Stainless Steel in the Pharmaceutical Industry

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For a number of years now, stainless steel has enjoyed widespread popularity in the pharmaceuticals industry, simply because it matches up very well with the criteria established in the industry for the requirements of industry-specific products. It’s very important in pharmaceutical usage that any metals used are highly resistant to corrosion, that they can be easily manufactured, and that they can be quickly and easily cleaned without surface particles coming off in the process.

Some specific examples of how stainless steel is used in the pharmaceutical industry include the areas of pumps, processing and reaction vessels, storage tanks, heat exchangers, tubes and pipelines, and valves and taps. All of these products are easily made, easily cleaned, and are highly resistant to corrosive action, but there are even more uses for the various types and grades of stainless steel in the pharmaceuticals industry.

Grades of steel and how they’re used

The most widely used grouping of stainless steels in the pharmaceutical industry is grade 1.4401 and its derivatives. This grouping has become the de facto standard of the industry, although other specific grades of stainless steel will still be chosen on the basis of their suitability to a particular service or action being performed.

In some cases, the grade of stainless steel selected is closely associated with the type of cleaning agents and the method of cleaning used in a particular facility. It’s also possible that the operational mode of a facility will influence stainless steel grade selection, because some facilities operate continuously while using a clean-in-place method, whereas others will close the facility down for a comprehensive all-at-once cleaning.

In mild environments where chloride content does not exceed 200 mg/L, an austenitic stainless steel grade such as 1.4031 might be used, while chloride content up to 500 mg/L might indicate a grade of 1.4401. When chloride content exceeds 500 mg/L, it’s very common to see duplex stainless grades such as 1.4362 and 1.4462 chosen, because they offer high resistance to stress corrosion cracking. For service environments which are even more aggressive, it may be necessary to use the super-austenitic stainless steel grade 1.4547, or the super-duplex grade of 1.4410.

Types of stainless steel

Austenitic Steels

The most common types of stainless steel are the austenitic types, whose structure is comprised of nitrogen, nickel, and manganese. This kind of structure is responsible for imparting characteristics such as formability and weldability to the finished product. The resistance to corrosion which stainless steel naturally has can be supplemented by adding more nitrogen, along with chromium and/or molybdenum.

These stainless steels do not get any harder with treatment, but they can be processed to extraordinary levels of strength. While austenitic steels are susceptible to stress corrosion cracking, they can be made more impervious by including a higher nickel content. Some of the most common applications which austenitic stainless steel grades are used in, include the following:

  • 304/304L – these kinds of stainless steel are generally used for producing cutlery, sinks, hollow-ware, architectural products, storage vessels, tanks, and pipes intended for use with corrosive fluids.
  • 309/310 – higher nickel and chrome content gives this grade of stainless steel greater resistance to oxidation, making it suitable for applications where high temperatures are involved, such as in furnaces, catalytic converters, and kilns.
  • 318/316L – a higher molybdenum content increases resistance to corrosion, making this grade of stainless steel ideal for use in pressure vessels, pipework, and tanks where the transportation of corrosive liquids and chemicals is indicated.
  • 321/316Ti – considered to be the stabilized grades of stainless steel, these are resistant to inter-granular corrosion, so they can be used in components which require high temperature strength and resistance to corrosion, for instance in super-heaters, expansion bellows, compensators, and after-burners.

Ferritic Steels

Ferritic steels are largely comprised of chromium, with small amounts of carbon mixed in. They are structurally similar to low-alloy steels and carbon, and since they are not particularly useful for welding, they are mostly used in thin sections where welding is not required. Ferritic steels are also known for being magnetic, but lack the powerful resistance capabilities of austenitic stainless steels. Some of the applications where ferritic steels are most commonly used include the following:

