Autoclaves

Types of Autoclaves

Steris Rennaisance 3011 autoclave.

Boiler, chamber, control system.

Switches

Main switch on wall; do not touch; Standby/Power switch on console; user operated. Cycle selector buttons on console; user operated.

Gauges snd Sensors

Sight glass showing water level and Bourdon gauge showing pressure in the boiler of the Steris 3011.

Boiler, chamber, jacket.

Valves

Hi/Low, steam, flush.

States of the Machine

Off: [main switch on wall]. Standby: power to computer but boiler is cold; [console switch]. Powered: boiler at full temperature and pressure; [console switch]. Running: cycle under control of computer; [started by console button].

Operating Procedure

Mark log. Switch from "Standby" to "Power". In approximately 20 minutes the boiler pressure should increase to ~60 psi. If you have not marked the log, do that while waiting. Flush boiler at 10-15 psi after about 10 minutes warmup. Load. A liquid should always be in a stainless steel tub. Close and seal door. Note double hinge. Choose one of the four cycles. Flash is a rapid cycle for solid material only. The Liquid cycle has long heating and cooling gradients. Check parameters. Check parameters. Check parameters. Adjust if necessary. Check Hi/Low valve. Change if necessary.

1.LIQUID STER=45m TEMP=250 F Valve=LOW

3.WASTE STER=40m TEMP=270 F DRY=20m Valve=HIGH

2.FLASH STER=5m TEMP=270 F DRY=1m Valve=HIGH

4.GRAVITY STER=30m TEMP=250 F DRY=15m Valve=LOW

Start cycle. Wait. A tone will signal completion of the cycle. Respect any instruction on the display when opening the door. Unload. Restore parameters. Record any abnormal observation in log.

Safety Precautions

Opening the flush valve when the boiler is hot can cause a small burn from a water droplet or from a leak at the sight glass. Use a glove. A sealed bottle can explode. Do not heat an enclosed fluid. Use the Liquid cycle when appropriate.

Abnormal Conditions

Operating with no record in log; ask user to update log. Alarm; press reset. If chamber fails to cool, shut off steam supply. Correct the problem and start cycle again. Door mechanism is stuck; press center hub in. Door will not open; look for loose screw on lower edge of the outer cover of the door. Door will not close; look for loose screw on lower edge of the outer cover of the door. Leakage of steam; report to Jen or Peter. Water splashing out of settling tank, probably from flushing at too high a pressure; skip the flush when pressure exceeds 20 psi.

Maintenance Procedures

Tightening and Replacement of Sight Glass Gaskets

A sight glass and peripheral components. The meniscus is at the water level in the boiler. The glass is 16 mm diameter. A white backdrop has been inserted for clarity. The pressure gauge is deliberately tilted to the left to allow clearance for maintenance of the sight glass and valves.

The sight glass is connected to the boiler through a valve at upper and lower ends. The glass is sealed into the valve by compression of a rubber gasket in the annular space between the glass and the valve body. Compression is by action of a large nut pressing against a compression ring bearing on the end of the gasket.

With time and thermal cycling a compression nut can gradually loosen. Also, the rubber gasket will gradually harden and deteriorate. Either of these factors can result in leakage of water between the sight glass and valve. In routine inspection and if leakage is detected, the compression nuts should be checked for tightness. Torque required to seal the gasket is relatively small; similar to tightening a garden hose onto a faucet. In some configurations the nut can be tightened with a gloved hand. A pair of water pump pliers can be used. If necessary a wrench such as an Armstrong 28-048 Thin Pattern Pump Wrench can apply enough torque in close quarters. Care must be taken to avoid over-tightening. The inexperienced operator can follow an iterative procedure of tightening and testing until a seal is achieved. The gasket should be compressed sufficiently to seal but not to extrude it into a gap between the glass and the valve body. Test by running the boiler as in a normal cycle of use.

When leakage occurs and can not be stopped by moderate tightening of compression nuts, the gaskets should be replaced following this procedure.

1. Shut down the boiler and lock out the main switch or steam supply.
2. Collect tools and two spare gaskets.
3. Open door or panel for good access.
4. Provide good lighting. If necessary connect a temporary lamp.
5. Check the sight glass, valves and peripheral plumbing are cool enough to avoid a burn.
6. Don heavy work gloves; essential for protection in case the glass is broken. Thin rubber gloves are not adequate. Find thick gloves with a grippy rubber coating. Leather gloves will not hold the glass well.
7. Remove the guard rods protecting the sight glass by lifting them out.
8. Open flush valve and allow water to drain to lower end of sight glass. A tray can be placed under the sight glass to catch spilt water.
9. Back off compression nuts and release compression rings from rubber gaskets.
10. By tying with a cord, fasten the compression nuts and ring near the top of the glass to prevent interference with further work.
11. Move the lower gasket upward until it is free of the annular space. An appropriate tool is essential. A heavy O-ring tool is one possibility. Care and patience must be exercised to avoid touching the glass with a metal tool. In normal circumstances, there is no justification for breaking the glass. If difficulty is encountered, find a more appropriate tool. If the rubber is hardened, it may come out in pieces.
12. Release the cord so that the compression nuts and rings rest at the lower end of the sight glass.
13. Move the upper gasket downward until it is free of the annular space.
14. The glass should then be loose in the annular space of the upper and lower valves. Hold the compression nuts and rings, lift the glass up, tilt the bottom end out clear of the lower valve and lower the glass clear of the upper valve.
15. Slide the old gaskets off of the glass and push new ones on.
16. Reassemble by inverting the preceding disassembly procedure.
17. Fit the glass with nuts and rings into the valves.
18. Slide the rings into the annular spaces. The glass must be approximately centered between the two valves. If the glass is displaced too far up or down a gap between the end of the glass and valve will allow extrusion of the gasket.
19. For each valve, slide the compression ring against the gasket, engage thread of nut and begin tightening. Take care to avoid displacing the glass too far up or down as mentioned in the preceding step.
20. Tighten the nuts to achieve a seal. Too loose is better than too tight for an initial test.
21. Restore electrical power or steam supply and energize the boiler while watching for leakage.
22. If leakage occurs, lock out power or steam again and adjust glass and compression nuts.
23. Repeat the preceding two steps until a reliable seal is achieved.
24. Power down boiler, replace covers and put tools away.
25. Monitor use through more than one cycle to be sure no leak develops.

External References

CDC: Disinfection and Sterilization

See Also

Sterilization
Autoclave