Confined Space Accidents #2
Accident #1
Two men were installing piping in an open
sump at a gasoline service station. A
tank bung was unplugged and left open, allowing gasoline vapors from within the
tank to accumulate in the sump. The
workers were heating the pipe and fittings with an electric heat gun to set the
glue when the vapors ignited. A third
worker brought a fire extinguisher over to the sump and put out the
flames. One of the men in the sump
suffered first degree burns to his face and missed work the following day.
Review
1. Isolation
of the confined space from another system (the storage tank) containing a
hazardous atmosphere was not performed, allowing vapors to migrate into the
work area.
2. The
work area (sump) was not monitored for the presence of flammable vapors.
3. Electrical
equipment (heat gun) not designed for use in a hazardous atmosphere was used in
an area where gasoline (flammable) could accumulate or otherwise be present.
Isolation, monitoring and the use of properly
designed electrical equipment are all requirements. Had even one of these requirements been met,
the accident would probably not have occurred.
Accident #2
A worker for a firm that was retained to
sandblast an underground storage tank turned on an electric vacuum to remove
the spent abrasive that had accumulated on the tank bottom. A spark from the vacuum cleaner ignited
vapors within the tank. He died later as
a result of his burns.
Review
1.
Sandblasting is a spark producing operation and should never be
performed in a space that contains sufficient flammable residuals that the
flammability level within the space can cause a combustible gas indicator to
indicate the presence of flammable vapors.
This following steps need to be assured A) isolation from an adjacent
tanks (through vapor recovery systems, manifolded vent lines, siphon piping,
etc.) B) flammable
residuals need to be removed to the extent possible (using pumps, manual
scraping/shoveling, drying with absorbents and ventilation) C) adequate ventilation of the space needs to
be maintained. Ventilation needs to be
sufficient to ensure that the rate of air exchange exceeds the rate of
flammable vapor generation.
2. The
work area (tank) was not monitored for the presence of flammable vapors.
3.
Electrical equipment (vacuum cleaner) not designed for use in a
hazardous atmosphere was used in an area where flammable vapors could
accumulate or otherwise be present.
Accident #3
Two repairmen went to inspect an underground
tank for leaks at a remote, isolated farm site.
Stored product had been removed from the tank the previous day by
another contractor. One of the men
entered the tank without respiratory protection or a retrieval harness and
without monitoring for vapors as it was assumed that the tank was clean. When he reached the tank bottom, he was
overcome by the vapors and collapsed.
The other worker realized that he could not retrieve his coworker
without help and immediately drove to the nearest farmhouse, nearly a mile
away. By the time rescue services
arrived at the site, the worker was already dead.
Review
1. It
is never prudent to assume that an atmosphere is safe based on the actions of
others (assume = ass + u + me). The
atmosphere within a confined space must be considered hazardous until proven
otherwise. Thus, this was a permit
required confined space entry.
2.
Confined space regulations require three persons to be present when the
confined space contains (or could contain) a hazardous atmosphere.
3.
Confined space regulations require a reliable means of communication be
available for contacting emergency services.
4.
Monitoring of the confined space for oxygen, flammability and toxicity
must be performed prior to entry.
5.
Entry personnel are required to wear a harness attached to a lifeline
for retrieval (non-entry rescue) purposes.
The lifeline must be attached to a fixed point outside of the confined
space, or, when the depth of the confined space is 5 feet or greater, to a
mechanical retrieval device (hoist and tripod).
6.
Respirators must be selected and used to protect workers from
atmospheric contaminants.
7.
Permit-required (those containing or potentially containing hazardous
atmospheres) confined spaces must be ventilated prior to entry and continuously
throughout entry.
These men were sent to investigate an
underground tank for leaks. Now that the
tank was empty, if a leak was present, vapors or raw product was free to
reenter the tank. Additionally, product
clinging to the walls, permeated into rust scale and under overlapping seams
can vaporize into the tank displacing oxygen and creating a flammable/toxic
atmosphere.
