The Significance of Oil Free Air in Pharmaceutical Industries

Anvar Jay Varadaraj
Head - Marketing and Corporate
Communication, ELGi

In pharmaceutical companies, there is high demand for clean and pure air during the manufacturing process such as Tablet Coating & Drying, Bottle cleaning, Nitrogen separation etc. There is dire need to ensure no impurities during the process. Air Compressors are used during the manufacturing process for the supply of clean air. However, air compressors releases micro volume of oil along with air. This might not be big problem on daily basis. But over a period of time, this might corrosion of the equipment, reaction with medicines etc.

Indian pharmaceutical industry is expected to reach USD 55 billion by 2020.1 India accounts for 20 per cent of global exports in generics. In FY15, the pharmaceuticals industry of India exported products worth USD15 billion and exports are expected to reach USD 40 billion by 2020. India is expected to be the third largest global generic Active Pharmaceutical Ingredients (APIs) merchant in market by 2016, with a 7.2 per cent market share. Contract Research and Manufacturing Services (CRAMS) industry is estimated to reach USD 18 billion by 2018. The Domestic market for formulations is valued at USD 11.2 billion. Double-digit growth expected over the next five years. The Biosimilar sector is expected to touch USD 1.4 billion by 2016 and the sector is expected to grow annually at a rate of 30 per cent in India. Quality consistency will be paramount to realise this growth.

The Cost of Poor Quality

2It is 2010 and The US Justice Department has ordered GlaxoSmithKline (GSK), the British Pharmaceutical giant, to pay USD 750 million dollars for failing to prevent contaminations in their products Kytril, Bactorban, Paxil Controlled Release (CR), and Avandamet. The Department found that Bactroban, Kytril, and Avandamet could be infected with microorganisms stemming from a contaminated production facility. For Paxil CR, an antidepressant drug, mis steps in the manufacturing process resulted in the pills splitting into two, resulting in pills that offered no therapeutic effect, while other pills did not have the controlled release effect. GSK is not alone in such cases. In 2012, Schering-Plough paid USD 500 million towards settlement for violation of product quality norms arising out of poor manufacturing practices for its allergy medication, Claritin. In September 2013, the the FDA imposed a ban on Ranbaxy's drugs that may have included human hair & oil spots in tablets. While the punitive amounts may seem large, the damage is irreversible as it is impossible to trace consumers who may have suffered from these product mishaps , thus making prevention paramount in such manufacture. Given that such manufacture involves compressed air at every juncture, oil and contamination free air is critical to making risk free products.

Compressed Air Applications in the Pharmaceutical Industry

Compressed air is vital to the pharmaceutical industry. Compressed air usage can be classified into two categories; Process Air and Direct Contact. Process applications employ compressed air for a specific kinetic activity. For example, during pill production, the uncoated are churned in a large drum as part of the coating process. Compressed air often drives the drum. Similarly, processes such as conveyance employ compressed air. Direct contact entails the direct contact of compressed air with the application, thus making air quality critical.

For example, compressed air is used to coat tablets to ensure their structural integrity. Impurities in this air will compromise the integrity and worse, contaminate the product. Such direct contact is also critical in Jet Milling, where compressed or nitrogen is used to reduce active ingredients. Specifically, the powder is fed into a milling chamber where compressed air or nitrogen, usually in a vortex motion, promotes particle-to-particle collisions. Particle classification is made by inertia, following reduction via impaction and abrasion. Compressed air is used for bottle cleaning to safely remove dust and small particles from containers before filling. The system is particularly suitable for removing loose contaminants that may have accumulated in the containers during shipping or storage. Containers first enter the rinsing area and are then bathed with ionized air generated by special trans vector air flow amplifiers. The static charge that attracts debris to the surface of the containers is neutralized (ionized air does not sterilize the containers). Rinsing heads are lowered into the containers and a blast of compressed air cleans the containers. A vacuum collects the loose particles, which are disposed in a bag behind the machine or directed into the extraction system of the facility.

As a final direct application, membrane technology with nitrogen generators uses compressed air forced through a polymeric hollow fibre to selectively permeate oxygen, water vapour, and other impurities out of its side walls while allowing nitrogen to flow through its centre and emerge as high purity N2 gas.

Generating Oil Free Compressed Air

Popular compressed air systems include piston driven reciprocating compressors, screw or rotary compressors, and centrifugal compressors. Typically, industrial air systems require air volume in the range of 200 to 2000 cfm and operate at pressures between 6-10 bar(g) using a packaged air compressor. The rotary screw is the most widely used of in the industry owing to its inherent reliability. These machines are available in wide range of oil lubricated and oil free versions.

