Changes
to NACE Standard MR0175-2003
The following information is intended to
provide strategy and guide users through the new
edition of MR0175, but it does not provide
interpretations.
Purpose
of Revisions:
Work was begun in 1995 to make NACE
Standard MR0175, Metals for Sulfide Stress Cracking
and Stress Corrosion Cracking Resistance in
Sour Oilfield Environments,” an ISO standard.
This was agreed and discussed at
CORROSION/1996 in
However, the groundwork was laid beginning
as early as 1950. After World War II, people
became interested in providing gas to industry.
As a result of gas discoveries, several technical
committee reports, including 1A152, “Sour Oil Well
Corrosion,” and 1B159, “Well Completion
and Corrosion Control of High-Pressure Gas
Wells,” were published during the 1950s.
In the 1960s, Unit Committee T-1B on
Corrosion in Oil and Gas Well Equipment,
published NACE Publication 1B163, “Recommendations
on Materials for Sour Service,” which
included Tentative Specifications 150 on valves, 51
on severe weight loss, 60 on tubular goods,
and 50 on nominal weight loss. Then the report
considered to be MR0175’s predecessor, NACE
Publication 1F166, “Sulfide
Cracking-Resistant Metallic Materials for Valves for Production and
Pipeline Service,” was published.
In the 1970s, the industry began dealing
with harsher environments, so metals needed to be able
to withstand higher temperatures and higher
pressures, and 41XX tubulars and high-strength
CRAs were introduced. 1F166 was revised in
1973, and in 1975 the original version of
MR0175, “Materials for Valves for
Resistance to Sulfide Stress Cracking in Production and
Pipeline Service,” was published. MR0175 was revised in 1978, and NACE
Standard TM0177,
“Testing of Metals for Resistance to
Sulfide Stress Cracking at Ambient Temperatures,” was
published as a complement to MR0175.
During the 1980s, operators continued to
search for materials resistant to harsh environments.
Technology improved, and laboratory testing
and CRAs were prevalent. NACE Standard
TM0284, “Evaluation of Pipeline Steels for
Resistance to Stepwise Cracking,” another
complementary standard, was published. Yearly updates to
MR0175 started in 1988 and have
continued until 2003.
In the 1990s, technology changed again in
response to the
milder environment. Users began asking whether
the same restrictions on strength were needed
for materials in this environment. Hardness
vs. H2S limits was discussed. Several standards
and
reports were published, including European
Federation of Corrosion (EFC) #16, “Guidelines on
materials requirements for carbon and low alloy
steels for H2S-containing environments in oil
and gas production,” and EFC #17, “Corrosion
resistant alloys for oil and gas production:
guidelines on general requirements and test methods
for H2S service.” The EFC developed
domains, and Vickers weld hardness testing came
into use. Stepwise cracking (SWC), stressoriented
hydrogen-induced cracking (SOHIC), and soft-zone cracking
(SZC) began to be
industry problems and EFC included information on
these, which were not covered by MR0175.
Partially in response to these concerns,
the “rewrite” of MR0175 was begun in 1995 and a
proposal to ISO was made to prepare an
international standard to cover the needed topics. ISO
approved the work item to write a standard to
address material requirements in H2S
service.
NACE and EFC members became co-leaders of
the ISO/TC 67/WG 7 project, which is now
nearing completion (ISO
15156, “Petroleum and natural gas industries—Materials for use in H2S
containing environments in oil and gas
production”). The plan is for
this ISO standard to merge
with MR0175 in 2004, and the new standard will
be designated NACE MR0175/ISO 15156 in
the
working closely to make sure the two documents are
technically aligned prior to the merger, and
a Maintenance Panel has been formed to
maintain the combined standard. An oversight
committee, NACE Task Group 299, has also been formed
to vote on changes to the standard.
Changes will then be submitted to ISO/TC 67
for vote.
This achievement was made possible because
of an identified industry need, funding made
available for parts of the effort, dedication of
many people including EFC and NACE volunteers,
NACE staff support,
and ISO support. NACE committee leaders involved in this effort are
excited about the new direction for this
world-recognized standard.
The impact of MR0175 on mitigating cracking
has been very high, and overall, use of MR0175
has reduced the cost of materials.
MR0175 is not expected to be technically
changed before it is combined with ISO 15156. ISO
15156 is in a different format, with most
information provided in tables, so it will not look the
same, but it will be technically equivalent.
Committee leaders are working on making sure the
technical explanations are correct.
Interpretations:
The Maintenance Panel will handle
interpretations, similar to the way NACE Task Group 081
handled requests for interpretation of MR0175.
There may be a delay in the short term regarding
getting replies to inquirers, until the process is
refined.
Three
Objectives for Maintenance Panel:
50-50 split between users and manufacturers
and international vs. domestic, with 2 not from
Europe or
chance to serve.
There is much more of a need for the user
to talk to the materials supplier. The ISO approach to
CRAs is identical to that of NACE Standard MR0175.
