E562, demonstrating a ferrite content of 35 to 65 vol%.
The PQR must indicate the heat input ud during creating the PQR specimen. The WPS must restrict the heat input to the same value ±10%.
The PQR must list the PQR specimen thickness, and the WPS must restrict welding in production to components with wall thickness that do not deviate by more than 20%
from that of the PQR specimen thickness.
Nickel alloys. Most of the acceptable solid-solution nickel alloys are covered by two compositional definitions:
9.0% Cr minimum, 29.5% Ni + Co minimum, and 2.5% Mo minimum
or
