Views: 105 Author: Good Du Publish Time: 2023-03-16 Origin: Site
Butt Weld 90° Elbow is the most commonly used elbow in pipeline installation. It is a pipe fitting that changes the direction of the pipeline in the pipeline system. NACE is the National Association of Corrosion Engineer. NACE MR0175 is the main material selection standard for equipment and pipelines upstream of H2S oil and gas fields. Including underground and ground facilities in oil and gas fields, this standard has been widely adopted and recognized by international oil companies and manufacturers.
Material Requirements of NACE MR0175
1. The materials used should accord with the requirements of NACE MR0175;
2. The material hardness should not exceed 22 HRC;
3. The measured tensile strength of the material should not be greater than 630MPa, and the yield strength should not be greater than 355MPa as specified in the standard;
4. Adopt vacuum degassing process or other alternative process, which is fine grain killed steel;
5. The material should be normalized or normalized+tempered;
6. The non-metallic inclusions A, B, C, and D in the material should not exceed Level 2, and the total number should not exceed Level 4.0;
7. The austenitic grain size of the material should be tested according to ASTM E112, and the average grain size should be grade 7 or finer;
8. Requirements for ultrasonic testing of materials;
9. Chemical composition limit: C ≤ 0.20% S ≤ 0.012% P ≤ 0.015% Ni ＜ 1.0% Mn ≤ 1.0% CE ≤ 0.43 Note: CE=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15;
10. The material should accord with the impact test requirements under MDMT;
11. Material Z-direction tensile requirements;
12. HIC test, Specification: NACE TM0284 solution, A solution Test time, 96h Test evaluation: CLR ≤ 15% CTR ≤ 5% CSR ≤ 2%;
13. SSC test specification: NACE TM0177 solution, A solution test time, 720h threshold stress: 80% AYS (actual yield strength of material).
Material Selection under NACE MRO175
Before selecting or qualifying materials using other parts of NACE MRO175, the user of the equipment shall define, evaluate and document the service conditions to whichmaterials 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 HS.
Factors, other than material properties, known to affect thesusceptibility 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.
The documented service conditions shallbe used for one or more of the following purposes:
a) to provide the basis for selection of pre-qualified SSC/SCC resistant materials ;
b) to provide the basis for qualification and selection based upon documented field experience ;
c) to define the laboratory test requirements to qualify a material for H2S service with respect to one or more of SSC, SCC, HIC,SOHIC,SZC and/or galvanically induced HSC;
d) to provide the basis for the reassessment of the suitability of existing alloys of construction, in the event of changes to the actual or intended service conditions.
Abbreviated Terms in NACE MR0175
BOP Blowout preventer
CRA Corrosion resistant alloy
HAZ Heat-affected zone
HIC Hydrogen-induced cracking
HSC Hydrogen stress cracking
SCC Stress corrosion cracking
SOHIC Stress-oriented hydrogen-induced cracking
SWC Stepwise cracking
SSC Sulfide stress cracking
SZC Soft zone cracking
We(Shanghai Zhucheng Pipe Fittings Manufacturing Co Ltd) is professional engaged in manufacture of Steel pipe(seamless/welded), pipe fittings（butt welding, socket weld, threaded），and flanges in pipe system of all kinds of materials(carbon steel, stainless steel,alloy steel,low temp steel,pipeline steel). In order to get to a successful cooperation with customers, normally we are willing to provide free samples to all customers if required.(The customer should be responsible for the freight and the samples should be in common size and material)