MR0175-2003
One of the most important paragraphs in the
2003 edition of MR0175 is 1.2 on Procurement.
The first sentence states, “It is the
responsibility of the user to determine the operating conditions
and to specify when the standard applies.” A
definition of user has been added to the Definitions
section:
“User: Someone who is responsible for operating
the equipment that is installed and operated in
the field.”
The task group tried to define who is
ultimately responsible for materials selection. There are
two more sentences on responsibility: “The manufacturer
is responsible for meeting
metallurgical requirements. It is the user’s responsibility
to ensure that a material will be
satisfactory in the intended environment.”
Paragraph 1.6.2 is a disclaimer-type of
statement: “Materials included in this standard are
resistant to, but not necessarily immune
to, SSC and/or SCC in stated conditions. Improper
design, manufacturing, installation,
selection, or handling can cause resistant materials to
become susceptible to SSC and/or SCC.” This is telling the user: You are
responsible for
materials selection. We cannot guarantee successful
use or no failures or cracking, etc.
Paragraph 1.7 or 1.7.2: The task group has
been asked more questions on this than any other
paragraph, and inquirers are more often not
satisfied with the reply: “This is not a quality
assurance document.” These are voluntary guidelines;
it is up to the user to determine how many
test to take, where to take tests, etc. THIS
HAS NOT CHANGED.
The new edition spells out more clearly
that materials selection is up to the user—NACE cannot
give advice and will not get involved in
negotiations or a dispute between users and
manufacturers. Paragraph 1.8.3.3.3 describes how
materials are listed in the standard, and a
diagram on the same page gives a “Road Map” for
navigating the standard.
Paragraph 1.10.2 is new. In the past, the
way the general section was used was that “If I
purchased an alloy in the past and used it for a
Christmas tree, if I replace it, I have to use
material that is acceptable according to the new
MR0175.” In the new standard, “I can continue
to use existing materials, if I feel the
field has stayed the same, etc.” Companies may be using
marginal alloys that have worked out all right.
The title of Section 4 has been changed to
include alloys for general use that are not covered in
Section 3. Another problem in the old MR0175 was a
“laundry list” of alloys—frequently
people requested an interpretation, saying they
had an alloy that “looks like __ SS, but it is
*__SS.” The result would be a ballot for this
material, and the committee received feedback
expressing frustration. Therefore, the task group
created alloy categories, with limits for a
particular category so that all 300 SS would fit
within it.
However, it isn’t that simple, so there are
categories with specific alloy requirements.
Following the general Sections 3 and 4,
there are sections on specific equipment and the
requirements—this is the most changed area. The
committee reinserted alloys from the general
section that are no longer there and put them in
Sections 9 and 10 with restrictions on
environmental limits for wellheads and Christmas trees,
e.g., 17-4 PH (UNS S17400) and UNS
N04400.
Sometimes a specific type of equipment is
prohibited for general use. Section 10 is designed to
give more flexibility to certain types of
equipment. The user must review the requirements.
New sections (Sections 13, 14, and 15) have
been added to the end of the standard, giving
guidance on the ballot process. Section 16, “Materials
for Application-Specific Cases Without
Proposing Adding New Materials to MR0175,”
was added to be consistent with the ISO strategy.
Users may submit their own data to support
usage in the following instances:
(1) alloys in the specific categories outside
MR0175,
(2) alloys
included in MR0175 but used outside the acceptable environments of MR0175, or
(3) alloys not
listed in MR0175 and not included in a specific category.
NACE will make these data available to the
public. In some cases these data may lead to
changes in NACE MR0175/ISO 15156, or the user may
decide to propose changes in the
standard—in this case the user must submit a
proposal to the Maintenance Panel.
Some new materials are harder and stronger,
and it may be possible to use them in H2S
service.
Users may submit data supporting the use of
materials that are not listed or are outside the scope
of the standard.
If a manufacturer simply wants to make data
available to customers, that is acceptable, but if the
manufacturer wishes to change industry’s mind, data
need to be submitted to NACE. It is the
committee’s attempt to give people another opportunity
and not to restrict usage unnecessarily.
However, manufacturers may have trouble
marketing to some customers. The user must accept
responsibility for materials selection. Even if data are
not within environmental limits, others
may still review the data if they are
submitted to NACE. Data give confidence that “if I engage
in a testing program and show successful
results, I can use the material.”
Question: If a manufacturer decides to qualify a
material outside the standard and above the
limits, is he required to inform the user and get
his approval? Answer:
The user is responsible
for what he uses. The manufacturer is not responsible
for what actually goes into the well.
Question:
Will the ISO document solve the
problems with black-and-white tables? Answer:
Tables will not require interpretations
because it will be black and white.
For detailed information on ISO 15156, refer
to Paper #03090 presented at CORROSION/2003
(available via the
NACE Store at www.nace.org).
http://www.nace.org/nace/content/technical/MR0175/MR0175Changes.pdf