Dryness, Superheat and Non Condensable Gases (NCG)
On occasion one of the channels on my Kaye Validator 2000 data logger reads “UNDER” or “OVER”, what’s the cause of this?
Typically a channel will read “UNDER” or “OVER” when water has entered the SIM of the Kaye Validator 2000 data logger and the cold junction has become wet. Check each thermocouple wire to ensure that you have added drip-cuts to each wire 1m from the SIM to allow the condensate to drain away from the sheathing. Sometimes a broken thermocouple is replaced with a new thermocouple but a drip-cut has not been added to the new wire and water finds it’s way into the SIM.
The SIM should be opened and allowed to dry out. Paper towels should be used to get rid of any excess water. A high pressure air source can be used to blow away excess water also. The channel should return to a room temperature value once it is fully dried out. Ensure that you have rectified the source of the water before proceeding with further studies. You may notice that the wire terminations have oxidized (looks like white powder) due to the presence of moisture. A small piece of emery paper connected to a narrow wire or flat head screwdriver can be used to restore the terminals.
Why does water appear in the Sensor Input Modules (SIM) at the back of my Kaye Validator 2000 data logger?
I take it that you only see this when you are performing thermal mapping studies on steam related equipment such as Autoclaves or Sterilizers. Or you are performing Steam In Place (SIP) of process equipment such as Bio-rectors and filter sterilizations?
If this is the case then what you are seeing is steam condensate (water). The steam condensate tracks back along the inside of the thermocouple sheathing as the condensate/steam is under pressure within the chamber. The water finds the easiest route out of the chamber via the TC sheathing and ends up in the SIM where the Thermocouples are terminated.
To prevent water from entering the data logger terminals you can add drip-cuts to the TC sheathing approximately 1m from the Kaye Validator 2000 data logger. Exercise good housekeeping by placing paper towels or a container under the cuts to collect the condensate.
Typically a channel will read “OPEN” when either the positive or negative wire of the thermocouple has been damaged or has cracked. The most common place to find this is at the tip of the thermocouple whereby the twisted pair junction needs to be re-made. Ideally the junction should also be welded using a thermocouple welder as this prevents the wires from becoming separated and hence prolongs the overall lifetime of the thermocouple loom. Welded thermocouples are less likely to result in repeat temperature mapping studies due to open circuits. QualUs have a range of thermocouple welders to suit all requirements, contact QualUs today for further details.