Thu May 09 2019

No pressure reading, but unit does reach required temperature.

Hi, I have a Sterilemax autoclave that I'm trying to get working again. The unit will run a cycle and get up to temperature but will not give a pressure reading. It never goes above 0, however the chamber is hot and I believe it is pressurized to some extent. After looking at the diagram I think it may be the pressure transducer but I'm hoping someone with a bit of experience may be able to help me do some trouble shooting. Any info would be much appreciated!

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Thu May 09 2019Reply from Phil_RPI
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Was there any pressure in the chamber prior to opening the door? Do you use a Lag thermometer inside the chamber to compare to the screen? What was the max temp. it reached? What happens if you simply leave the machine alone? Does it over temp.? Any error codes? Have you paid attention to the valves with respect to them opening and closing at specific pressures / temps.? 


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Thu May 09 2019Reply from MikeEMES
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There was pressure in the chamber before opening the door. The pressure pin held the door closed until it was vented. When I hit the stop button there was also a release into the reservoir. I do not use a lag thermometer. The machine reached a max temp of 135 degrees C when I tried to run the wrapped cycle. If I just leave the machine alone it will stay in the heating cycle indefinitely even when temp is reached. It will not enter exposure/steriliziation phase of cycle. We don't get any error codes or an over temp. The vent solenoid appears to function correclty. The vent remains open until around 100 degrees celcius then closes. The water fill and water removal solenoid also appear to function correctly. All the while, the pressure remains at 0 psi. I hope that helps.

Thanks!   


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Thu May 09 2019Reply from Phil_RPI
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It's odd the machine would remain at 135C and not run out of water and over heat. I do not have much experience with this machine, but other electronic machines use temp. to trigger the Sterilize cycle. If the machine can sit at 135C and not over heat I wonder if itis actually 135C? You should be able to attach an external pressure gauge and use a Lag thermometer to verify the display values. Swapping out the pressure transducer should be fairly simple but not sure if it's actually the problem. Do all cycles sit at 135C? 


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Thu May 09 2019Reply from MikeEMES
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No, the liquid cycle sits at 121 degrees C. Temp registers correct on the read out when I run a liquid cycle as well. Unit heats up to 121 and stays there without entering the sterilization phase. It definitely gets up to 121 degrees. I put a flask with some autoclave tape to chekc and the black stripes appeared. How would I connect an external pressure guage? Would I have to find something that will run from the piping that would normally go to the pressure transducer? I have a transducer on order so I can see if that works. Are there any other potential sources causing my issues?


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Thu May 16 2019Reply from Chris35
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If you are making those temps, can hear the unit vent back to the tank, and dont have a chamber full of water when you open the door, then you have pressure above 0 PSI.

Verify you don't have any blockage in the port and piping between the chamber and transducer;

Verify the wiring and connections, then find out which part is cheaper, transducer or control board.


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Thu May 16 2019Reply from MikeEMES
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Thanks for the reply! I found a pressure transducer for 25$ CAD. Replaced it and it is now reading correctly and cycling. I will check and clean the piping between the transducer as a precaution. 


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Thermo Scientific - Harvey Sterilemax
by Thermo Scientific

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