NASH HALL AUTOCLAVE OPERATING INSTRUCTIONS:  ROOMS 236, 440, 550

1.  Ask for instructions from:  ______________________________________________________________________
in Room: _____________________________________________________  If anything is unclear.

2.  Sign In: 

  • Second Floor:  Clipboard is hung on the wall opposite the door.
  • Fourth Floor:  Clipboards are on the small desk; one for LARGE autoclave and one for SMALL autoclave
  • Fifth Floor:  Clipboards are  hung on the right side of the small and large autoclaves.

 

DATE

 

START TIME

 

RUN TIME

 

CHAMBER PRESSURE

 

CONDITION OF AUTOCLAVE

 

LAB NAME

 

USER NAME, FIRST AND LAST

NOTE: Items to be autoclaved MUST be in Secondary Containment containers – “coffins”, autoclavable plastic bins, etc.

3. Place containers in the autoclave.

4. Check the strainer to see if it is clogged. The strainer is located on the bottom of the chamber near the door. The autoclave will not come up to pressure if the strainer is clogged.

5. Close door.

For the SMALL autoclave, rotate the handle clockwise until it is snugly closed.      

For the LARGE autoclave, rotate the small, inner handle clockwise first until it locks. Then rotate the large outer handle clockwise until it is snug.

6. Open the glass-faced door in the upper right corner. Set STERILIZE time and, if needed, set DRY time.

7. Select the SETTING you want by pushing in the colored button that corresponds to:

ON-OFF FAST EXHAUST FLUIDS DRY

GREEN= FAST EXHAUST:  Pressure will decrease rapidly at the end of sterilization. Fluids will bubble over if you use this setting.

YELLOW= Fluids: Pressure decreases more slowly at the end of sterilization.

BLUE=Dry:  Use this setting for paper goods, cotton swabs, etc.

8. Push in the RED button to turn the autoclave on.

9. Wait until the temperature reaches 121°C and the RED sterilization light in the glass-faced box turns on before recording the Chamber Pressure on the Log. The chamber pressure should be 16-20 psi once the sterilization cycle starts. Anything below 16 psi should be reported to your lab manager/supervisor who will email the information to Building Manager Cindy Fisher @fisherc@oregonstate.edu

10. At the end of the run, insure the CHAMBER PRESSURE has returned to ZERO before attempting to open the door.  The FLUIDS cycle takes much longer than FAST EXHAUST – be patient.  If the door cannot be easily opened, WAIT 10 minutes before trying again. If you wrench on the door and  attempt to force it open, the internal metal rod that connects to the door handle will twist from the pressure. Replacement parts and labor were

$5000 in 2013. PRESS the ON/OFF red button to turn OFF the autoclave.

 11. To open the door:

SMALL autoclave: rotate the handle counterclockwise. Be careful, steam burns!  Step to the side and crack open the door. Allow the steam to escape from the chamber then open the door and remove your items.

LARGE autoclave: First rotate the LARGE OUTER handle counterclockwise until it is loose. Next, rotate the SMALL INNER handle counterclockwise until the door opens. Be careful, steam burns!  Step to the side and crack open the door. Allow the steam to escape from the chamber then open the door and remove your items.

12. As a courtesy to others needing to use the autoclave, promptly remove your items when the cycle is completed and you can easily open the door. Wear protective, heat resistant gloves when removing items.

13. Autoclaved waste materials are to be taken directly to the dumpster for disposal. Orange autoclave bags must be put into black trash bags before disposing in the dumpster.

 

STEAM STERILIZATION CYCLES:  LIQUIDS, GRAVITY, AND VACUUM

The Liquid Cycle

Liquids rely on the Liquids Cycle to avoid a phenomenon known as “boil-over.” Boil-over is simply a liquid boiling so violently that it spills over the top of its container.  Boil-over will occur if the pressure in your autoclave chamber is released too quickly during the exhaust phase of the cycle.  Significant liquid volume can be lost to boil-over, and this can result in unwanted spills on the bottom of the autoclave chamber that must be cleaned up to avoid clogging the drain lines and the subsequent repair costs to the department.

To help prevent boil-over during the exhaust phase, the chamber pressure must be released slowly.  This process is controlled by the sterilizer’s control system. Controlling the exhaust rate allows the liquid load to cool off as the surrounding chamber pressure is decreased.

The exhaust rate for a Liquids Cycle is different from a standard Gravity or Vacuum Cycle, where the chamber pressure is released quickly. To prevent boil-over, the chamber pressure must decrease slowly to allow the temperature of the load to remain below the boiling point.  If the pressure is exhausted all at once, the temperature of the load will be above its boiling point, resulting in instant and violent boiling.

NOTE: It is important to recognize that larger liquid loads will take longer to both heat up and cool down. See the chart below.

TEMPERATURE SETTING LIQUID QUANTITY (ml) TIME SETTING  (minutes)
250°F (121°C) 75 25
250°F (121°C) 250 30
250°F (121°C) 500 40
250°F (121°C) 1000 45
250°F (121°C) 1500 50
250°F (121°C) 2000 55

Steam Sterilization Cycles:  Boil-Over

The autoclave operator should keep this in mind, especially for large beakers or carboys.  For instance, a 30-minut Liquids Cycle for a 500 ml flask won't necessarily achieve the same results if sterilizing a 5 L flask.

It is best to practice to (a) validate your liquid loads with hermetically sealed biological indicators and (b) minimize container volumes so that cycle time remains manageable.  Steam sterilization relies on three (3) parameters to eliminate microbes and organisms:  time, temperature, and pressure.  And these parameters can be manipulated into different cycle recipes to sterilize various types of loads.  However, the cycle requirement for every load type--such as autoclave bags, media, glassware, and pipette tips--can vary significantly.

 

Basic Cycles Description Typical Application of Load Type
Gravity Fast Exhaust Cycle  
  The most basic sterilization cycle.  Steam displaces air inthe chamber by gravity, (i.e., without mechanical assistance) through a drain port. Glassware, unwrapped goods, waste, utensils autoclvave bags.
Vacuum Fast Exhaust Cycle with Timed or Dry Cycle  
  Air is mechanically removed from the chamber and load through a series of vacuum and pressure pulses. Wrapped goods, pipette tips, glass pipets

 

The Gravity Cycle

The traditional “Gravity Cycle” is the most common and simplest steam sterilization cycle. During a Gravity Cycle, steam is pumped into a chamber containing ambient air. Because steam has a lower density than air, it rises to the top of the chamber and eventually displaces all the air. As steam fills the chamber, the air is forced out through a drain vent. By pushing the air out, the steam is able to directly contact the load and begin to sterilize it.

At the end of the cycle, the steam is discharged through the drain vent. However, the load can still be hot and possibly wet. To address this issue, gravity autoclaves can be equipped with a post-cycle vacuum feature to assist in drying the load. The sterilizer runs a normal Gravity Cycle and after the load is sterilized, a vacuum pulls steam and condensation through the drain vent. The longer the vacuum system runs during the dry phase, the cooler and dryer the goods will be when removed from the chamber.

Gravity Cycles are commonly used on loads like glassware, bio-hazardous waste (autoclave bag waste), and wrapped and unwrapped instruments.

 

*Information adapted from the  Consolidated Sterilizer Company, 2014.

AUTOCLAVE PROBLEM SOLVING 2019