Re: [DCHAS-L] NFPA math

Any NFPA gurus (Richard Palluzzi?) out there want to interpret for me what this means:

From NFPA 45

"A.9.5.3 The requirements of 9.5.3 can be accomplished by either of the following:

 (1) Limiting the temperatures of internal heated surfaces that can be exposed to the vapors to no more than 80 percent of the autoignition temperature of the material being heated"

(2) [cut since I'm trying to figure out what 1 means]

Say you have an autoignition temp of 225C (hexane); what is "80%"?

Of course if you stay in celsius ("80%" of 225 is 180) you're not doing a true ratio.

If you convert to Kelvin and back 225=489.15K; 80%=398.52K = 125.37C

There's a bit of a difference between 125C and 180C.

Does anyone know if NFPA inted it to be a "true" 80% ratio, i.e. in K?

In this case, the proposed heating temp is well below both those numbers, but there are other solvents potentially being used for this project so  I'd like to look at all of them.

Jeff

--

Jeff Lewin

Director of Chemical Laboratory Operations

Research Integrity Office

Laboratory Operations

205 Lakeshore Center 

Michigan Technological University

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