Accident #4
A worker entered a toluene tank to begin
cleaning operations without wearing an available respirator that had just been
tested moments prior to entry. He
quickly was overcome by the vapors in the tank.
When firemen arrived on site, they began using an electric saw to widen
the opening to allow for entry wearing an SCBA.
Review
1.
Monitoring of the confined space for oxygen, flammability and toxicity
must be performed prior to entry.
2.
Entry personnel are required to wear a harness attached to a lifeline
for retrieval (non-entry rescue) purposes.
The lifeline must be attached to a fixed point outside of the confined
space, or, when the depth of the confined space is 5 feet or greater, to a
mechanical retrieval device (hoist and tripod).
3.
Respirators must be selected and used to protect workers from
atmospheric contaminants.
4.
Electrical equipment (saw) not designed for use in a hazardous
atmosphere was used in an area where flammable vapors could accumulate or
otherwise be present.
Toluene has a permissible exposure limit of
100 ppm, but quickly becomes an imminent danger (IDLH = 500 ppm). Ventilation, if used, was incapable of
changing out the air frequently enough to maintain the atmosphere within the
acceptable range for breathing without a respirator (it can be presumed that no
ventilation was used as the atmosphere reached the flammable range during
rescue operations). The removal of the
toluene residual (cleaning) is a process that inevitably disturbs the product
causing it to emit vapors more rapidly than undisturbed product, warranting the
use of a respirator even when initial monitoring shows an acceptable
atmospheric concentration. Further,
monitoring form the outside of a storage vessel provides incomplete information
as to the actual atmospheric concentrations that may be encountered within the
vessel. The slope and configuration
(i.e. baffles, etc.) of the vessel and the ventilation configuration can allow
for hot spots in areas that are not monitorable prior to entry. The first duty of the entrant is to assure
that there are no localized areas of increased atmospheric concentrations
within the confined space prior to initializing work procedures.
Accident #5
A welder was repairing a steel tank. He had just placed his cutting torch inside
the tank when the break-time whistle sounded.
After taking a 15 minute break, the welder returned to the tank, climbed
inside and struck an arc with his cutting torch. The welder was unaware that his cutting torch
had leaked acetylene into the tank through the duration of the break. The arc caused ignition of the acetylene gas
that had accumulated in the tank and the welder caught fire. He later died as a result of his burns.
Review
1.
When the break-time whistle blew, the welder should have secured the
cutting torch and shut off the flow of gas from the regulator on the acetylene
canister.
2.
Cutting and welding are hot work operations that require a fire watch to
be present.
3.
Cutting and welding operations can emit toxic vapors into the air and
require exhaust ventilation, at minimum.
Accident #6
A contract employee was cleaning paint chips
out of an 8,000 gallon steel above ground storage
tank. He was overcome by the
cyclohexanone vapors from the solvent.
Two workers attempted to rescue him, but also collapsed. No monitoring of the tank atmosphere was
performed prior to entry or subsequent to entry. All three men died.
Review
1.
Monitoring of the confined space for oxygen, flammability and toxicity
must be performed prior to entry.
2.
Entry personnel are required to wear a harness attached to a lifeline
for retrieval (non-entry rescue) purposes.
The lifeline must be attached to a fixed point outside of the confined
space, or, when the depth of the confined space is 5 feet or greater, to a
mechanical retrieval device (hoist and tripod).
3.
Respirators must be selected and used to protect workers from
atmospheric contaminants.
4. Coworkers need to be trained and reminded
that entry rescue can only be performed in a higher level of personal
protection than that worn by the entrant (if he collapsed, the atmosphere is
IDLH and level B PPE is the minimum acceptable level) by properly equipped and
trained personnel.
About half of all confined space fatalities involve would-be rescuers.
5.