  • 409 – this grade of ferritic steel is commonly used in catalytic converter casings, and sometimes in exhaust tubing.
  • 430 – often used in wash troughs, cutlery, catering equipment, and kitchen sinks, Grade 430 is considered quite versatile.
  • 1.4509 – a special grade produced by Columbus Stainless, this grade is frequently used in automotive components because of its mechanical strength at high temperatures. It’s also frequently used in heat exchanger tubes.
  • AISI 444 – this stainless steel grade has similar characteristics to Grade 316, in that its resistance to corrosion is very strong in aggressive outdoor environments.
  • 3CR12 – this is another special grade developed by Columbus Stainless for the purpose of overcoming problems with weldability. It has high resistance to corrosion and is particularly useful in wet or abrasive applications. Unlike most other types of ferritic stainless steel, this special grade can be welded, even to higher thicknesses. It is frequently used in material handling, mining, and in the sugar industry, because of its increased resistance to atmospheric and abrasive corrosion factors.

Duplex Steels

The structure of duplex steels is comprised of approximately 50% ferritic and 50% austenitic, and this composition gives them greater strength than either of their sources, as well as high resistance to stress corrosion cracking. The subcategory known as lean duplex steels are manufactured to approximate the standard corrosion resistance of austenitic steels, but with greater resistance to stress corrosion cracking and with increased strength. The subclass known as a super duplex steels have greater strength and greater resistance to all kinds of corrosion, compared to ordinary austenitic steels. Duplex steels can be welded, if care is taken with heat input and welding consumables.

Martensitic Steels

Martensitic steels are much like for ferritic steels in that their primary ingredient is chromium, although they have a greater carbon content than do the ferritic steels. This being the case, they can be tempered and hardened in the same fashion as carbon or low-alloy steels. Their usage comes in play primarily in settings where moderate resistance to corrosion is necessary, but high-strength is a solid requirement. Martensitic steels are more commonly manufactured into long-ish products, rather than in plates or sheets, and have relatively low formability and weldability.

Precipitation-hardening Steels

Precipitation-hardening steels can achieve extraordinary strength when components such as aluminum, niobium, and copper are added in. These types of steels are often machined into shapes that are fairly intricate and delicate, because they sustain very minimal distortion during the final treatment process. This is in stark contrast to more conventional martensitic steels, where greater distortion typically occurs during hardening and tempering.

3 Critical Distinctions Between Clean Room Carts and Laboratory Carts

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Clean Room Cart Product Line

We will consider some important features available in the various mobile cart options throughout the internet. This article focuses on three of those features and will compare them to clean room carts and laboratory carts. This comparison is meant to help readers select the correct cart for their specific application. The three features we will be considering are (1) connection types (2) materials and (3) design.

Connection Types

Carts are assembled in many ways and can have various types of connections. It is important to be aware of these since one type may be applicable to you and another may not. A few common connection types can be the use of rivets or bolts to connect frame members to other components.

This is an inexpensive and simple method of assembling the cart. However, with this method the cart will be subject to these connections becoming loose and risk coming apart. This can be an obvious safety issue for the operator and a quality issue for the items on the cart. The items being carried on the cart can become damaged. The operator can also be harmed during such an incident.

A cart that is riveted or bolted together is acceptable in certain areas. One area is where the items the cart will be carrying are light weight. If the cart is meant for light duty applications then it is likely it will hold together sufficiently for the life of the cart.

Another area is where the cart will not need frequent cleaning and sanitizations. Each connection produces a seam where dirt and debris will collect. It is too difficult to ensure these types of carts are thoroughly cleaned if it is to be used in controlled environments such as clean rooms. Therefore, they should only be used in laboratories or packaging areas where the environments are less strictly controlled.

A second connection type is a welded connection. This is a more complex and expensive option but yields much better results. One advantage is the number of seams is reduced by welding many areas of the cart instead of bolting or riveting them together. This assists in cleanability and increases effectiveness of sanitization. This option is critical for areas such as clean rooms where the cart is being cleaned often.

