HE.net, Fremont-2 outage?

Joe Greco jgreco at ns.sol.net
Wed Nov 4 12:26:15 CST 2009


> On Wed, Nov 4, 2009 at 8:19 AM, Michael Holstein
> <michael.holstein at csuohio.edu> wrote:
> >>> FWIW: http://www.he.net/releases/release18.html
> >>>
> > Well, they say it's a Cat unit, so probably one like this :
> > http://www.cat.com/cda/components/securedFile/displaySecuredFileServletJSP?x=7&fileId=1081064
> >
> >> How long can they go on those 3000 gallons under their current
> >> load?
> >>
> > That engine is rated to consume 70.9g/hr at 50% .. so using a conservative
> > estimate, I'd say about 42 hours.
> 
> Wouldn't the conservative estimate be 21 hours?  (3000 gallons, 142
> gal/hr at 100% load);
> you'd get more hours out by guessing at what fraction of full load the
> generator is
> running, but anything longer than 21 hours is fudge-factor guesstimate
> based, and not
> to be counted on.

The mildly conservative estimate is 21 hours minus the guaranteed 
turnaround time for your fuel vendor to show up, minus some more
fudge factor to allow for someone to actually hook up and actually
refuel, etc.

The paranoid conservative estimate is more complex; you have to assume
you call the primary vendor, they don't show, and then you have to 
call your backup(s).  If you have a three hour guarantee in the contract,
you have to remember that this can still represent some scrambling by 
your vendor, and if you're lights out, it's quite possible that others
are as well, and hospitals and city hall might rate as more urgent.
It's also possible that the truck'll have a flat, mechanical problems,
or try to rush through the railroad crossing about to be rendered
unpassable by a slow-moving freight train.  It'll probably take you
an additional hour to panic and call your backup supplier; now you are
a bunch of hours shorter on capacity than you thought.

Of course, a lot of this is simply how you look at the problem.  If
we're talking runtime-until-dry, yeah, 21 hours.  If we're talking a
practical number of how long can you go until it's proper for some
panic to set in and calls to get made, it's more like half that.  ;-) 

With power:

N+1 is usually better than N
Best to assume full load when doing math
Things will go wrong, predict common failures
The best plans are still prone to failure
Safety margins can save your rear
etc

... JG
-- 
Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net
"We call it the 'one bite at the apple' rule. Give me one chance [and] then I
won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN)
With 24 million small businesses in the US alone, that's way too many apples.




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