Author Topic: Thermometer Blowout  (Read 1045 times)

Offline musseldoc

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Thermometer Blowout
« on: December 24, 2011, 04:59:31 AM »
I have a brewing thermometer installed on my HLT, MT and BK.  On both the MT and BK, the thermometer burst.  And by burst, I mean literally sent shards of glass flying across my driveway.  From what I can figure, the pressure inside the thermometer must have built up as heat was applied and finally the pressure was more than the glass could hold.  I have a hard time believing there isn't/shouldn't be a pressure relief port (even a pinhole or something) built into the thermometer case. 

Anyone else had this problem?  Is this a design flaw of the thermometer or is there something I should have been doing as maintenance to prevent this from occurring?  The thermometers are 1-2 years old.  The first one blew out last year, the second yesterday.  Should the manufacturer still warranty these?
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Offline mabrungard

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Re: Thermometer Blowout
« Reply #1 on: December 24, 2011, 05:29:10 AM »
I assume these were glass-faced, dial thermometers and they were located on gas-fired kettles?  Were they liquid-filled guages?

If that's the case, then you might have overheated the dial area.  I notice that Blichmann sometimes has heat guards around the thermometers in that case to prevent the heat from the flame from swirling around the dial. You probably need to protect them more from the heat of flame.  The probe is made for taking the heat, not the dial.
 
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Offline musseldoc

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Re: Thermometer Blowout
« Reply #2 on: December 24, 2011, 06:08:13 AM »
Yes, yes, yes and no. 

I do slide the pot forward on the burner to prevent the plastic-rubber guards on the valve handles from melting.  This directs a lot of the heat towards the back of the pot.  Also, the valve serves somewhat as a heat deflector as it is directly between the thermometer and heat source.  If I were getting too much heat going up the front of the pot, then I should melt the cheap guards before bursting 1/8" glass, but they are fine.  Still, shouldn't there be some means of allowing gas expansion within the thermometer to prevent pressure buildup?
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Offline rjharper

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Re: Thermometer Blowout
« Reply #3 on: December 24, 2011, 11:41:10 AM »
If I recall, the brewmometer dial shouldnt be allowed to get above 145F (if its too hot to touch, its too hot), meanwhile the dip coat rubbers usually have a melting point of at least 300F (it has to be greater than 212F otherwise the heat conducted from the boiling wort would melt it).
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Offline Gribble

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Re: Thermometer Blowout
« Reply #4 on: December 24, 2011, 01:03:08 PM »
How far up your kettle is the thermometer?  I have mine (morebeer dial thermo's) place exactly half way up the kettle (14.5") and haven't had a problem with them getting too hot, although the HLT is the only kettle with a thermo that is direct fired, but it runs for an hour heating up for the first brew of the day, so i assume that it would experience the same temps as your MT and BK being direct fired.
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