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IMPROVEMENTS TO MATERIALS QUALIFICATION TESTING – An Update of NORSOK M-710 Rev 2 6 th MERL Oilfield Engineering with Polymers Conference 2008 Glyn MORGAN, Barry THOMSON and Rod MARTIN
IMPROVEMENTS TO MATERIALS QUALIFICATION TESTING An Update of NORSOK M-710 Rev 2 6th MERL Oilfield Engineering with Polymers Conference 2008
Glyn MORGAN, Barry THOMSON and Rod MARTIN
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
2 MERL 2008 slide
Introduction
NORSOK M-710 was developed in the 1990s to improve materials selection and service life assessment of polymers intended for use offshore.
The procedures and intent were partly based on the MERL Seal Life JIP sponsored by many companies present today.
Those procedures are common and relevant to the materials and environment being evaluated and qualified.
Two aspects of material performance are addressed:
chemical ageing (usually sour) rapid Gas Decompression (RGD)
The methodologies have been well established and many materials have been tested.
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
3 MERL 2008 slide
Background
NORSOK M-710 is often the default specification for many operators.
Therefore, many service providers, component suppliers and material suppliers now have to conform to its requirements.
Over the last 6-10 years, all involved have gained experience and the level of polymer knowledge has increased.
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
4 MERL 2008 slide
Background
Therefore, further developments to NORSOK M-710 were recognised as beneficial, based on the following issues:
incorporate new knowledge into M-710 to provide increased confidence in materials selection and use
procedures to reflect service environments as much as possible as well as addressing some of the practical challenges associated with the testwork itself
materials already qualified remain so transition of M-710 into an ISO standard would bring wider acceptance
and industry conformity to materials specification.
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
5 MERL 2008 slide
Revising NORSOK-M710 Rev. 2
AGEING - Chemical versus Physical
Physical changes (swelling, softening) occur when a fluid is absorbed into a polymer causing reversible changes in property level.
Chemical ageing occurs as a chemically-aggressive fluid causes chemical bonds to break or form permanently within the polymer. Property levels change continuously and irreversibly.
Both mechanisms can occur, causing different effects over different timescales and probably at different rates.
Background information and a procedure on how to identify and report these phenomena is proposed to be added to Rev 3 in an accompanying technical note/appendix.
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
6 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
Ageing time
0 10 20 30 40 50 60
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10 STEP 1 Measure property change with time at eachtemperature (T black (service), blue to red)
STEP 2 Plot ln(1/t) vs 1/T and extrapolate to service temperature and hence life
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
7 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
AGEING - Chemically Resistant Materials
Some materials are chemically resistant and their properties do not degrade during the exposure to enable a service life prediction to be made. In other words, only physical ageing occurs (swelling). Eg. unfilled PFTE, PEEK.
Hence it is not possible to establish an Arrhenius plot.
The Standard needs to address this situation and appropriate words are needed which can be proposed for addition to the Standard.
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
8 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
AGEING - Material Reference Points
The current control/reference point is the unaged (dry) polymer (X).
It may be more appropriate to use the oil-soaked (but unaged) material as the reference condition (for tensile property changes); that is, Y.
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
9 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
AGEING - Property Change Criteria
The Standard currently uses a 50% tensile property change as the acceptance criterion (what is relevance of 50% change NOT being attained?)
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Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
10 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
AGEING - Fluids
The current NORSOK fluid consists of an oil, water and gas mixture. The oil has an average solubility parameter which governs its swelling tendency.
Model oils are chosen by mixing three hydrocarbon liquids representing paraffinic (or aliphatic), naphthenic, and aromatic components.
Higher levels of H2S are now frequently encountered which can affect ageing.
It is proposed to add oils with medium and high aromaticity (10, 25 and 40%). A higher level of H2S will also be included (10%).
Completion fluids and other special fluids will be given more prominence in the standard.