Materials

The material of the cart can vary greatly between a clean room cart and a laboratory cart. The material the cart is constructed from contributes largely to it’s strength and durability. It is vital to select the appropriate material for the specific environment it will be used in.

Carts made of plastics can be utilized for their specific chemical resistances while painted or chrome plated steel can be used due to their low cost. While plastic carts offer certain advantages to transporting chemicals they do not offer any advantages in durability and cleanability. Additionally, painted or chrome plated steel carts offer durability and strength but very little for corrosion and chemical resistance.

An alternative material in the construction of carts is the use of stainless steel. This option being more expensive but offering greater capabilities in environment-controlled areas. Stainless enables the fabricator to weld components together versus bolting or riveting them together. As discussed in the previous section, this reduces the number of dirt harboring seams and increases it’s cleanability. Stainless steel carts also have good chemical resistance and excellent corrosion resistance similar to that of the plastic carts. However, stainless steel provides the strength and durability of a plain steel cart.

Design

The third and final feature that sets clean room carts apart form laboratory carts is the design of the cart. This design is what determines the combination of the previously discussed areas of (1) connection types and (2) materials.

The design of a laboratory cart is much broader in scope since it doesn’t have the same requirements of a clean room cart. Thus, we find these carts in a broad spectrum of materials and with various connection types. Typically making them an inexpensive option.

A clean room cart’s design is more specific and rigid. It has to withstand harsh environments where corrosive sanitizing agents are routinely used. The design needs to allow for easy cleaning with fewer seams. These carts are also constructed of thicker materials for high strength. They are typically intended for industrial use because they are under a heavier load.

Additional Considerations

While a slightly less common application it is still important to consider the ability to be used in an autoclave. Carts must be specifically designed to have this ability due to the high temperatures of an autoclave. It must consist entirely of a high temperature materials, welded construction, and corrosion resistance. As discussed, a clean room cart should already be constructed from stainless steel and welded together making it a perfect candidate for an autoclave cart.

Note there is one important adjustment to make to a properly designed clean room cart to make it autoclavable. Let’s consider the material of the wheel on the caster. There are many acceptable materials for a wheel. One common choice is a non-marring and non-damaging material. This ensures the facilities floors stay clean and undamaged. However, many of those materials are not capable of standing the high temperatures of an autoclave. By simply changing the wheel to a higher temp material you can make the clean room cart autoclavable.

Conclusion

A welded stainless steel cart creates benefits across several areas we have discussed. Welding the different stainless components of the cart together contributes to:

  • Higher cleanability and sanitization assurance
  • Greater durability and strength
  • Longer service life
  • Greater capabilities such as use in an autoclave

Whether the application for your cart is the laboratory of the clean room please keep in mind the factors that have been discussed. Considering these 3 critical areas will help you to pick the correct cart for the correct application.

Custom Stainless Steel Fabrication

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Inside a Custom Stainless Manufacturer

Stainless steel is widely used in the food, pharmaceutical, and medical fields. A competent stainless steel fabricator therefore must provide solutions for these industries. These solutions should be designed for use in clean and sanitized locations. Experience with materials such as stainless steel, Teflon (PTFE), Delrin (Acetal), and polycarbonate (Lexan) is necessary for such fabrication companies. These companies need to provide custom fabrication of such materials and posses the flexibility to manufacture custom designs.

Custom Fabrication and Design Flexibility

One important element is the flexibility to adjust designs and manufacturing processes to accommodate a customers specifications and ongoing input in the design process. To accomplish this the manufacturer must own the necessary equipment to create the custom designs of the customer. This equipment is highly specialized and not easily found in the industry. Some common pieces of equipment that are used in custom stainless fabrication can include waterjets, milling machines, TIG welders, press brakes, 3D design software, and stainless passivation.

