Vacuum System For Autoclave

A steam-powered eductor (also called ejector or venturi) would be ideal for this, as you already have steam for the autoclaving process. A Web search on "steam eductors" should turn up some sources.

I don't understand the reasoning here. Wouldn't injecting steam into a vacuum also bring air along with the super heated water vapor? I would also expect an initial drop in temperature of the injecting steam that might cause droplet condensation. Without knowing the big picture application, this just seems to me to be a pointless waste of power.

auto claves are vacuumed down to remove air from the chambers.But they also pulse at the same time to alow more steam into them as they are being vacuumed down and so removing the air inside with steam.

This is the reconised operation of hospital autoclaves for linnen and utencils for sterilisation.

An eductor is configured so that the driving fluid is not injected into the space to be evacuated. Rather, the driving fluid entrains air from the autoclave and discharges both itself and the air to atmosphere, perhaps through some post-treatment.

Spacecannon's point applies here. The air from the autoclave comes into contact with steam, possibly even superheated. However, the contact time is short, so the question could remain about biohazards in the discharge stream.

this is an industrial autoclave. normally we inject hot steam in to remove air. autoclave need to have only steam so that "cooking" process is not affected by insulation cause by air.

this ramping up process normally takes a few hours. it seems that there is a vacuum system to speed up this process.

Any good Vacuum pump with a material/condensation separator will work, since its on the back end of the process loop, of the sterile media, any contamination would stay within it, however its exhaust needs to be delt with as if its spewing biohazards, which it would be.

Spacecannon

tofumaster, I will make the following assumptions:

1. You are using the autoclave to sterilize products (not cook them) - can you confirm if this is correct.

2. You are using Dry Saturated Steam (probably between 0.95 and 0.97) and not Superheated steam.

Based on the assumption that point 1 and 2 above are correct then your best bet is to install a liquid ring vacuum pump (probably need quite a few of these to evacuate that size of chamber in a reasonable timeframe).

You should consider using sub and super atmospheric pulses to remove remove the air from the chamber (start with the sub atmospheric and the proceed to super atmospheric).

You are correct in that removing the air from the chamber will speed up the heat-up phase. Some sources suggest that a layer of air only 1mm thick can offer the same resistance to the flow of heat as a layer of copper 13 meters thick (Spirax Sarco - Basic Steam Engineering Principles).

Can you indicate the type of load that you are wishing to sterilize?

Have you spoken to the Autoclave supplier? If they cannot help then perhaps try contacting Steris Finn Aqua, Getinge or Fedegari just to name a few.

Regards

Mr. W.A Snow

HoleInTheSnow,Auto

1) The autoclave is an industrial one to cook cement boards.

2) Correct. Around 9.5 bar. The steam came from a boiler.

After a search through internet i found the venturi system. i hope to get more similar vendor.

http://www.foxvalve.com/frameset-air.html

liquid ring vacuum pump will need an additional water system and will need water system.

Try Schutte & Koerting www.s-k.com.

Common practice is to displace the air with steam in the Come-Up / Vent Open step of the thermal processing "recipe", assuming you are processing with saturated steam. If water immersion or water spray is the heating medium then air pockets are not an issue.

I recommend a liquid ring vacuum pump for this size industrial autoclave, google it.

Although you'll need vacuum to create high autoclaving temperature, it is not quite possible to achieve a complete the vacuuming process while or during the process of injecting steam! The steam injection process and cold air evacuation are done simultaneously in an autoclave machine.

vsar, I think you misunderstand the autoclaving process. Typically it is as follows:

1. Pull vacuum in chamber - removing the air in the chamber.

2. Inject staurated steam so that the pressure is slightly under atmospheric

3. Pull vacuum in chamber - removing the air and steam oin the chamber

4. repeat steps 2 - 3 a number of times

5. Perform super atmospheric pulses (more common in the UK & Ireland). Perform this a number of times.

Steps 1-5 dilutes/ removes the air from the chamber and the autoclave load.

6. Start the heat-up phase.

7. Enter the sterilization phase

8. Drying/ cooling phase - may use vacuum and steam pulses here aswell.

9. Pressure equalization.

The vacuum pulses do not affect the autoclaving temperature, this is controlled by the steam pressure. The only purpose of air removal (steps 1-5 above) is to allow steam penetration into the load. Typically porous loads require forced air removal wheras a liquid loads would typically not.

Regards

Mr. W.A Snow

No need to use big vacuum pumps if a storage tank is used.

If you use a vacuum storage tank a smaller sized pump can be used, but the inside of the tank and the the water drain need tobe traeted as biohazard.