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
11 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
AGEING - Checking for Ageing, Test Piece Format, Weighing and Storage
Immersion of aged specimens in a low viscosity solvent will provide an additional check on the influence of hostile species on material crosslink density. Dry first.
Time in solvent (hrs1/2)
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For elastomers, use flat sheet rather than O-rings for ageing tests.
Develop a consistent method for removal, weighing and storage of samples prior to mechanical testing.
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
12 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
AGEING - Summary
Guidance on ageing/non-ageing situations
Service life prediction
Chemically resistant materials
Arrhenius deviations
Material reference points
Failure criterion (or criteria) for tensile properties
Oil composition
H2S level
Post-exposure determination of ageing (swelling)
Test piece format, replication level, weighing/storing procedure
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
13 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
RGD - Introduction
Soak Test Leak Test
The soak test is a materials tests based on inspection which does not necessarily signify that leakage will occur in 4/5-rated seals and not in those rated 3 (although more likely).
NORSOK M-710 not a functional test leave that to ISO 10423 etc.
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
14 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
RGD Introduction
Relationship between RGD resistance, temperature and pressure.
Risk of RGD damage high med low
Low . . . Medium . . . . . Highgas conc. High
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Low modulus, tear strength outweigh high D and low gas
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High modulus, tear strength outweigh low D and high gas
conc.
Increasing temperature
PRESSURE TEMPERATURE
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Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
15 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
RGD Introduction
Ratings for 21 compounds after 1 cycle.
5555, 55555555, 54445555, 44445555, 44435444, 44445430, 41105432, 00004444, 44444444, 44444410, 44004211, 33114000, 10004000, 10001000, 10000000, 00000000, 00000000, 00000000, 00000000, 00000000, 00000000, 0000
GOOD
POOR
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
16 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
RGD Test Piece - O-Ring Section
Currently, the Standard test specimen shall be an O-ring seal of size No. 325 rarely used. The seal section is critical. There is little point testing 5.33 mm O-rings, if the service CS is 6.99 mm. The service section(s) should be tested.
It cannot be assumed that if 5.33 mm passes then all sizes up to this are qualified to the same conditions. It should be possible to justify this if the housing details are identical. If 6.99 mm CS O-rings are being RGD-tested, the test seals are likely to be specially moulded, since the smallest Standard size is BS425.
A table, or series of guidelines is needed to show users the number of variables including size which can contribute to RGD resistance and their relationship with one another. Background info.
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
17 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
RGD Test Piece - Housing
The exposure of constrained materials is useful for obtaining information on the materials behaviour to compare with other materials. However, it may not be representative of how the materials will actually be used in service.
It is proposed that additional tests are added to the Standard where the seal section and the housing geometry should represent service or, if these are not known, representative geometries should be employed in testing.
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
18 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
RGD Test Piece - Large O-Rings
Because of the different volume of material under test, there is a different probability of damage zones within that volume.
In reality, larger O-rings are likely to be used in leak tests. For instance, recent MERL leak testing used O-rings having ODs in the 40-50 mm range. Moreover, the larger the seal, the larger the cell required to house them.
It is proposed to add the requirement for more sectioning for larger O-rings, where the number of sections is related to the size (volume) of the O-ring.
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
19 MERL 2008 slide
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
20 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
RGD Test Variables Gas
Currently, M-710 restricts choice of gas to three: 100% CO2, 97/3 CH4/CO2, 90/10 CH4/CO2.
From these three, a Standard mixture should be specified: 90/10 (the most commonly used in MERL tests).
It is proposed that the gas mixture certification (if purchased) should be part of test report.
Rev 2 also notes that sweet RGD testing qualifies for sour service as well. This is acceptable if substitute gas equivalent to H2S. It is proposed to explore this.
Rev 2 also assumes dry gas use, but even in gas lines there will be treatment chemicals applied. Gas mains (low pressure) is the only obvious dry application. It is proposed to include the use of wet gas if appropriate.
