18 MAY 2015 ■ IndustrialHeating.com
good idea, but the reality was that most of the company’s
integral-quench furnaces were not equipped with this
feature. A management action item was undertaken. One
interesting part of the discussion centered on a sintering
furnace in which the empty nitrogen-purge cylinders had
been replaced by oxygen cylinders (despite the fact that
they had left-handed threads). One of the engineers stated
that it is still the single loudest explosion he has ever heard
... and he was in an adjacent building.- Also discussed was educating supervisors not to give
instructions to “shut everything off ” (which included the
nitrogen-purge cylinders) in the hopes that the fire will
burn itself out. An entire plant was lost because of this
mistake. - The question was raised if the front door should ever be
opened “ just to take a peek” while f lames are erupting and
the hot load is still volatilizing the quench oil. Surprisingly,
this sparked a heated debate as to whether this technique
should or shouldn’t be used. Several managers stated that
they gather a crew of trained individuals in proper personal
protective equipment; open the door; and, using long rods,
attempt to clear the jam in an effort to move the load either
down or up out of the oil. Others, including The Doctor,
view this as putting personnel in unnecessary danger. - Who should be your first call? Is it to your supervisor,
his boss or 911? While most fire departments do not
train for heat-treat-related emergencies, they are trained
professionals that deal with fire events all the time. Since,
for example, a grease fire in a kitchen can get out of control
in as little a 30 seconds, remember to act quickly and
responsibly. Confirm by asking that someone has indeed
called the fire department. - Should the furnace ever be placed in manual mode and
the operator attempt to reposition the load? The consensus
was that this is a prudent act to perform provided one can
do it safely and it does not involve attempting to open the
front door.- Where is the control panel in relationship to the front
door? In many instances it is next to it, perhaps convenient
during normal operation but unsafe to stand in front of
in emergency situations. While relocation of the control
panel may not be an easy task, everyone was in agreement
it should be on the side of the furnace, away from the
door area. Remember that the pressure inside the furnace
builds up, and one of the ways it will relieve itself is to
push the front door outward away from its mating f lange.
The Doctor has seen 1-meter (3-foot) f lames driven out
horizontally under high pressure at the front door during
such situations, so beware! - How often should grids and baskets be inspected, and do
you attempt to weld repair a grid in order to extend its life?
Grids and baskets should be inspected daily for cracks,
warpage or other signs of damage. If your application is
carburizing, weld repairs will fail quickly. Grids that tear
apart are a major cause of load jams. - What other scenarios can cause fires? There are obvious
dangers that most of us are taught to watch out for, such as
water in quench oil that can cause a quench tank to erupt
into f lames. Another subtle but important consideration
is the makeup of our workloads. We must pay attention to
surface area and remember that whether we are running
tiny fasteners in an integral-quench furnace or moving
large, heavy parts by crane for quenching into an open tank,
the transfer must be smooth, performed in a timely manner
and the load must be fully submerged. Huge evolutions of
f lame may be dramatic, but they are deadly!
Conclusion
While we all had a good laugh over the fellow who uttered “run
baby, run” when faced with immediate danger, his comment
hits the mark in many ways. When faced with an emergency,
it is only human nature to protect one’s life first. This is where
knowledge, understanding and training of operators, supervisors
and managers helps everyone make informed decisions.
When is the last time your shop had an emergency drill
to practice various dangerous scenarios that can arise? Never
assume that the person next to you has clearly heard or
understands your commands. Asking them to repeat your
instructions is always a good idea. The Doctor still remembers
shouting “don’t spark the pilot” then holding on to a ladder
about 20 feet in the air (in a horizontal position to the f loor)
because the salesperson, trying to be helpful, thought he heard
“spark the pilot.”
The bottom line is accidents happen, but we don’t want
people injured because of them. Train, train and train some
more.THE HEAT TREAT DOCTOR
®Figure 2. Nitrogen-purge setup with redundant cylinder banks