Steam Sterilizers & Autoclaves Introduction
Steam sterilizers, a subcategory of autoclaves, are utilized in three major applications: hospitals, pharmaceutical manufacturing, and research institutions. They are used to disinfect (1) surgical instruments in hospitals and (2) instruments and apparatus used in the research and manufacture of products where sterilization is essential. The purpose of sterilization is to destroy all living microorganisms, which include spores, viruses, and bacteria, including those that cause infection or disease (pathogens). Although other types of sterilizers exist, including dry heat, ethylene oxide, and radiation, steam sterilizers are by a large margin the most widely used form of sterilization. Steam sterilizers present a major opportunity for water efficiency because water is used in these units when they are both in operation and when they are at idle.
Water is used in sterilizers in two main areas: jacket and chamber trap cooling and in the ejector, which is used to create the vacuum. Depending upon the unit’s usage pattern and size, water and sewer rates, operator practices, and other factors, trap way cooling and/or ejector vacuum water usage may be a candidate for water efficiency.
Many units are kept in the standby mode 24 hours a day and therefore do not require a flash cycle during start-up. To keep the unit in the standby mode, most units require small amounts of low-pressure steam are passed into the chamber to maintain a specific temperature in the chamber to keep it sterile. As this steam condenses, it is bled off to a floor drain where it mixes with municipal water to cool it below 140º F (60 C)before it goes into the sanitary sewer lines. (Most local codes require water to be cooled below 140F (60 C) before entering the sewer lines.) Water can be saved by technology that uses methods other than steam to keep the sterilizer warm during standby modes.
New innovative technology can be retrofitted to reduce or eliminate the need to add fresh cool water to the condensate. Among many strategies, most sterilizers can be retrofitted with heat exchangers to cool the condensate from 200F (93.3 C) (to below 140F (60 C) (as required by law), without the need to dilute the hot condensate water with tap water. Some new sterilizer models include these innovative designs in the product. This new technology can reduce water use 250,000 to 650,000 (946.1 m3 to 2,460 m3) gallons annually for each sterilizer.
Before investing in new equipment, or retrofitting or replacing steam sterilizers; the question should be raised wether steam or wet type sterilization is even required for the sanitation application. Many advanced technologies can achieve equal or better sterilization without the use of a connection to a steam boiler. Such available technologies should be investigated to determine the best equipment to serve the specific needs.
For more detailed information download the following research reports:
TKD (2005) Sterilizer Water Savings
CUWCC (2004) Potential Best Management Practices (PBMP) Report – Includes a section on Steam Sterilizers
Van Gelder, R (2003) Field Eval of Water Cons Kits for Sterilizer Trap Cooling