    • Waterjet Cutting

This form of material cutting works in tandem with a well planned 3D design. Many features are easily added in a flat pattern cut file. This file is then quickly cut on the waterjet. Waterjet cutting gives is perfect for providing the squarest edge on thicker materials as well as excellent edge quality. It is superb for cutting stainless since stainless steel can be distorted by high heat cutting methods (i.e. laser and plasma cutters). A waterjet does not distort the material in any way caused by heat because a waterjet has a zero HAZ (Heat Affected Zone).

    • Multi Axis Milling and Machining

This process is best for removing material in pockets, slots and tapped holes or any three dimensional features. It also keeps the edges true and square which leaves a smooth finish. This is particularly important when making stainless steel parts since the machining process is often producing a finished product.

    • TIG Welding

This method of welding is ideal for stainless steel fabrication because it produces a strong weld that can be ground down and polished smooth for cleanability purposes. It is a very controlled and precise method of welding that prevents excess heat and therefore unwanted distortion. There is zero slag or unwanted bi-products which makes the entire process cleaner than other forms of welding.

    • Polishing & Surface Finishing

High performance abrasives are needed to polish and finish stainless steel. It’s also important to use only certain abrasives on stainless and not on other materials. This keeps the stainless clean and free from impurities. The use of specialty abrasives further protects stainless from unnecessary heat and distortion by more quickly removing material. A very complex procedure of polishing specific to stainless steel is electropolishing. This method produces an extremely high polish by using electricity and a specially formulated chemical solution. Due to it’s complexity this form of polishing is usually reserved for smaller stainless parts only.

    • 3D Design Software

This piece of the stainless manufacturing process brings all the necessary pieces together as a whole. It collects the input from our customers and conceptualizes it for them. It aids in design approval by providing a scaled picture for a customer. The 3D design keeps all manufacturing data in one place. This ensures a quick and accurate retrieval of all manufacturing data for future orders.

    • Press Brake Sheet Metal Forming

Stainless steel is commonly used for guards, covers and enclosures because of it’s corrosion resistant nature. Most of these items are formed or bent out of sheet metal and requires a precision CNC controlled press brake. The 3D design works well with the press brake. A properly designed and flattened sheet metal part can then be precision formed.

    • Passivation Surface Treatment

Passivation is a typical requirement for pharmaceutical companies. This process reintroduces a passive film on the surface of stainless steel that has been either machined, cut, polished, welded or otherwise altered in someway. The stainless parts are immersed in a specialized solution for a specified amount of time to produce a passivated part.

Many companies may only specialize in just one of these areas listed above. However a competent custom stainless manufacturer specializes in the use of all these areas and not just one. A fabrication company should not subcontract or outsource any of the above mentioned functions. They should possess all of these abilities in house. After looking at the complete custom manufacturing process it is difficult to picture it without one of these elements. Each process assists the next. Starting with the 3D design all the parts are expertly fitted and laid out with all necessary information to be created in all later steps. Next the waterjet cuts all the parts from raw materials for all later processes.

Pharmaceutical Equipment

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stainless clean room equipment

Grades of Stainless Steel in Pharmaceutical Equipment

Equipment used in the pharmaceutical industry is highly specialized and must maintain a cleanable exterior. This equipment is likely located inside a strictly environment controlled area such as a clean room. Clean rooms have extreme sterility requirements. Their cleaning procedures often use strong chemicals that corrode and even damage most materials. Materials such as stainless steels and high performance plastics are commonly used in the manufacturing of pharmaceutical equipment due to it’s resistance to these chemicals.

304 and 316L Stainless Steel

304 stainless steel is often used for the exteriors of machines and for protective coverings. It can be very useful for skirting and trimming around and between the areas of a clean room that are difficult to sanitize and clean. 304 stainless is an economical grade of stainless used widely across industries.

316L stainless steel is a special grade of stainless being adopted in the pharmaceutical industry. 316L is very similar to 304 for fabrication purposes. It welds, polishes, cuts and bends much as 304 does. However 316L stainless has a greater corrosion resistance and is therefore used when manufacturing product contact parts and associated equipment.

