Steam-in-Place (SIP) operations use the thermal energy of condensing steam for a controlled period to reduce bioburden in manufacturing settings and are widely employed and highly effective in the Food & Beverage and Biotechnology industries.
SIP operations may be used for varying purposes, including the following:
- Process disinfection to kill pathogenic (disease-producing) organisms
- The thermal inactivation of a target organism
- Steam sanitization to achieve a 99.9 percent bio-kill of all present organisms.
The most stringent SIP application achieves sterile conditions throughout the entire equipment set to sterilize the process system as an entity. The process system may include processing vessels and piping, filtered gas overlay supplies, process liquid filters, valves, pumps and processing instrumentation.
Haskell's Process Engineering team has prepared a list of 10 effective rules to help manufacturers reliably achieve sterile conditions when SIP’ing a process equipment set.
1. Perform Clean-In-Place (CIP) Operations Before SIP Operations
Perform effective CIP operations prior to initiating SIP operations to remove processing soils. The thermal resistance of microorganisms and spores can be enhanced by the protective effects of process soil.
2. Confirm Saturated Steam Supply
Operations should confirm steam supply header pressure and temperature to ensure a saturated steam supply. Superheated steam or an insufficient steam supply will result in a failed SIP program. Steam quality in the food industry must meet “Culinary Steam” requirements, and in the biotech industry they must meet specifications for “Clean Steam.”
3. Introduce Saturated Steam Supply as High as Possible
The SIP operations should be configured to introduce the saturated steam supply as high as possible in the equipment set, leveraging the steam supply pressure and temperature differences to push out ambient system gases through monitored process low points. The ambient gases will sink to process low points for effective evacuation.
4. Install Low Point Trap Blocking Valves and Temperature Sensors
Install steam-trap blocking valves and a steam trap at each process low point and include a temperature-monitoring device between each. Be sure to locate the element above the trap’s condensate leg for accurate temperature measurement. If possible, use trap-bypass valves for efficient air purging at the process low point to minimize the mixing of steam and air.
5. Use Monitored High Point Air Bleeds
The importance of complete air elimination from the processing system cannot be overstated. To assist in the complete replacement of air with saturated steam, use monitored high-point air bleeds to push high air pockets out of the system. High-point air bleeds are recommended on large filter housing, process vessel vent and overlay gas supply lines.
6. Avoid Parallel Steam Paths
Whenever possible, avoid parallel steam paths within the processing system sharing a common steam trap. As pressure differences occur during air removal stages, a parallel line pockets air, which prevents proper steam exposure and results in sterility failures.
7. Plan Steam Flow and Process Flow in the Same Direction
Plan the SIP operation to have steam flow in the same direction as the process flow to take advantage of the existing process piping pitch and support for process drainability. Plan the piping system to avoid hoses, dead ends, and non-drainable low points that can create condensate pools or air pockets. These pools and air pockets can provide an insulating effect on the targeted microorganisms. Prompt and effective condensate elimination is critical to SIP operations success.
8. Include a Time Delay
After process air has been fully removed and the system charged with saturated steam, a time delay is recommended for all system components to achieve the desired set point temperature. To achieve sterile conditions, universally expose the system to the FDA Center for Biologics Evaluation and Research (CBER) 21 CFR Guideline (Section 600.11), which calls for a level equal to that attained by exposure to a temperature of 121.5°C for 20 minutes by saturated steam. Consider adding 1.5°C to the SIP set point to cover temperature element accuracy concerns. The 20-minute thermal exposure must be continuous, without the temperature dropping below the set point.
9. Active Steam Flow During SIP Hold
Providing a means of active steam flow to the process as the SIP timer counts down can help ensure the required thermal treatment. This steam “activity” can be achieved through positioning the process vessel vent pressure control valve slightly open or using orificed steam traps or bypass valves.
10. Protect Sterile Process Boundary
After the desired exposure to saturated steam has achieved a complete thermal bio-kill, the sterile process boundary must be protected as the condensate is drained from the system. The equipment is cooled to prepare for sterile process operations.
Once the sterile boundary has been created, the question is often raised “How does one protect and maintain a sterile process boundary?” Using overlapping sterile boundaries, active or passive air overlays, and steam blocks is highly effective.
About the author: Mike Byron is Haskell’s lead process engineer and has been with the company since 1993. He is intensively involved in Process/CIP/SIP system design for food and pharmaceutical manufacturing facilities. His diverse process engineering knowledge includes automated sterile/aseptic processing systems for cell culture, harvest, purification and sterile filling operations. He earned bachelor’s degrees in agricultural engineering and biochemistry from Purdue University.
Discuss your CIP/SIP needs with Haskell’s Process Engineers, an integral part of the Food & Beverage Manufacturing Contracting team ranked No. 1 two years in a row by Engineering News Record.
