Leaking MLT - Cracked Brass

[BendBrewer]

I was preheating my FlyGuy MLT yesterday and noticed it was leaking for the first time and it was leaking like a sieve. I tried to tighten the ball valve but it wasn't that loose. Filled it back up and still leaking like crazy.

I took the valve off and this is what I discovered:

I have to think that I would remember dropping the thing off of a 5 story building. Can anyone think of what could have caused this brass pipe to essentially shatter? It is cracked all the way around and all up and down the threads.

 

[tigmaster]

yeah thats a real easy one for me....u tighted it too tight....it also looks old and used....brass is soft....use 304 stainless...way better

 

[BendBrewer]

Well of course it is used. It's got about 200 gallons through it.

Hmmm, thanks for the easy answer. I don't remember cranking on it before noticing the leak and didn't touch the thing between brews. We have had some really cold weather. Maybe that exasperated the stress on the thing. If and when it happens again, I guess I'll be going with SS. Thanks again. I would never have thought it was that soft.

 

[tigmaster]

yeah i didnt think about ur local. goin from cold to hot could have defin. done that...u should be good with stainless...use a good amount of teflon tape...ss will gale real easy

 

[BendBrewer]

Yeah I took the tape off of that to show the cracks better. Had to run to HD and replace it yesterday and just got brass again. Will pick up a SS back-up next time there.

Cheers!

 

[RobBug]

I have to think that I would remember dropping the thing off of a 5 story building. Can anyone think of what could have caused this brass pipe to essentially shatter? It is cracked all the way around and all up and down the threads.

Brass is a super soft alloy. When you put it together you applied a lot to tensile stress on the pipe. That alone wouldn't cause it, but if you did that many batches, you applied quite a bit of cyclic stress to it also. Over time the metal will fatigue under the continual cycle of cooling and heating rapidly. Classic example of fatigue failure. You have some plastic deformation (stretching) with brittle fracturing (cracking and the clean break).

Another thing - this was an adapter fitting on the ball valve correct? If so it may have been subjected to high enough temperatures to cause "creep" (metal more likely to "flow" over time). The melting point of brass is around 1600F vs 2550F of stainless steel. Your burner may put out around 1980F ish. So if the pipe connector reached 30% of the value of the melting point (~1120) creep began and you had plastic deformation over time leading to the fatigue failure.


In short, the life span of brass under those conditions are numbered.

Hope that explains it.

 

[Alemaker]

yeah i didnt think about ur local. goin from cold to hot could have defin. done that...u should be good with stainless...use a good amount of teflon tape...ss will gale real easy

I'm not familiar with this term. What does "gale" mean?

 

[tigmaster]

ss will baiscally cold weld itself together if u dont use teflon tape...and tighten it to tight

 

[RobBug]

I'm not familiar with this term. What does "gale" mean?

I think tig meant to spell it thus: (not knocking on spelling but just making sure it's clear)

gall   /gɔl/
[gawl]
–verb (used with object)
[...]
4. Machinery . (of either of two engaging metal parts) to lose metal to the other because of heat or molecular attraction resulting from friction.
5. Metallurgy . (of a die or compact in powder metallurgy) to lose surface material through adhesion to the die.


SS is very susceptible to this type of issue under certain circumstanced. As stated before by tig, Teflon tape prevents this.

 

[BendBrewer]

I wonder if I can get FlyGuy to edit his parts list with this pic.