To understand the generation of oil free compressed air, it serves to understand the role of oil in regular compressed air. Focusing on screw compressors, the heart of the compressor or the "Airend" works by two rotorsor screws in an enclosing housing moving in opposing directions sucking air from the atmosphere and compressing it for use in the end application. As air travels through the Airend, it is compressed to high pressure. Oil is injected into the compressed air and discharged from the compressor mixed with the air. The oil and air mixture from the compressor discharge line flows into a gas and oil separator, which separates oil from the air.

After separation, the oil is cooled and filtered, then pumped back in to the compressor housing, gears and bearings. The flow of oil will takes place into the compressor either due to the pressure difference that exists between the separator tank and the point where it is injected into the compressor or can alternatively be pumped in to the compressor. The oil that is injected serves three main functions, cooling, sealing and lubrication. In reciprocating and rotary systems, the prevailing systems, oil serves as lubricant, sealant, and coolant. So, how do oil free systems function without oil serving these critical functions?

An oil free screw compressor compresses air with out any contact with oil. An air cooler removes the heat from the compression chamber. Without oil , the rotors rotate at high speeds to get volumetric efficiencies equivalent to oil injected screw compressors. Timing gears synchronize rotor rotation to ensure no contact. A separate lubrication system lubricates the timing gears. This calls for an efficient sealing system to prevent the entry of lubricating oil in to the compression chamber.

Figure 1.

There is a growing industrial need for compressed air, free of entrained oil. For many requirements oil flooded screw compressors will satisfy with multi stage filtration. However, oil free compressors are ideal owing to the hassle of pressure drops and added maintenance stemming from filter equipped lubricated compressors.

Quality By Design (QbD)

Pioneered by Joseph M. Juran, Quality by Design is an approach that helps prevent the occurrence of quality lapses in high risk industries such as drug manufacture. Design for quality and innovation is one of the three universal processes of the Juran Trilogy. The focus of this concept is that quality should be built into a product with an understanding of the product and process by which it is developed and manufactured along with a knowledge of the risks involved in manufacturing the product and how best to mitigate those risks. Applying this to oil free air in the pharmaceutical industry, QbD principles would dictate design measures to prevent contamination in the delivered air.

As an example of this, ELGi's oil-free rotors employ a two-layer non-metallic coating and coating process to preserve the rotors. This coating comprises PTFE + PFA ((Poly Tetra Fluoro Ethylene + Per Fluoro Alkoxy), with PTFE on the first layer and PFA on the top. The process is illustrated in the Figure 2.

PFA has layering and formation properties which ensure homogeneous coating and avoids the formation of pin holes. This enhances the coating reliability and provides highly efficient corrosion protection. In addition; the coating serves as a dry lubricant. The coating's food and medical grade certification ensures its safety for pharmaceutical applications. Though there is no oil injected in to the compression chamber, the timing gears and bearings need lubrication and are lubricated through a separate lubrication system. The oil used for this purpose needs to be prevented from entering the compression chamber. ELGI employs an efficient internally designed sealing system comprising of floating carbon seal and viscose on each rotor to prevent oil entering the compression chamber. These seals are non-contact seals and their reliability is significantly higher than any contact seals hence ensuring continuous clean air supply.

The Future of Oil Free Air

Rough estimates indicate that oil flooded screw compressors have expelled nearly 10 million liters of oil into the atmosphere over the past ten years. The amount is humbling given the growing stresses placed on the planet. Thus, it is clear that oil free air is set to grow in relevance not just for the pharmaceutical industry but for all applications. Cost and efficiency are crippling barriers for oil free adoption. For applications that don't require oil free air, the current oil free technology struggles to compete with traditional oil flooded machines. Given the higher rotor speeds, rotor complexity, and increased parts for cooling, oil free machines are typically more expensive and less efficient. To overcome this, companies such as ELGi are taking a two pronged approach. The first is a philosophical shift to no longer look at oil flooded and oil free as distinct segments. Following from this, to simplify current oil free technology to reduce cost and improve efficiency, ELGi is working on technology such as water injection, which allows for lower cost and higher efficiency. For the pharmaceutical industry, companies expanding production can move up the compressed air chain to consider centrifugal machines, which offer oil free air at high efficiency assuming the required vol-ume is north of 4000 CFM. Companies are also working on reducing the size of centrifugal machines to be competitive at lower volumes.

Companies can use data to reduce quality risks and manage efficiency. ELGi, for instance, has started delivering compressors with data transmitters. The sensors pick up variations in volume, pressure, temperature, moisture, etc. and feed this data back to the service and quality team in the head office to proactively address failures and issues in the line. This technology will likely be extended to detecting air contamination, which can allow ELGi to partner closely with its customers in ensuring quality. Compressed air will be relevant to the pharmaceutical industry for the foreseeable future barring major scale advances in technologies such as 3D printing. Within this context, oil free will become more prevalent supported by design initiatives to improve cost and efficiency. Data will serve as a key enabler in the process, where compressor suppliers and manufacturers partner to eliminate quality concerns.