Page 16 - Sterilization Training Manual

In Chamber H2O Condensation Considerations
Steam enters the chamber at a temperature higher than the chamber temperature. As the steam temperature cools to the chamber temperature, the steam will condense to liquid water until saturation density is reached for that temperature. The condensation usually occurs on chamber surfaces since they are cooler than the steam/gas mix in the chamber. Condensation on the optical surfaces of the sensor distorts the light and usually causes an erratic output. The signals can be positive, negative or cycle positive and negative. This is why the sensor must be operated at a temperature elevated above chamber temperature.
There are two types of condensation:
1) Flash...This is where a large volume of steam is introduced very rapidly. A film of liquid water is deposited on virtually every surface in the chamber. The water evaporates off warmer surfaces, such as the optical surfaces, fairly quickly.
2) Hard...This is where the surface is running cooler than the chamber temp. These cool surfaces attract liquid water and tend to hold it for an extended time.
Factors:
Injecting steam upstream from the sensor will cause more condensation in the sensor. Steam will tend to condense on the first cool surfaces it encounters. Injecting steam downstream from the sensor gives the steam mores surfaces and more opportunity to condense before encountering the sensor.
If the recirculation line is cooler than the chamber two things can happen.
Water density is lowered in the recirculation line as water condenses on the cooler surfaces. This lowers the H2O readings on the SEC Signature DIR and generates liquid water in the line which can enter the sensor’s optical chamber and cause erratic outputs. The sensor employs hydrophobic filters but liquid water and significant pressure change can over whelm the filters.
A cool recirculation pipe can conduct heat away from the sensor making it more difficult to maintain a temperature rise in the sensor.
Over the years we have seem may issues with water condensing on the optical surfaces of the SEC Signature. To reduce or eliminate the water issue the user must verify that the SEC Signature’s temperature is 5 degrees C warmer than every step in every cycle. In some cases an external heat source is necessary to achieve the necessary heat rise.
Sensor Electronics Corporation 5500 Lincoln Drive Minneapolis, Minnesota 55436 U.S.A. (800) 285-3651  (952) 938-9486  FAX: (952) 938-9617 www.sensorelectronic.com