In the pharmaceutical manufacturing and health-care industries, there are basically two types of steam–process steam and pure steam. Process steam is also known as plant steam, black steam, utility steam, boiler steam etc. Pure steam is sometimes known as clean steam.
Process steam is defined as a general purpose steam whose quality is not been optimised for sterilisation. Where it is not intended to be in direct contact with medical devices, medicinal or culinary products, no specific physical, chemical or biological contamination limits are set. The steam may contain various volatile additives (such as those intended to inhibit corrosion in condensate return pipes) which are unacceptable for topical or parenteral administration to human beings.
Contamination of process steam is mainly due to the contaminants from source of water; contaminants arising from treatment of boiler feed water and contaminants arising from the steam distribution system.
Pure steam is a purest form of available steam whose condensate should meet all the parameters of Water for Injection (WFI). In general terms it is defined as the steam which is free from all chemical and biological impurities.
Pure steam is used in the pharma and healthcare industries in process where the steam or its condensate can come into contact with a pharma or medical product and cause contamination. In such cases, steam from a conventional boiler is unsuitable because it may contain boiler additives, rust or other undesirable materials.
The use of pure steam is determined by the rules of Good Manufacturing Practice (GMP). These are general rules applicable to pharma manufacturer, detailed in the Code of Federal Regulations (CFR Title 21, Part 211). They do not provide any specific recommendations regarding steam, but do present the general requirements of facilities, systems, equipment and operation needed to prevent contamination of pharma products during their manufacture.
The main use of pure steam in pharma manufacturing is for the sterilisation of products or, more usually equipment. Steam sterilisation is encountered in the manufacture of injectable or parenteral solutions, which are always sterile; biopharma manufacturing, where a sterile environment must be created to grow the biological production organism (bacterium, yeast or animal cell); and manufacture of sterile solutions, such as ophthalmic products.
Typically, in these processes, pure steam is injected into equipment or piping to create a sterile environment, or into autoclaves where loose equipment, components (such as vials and ampoules) or products are sterilised. Pure steam may be used for some other functions where conventional utility steam might cause contamination, such as humidification in some clean rooms, and injection into high purity water for heating prior to Clean-in-place (CIP) operations.
| Physical properties required for pure steam | |
| Non Condensable gases | 3.5 percent (max) |
| Dryness Value | 0.9 percent (min) |
| Super Heat Value | 25° C (max) |
