NEAFC 31st Annual Conference.pdf - New England Association of ...

NEW ENGLAND ASSOCIATION OF FIRE CHIEFS
~skance at automatic gas valves on large lines, even though they xre permitted ff not
even encouraged by all present state gas cedes excepting New York. For this reason,
the area behind an automatic valve should be listed as a zone of potential hazard.
While gas companies habitually minimize the hazardi of fires and explosions as
applied to natural gas systems, tangible proof is seen in reports to the Federal Power
Commission listing over 1,700 failures, ranging in impe.rtance from those with nominal
damage to one which involved injuries to 18 persons and property damage of over
$1,o00,000.
_As approximately half of these fires and breaks occurred while lines were being
tested, this suggests the desirability of alerting the local fire companies whenever such
tests are scheduled.
A tabulation of thc.se reports which included data on lateral damage showed that
.~0% of all reportedl pipeline breaks caused substantial physical or property damage
up to 333 feet from the center of the pipe; 33 % caused such damage up to 500 feet;
with a maximum damage range of over 3,000 feet.
Nor are these 1,700 breaks the isolated experiences of a few careless companies
a.s is shown by the following analysis in which:
,
14 cc,mpanies reported 1 to..!9 failures
20 or more failures
2 .... 40 ....
2 .... 50 " ~
1 .... 80
3 .... 100
The question most frequently asked is that with the good safety, record of manufactured
gas, why should natural’. gas b( different. There are several, answdrs to this,
(~e most important of which is one of relative pressures.
From its point of manufacture to its ultimate use, manufactured gas usually remains
at lo.w pressures. Even in the few instances where the gas is compressed for
distributional purposes the pressure never even approximates the 400, 750, and even
~00 psig of natural gas. Thus all of the pressure hazards describedi apply to natural
gas in much greater force than to manufactured gas. This point becomes particularly
important when it is noted that the explosive force varies as the cube of the pressure.
Thus gas at250 pounds has a potehtial’f0rce 1,000 times that of 25 ~pounds and n’ot ten
times as might be expected.
i- Another important difference is that manufactured gas is so made that no plant
accident can increase its original pressure beyond the ounces provided by the weight
Of the gas holder. Even when such gas is compressed an4 delivered to remote localities
at higher pressures much of it is usually placed in district holders for distribution at
an insured low pressure. In contrast, nearly always the several hundreds of pounds
pressure in natural gas is reduced in a series of mechanical regulators; the failure of
one or more of which can, and has, sent much higher pressures into consumers lines
than they were designed to handle.
Just such a regulator failure was reportedly responsible for cne of our worst gas
disasters--that at Brighton, a suburb of Rochester, New York. Here a relatively
minor fire disrupted two series regulators to such an extent tha~ som:~q~\’g5 pounds
pressure was sent into the residential district, instead of the ounces for which
designed. As a result, thin sheet metal.meters burst, pilot lights burned three feet
99