Introduction to NACE MR0175 pipe and fittings
Steel pipe and related fittings which are made from the NACE material (complied with NACE MR 0175 or ISO 15156 standard). We call them NACE pipe, or NACE pipe fittings.
Therefore, these products are specially used in the oil and gas environments that contain the H2S etc corrosive chemicals.
Chemical Composition
For carbon and alloy steel pipes, NACE MR0175 has limits for content Sulfur (S ≤ 0.002%), Phosphorus (P ≤ 0.020%) and Carbon (C ≤ 0.10%).
Mechanical Strength
Mechanical properties of tensile strength, and yield strength is same with general pipes referred to corresponding standards.
NACE MR0175 seamless steel pipes
NACE Test Methods
For sour service steel pipe, plate, fittings, commonly there are two test methods referred NACE. HIC and SSC.
HIC is Hydrogen Induced Cracking. HIC test is a mandatory test for NACE pipe and fittings. But if there is certificate to proof the material (Raw material for making pipes or fittings) comply to NACE MR0175, then there is no need to do this test again.
SSC is Sulfide Stress Cracking. SSC test is a long time lasting experiment. The test is specially to alloy steel, to put test material in corrosion environment plus with constant pulling force (Under situation of working force and metal inside force). In these two factors (Corrosion + Force) affects, material havs the brittle rupture. So this is SSC cracking.
(SSC cracking is one of the most harmful corrosion types, during corrosion, if there is any small cracks, the broken speed is far more soon than other type of corrosion. So SSC corrosion is an “Corrosion Disaster”. This happened in Bridge damage, Airplane accidents, boiler tank explosion. These are bring big loss for people’s life and property. Other than this, power station, Ship, boiler tank, petroleum industries all happened SSC accidents.)
NACE MR0175 180 Degree Elbows
NACE MR0175 pipe and fittings Applications
The material shall be used in water-containing liquid and media which include all kinds of gas, or H2S containing crude oil, the H2S absolute partial pressure ≥0.0003 Mpa (0.05 psia).
On the other hand, under these conditions there is no need apply to MR0175. (It’s up to users.)
- Low pressure gas: the total pressure is lower than 0.4 MPa (65 psia).
- Low pressure gas and oil multi phases media: the total pressure is lower than 1.83 MPa.
MR0175 standards of general material requirements for selecting of cracking-resistant material, cracking-resistant carbon and low-alloys steels, cast irons, cracking-resistant alloys and other alloys. And details requirements for H2S containing equipment.
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