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
21 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
RGD Test Variables Temperature and Pressure
Test temp Test pressure
Rating max Rating max A 50 1 2175 B 82 2 3000 C 100 3 4000 D 121 4 5000 E 150 5 7500 F 177 6 10000 G 200 7 15000 H any 8 any
Current NORSOK minimum ISO 10423 levels
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
22 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
RGD Test Variables Soak Period
The first soak period should be long enough to saturate seals, the larger the seal section, the longer the time that is required to soak. It is proposed that the initial soak period is reduced for small section seals, with justification.
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
23 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
RGD Test Variables Decompression Rate
The depressurization is usually to atmospheric pressure between cycles (worst case but may not represent service). It is proposed that the standard states that de-pressurisations will be to atmospheric pressure, unless required by service conditions.
Time (hrs)
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Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
24 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
RGD - Characterisation of Damage Sectioning of O-Rings
No guidance is given where to section the seal to conduct the inspection. It is possible to section a seal with RGD damage to avoid the damage. It is proposed to add a requirement to section through visible damage.
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
25 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
RGD - Characterisation of RGD Damage Damage Rating System
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
26 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
RGD - Test Certificate
Compound gradeElastomer typeSeal manufacturerLot/batch no.Seal typeSeal sizeNominal CS mmNominal OD mmActual CS (optional) mmActual OD (optional) mm
Temperature CPressure barNo. of cyclesDecompression rate (mean) bar/minGas typeDwell time hr
Seal compression radial/axialSqueeze %Groove fill %Groove width (optional) mmGroove height (optional) mmClearance (optional) mmSeal replication
Test labTest dateTest gas cert ification Y/NTransducer cal info available Y/NP/T log available Y/NMean dwell time hourMean decompression rate bar/min
Crack length reference CS nominal/actualNORSOK ratings
REPLICATE1234
actual
YES
RATING3000, 2000, 1000, 0000
PASS/FAILPASS
10-15 August 2008
YES
44.955.3544.89
YES
19Results
radial1370
4
Ace Test Company
Housing details
General
1
RGD test conditions; required
Material
5.33
3501020
90/10 CH4/CO2
120
1110, 1000, 1000, 10001100, 1100, 1100, 00003120, 1000, 0000, 0000
PASSPASSPASS
2344rw4r/07O-ringBS 324
STAMP/SIGNATURE
ABC1HNBRAcme Seals, Inc
1.05
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
27 MERL 2008 slide
Revising of NORSOK-M710 Rev. 2
Test Plan
To validate all these points, a large test plan has been embarked upon, the details of which are in the paper. In summary:
AGEING RGD
Aromaticity, % H2S Align conditions across Standards
Chemical vs physical. Mech. ref. point Does big CS qualify smaller sections?
Failure criteria >> service life predictn Squeeze, groove fill, housing design
Curve fitting methods Large diameter rings (sectioning)
Ageing check H2S substitute
Weighing/storage procedure Decompn rate, ramped, to > atmos. P
Dwell time, no. cycles, 1 and 5 cycle
Degas conditions
Damage characterisation
Improvements to Materials Qualification Testing An Update of NORSOK M-710 Rev 2
28 MERL 2008 slide
Summary
The intention of the JIP is to produce a comprehensive and robust revision of NORSOK M-710 that can be understood by novice specifying engineers and polymer experts alike.
Changes implemented will be reinforced by testwork.
This experience will be used to support ISO TC67 WG7 to draft the documents for ISO 23936 Parts 1 (Thermoplastics) and 2 (Elastomers).
Once these ISO documents are accepted, NORSOK M-710 will be phased out.
IMPROVEMENTS TO MATERIALS QUALIFICATION TESTING An Update of NORSOK M-710 Rev 2 6th MERL Oilfield Engineering with PolymersIntroductionBackgroundBackgroundRevising NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Revising of NORSOK-M710 Rev. 2Summary
