Subject: Risk of CO Fires
Date: 20 Oct 89 00:11:27 EDT (Fri)
From: Larry Lippman <kitty!larry@uunet.uu.net>

In article <telecom-v09i0461m07@vector.dallas.tx.us> amc-gw!ssc!tad@beaver.cs.
washington.edu writes:

> I enjoyed Larry Lippman's description of cable splicing and mining.
> Wasn't it a cable mining operation that set off the Hinsdale fire?

	It could be, but I am not certain; I have encountered different
versions of an explanation for the Hinsdale fire, both from public and
"inside" sources, so I don't know what to believe. 

	In any event, cable mining DOES INDEED provide an opportunity
for a fire under some circumstances if care is not exercised.

	The problem is that in older CO buildings the -48 volt office
battery is distributed using wires having RH and RHW insulation types.
This insulation is rubber, and covered with varnished cloth.  Prior to
1950, the rubber used was natural, with newer cable using neoprene or
butyl rubber.  Over the years much of this rubber will age and
devulcanize, especially on cable which has been subject to excess heat
from overload conditions.  As a result, the insulation will
deteriorate such that movement of the cable would cause the rubber and
outer cloth covering to literally crumble to dust - thereby exposing
bare conductor.

	DC power distribution in large electromechanical CO's results
in some serious current.  In WECO CO's, most major battery feeders use
750 MCM copper conductors, in which the copper is almost one inch in
diameter.  A heavy conductor is also used to keep the battery feed
impedance to a minimum, thereby reducing impulse noise and crosstalk.
A 750 MCM conductor may intermittently carry with safety about 750
amperes, and hence will be fused between 500 and 1,000 amperes,
depending upon the power distribution design.

	Such a 750 MCM conductor has the capability of a *SERIOUS*
amount of short-circuit current.  Almost all battery feeders in older
CO's are protected by fuses which have a certain amount of thermal
delay before opening on an overload condition.  The ability of such an
exposed conductor to strike and maintain an arc - all before blowing a
fuse - is simply *AWESOME*.  While I did not witness the event, I have
seen the aftermath of a 750 MCM conductor carrying -48 volts burn
through a 5/8" steel threaded rod cable rack support - like a knife
through butter, but instead spewing molten metal - BEFORE the fuse
ever opened the circuit!  Power cables run directly on cable rack,
protected from the supporting metal only by a small, thin piece of
fibre insulation.

	I have also, ahem, personally destroyed my share of small
tools in past years due to accidental short circuits between -48 volt
battery and ground.  It is EASY to start a fire if one is careless.

	The risk associated with cable mining is that old power
cables, whose insulation is being held together on a wing and a
prayer, will then crumble upon being disturbed, thereby exposing the
conductor to potential short-circuit.  Power feeders will usually
survive more than one generation of telephone apparatus, which is why
power feeder cables many years old will still be in service.  While
ESS apparatus is usually installed with new batteries, power apparatus
and power distribution wiring, older power feeders often remain to
supply trunk circuits, carrier, transmission and ancilary facilities.

	As I see it, the former Bell System and present RBOC's must
shoulder some responsibility for the risk of CO fires.  It has only
been in recent years that smoke detectors have been commonplace in
CO's.  The traditional method of fire detection - still in service in
many CO's - is to run "fire wire" around cable rack and apparatus
which is deemed to be vulnerable to fire.  Fire wire is a low-melting
point wire similar to solder; it is about 10 AWG in size.  When the
temperature reaches a certain point (I don't remember the setpoint),
the fire wire melts and opens a circuit.  The problem with fire wire
is that it is fragile, easily damaged and the fire wire splices are
often intermittent.  The result is that fire wire causes many a false
alarm - which is then ignored.  Also by the time fire wire melts due
to an actual fire, one is in *deep* trouble since this is hardly an
early warning detection system.

	Another problem is that the Bell System has traditionally
sought to "take care of its own" and has thereby tried to avoid any
embarassment with a fire department due to false alarms.  The net
result is that it has been rare for a CO fire alarm to be called into
a fire department without a craftsperson investigating the matter
first - a situation which can lead to serious delay and damage in the
event of a real fire.

	The above attitude of avoiding "embarassment" and "adverse
publicity" still exists.  I personally know of an example which rather
shocked me.  A few years ago an employee of a contractor accidentally
fell off a truck at the New York Telephone Franklin St.  CO in
Buffalo, NY.  The employee was knocked unconscious.  The security
guard (this is the main CO in Buffalo, so there are full-time guards)
did NOT call 911 for an ambulance, but instead called a *private*
ambulance service which resulted in a significant delay in response as
opposed to 911.  The security guards apparently have standing
instructions to call a private ambulance, and NOT to call 911 unless
it is a "dire emergency".  Why a private ambulance?  Because then
there will be no public record of any accident and no risk of a police
report.  Not a good attitude.

<> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp.
<> UUCP  {allegra|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry
<> TEL 716/688-1231 | 716/773-1700  {hplabs|utzoo|uunet}!/      \uniquex!larry
<> FAX 716/741-9635 | 716/773-2488      "Have you hugged your cat today?" 

