16 MAY 2015 ■ IndustrialHeating.com
O
nce upon a time (a long, long time ago),
The Doctor was called in to investigate
an industrial accident that resulted in
serious burn injuries to personnel in the
heat-treat shop. As part of that investigation, the
subject of what to do in the case of a quench-oil
fire came up and became legend, when in a late
night meeting the infamous phrase, “run baby,
run” was uttered. Let ’s learn more.
Our story begins with an innocent-looking
batch integral-quench furnace, one that sent
six people to the hospital suffering from
severe burns. This particular furnace was
manually operated, and its front (outer) door
burn-off exited from a circular hole near the
bottom of the door, about 50 mm (2 inches)
in diameter. The burning endothermic gas
exited horizontally. It was reported that f lames
suddenly erupted from the opening during
production runs, and anyone caught standing
in front of the furnace – as far as 4.5 meters (
feet) away – was in danger of being burned.
Tw o supervisors, several heat treaters and a
fellow from the nearby plating department were
unlucky enough to be within range of the flames
and were seriously burned. What caused the
furnace to erupt the way it did, and what could be
done to fix the problem, was the subject of intense
debate. Enter The Doctor.
First, this puts renewed emphasis on the fact
that no one should stand in front of a furnace
door for longer than is absolutely
necessary. Yo u would be amazed by
how many conversations are held by
people standing in close proximity to
a furnace door. Don’t do it!
Second ly, a temporary solution
to the problem was to change the
direction of the burn-off by adding a
90-degree elbow into the outer door,
thus changing the f lame direction
from horizontal to vertically upward.
A small hole in the bottom of the
elbow allowed the pilot f lame to
ignite the endothermic gas. This is
one of the reasons that many furnace
atmosphere burn-off cans are moved
up and away from personnel (Fig. 1).The investigation then began in earnest. A
careful check of the furnace and transfer sequence
found nothing out of the ordina r y. In fact, the
f lame eruption was occurring mid-cycle and not
during load transfer. One rather strange clue was
found on the factory f loor, an “X” marked in
chalk that coincided with the distance the flames
traveled horizontally outward from the outer door
when the inner door was opened (such as when a
load was being transferred to or from the quench
vestibule). A second clue was a small remnant
of twine wrapped around the manual-activation
handle for the inner-door cylinder. Could this be
a case of deliberate intent to harm?
It turned out that a disgruntled furnace
operator had indeed discovered how to make the
furnace belch f lames and how far the flame would
extend out in front of the furnace. Positioned out
of sight behind the furnace when someone he
didn’t like “came within range,” he tugged on the
string attached to the inner-door open activation
handle, causing the inner door to open with an
eruption of f lames out the front door. This is
only one of two instances of criminal acts The
Doctor has ever witnessed in the heat-treat shop.
Amazing but true.
As part of the investigation, managers from
several operating divisions had gathered to learn
from the event. One of the other subjects of
intense interest was what to do in the event of a
quench-oil fire. What started as a lively discussion
over lunch extended far into the evening talking
about the do’s and don’ts related to quench-oil
fires. Since one of the most dangerous conditions
is a load jammed half in and half out of the
oil, this was the principal focus of everyone’s
attention. Oil discharge from the overf low pipe
into the pit was also mentioned, however. At
this time The Doctor related a true story about a
similar situation, where up to 100 mm (4 inches)
of oil had accumulated in the pit and was ignited
by a careless employee, destroying seven integral-
quench furnaces and a large portion of a heat-treat
department.
A brief recap of the discussions follows.- The subject of equipping furnaces with a
nitrogen purge (Fig. 2) was raised almost
immediately. Everyone agreed it was a
“Run Baby, Run” – A Safety Story
THE HEAT TREAT DOCTOR
®DANIEL H. HERRING
The HERRING G R O U P, Inc.
630-834-
[email protected]Fig. 1. Preferred location of burn-off can