How Hot Did It Get?
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Presented by
Jeffery H. Warren, Ph.D., P.E., CSP, C.F.E.I.S. Dyer Harris, Ph.D., P.E., C.F.E.I
Typical Installation
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2 by 6 studs
Cement Board
Stainless Steel Sheet
2 by 6 or 2 by 12 Blocking
Maximum Temperature Distributions in Wall at Point A
Inside of
Cheese
Melter
Back of
Cheese
Melter
Bolt Head
Location
Betw een
Stainless
Steel &
Duroc
Front of 2 x
12 Wood
Blocking
Back of 2 x
12 Wood
Blocking
Interior
Surface of
Back Wall
Panel
Location in Wall
Tem
pera
ture
F
Test 1: Cheese Melter
Test 2: Cheese Melter & Steak Grill
Test 3: Cheese Melter & Fryer w ith Water
Test 4: Cheese Melter & Fryer w ith Grease
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Report 60093
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Left Mounting Bracket
Right Mounting Bracket
Gas Control Valve Knob
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Prolonged, especially cyclic, exposure to heat decomposes wood.
Temperatures do not have to be high to cause charring.
Carbonaceous material self-heats from C + O2 CO2
Key: Can the heat be removed (conducted out) faster than it
is generated? If not, ignition and fire can result
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An estimate is given by Fourier’s equation, a century old.
Note the factors involved: T, x, q, material α, and time
(leave the solution details to us)
Allegations Made
• Regulator defectively manufactured
• Leaks existed before the fire
• Lever arm was not inserted in diaphragm plate
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Testing Regulator
• ½ inch NPT
• ANSI Z21.18 gas appliance regulator
• ANSI Z21.80 line regulator
• Rated for 250,000 BTUH of natural gas
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Results: Housing Integrity
• Some leakage when exposed to temperatures at or above 500°F
• Housing did not leak below 500°F
• Onset of leakage correlates well with first stage degradation of NBR diaphragm
• Amount of leakage not always greater when exposed to higher temperature
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Conclusions:
• Regulator operated at temperatures well above manufacturer’s stated limit
• Post fire examination and testing of regulators can be used to determine fire exposure and explain post fire damage
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