Chro-KNOWS, Chro-KNOWS, Chro-KNOWS
::uh, am I mispronouncing that?::
Aprroximately in order:
bibliophage: I’ve never hacked into a system where I didn’t already have legitimate access, and even then, it was through pure luck.
DRY: So, to whom did you predict this? Enquiring minds want to know!
2sense: Um, what’s a link harpie, and is it a good thing or a bad?
CnoteChris: The discussion was mostly via e-mail… I suppose they didn’t want to confuse/upset anyone should I not be chosen. I was trying not to act any differently, but… Very perceptive of you, I suppose.
Phobos: But if I close them, then I won’t have a chance to tell everyone about wormholes!
John Corrado: Thanks, but I’ve yet to figure out just where/when my particular continuum is…
Ukulele Ike: I am named after the titan (indirectly), but because the titan Chronos is commonly assosciated with time. Call it an obsession, if you like.
Anthracite: Nobody said anything about the SDSAB, but there is precedent for guest contributors. I’m sure that if the board gets a coal question, you’ll be the first one they ask.
DrMatrixWell, in the first e-mail, TubaDiva did call it a warning…
sailorWell, there was that thing with the coincident 1000th posts, but you seemed to take more offense at that than I… And yes, I do have a long memory.
RM MentockActually, the final S has a soft “s” sound, not a hard “z” sound as in English words… I think.
And the rest of you, I’m not ignoring you, I just couldn’t think of anything witty to add.
Oh, by the way, TubaDiva, does this mean I don’t have to keep this under my hat anymore?
Chronos, you may inform the media of your new status. And everybody else, too. 
For those that aspire to moderator status, drop me an email and I will send you an application. Please remember that manny are called but few are chosen, 'tis the nature of the situation. Nothing is to be inferred or implied by our action in any event.
your humble TubaDiva
Administrator
(asterisks mine)
Tee hee! I love a good typo.
Yeah, RIGHT.
Everybody knows you always loved Chronos BEST.
I’m going to my closet now.
Hey Scarlett, methinks, TubaDiva can spell just fine, the ‘mannny’ is an inside joke. But, maybe you don’t give a darn? 
Mr Chronos oh Great Moderator, SIR:
( Practicing my sucking up technique. )
A link harpy is like a grammer harpy except that the harpy harps on the custom of including a link to the Master’s column you are commenting on.
Scarlett67:
Here is a link to OpalCat’s Teeming Millions Homepage ( which is maintained by Opal and is in no way officially connected with the Straight Dope ).
If you scroll down and look on the left under “Collections” you will find a link called “Inside Jokes”. This page will explain the manny comment and others that you will see around here.
I hope this helps.
( Oh BTW- Feel free to add a joke to the Joke Warehouse if you know a good one. )
TubaDiva said:
So it’s not meantas a punishment, anyway.
Congrats, Chronos. I’ll save the condolences for after we drive you nuts.
Congratulations, Chronos!
Hey, Anthracite, if you want, we can all send in coal questions for you to answer.
Do your worst!
It was either to Grace, Scotticher or Tatertot. I believe it was Grace. If whoever it was reads this thread, maybe she’ll remember. Prediction was made within the last two weeks.
I noticed that you’d been very helpful to newbies and answering technical questions and providing links, like moderators normally do. Had no idea when it was going to be, or what forum. Just that it seemed like you were an obvious candidate to be one.
As someone who hangs out almost exlusively in GQ, it’s nice to have Chronos aboard! Discussions I can only sit and watch are some of Chrono’s best work. I guess congratulations and all too.
A side note: we’re going to need a friendly nickname to pad you when we’re about to post something that treads the line between MPSIMS and GQ, like “Apologies to you, manny, but I was wondering…”. Cronie?
Ok. This might not be that hard, but what’s the minimum PPM for airborne coal dust in an enclosed space without risking an explosion?
That didn’t come out quite right.
What’s the maximum PPM for airborne coal dust in an enclosed space without risking an explosion?
That’s not an easy question to answer at all, due to the fact that coal, unlike gas or oil, has a tremendous amount of variability in it’s chemical makeup, structure, morphology of minerals, and volatile/fixed carbon ratios (the last being the most critical).
Even working with one fixed sample of coal, reproducability is a serious problem. A paper abstract I just read recently on the Web claims a literature review revealed:
Where references (1) and (2) in above refer respectively to:
Taken from: Explosion Characteristic of Coal Dust-Air Mixture
However, according to the South African Government’s “Guideline for the Compilation of a Mandatory Code of Practice for the Prevention of Coal Dust Explosions in Underground Coal Mines.”,
which translates to 0.05 g/l of air, to compare with the first reference.
Another thing to note - are you just talking about coal dust alone, or is your question more looking for the source of coal dust explosions in mines? Coal dust explosions in mines are often secondary exlposions. The primary explosion typically results from the release of coalbed methane (which comes naturally as the coal devolatizes during mining). This primary explosion typically raises a cloud of coal dust in the air from working surfaces, roadways, etc. that results in a larger, secondary explosion of the coal dust itself.
Oh yes, you asked for a “ppm” value. Well, most all studies assume that the coal is in a particle form that has 100% passing through a 200-mesh screen, or about 74 microns in diamter. Well, density of coal varies over various ranks:
Anthracite - 1.47 g/cm[SUP]3[/SUP]
Bituminous - 1.32 g/cm[SUP]3[/SUP]
Subbituminous - 1.30 g/cm[SUP]3[/SUP]
Lignite - 1.29 g/cm[SUP]3[/SUP]
DISCLAIMER - I DO NOT HAVE MY CALCULATOR, SO SOME MISCALCULATIONS MAY OCCUR.
So for fun, let’s take 1.32 as an average value. So assuming an explosive concentration of 50g/m[sup]3[/sup], we get:
50g/m[sup]3[/sup] * 1cm[sup]3[/sup]/1.32g = 37.88 cm[sup]3[/sup] coal/m[sup]3[/sup] air.
If we assume all particles have a diameter of 74 microns (0.000074 m, or 0.0074cm) we get a volume per particle of:
4/33.14159 (0.0074/2)[sup]3[/sup] = 2.122e-7 cm[sup]3[/sup] per particle.
So dividing this out, we get:
37.88 cm[sup]3[/sup] / 2.122e-7 cm[sup]3[/sup] per particle = 1.785e+8 particles coal/m[sup]3[/sup] air
Or wait - I guess if you just wanted ppm by volume, we could do it easier and say 37.88 cm[sup]3[/sup] per m[sup]3[/sup], which of course is 37.88 ppm if you look at it that way.
Have I answered your question yet? My calculator is gone, so I’m trying to do some of the math by hand…but I think the process overall works.
However - due to the high variability of coal and it’s volatile matter content (IMO the most critical measure of it’s explosibility), you may want to set a large safety factor of 10.0, and with a PRB-type Wyoming coal maybe 50.0. Note the wide variability referred to in the first reference.
Una
:eek:
:applause:
[Elvis]Why thank you, thank you very much.[/Elvis]
Although it is a difficult question to answer though. The absolute most drop-down dead difficult one that anyone could ever ask me, and one that I would be very reluctant to answer on the board, is:
“What is the best coal?”
Which would require about the same length of typing as answering “which is the one true religion.”
Una
Anthracite screw a mod. job you should go for Cecils job. Absolute class 
:: Waiting for lightning to stike me down ::
Oh, that’s easy. I mean, Natalie has a nice voice and all, but I think everyone agrees that Nat is the best Cole.
(rimshot) You big teaser!