Proactive Protection in Classified Areas
How can safety measures be improved to prevent mobile equipment operating unsafely under hot work permits or within the fringes of the classified areas?
Several highly publicized explosions and fires
in the refining and fuel storage industries
have resulted from vapor leaks followed by ignition.
Heavily regulated by governments
throughout the world, refineries and similar energy industries
have a responsibility to ensure any explosion risk
is kept to a minimum.
Within the United States, refineries have been required
to comply with the codes and regulations for the use of
powered industrial equipment in explosion hazardous
areas.However, due to code interpretation and explosion
hazardous areas rating variances, equivalent levels of regulation
and worker protection have not been established.
This means many refineries workers remain at risk today.
To start a fire and/or explosion takes three constituents
coming together: an oxidizer, a hazard
(gas/vapor), and an ignition source.While it is not possible
to eliminate the oxidizer (air), it is possible to plan
processes and protect equipment to limit, wherever possible,
the chances of the hazard’s getting in contact with
an ignition source. However, it is a matter of fact that
when it comes to the control of mobile equipment,many
responsible for site operations lack the experience, site
discipline, or budget to enforce safe and acceptable practices
in terms of control of the equipment’s movement.
Before examining how to better manage the movement
of mobile equipment under work permits or in
“low” risk areas, we should agree that when in areas that
are formally classified, the equipment used should be designed
and certified to operate safely in those areas.Again
referring to the codes and regulations, if an area is classified
as Class 1, Division 1, or Zone 1 certified, then only
equipment certified to EX Class 1, Division 1, or Zone 1
codes and regulations should be used in those areas. For
Division 2 or Zone 2 hazardous areas, equipment should
at least be tested and certified according to the codes and
regulations applicable to equipment in those areas.
Insisting that only Division 1, Zone 1, Division 2, or
Zone 2 certified equipment can be allowed to operate in
the refinery is often neither practicable nor desirable.
Imagine insisting that a 100-tonne mobile crane required
for a maintenance job must be converted to fully explosion
proof before being permitted to operate on site. I
doubt any rental company can afford to keep an explosion-
proof crane on standby for the occasional job in an
explosion hazardous area.The same thing applies to personnel
carriers, vans, tractors, tankers, mobile compressors,
and gen-sets operating inside the refinery perimeter
and not being permitted into formally classified areas
without first being made fully explosion proof. In these
situations, most refineries rely on the use of hot work
permits and risk management processes. In most cases,
the person(s) responsible for issuing the work permit
have the relevant experience and the necessary authority
to manage the risk involved with the task at hand.
Limiting the Risk through Gas Detection
How do we limit the chances of hazard and ignition
source coming together? When diesel powered equipment
is used, it is common to insist that an engine overspeed
air shutdown valve and an exhaust spark arrestor
are installed.Provided these components are correctly fitted
and correctly serviced, they should alleviate some of
the many ignition sources to be found on a forklift truck,
crane, tanker, compressor, or gen-set.
But what about the other ignition sources, such as
electrostatic releases, flame flashback through the inlet
system or flame emission (not sparks) from the engine
exhaust, and sparks from any electrical equipment, such
as alternators, lighting, instrumentation, or engine management
systems? What about the potential of hot surfaces’ causing auto-ignition? Who will ensure
that the over-speed valve has been correctly
calibrated before the operation begins? And
if so, how will the operator of the crane,
truck, van, etc. know whether the area immediately
surrounding his equipment has
reached an explosive gas or vapor level? Besides
working under a hot work permit, it is
common practice for the operator to carry a
hand-held gas detector. But who or what
procedure ensures the gas detector has been
specifically calibrated against the gases and
vapors that could be released into the operating
area? Does the gas detector always remain
with the equipment and its operator
throughout the permit process, or does the
operator stray away from the equipment? A
hand-held gas detector relies on an operator
to “kill” the equipment before it ignites the
explosive atmosphere that has developed unexpectedly.
Unfortunately, it is an undeniable
fact that most accidents are caused by human
failure or response time.
One could rely on gas detection systems
monitoring the site, but it would be necessary
to ensure sufficient gas detector points cover
all areas where mobile equipment is operating—
because, if not, the hazard and ignition
source may combine before appropriate action
can be taken.
A better approach may be to have the
equipment and its ignition sources ringfenced
by dedicated gas detectors that will automatically
shut down the gen-set or compressor
when flammable gases or vapors are
detected. However, if the equipment is mobile,
such as cranes or vans, the process becomes
rather impracticable. Besides that,how
do you prevent equipment that has automatically
shut down from being restarted before
it is safe to do so?
Relying on engine over-speed valves,fixed
gas detectors, and hand-held gas detectors
may have been the traditional reactive protection
methods of yesterday. However, with
today’s powered industrial equipment relying
on sophisticated electronics, the use of overspeed
valves and the limitations of relying on
hand-held gas detectors being held by fallible
workers does not appear the way to improve
facility safety going forward.
Today’s proactive gas detection technologies
limit the risks to workers and at the same
time allow the operator the flexibility he needs
to perform his job safely and efficiently by:
• Ensuring the equipment that is operated
has its own integral gas detection system that
will allow the equipment to function only
when the immediate area surrounding the
equipment is free of flammable gas or vapor.
• Ensuring before the operation begins,
the equipment performs a forced automatic
gas test to ensure it is calibrated correctly.
• Ensuring equipment that is operated
has its own integral gas detection system that
shuts down the equipment automatically and
immediately when an unexpected increase in
flammable gas or vapors is detected in the immediate
area surrounding the equipment.
• Ensuring if shutdown does occur, any
restart is controlled by a person in charge of
• Installing protection systems that are
simple to fit, simple to use, simple to maintain
and, most importantly, designed to isolate
most of the ignition sources from explosive
This article originally appeared in the July 2008 issue of Occupational Health & Safety.