Materials of pharmaceutical plant construction
Learning objectives
Enlist the factors affecting selection of plant material
Understand the physical, chemical and economic factors
Classify materials
Discuss the metal and non-metal materials
Enlist the non-ferrous materials
Discuss non-metals used for plant construction
Discuss thermoplastics
Materials of pharmaceutical plant construction
Constructing a pharmaceutical plant is a complex and highly regulated process that demands careful consideration of various materials to ensure the facility meets stringent industry standards. The choice of materials used in pharmaceutical plant construction is critical for maintaining cleanliness, sterility, and compliance with Good Manufacturing Practices (GMP). Here, we’ll explore some of the key materials commonly used in the construction of pharmaceutical plants.
Factors affecting selection of material for pharmaceutical plant construction
The success or failure of s new chemical plant or in the improvement of an existing facility depends on
- Design of equipment-easy to clean, install, operate
- Selection of material-Physical, chemical, Economical
Physical
- Strength: to withstand the stress and and rigours
- Mass: to transport
- Wear and tear: to mill and grind
- Thermal conductivity: evaporators, dryers
- Thermal Expansion: material should maintain size, should not expand.
- Cleansing: Smooth and polished surfaces
- Sterilization: Material should withstand the heat and pressure.
- Transparency: permits the visual observation of reactions and processes.
Chemical
Contamination: Substance’s such as glass, silica, lead, cast iron, steel, tinned iron and variety of alloys are used in construction of pharma plant and most of them produce contamination. Ex: Heavy metals inactivates penicillin, Appearance changes, may be toxic etc
Reactivity with chemicals: At extreme pH, temperature and pressure, materials get corroded.
Economical
Cost of the material plays an important role in the design of the plant.
Cost and utility of the material is studied before making buying decision.
Classification of material
Metal
- Ferrous
- Cast Iron
- Steel Carbon
- Stainless steel
- Non ferrous
- Aluminium
- Nickel
- Lead
Non metal
- Inorganic
- Glass
- Asbestos
- Organic
- Rubber
- Timber
FERROUS METALS
Iron metal is one of the used materials for the construction of plants because of its mechanical strength, abundent availability and lower cost. Some varieties of iron are discussed.
1. Cast iron:
It consists of iron with a proportion of carbon (>15 %). The properties of iron depend on the amount of iron present in it.
Cast iron is abundently available, inexpensive and therefore widely used. A number of types of cast iron are available.
Advantages:
Cast iron is cheap. Therefore, it is used in place of expensive plant material for coating
Since cast iron has low thermal conductivity, it is used for the construction of outer surface of jackets of steam pans.
Low melting temperatures 1140/1200*C
Disadvantages:
Cast iron is very hard and brittle. Therfore, it is difficult to machine. This disadvantage can be overcome by the addition of different materials to improve his performance.
Cast iron is attacked by dil.H2SO4, dil. Nitric acid and dilute as well as con HCl.
It is resistant to conc. H2SO4, nitric acid and alkalis.
Since cast iron has low thermal conductivity, it cannot be used for heat transfer in steels.
Uses:
It is commonly used for the construction of:
- Supports for plant
- Jackets of steam pans
- Linings with enamel, plastic or suitable protective material.
Modification of cast iron: Cast iron is not considered corrosion resistant. The characteristics of cast iron can be altered by alloying with other elements such as silicon, nickel and chromium
Commercial types: duriron and durichlor.
2. Carbon steel
Carbon steel is an iron alloy, which contains only a small % of carbon.
Advantages:
Carbon steel is cheapest. Therefore, it is preferred.
It is easily weldable and is freqently used in fabrication
Disadvantages:
Carbon steel has limited resistance to corrosion. This property can be improved by preparing alloys.
It reacts with caustic soda, brine and sea water. Alloying it can reduce this reactivity.
Uses:
Carbon steel is used for the construction of bars, pipes and plates. It is used to fabricate large storage tanks for water, sulphuric acid, organic solvents etc.
It is used for supporting structures such as grinders and bases for plant vessels.
VARIENTS OF CARBON STEEL:
The properties of carbon steel can be altered by alloying it with other metals. Some of the metals and their properties are:
Nickel (Ni) – improves toughness, corrosion resistance and low temperature properties.
