Problems with LIG thermometers

[OlDave]

Has anyone here done any research or extensive testing on the new generation LIG thermometers that are filled with various organic liquids?

We are having problems with a few of the ERTCO thermometers that are filled with a red kerosene. After heating them to near maximum and then allowing them to cool to ambient, they will develop a split in the column after a period of time.

Details of the thermometer:
Range: 50°C to 110°C
subdivisions: 0.5°C
immersion depth: 30mm
Overall length: 145mm
First division (50°C) about 55mm from the tip of the thermometer
Contraction chamber about 40mm from the tip

Test scenario:
Placed in a stirred liquid bath to the immersion line and tested at 55°, 80°C and 105°C
Removed from liquid bath and left in the vertical position for cooling.

Problem noted:
After a period of time, anywhere from 2 hours to 30 hours, a bridge of the liquid will form in the capillary. This bridge will form between the lowest graduated division and the start of the contraction chamber.

My guess is the kerosene leaves a thin film on the wall of the capillary. Over a period of time, gravity will draw this thin film downward so that the film becomes thicker as it drains. Eventually this film becomes thick enough to bridge the capillary and BAM, there is my problem.

To rejoin this split you have to heat the thermometer up to where the column enters the upper expansion chamber, but then you have the same problem as before when you cool it down. I have even cooled the thermometer slowly at a ramp rate of 0.1°/minute hoping that would allow enough draining time to eliminate the problem. No help.

Anyone else have any similar observations?

[USMCPMEL]

http://www.coleparmer.com/techinfo/techinfo.asp?htmlfile=Reunite_Cols.htm&id=638


http://www.bing.com/search?q=THERMOMETER+LIQUID+SEPERATION&src=IE-SearchBox&FORM=IE8SRC

Looks like some information is available. Good luck let us know if you have any success.

[username_7]

If you're interested in replacing your LIG thermometers, Fluke (formerly Hart Scientific) has a new digital thermometer that is intrinsically safe and designed specifically to replace LIGs.  See specs and temp range here:

http://www.fluke.com/fluke/usen/Calibration-Instruments/Temperature-Calibration/1551A-Ex-and-1552A-Ex-'Stik'-Thermometer.htm?PID=72061

[spanishfly25]

Try lowering the temperature below the bulb and collect all the liquid at the bottom instead of the top.