Requirement of NACE MR0175 pipe
SSC Cracking factors
Sulfide Stress cracking affected by following factors:
1) Subjected by chemical ingredients, hot treatment and micro structural etc. Influences metallurgy conditions and strength.
2) Hydrogen iron concentration in aqueous phase (Ph index)
3) H2S partial pressure, that is H2S concentration and the overall absolute pressure ratio.
4) Total tensile stress
6) Exposure time to acid environment
7) Power storage effect
8) Chloride or other halide ions concentration
9) Oxidizing agent
10) Non-secondary fluid (including fluid used for acid excitation and packers)
As a matter of fact,pipe corrosion speed also influenced by cold working of metal.
Although steel pipes, pipe fittings, production and equipment meets the standard NACE MR 0175, have the function of anti-H2S corrosion. But in case unsuitable design, manufacturing, installation, material’s choosing and processing etc, all these factor could leading corrosion-resistant materials to sensitivity.
Material Cost of NACE MR0175 than General pipe
The price for NACE pipe itself is not too much higher than general steel pipe, (Especially for API 5L pipe or ASTM A106 pipe, the price is higher but not more than 100 dollars).
On the other hand, the hard and expensive part is HIC and SSC test fees. If the quantity is very less, and there is no stock available, it is almost impossible to get this material.
Working conditions for the NACE MR 0175 steel pipe
The standard should suitable for destruction by SSC or SCC in H2S containing productions and equipment in the following conditions:
1) Resulting in equipment cannot work as usual under pressure.
2) Could not make sure to bear the pressure of the system.
3) Lead to equipment basic function cannot sustain. But under usual or low pressure.
It shall be noted that,to choose the NACE material in these working conditions: such as water treatment equipment, sucker rods and liquid pump etc. All these products have detailed specifications, but not belong NACE MR0175 standards scope.
Things you should know before purchase NACE MR0175 steel pipe and fittings
The responsibility of users is to make sure whether the standards is suitable for the work conditions.
The materials of NACE steel pipe and fittings that included by this standards could be used for any given parts.
From manufacturers side, their responsibility is to make sure the specified material satisfied requirements of metallurgy, while the users’ responsibility is to make sure selecting the right material for the environments.
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