The processes and equipment found in the pharmaceutical industry differ substantially from those used in other industries due to the requirements they have to meet.
The Food and Drug Administration (FDA) aims to protect public health through regulations that govern how certain products are placed on the market, including drugs, foods, food supplements and additives, veterinary feeds and drugs, and cosmetics.
Bioprocessing through mixing can greatly affect the purity of final products.
The manufacturing choices made regarding equipment and the sealing systems used on rotating shafts significantly affect process efficiency and quality.
Agitators, dryers and fermenters with top, bottom, rotating shafts, should be designed to prevent the growth of undesirable microorganisms.
Besides preventing process contamination from the external atmosphere or from double seal lubrication and cooling liquids, the mechanical seals installed on the rotating shafts of this kind of equipment should also ensure a constant positive pressure or vacuum inside the tank and prevent wear of the contact material that might cause the product to be rejected, especially if it is in the process of being finished. Seal design should consider two key aspects:
- Avoid contamination of both the process fluid and the atmosphere when the substances are hazardous to people and the environment. If the process takes place in a vacuum, no atmospheric infiltration is allowed.
- Allow cleaning and sterilization between production batches without seal removal.
FLUILIFT TECHNOLOGY
Using a pressurized inert gas – normally nitrogen – as a barrier fluid between the process and the atmosphere prevents product leakage and contamination from the atmosphere or seal lubrication barrier fluid. The rotating ring of the mechanical seal has microscopic grooves. If they are appropriately sized, they provide a small lift from the stationary ring caused by the pressurized barrier gas.
FLUIDIAMOND
A chemical deposition on silicon carbide rings can improve the tribological properties of the material which otherwise would not tolerate even transient ‘contact operation’ in the absence of liquid. A diamond coating allows the seal to tolerate the start-up stage, or in the case of mechanical stresses on the rotating shaft, contact between the rotating and stationary rings, while keeping friction and overheating down to acceptable limits.
GAPLESS PART IN CONTACT WITH THE PROCESS
The parts of the mechanical seal in contact with the process should be cleanable in place (CIP) and sterilizable in place (SIP). The design should:
- Have no recesses where the process liquid can become stagnant and difficult to remove.
- Involve materials that do not contaminate the process. Non-metals must be FDA approved while AISI 316L steel or higher quality is normally acceptable for components.
