RE: Requirement of NACE MR0175 / SS

[pgoswami]

Hi Idris,

 

As I understand about MR-0175, hardness requirement is only one of the requirements for NACE -0175.To meet NACE 0175 requirements any material has to undergo a series of evaluations so as to justify and meet the design and service requirements in H2S containing environments in oil and gas production.It supplements, but does not replace, the material requirements given in the appropriate design codes, standards or regulations

 

MR0175/ISO 15156 describes general principles, requirements and recommendations for the selection and qualification of metallic materials for service in equipment used in oil and gas production and in natural gas sweetening plants in H2S-containing environments.It addresses all mechanisms of cracking that can be caused by H2S, such as sulfide stress cracking, stress corrosion cracking, hydrogen-induced cracking and stepwise cracking, stress-oriented hydrogen induced cracking, soft zone cracking and galvanically induced hydrogen stress cracking. For all the above cracking to happen BM/WM/HAZ hardness is a very important  factor. Hardness depends a lot of factor, chemical composition,  type of processing and related thermal properties, subsequent heat treatment and others. Hence just by through controlling hardness an alloy does not qualify for NACE MR-0175.

 

Basically any material conforming to NACE MR 0175 has to meet a list of requirements specified by the designer and the requirements have to be met by the manufacturing mill or the suppliers.This applies to any finished product and may apply to welding consumables also.

 

Before selecting or qualifying materials using other parts of NACE MR0175/ISO 15156, the user of the equipment shall define, evaluate and document the service conditions to which materials may be exposed for each application. The defined conditions shall include both intended exposures and unintended exposures which may result from the failure of primary containment or protection methods. Particular attention shall be paid to the quantification of those factors known to affect the susceptibility of materials to cracking caused by H2S.

Factors, other than material properties, known to affect the susceptibility of metallic materials to cracking in H2S service include: H2S partial pressure, in situ pH, the concentration of dissolved chloride or other halide, the presence of elemental sulfur or other oxidant, temperature, galvanic effects, mechanical stress, and time of exposure to contact with a liquid water phase

Materials for NACE environments may be pre-qualified -based on documented service experiences and through laboratory testing.

The above is a general guideline on Material requirements for MR.-0175.If you have any specific problem, query, feel free to ask.

Regarding the other query:- Why does weldable stainless steels (i.e. 316L) contain less carbon than standard grade stainless steels?- TO IMPROVE CORROSION RESISTANCE, ESPECIALLY TO  IMPROVE INTERGRANULAR CORROSION RESISTANCE AND STRESS CORROSION CRACKING RESISTANCE IN SOME MEDIAS, THROUGH CONTROL OF HARDNESS.

 

Hope this will clarify your query.

 

Thanks

 

Pradip Goswami,P.Eng.

Welding & Metallurgical Specialist & Consultant

Email-pgoswami@sympatico.ca,

pgos...@quickclic.net

 

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From: Idris Mohiuddin [mailto:idri...@gmail.com]
Sent: Sunday, January 09, 2011 6:44 AM
To: pgos...@sympatico.ca; pgos...@quickclic.net
Subject: Requirement of NACE MR0175 / SS

Dear sir,

 

Sorry for mailing you on your personal email, but I didnot received any response for this query posted on material & Welding blog.

 

So please answer me for the below mentioned query's:

Please specify In addition to hardness testing, what is the other main requirement in NACE MR0175?

Why does weldable stainless steels (i.e. 316L) contain less carbon than standard grade stainless steels?

 

Thanks in advance

Regards,

 

MIM

Inspection Engineer

FAHSS / TUV

KSA

[Suresh Babu]

Hi Idris,

 

The simple Answers for your query is:

 

Que No.1.  In addition to hardness testing, what is the other main requirement in NACE MR0175?    Answer->           Heat  treatment 

 

Que No.2.Why does weldable stainless steels (i.e. 316L) contain less carbon than standard grade stainless steels? Answer-->  For better weldability for high pressure services, but standard grade is for lower pressure services.

 

Regards,

SURESH.

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[nandakumar pandit]

It is actually concerned with the resistance to corrosion. With lower carbon content in aust. steel the resistivity increases at the sacrifice of physical strength.

Regards
nspandit