Stainless Steel Treatments

Pharmaceutical manufacturing requires that all parts contacting medicine or product maintain the highest levels of sterility. One way to ensure this is to reduce a parts surface roughness. On a microscopic scale materials have peaks and valleys on it’s surface. The greater the difference in a materials peaks and valleys will increase it’s surface roughness. A rough surface is likely to harbor microorganisms and is therefore unfit for pharmaceutical production. A few treatments that enhance the corrosion resistance and surface quality of stainless steel are Electropolishing and Passivation.

Electropolishing

Mechanical polishing or buffing can greatly reduce the surface roughness of stainless steel. However electropolishing can further smooth a stainless surface on a microscopic level. We can measure how smooth a surface is with the use of a profilometer. This device measures an items Ra (Roughness Average) and allows us to compare how smooth or rough a surface is.

Passivation

Stainless steel forms a passive film on its surface once presented to the open air. During the manufacturing of stainless parts there are several processes that disturb this passive film such as polishing, cutting, welding, etc. The passivation process reintroduces this passive film and provides further corrosion resistance to the stainless parts.

Clean Room Equipment Manufacturers

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Selecting an Equipment Manufacturer

It is an important step in selecting an appropriate manufacturer of clean room equipment. Manufacturers should maintain high standards in all fabrication methods and processes. They should be specifically skilled in stainless steel fabrication. Much of the equipment in a clean room is from stainless for many reasons.

Stainless Steel Fabrication Advantages

1. Strength
2. Cleanability
3. Corrosion Resistance

1. Strength

Clean room equipment fabricated from stainless steel provides the highest industrial strength construction. It allows your equipment to withstand the daily abuse of personnel. Stainless equipment will give the greatest level of durability over other materials. Many components are now able to be welded instead of fastened. This ability further extends its industrial strength by minimizing bolted connections that requires maintenance and tightening over time.

2. Cleanability

Stainless steel is smooth and easy to clean. It’s chemical properties make it highly resistant to most cleaning solvents. Clean rooms with vial and syringe conveyors will face problems with broken glass. Constructing equipment of weaker materials may allow this broken glass to embed itself in the surface of the material. Stainless clean room equipment withstands such contact with broken glass. It’s rigid properties keep your equipment’s surface smooth and easy to clean

3. Corrosion Resistance

Stainless is resistant to corrosive chemicals and maintains much of it’s corrosion resistance even after being damaged, nicked, or gouged. Other materials require a protective layer to add any level of corrosion resistance. This added layer is easily removed once damaged even slightly. After this occurs the base material is susceptible to rusting and harboring of other contaminants. Stainless fabricated equipment removes this problem.

Manufacturing with Quality Assurance

Metal fabrication companies typically work with a wide range of materials and equipment. Rarely do they specialize in a particular material and industry. They often outsource and subcontract much of their fabrication process to outside companies. This provides greater capabilities for the original equipment manufacturer. However it introduces issues with the quality of the end product.

1. Cross Contamination
2. Specification Adherence

1. Cross Contamination

Manufacturing equipment made of regular steel can contaminate tools, dies, and fixtures that were used in the fabrication process. These items are often used on both regular steel and stainless steel products with no regard to maintaining the inherent corrosion resistant properties of stainless steel.

2. Specification Adherence

Lacking the control of an entire fabrication process can be a serious problem in quality. This is especially important when creating equipment for clean rooms. Such equipment requires an above industry standard of cleanliness and aseptic features. Specific requirements for surface roughness, polished welds, and passivation are just to name a few. A common requirement is to upgrade the material from 304 stainless to 316 stainless. However there are no visual differences between the two grades of stainless and can easily be mistaken for one another. Further material classifications and tracking must be in place to ensure the correct material is being used.

These are all common quality issues when outsourcing any of the fabrication process. A company simply cannot control, monitor, or ensure the quality of their product while outsourcing fabrication processes. Always search for a quality stainless steel manufacturer that meets the above mentioned requirements.