Chromium (Cr)/ increase hardness, more abrasive resistant and resistance to oxidation.
Silicon (Si)/ increase hardness, more abrasive resistant and resistance to oxidation.
Molybdenum (Mb)/ provides strength at elevated temperatures.
3. Stainless steel
It is an alloy of iron. Usually, it contains chromium and nickel, which make the steel corrosion resistant.
Stainless steel is stabilized by the addition of titanium, niobium, and tantalum. Minor amount of other elements such as copper, molybdenum selenium are added. Stainless and steel also has the advantage of ease in fabrication.
The abundant use of stainless steel is due to the properties such as
Heat resistance
Corrosion Resistance
Ease of fabrication
Cleaning and sterilization
Tensile strength
Depending on the composition, stainless steel alloys are available in 3 groups viz., martensitic, ferritic and austenitic.
Alloys of stainless steel (SS): are allowed with other metal so an to modify its properties. The metals incorporated into SS are,
Titanium (Ti)
Niobium (Nb)
Tantalum (Ta)
Chromium (Cr)
Carbon (C)
Silicon (Si)
Nickel (Ni)
Manganese (Mn)
Copper (Cu)
Non Ferrous metals
Aluminium
Lead
Copper
Nickel
Chromium
Silver
Platinum
ALUMINIUM
A number of aluminium items are used in regular day to day life. Aluminium is cheap, light in weight and offers adequate mechanical strength. In addition, aluminium equipment can be easily fabricated. Further, aluminium can be strengthened by cold working. Their maintenance and cleaning is also easy. Hence, its utility is mostly recommended. However the use of aluminium in the construction of plant and equipment is limited.
Advantages:
High resistance to atmospheric conditions, industrial fumes, vapour and fresh or salt waters. Aluminium can be used with conc. Nitric acid (above 82%) and acetic acid.
Thermal conductivity of aluminium is 60% that of pure copper.
Disadvantages:
The mechanical strength decreases greatly above 150*C.
aluminium cannot be used with strong caustic solution.
Many mineral acids attack aluminium.
Oxide and hydro/ oxide films are formed rapidly, when its surface is exposed. Normally this film is thickened by chemical and electrolytic means. This provides so called anodised finishes.
SILVER
Because of its high cost, silver is used only as a material of plant construction in special cases and usually silver coated material is used rather than solid silver.
It is not resistant to concentrated HCl or H2SO4, any strength of nitric acid, and sulphur and sulphur compounds.
It is resistant to organic acids and their salts. It is even more malleable and ductile than copper and, therefore, capable of being readily worked. It has a higher thermal conductivity than all other metals.
A few e.g. of its special uses are – plant for the manufacture of salicylates and acetic acid; a silver/ plated basket for a hydroextracter used in vitamin crystallisation; a solid silver vessel in a cast/ iron jacket for bromination.
TITANIUM
Titanium has become increasingly important as a construction material. It is strong and of medium weight.
Titanium is usually not bothered by impingement attack, crevice corrosion, and pitting attack in seawater. Its general resistance to seawater is excellent.
Titanium is not easy to form, it has a high spring back
NICKEL
Nickel is resistant to oxidation and alkalis but is attacked slowly by dilute mineral acids and rapidly by concentrated acids.
It is resistant to the weak organic acids occuring in pharmaceutical preparations, e.g. citiric, tartaric and stearic.
It is also resistant to phenols. Its salts are non oxic. It is useful for such plant as pans, vats, tanks, mixers, valves, and pumps, nickel wire may be woven to form filter cloths.
CHROMIUM
Although Hard and resistant to corrosion, chromium is not normally used as material of plant construction.
It forms resistant alloy with nickel and, probably, its most important use is in the manufacture of stainless steel.
It is also, of course, used as a plating to protect steel.
Non Metals
Glass
Rubber
Plastic
- Thermosetting Plastic
- Thermoplastic
General properties
Resistant to chemicals
Resistant to contamination
Corrosion resistant
Easy to fabricate
Application
Flooring
Roofing
Windows & doors
Piping
Storage tanks
Insulation materials
Thermosetting Plastic
Permanently shaped to rigid structure during manufacturing.