Subject: Lorain Products Co. & More on Telephone Power Plants
Date: 31 Mar 91 00:37:11 EST (Sun)
From: Larry Lippman <kitty!larry@uunet.uu.net>

In article <telecom11.238.2@eecs.nwu.edu> 0004133373@mcimail.com
(Donald E. Kimberlin) writes:

> > By the way, there is another Ohio name to add to the saga.  C. P.
> > Stocker designed the first magnetic 60-20 hz converter, called it the
> > Sub-Cycle, and founded Lorain Products Inc. just west of Cleveland.
> > They also made no end of telco power equipment.

> Lorain Electric is, of course, still in business, providing many a
> Sub-Cycle to this very day.

	Lorain Products has unquestionably been the largest outside
supplier of power plants to WECo and the Bell System.

	It is interesting to note that while WECo designed and
manufactured many power plants, in many instances they simply chose to
use a Lorain product - which says a great deal about the engineering
and manufacturing quality of Lorain Products.

	One thing I could never figure out was what motivated WECo to
design and manufacture a power plant internally as opposed to
obtaining one from Lorain Products under a KS-spec.  No one I knew at
WECo had the answer either, and the best we could figure was that with
every new power plant requirement, someone in upper management at WECo
would flip a coin having two sides: WECo on one, and Lorain on the
other! :-)

> Voltages of 24, 48 or 52 Volts at 2,000 or
> 5,000 or even 10,000 Amps weren't (and still aren't unusual to provide
> talk battery for a whole telephone exchange.  They consist simply of
> an AC-powered set of rectifiers charging ("floating") a large string
> of lead-acid batteries, just like the one in your car, to power the
> phones and for that matter the switching and transmission equipment as
> well.  What's fun is to happen to be near the cells when the AC fails.
> The current draw is such you can see the plates in the glass cell
> tanks bend and flake under the stress.

	One can also *hear* the plates in the cells creak, along with
hearing an immediate evolution of hydrogen gas bubbles which are thus
displaced when the plates are stressed.

> It consisted of *forty-two* 6 Volt automobile batteries
> connected in series, floated across a rectifier.  THAT not only could
> shock you; it could do a nice burn at the same time. Needless to say,
> one works *very* carefully in such plant!

	While I did not see it happen, I once saw the aftermath of a
500 MCM 130-volt power feeder cable which shorted to a cable rack when
its aged rubber insulation disintegrated during cable "mining" work.
The resultant arc burned through a 1/4" by 1-1/2" piece of steel like
a knife through butter.  The craftsperson doing the work suffered only
minor injuries - not from the arc or spewed molten metal, but from
falling off a ladder in surprise! :-)

	A truly scary experience is to move a piece of old RH or RHW
rubber-insulated power feeder cable, watch both the outer insulation
and the rubber flake into dust, and see exposed conductor within a
fraction of an inch of grounded metal!  I could never understand why
WECo continued to use potentially unstable rubber-insulated power
cable for almost forty years after far superior plastic insulation was
available following World War II.

	A cardinal rule in working around batteries is to always use
tools that are wrapped with insulating tape - in order to prevent
accidental short circuits.  I must confess that I did not always
follow this rule, and that I have suffered the consequences - which
fortunately were minor.


Larry Lippman @ Recognition Research Corp.  "Have you hugged your cat today?"
VOICE: 716/688-1231       {boulder, rutgers, watmath}!ub!kitty!larry
FAX:   716/741-9635   [note: ub=acsu.buffalo.edu] uunet!/      \aerion!larry

Subject: Western Electric Power Cable
Date: 6 Apr 91 00:24:11 EST (Sat)
From: Larry Lippman <kitty!larry@uunet.uu.net>

In article <telecom11.263.4@eecs.nwu.edu> DAN@gacvx2.gac.edu (Dan
Boehlke) writes:

> > 	A truly scary experience is to move a piece of old RH or RHW
> > rubber-insulated power feeder cable, watch both the outer insulation
> > and the rubber flake into dust, and see exposed conductor within a
> > fraction of an inch of grounded metal!  I could never understand
> > why WECo continued to use potentially unstable rubber-insulated
> > power cable for almost forty years after far superior plastic
> > insulation was available following World War II.

> It is my understanding that good real rubber products resist acid
> better than even most of today's plastics.  Acid resistance would be
> very important around batteries.

	Synthetic rubber does have good chemical resistance to acids
in concentrations likely to be found in storage battery electrolytes.
In fact, common telephone industry practice for cable connecting
directly to battery terminals is to use finely stranded welding cable
with "SO"-type rubber insulation.

	However, WECo traditionally used type RH or RHW rubber
insulation for ALL power cabling in gauges ranging from 14 AWG to 750
MCM.  Chemical resistance to acids was not really an issue once
outside of the battery room.

	As a somewhat interesting aside, WECo 750 MCM power cable had
"non-traditional" uses.  A sixteen inch length (which weighs about
three pounds) makes an excellent "attitude adjustment tool" for
telephone company personnel who have to work in crime-ridden urban
areas.  I once saw its effectiveness in deterring a car theft in the
parking lot of a New Jersey Bell central office in Newark.  The power
cable section also had the advantage of not being an unlawful weapon.
After all, it's an engineering sample, right? :-)


Larry Lippman @ Recognition Research Corp.  "Have you hugged your cat today?"
VOICE: 716/688-1231       {boulder, rutgers, watmath}!ub!kitty!larry
FAX:   716/741-9635   [note: ub=acsu.buffalo.edu] uunet!/      \aerion!larry