PMI on Duplex Stainless Steel and Stainless Steel

Positive Material Identification (PMI) is essential for the various types of stainless steels and corrosion-protection steel alloys.
Hence, PMI is essential for:
Stainless Steel 316, 304, 410, etc;
Duplex Stainless Steel (22% Cr);
Super Duplex Stainless Steel (25% Cr);
Hastelloy;
Inconel;
Monel.

For Duplex Stainless Steel and Stainless Steel valves, PMI is conducted by using PMI XRF portable test gun, pointed at the external surface of completed valves.  Parts of valves to be PMI tested are:
a)  Body,
b)  Bonnet;
c)  Stem (for all valves having externally-exposed stems).

For Duplex Stainless Steel and Stainless Steel, which are the more common materials used for oil and gas industry, the main material composition to be PMI tested are Chromium (Cr), Nickel (Ni) and Molybdenum (Mo).

Composition to be tested are as follows:

Material type	Steel Grade	Cr	Ni	Mo
Stainless Steel Casting	ASTM A351 Gr CF8M	18.0% - 21.0%	9.0% - 12.0%	2.0% - 3.0%
Duplex Stainless Steel Casting	ASTM A890 Gr 4A	21.0% - 23.5%	4.5% - 6.5%	2.5% - 3.5%
Stainless Steel Forging	ASTM A182 Gr F316L	16.0% - 18.0%	10.0% - 15.0%	2.0% - 3.0%
Duplex Stainless Steel Forging	ASTM A182  Gr F51	21.0% - 23.0%	4.5% - 6.5%	2.5% - 3.5%

The above are the most common types of stainless steel and duplex stainless used in valves for petrochemical, oil and gas industry.

For me, as a Quality Control Consultant for the past 2 decades, PMI (positive material identification) is the most important Quality Control practice for ensuring correct valve material, hence, the strength and properties of the specific types of steel.

 

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