- Phenol formaldehyde
- Bakelite (cookwear handle)
- Melamine (iron)
Thermoplastic
Soften under the influence of heat
- Poly vinyl Chloride (PVC)
- Polyethylene/Polypropylene
- Polystyrene
- Acrylonitrile Butadiene Styrene (ABS)
- Cellulose Acetate Butyrate (CAB)
Poor resistance to organics
Polyvinyl chloride
Clear, tough, inert
Stabilizer or colorant can be incorporated
Resistant to acids
Resistant to alkali
Crack readily (plasticizer added to reduce this)
Turn yellow when exposed to UV
Polyethylene
Economical
Density (0.91-0.96) determine stiffness, transluscency, vapour transmission
More density-> more stiffness, less permiable, less, resistant to cracking
Pipe of Polyethylene must be fully supported
Stable upto 1200F
Polyporopylene
Good resistance to chemical, acids, alkali
Tough and flexible
Resistance to fatigue (weakening of a material caused by repeatedly applied loads)
Stable upto 2500F
Brittle at low temperature, Used for manufacturing piping systems
Polystyrene
High mechanical strength
Chemical resistant
Rigid
Clear
Easy to scratch
Brittle (rubber or acrylic compounds can be mixed to improve properties)
Stable upto 1900F
Acrylonitrile Butadiene Styrene (ABS)
Acid resistant
Resistant to organic solvents
Not resistant to alkali
Summary
The success or failure of s new chemical plant or in the improvement of an existing facility depends on:
- Design of equipment
- Selection of material
Alloys of stainless steel (SS): are allowed with other metal so an to modify its properties.
A number of aluminium items are used in regular day to day life. Aluminium is cheap, light in weight and offers adequate mechanical strength. In addition, aluminium equipment can be easily fabricated.
Although Hard and resistant to corrosion, chromium is not normally used as material of plant construction. It forms resistant alloy with nickel and, probably, its most important use is in the manufacture of stainless steel.
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Frequently asked questions (FAQ)
Q1: Why is stainless steel a preferred material in pharmaceutical plant construction? A1: Stainless steel is highly corrosion-resistant, durable, and easy to clean, making it ideal for maintaining the cleanliness and sterility required in pharmaceutical manufacturing.
Q2: What type of glass is commonly used in pharmaceutical applications? A2: Borosilicate glass is frequently used due to its resistance to thermal shock, making it suitable for items like sight glasses, laboratory equipment, and vials.
Q3: Are plastics used in pharmaceutical plants, and if so, where? A3: Yes, plastics like high-density polyethylene (HDPE) and polypropylene (PP) are used in non-contact parts such as piping, containers, and packaging materials.
Q4: Why are cleanroom panels necessary in pharmaceutical manufacturing? A4: Cleanroom panels help maintain a sterile environment, ensuring that pharmaceutical products are produced in a controlled, contaminant-free setting.
Q5: What materials are used for pharmaceutical plant flooring, and why? A5: Epoxy and polyurethane coatings are commonly used for pharmaceutical plant flooring due to their easy cleaning, resistance to chemicals, and compliance with regulatory requirements.
Q6: Why are airtight doors and windows important in pharmaceutical facilities? A6: Airtight doors and windows prevent contamination, helping to maintain the required sterile conditions in pharmaceutical manufacturing.
Q7: What materials are used for HVAC ducting in pharmaceutical plants? A7: Stainless steel, aluminum, or galvanized steel are often chosen for HVAC ducting due to their resistance to contamination and ease of cleaning.
Q8: Why is insulation important in pharmaceutical plant construction? A8: Proper insulation, using materials like closed-cell foam or fiberglass, helps maintain temperature and humidity control, which is critical in pharmaceutical manufacturing.
Q9: What materials are commonly used for gaskets and seals in pharmaceutical equipment? A9: Gaskets and seals are often made of materials such as silicone, EPDM, or PTFE to maintain a seal between moving parts and resist chemical corrosion.
Q10: How can I ensure that the materials used in pharmaceutical plant construction meet regulatory requirements? A10: To ensure compliance, it’s essential to work with architects, engineers, and contractors experienced in pharmaceutical construction and to adhere to industry-specific regulations and guidelines.
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