Haffmans CO2 meter problems

[magnemelhus]

I recently ran a brett beer through my Haffmans analog CO2 meter and therefore had to clean it before further use. I ran hot (80+C) water through it, which I seem to remember having done defore, but this time when it cooled down, the liquid in the thermometer did not recede into the bottom but separated with air bubbles in between, so there is no way I can read the temp of the beer running through the meter. I don't know if it's because I cooled the thing down too quickly by running beer through it prematurely or because it simply got too hot and the liquid began to boil in the thermometer, but this is seriously hampering my ability to accurately check the CO2 in the beer... has anyone else had this problem or know of some way I can get the air bubbles to rise out of the thermometer liquid? Thanks.

Charlie Magne Melhus
Brewer/Chef, Lervig Aktiebryggeri

[TL Services]

Hi,

Is this the L-shape thermometer? Usually these are mercury, so any spaces would mean the mercury thread has broken. You may be able to fix this by taking the thermometer out and putting it into a fridge/freezer to cool it right down.

If this doesn't work, we have Haffmans thermometers on stock.

[magnemelhus]

Fixed-ish

Yes, it is the L-shaped thermometer, and I found a backup which I replaced the broken one with, and it is working fine. I'll try the fridge with the messed up one, it's always nice to have a backup!

Cheers!

[TGTimm]

The cure for a "broken" thermometer thread is to heat it, not cool it. To get all the mercury into the bulb would require a temperature considerably below that of a freezer. Dry ice might do the job, but....

Using a cigarette lighter, very carefully heat the bulb until the liquid hits the top of the thermo. Remove the heat immediately or you'll bust the bulb and spill mercury. This usually works, but it might take a few tries.

[TL Services]

The cure for a "broken" thermometer thread is to heat it, not cool it. To get all the mercury into the bulb would require a temperature considerably below that of a freezer. Dry ice might do the job, but....

Using a cigarette lighter, very carefully heat the bulb until the liquid hits the top of the thermo. Remove the heat immediately or you'll bust the bulb and spill mercury. This usually works, but it might take a few tries.

Cooling a thermometer is both more effective and an awful lot safer than broken glass and mercury, which are the risks with heating. Having used the former method through over 25 years in laboratory QA roles, I would never advocate heating thermometers, especially with absolutely no control over temperature.

For straight-stem thermometers, these can be restored by swinging/rotating with the bulb outermost; the right-angle bend in the Haffmans model makes this impossible, however.

Returning to the OP, glad to hear you found a spare!

[TGTimm]

So, what do you use to cool the thermo enough? Dry ice? Ethanol and water? This obviously would be safer, if less challenging, than heating a mercury thermometer.

[TL Services]

The choice of coolant is dictated by the scale of the thermometer; for instance as most analyses on this side of the pond are carried out at 20 deg C, we had a lot of thermometers that only started at 15 deg C. This meant we could cool into the bulb with just ice/water mix.

For lower levels, the 'frost' on bulk CO2 tanks is pretty cold...and, although I don't recall needing it, we also had liquid nitrogen on site (which I admit isn't too common!).

As also mentioned, swinging/flicking a straight-stem thermometer can also restore a broken thread...just make sure you hold it firmly and don't let go!