Commonly used Materials and 316L Properties
In the Biotech, Pharmaceutical Industries
By V. Swaminathan, (Swami) Director of Technology
UNIVERSITY MECHANICAL & ENGINEERING CONTRACTORS, INC.
Evolution of materials from the Stone Age of the human life in this planet, is a constant
and continuous process. Starting from using stone as a material until today, we have
developed various materials dictated by need, creating different alloys to meet a variety
of properties like chemical, mechanical, physical, thermal, electrical and magnetic.
Even though there are many basic metal elements like aluminum, copper, iron, nickel, by
mixing these various elements, there are alloys developed and used for different
applications. The following is a list of materials commonly known to our industry.
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•
•
•
•
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Carbon steel like: ASTM A36, A285C, A516-70
Chrome - moly alloy like: ASTM A387, A691
Hast Alloy (various grades)
Ferritic or Martensitic stainless steel like: ASTM A400 series S.S.
Austenitic stainless steel like: ASTM A 300 series S.S.
High nickel alloys like: INCO 600, INCO 625, INCO 800, INCO 825, MONEL 400,
NICKEL 200
TANTALUM (ASTM-B521)
Out of all of these varieties of choice materials, our industry uses mostly T316L, which is
part of the ASTM A300 Series, Austenitic Stainless Steel family.
Although we use these materials in our systems for various applications, we are not
aware of or familiar with the following properties. Whereas, the system design engineer
has to consider these during material selection process for the system.
• Allowable tensile stress (both ambient and at design temperature).
• Also other type of stress like shear, torsional shear, bearing, bending and
compression (both ambient and at design temperatures).
• Modulus of elasticity (Young’s Modulus) at ambient and at design temperature
• Yield strength at ambient and design temperature
• Coefficient of thermal expansion
• Creep strength (at the required temperature)
• Chemical compatibility of the material with the flow media
These properties are important to know while designing any system using any of these
materials. However in our Biotech, Pharmaceutical and Micro Electronics industry the
only primary factor considered for the use of these materials is chemical compatibility of
the material for the application or of the chemistry of the media flowing through.
In addition, other properties like dimensional physical and surface properties are also
considered to be very critical and we should be very familiar with all of these.
TABLE I
Quick reference table for the percentage of chemical composition of T316L grade,
various ASTM designated tubing:
Material
Element
Carbon
(max)
Manganese
(max)
Phosphorus
(max)
Sulfur
(max)
Silicon
Nickel
Chromium
Molybdenum
A213
0.035
A249
0.035
2.00
2.00
0.040
ASTM
A269
0.035
A270
0.035
A511
0.035
A632
0.040@
2.00
2.00
2.00
2.00
0.040
0.040
0.040
0.040
0.040
0.030*
0.030*
0.030*
0.030*
0.030*
0.030*
0.750
10 to 15
16 to 18
2 to 3
0.750
10 to 15
16 to 18
2 to 3
0.750
10 to 15
16 to 18
2 to 3
0.750
10 to 15
16 to 18
2 to 3
1.00@
10 to 15
16 to 18
2 to 3
0.750
10 to 15
16 to 18
2 to 3
Note: All of the above values are in percentages.
*
Even though the ASTM specification permitted value shall be 0.030 maximum,
for achieving good weld we limit the Sulfur content to be 0.005 to 0.017.
@
This value is different than others.
Commonly used
316L STAINLESS STEEL TUBING
Diameter
(In)
0.125
0.250
0.375
0.500
0.750
1.000
1.500
2.000
3.000
4.000
Wall
(In)
0.020
0.035
0.035
0.049
0.065
0.065
0.065
0.065
0.065
0.083
Length
(ft)
10
20
20
20
20
20
20
20
20
20
Dimensional/Physical Properties
Permitted/Variations/Tolerances:
Wall Thickness:
Circularity/Ovality :
(out of roundness)
+/- 10%
+ 1/64” / - 1/32”
or
2% of O.D. (max)
or
+/- 0.01”
whichever is smallest
Straightness/Cylindricity =
Length (up to 24ft. long):
0.01” per ft.
Under 2” Ø = + 1/8” / -0
2” Ø and over = + 3/16” / -0
All of the above are per the ASTM standards.
Surface Finish:
This requirement is special and implemented by our industry.
ID (Surface with media/product contact) = 15 Ra or better and EP.
OD = 30 Ra or better.
Note:
Identifying the surface finish by the grit size is not the proper way.
Advantages of Electro polishing
• Corrosion resistance is maximized by electro polishing because the surface is
equipotentialized - galvanic differences resulting from stress are removed.
• Surface passivation is maximized by electro polishing because the surface
contains very low levels of Fe in zero oxidation states.
• Surface contaminants are minimized because electro polising removes them.
• Surface smoothness is maximized because electro polishing has a leveling
action and can improve surface smoothness by up to 50% as measured by a
surfanalyzer using ANSI B46.1 standard.
SUMMARY / CONCLUSION
The above attempt is to highlight the history of development of various materials, with
emphasis on T316L tubing and its minimum, but not necessarily all requirements. I
would like to conclude with a question, which would be, “Is T316L the only material
available for our use or is there any better material?”
Swami