INTRODUCTION TO MATRIAL SELECTION AS PER GMP GUIDELINES:
Unit Operations in manufacturing industries such as Pharmaceutical, Foods, Cosmetics and in some cases Chemicals many a times deal with corrosive environment. The ingredients and the parameters in used may lead to serious corrosion leading to erosion of the process equipments, followed by contamination and cultivation of impurities in the end product. Therefore, selection of the Material of Construction of the machines or equipments become the most important paramter.
As a Process Design Engineer, the ideal reasoning behind making appropriate selection of MOC should be in accordance with the following premises:
# Does the Unit Operation Or Process demand Or needs to follow a statutory mandate Or Standard, such that it has to be a corrosion-proof operation?
# Even if it doesn't, are there any chances of corrosion taking place during the reaction or during the course of the operation?
# Does the operation under consideration involves elevated temperatures/pressures Or use of salts or acids Or use of Halides Or other corrosion provoking materials?
# Does it involve too complex a process Or involves highly expensive Or sensitive products?
# How can the MOC selection increase the longevity of the equipments and hence help build on ROI and Profit?
UNDERSTANDING THE GUIDELINES AND LIMITING PRICIPLES USED IN SELECTION OF MATERIAL (METALS) FOR FABRICATION:
GMP (Good Manufacturing Practice) and cGMP (Current Good Manufacturing Practice): These are the regulations which are mandated by the FDA i.e. Food and Drugs Administration.
Usually, the FDA controls and regulate the quality parameters applicable in industries like Food manufacturing, Medicines manufacturing etc. GMP guidelines have been especially formulated as a preventive and corrective measure on the possible grave quality issues, hence are mandatory and statutory in most of the cases.
GMP and cGMP guidelines (especially applicable for the process equipments) revolve around the premise of protecting the equipment from any kind of corrosion, thus, preventing the product from contamination. Some examples includes the High Quality Surface Finish of an equipment, smooth and buffed, crevice free surface, absence of any sharp corner Or edge etc.
CORROSION, TYPES AND REMEDIES: Corrosion is a phenomenon by which the material (especially metals) deteriorates Or gets eroded Or degraded in terms of its mass, shape, size and volume under the influence of the surrounding parameters. These changes takes place at a molecular level, wherein electrons flow from one part of the metal to another part. The part from where the flow of electrons starts gets eroded.
(Pic Ref: www dot sciencedirect dot com slash topics slash materials-science slash crevice-corrosion)
IMPORTANT METALS USED IN PHARMACEUTICAL, FOOD, COSMETICS AND CHEMICAL MANUFACTURING PROCESS:
Selection of the material of construction for the process equipments becomes easy upon understanding the concepts like Corrosion, GMP, Non- GMP etc.
GMP guidelines asks for Corrosion-Resistant material to be used for construction of the process equipments. Hence, Stainless Steel and some other alloy steels mostly becomes the natural choice for the construction of the Equipments used for Pharmaceutical, Nutraceutical, Herbal and Food production.
Inorder to discuss about the Alloy Steel and other types of Austenitic Stainless Steel (i.e. specially heat treated alloy steel containing Chromium and Nickel), lets first understand the properties and importance or the components of the most common Alloy Steels.
Chromium (Cr): Imparts the lustrous finish to the alloy. Improves corrosion resistance properties. Most importantly, allows the alloy to withstand a very high temperature.
Nickel (Ni): Imparts Hardness, Ductility and Formability to the alloy steel.
Carbon (C): Imparts Hardness and Strength to the alloy steel. However, lower is the Carbon content, higher is the corrosion resistance.
Molibdenum (Mb): Improves metal surface properties such that the pitting and surface unevenness is minimized.
Titanium (Ti): Imparts Hardness, Ductility and Formability to the alloy steel.
Manganese (Mn): Imparts Strength, Toughness and Hardenability of the alloy steel.
Let's see some of the common types of Alloy Steels used as per GMP and GMP guidelines.
SS316 (ASTM A240/ ASME SA 240 Grade 316 Stainless Steel Sheet):
(Cr - 16 to 18%, Ni - 10 to 14%, Mo - 2 to 3%, C - 0.08%, Mn - 2%)
SS316L (ASTM A240/ ASME SA 240 Grade 316 Stainless Steel Sheet):
(Cr - 16 to 18%, Ni - 10 to 14%, Mo - 2 to 3%, C - 0.03%, Mn - 2%)
SS304 (ASTM A240/ ASME SA 240 Grade 304 Stainless Steel Sheet):
(Cr - 18 to 20%, Ni - 8 to 10.5%, Mo - Not Applicable, C - 0.08%, Mn - 2%)
SS304L (ASTM A240/ ASME SA 240 Grade 316 Stainless Steel Sheet):
(Cr - 18 to 20%, Ni - 8 to 12%, Mo - Not Applicable, C - 0.03%, Mn - 2%)
SS321 (ASTM A240/ ASME SA 240 Grade 321 Stainless Steel Sheet):
(Cr - 17 to 19%, Ni - 9 to 12%, Mo - Not Applicable, C - 0.08%, Mn - 2%)
Hastelloy C22 (UNS N06022, Alloy C22):
(Cr - 20 to 22.5%, Ni - 50 to 55%, Mo - 12.5 to 14.5%, C - 0.01%, Mn - 0.5%, CO - 2.5%, Fe - 2 to 6%, P - 0.02%, Si - 0.08%, S - 0.02%, W - 2.5 to 3.5%, V - 0.35%)
Hastelloy C276 (UNS N10276, Alloy C276, Inconel 276):
(Cr - 14.5 to 16.5%, Ni - 50 to 55%, Mo - 15 to 17%, C - 0.01%, Mn - 1%, CO - 2.5%, Fe - 4 to 7%, P - 0.04%, Si - 0.08%, S - 0.03%, W - 3 to 4.5%, V - 0.35%)
Please watch out for the next part of this blogpost emphasizing more on Types of Corrosion and Live Examples of failures of Pharma Equipments!
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