Permit-required (those containing or potentially containing hazardous
atmospheres) confined spaces must be ventilated prior to entry and continuously
throughout entry. The ventilation needs
to be capable of changing the air in the confined space often enough that
toxic/flammable atmospheric contaminant concentrations will not build to
hazardous levels.
Accident #7
Prior to sandblasting a tank, an expanding
plug was placed in the product line from the tank interior. While sandblasting the tank, the expanding
plug was punctured by the abrasive and deflated, causing it to fall from the
opening. Accumulated fuel no longer
being held back by the plug caused the employee in the tank to be soaked with
fuel. Fortunately, no injury resulted.
Review
1. Isolation needs to be accomplished by a
secure and reliable means. An inflatable
plug may be acceptable under certain conditions. When the operation being conducted has the
capability of puncturing the plug, a more durable method needs to be employed.
Accident #8
Two workers were preparing to cut an access
entry hole into an underground tank.
They had traveled more than 100 miles to the site in a shop truck over
mostly secondary roads. Before they
began cutting the tank opening, they purged the tank to remove vapors and
inserted a combustible gas indicator probe into the fill pipe to measure the
flammability of the atmosphere within the tank.
The readings on the meter indicated that it was safe to begin cutting
the tank. However, the meter had unknowingly
been damaged enroute to the job site because it had been free to bounce around
in the back of the shop truck. When the
electrical saw was turned on, a spark caused an explosion, killing one worker
and seriously injuring the other.
Review
1. Sensitive
electronic equipment needs to be secured prior to travel.
2.
Monitoring equipment requires the use of a daily "bump test"
to assure that the monitor is functioning properly. The bump test is accomplished by attaching a
tube from a container of calibration gas to the meter and checking to see if
the meter detects the calibration gas accurately.
3.
Electrical equipment (saw) not designed for use in a hazardous
atmosphere was used in an area where flammable vapors could accumulate or
otherwise be present.
Accident #9
Two large tanks were being internally coated
in preparation for fertilizer storage. A
workman was making his way out of the tank after applying the first coat of a
rubber-based lining to the tank interior.
As he was working his way out, he kicked a mechanics light, causing it
to break. The non-explosion proof light
ignited solvent vapors. The force of the
vapor expansion caused the worker to be ejected from the tank through the
manway and into the side of an adjacent tank.
He died as a result of his injuries.
Review
1.
Electrical equipment (light) not designed for use in a hazardous
atmosphere was used in an area where flammable vapors could accumulate or
otherwise be present.
2.
Permit-required (those containing or potentially containing hazardous
atmospheres) confined spaces must be ventilated prior to entry and continuously
throughout entry. The ventilation needs
to be capable of changing the air in the confined space often enough that
toxic/flammable atmospheric contaminant concentrations will not build to
hazardous levels.
Accident #10
A four man crew was cutting the top off of a
tank at a refinery location. A piece of
equipment apparently ignited vapors inside the tank, causing an explosion that
killed the three workers that were in the tank.
Review
1.
Cutting (hot work) can only be performed in locations that have been
made safe by either eliminating flammability/combustibility hazards or
protecting them.
2. The
atmosphere within the tank had reached the flammable range. Entry into and hot work on (even the outside
of) the tank were prohibited conditions.
3.
Monitoring was inadequate to warn of the flammable vapor accumulation.
4.
Permit-required (those containing or potentially containing hazardous
atmospheres) confined spaces must be ventilated prior to entry and continuously
throughout entry. The ventilation needs
to be capable of changing the air in the confined space often enough that
toxic/flammable atmospheric contaminant concentrations will not build to
hazardous levels.
The use of respirators can give a false sense
of security. When wearing the
respirator, your senses (smell) are incapable of telling you that a hazardous
situation is developing. Thus, you are
even more dependant upon your monitoring instruments to alert you. Note: this is not an endorsement of using
your nose as a means for alerting you to hazards. Many hazards are incapable of being reliably
detected by the nose and others are already very toxic before the nose will
detect them.
Accident #11
A worker was cleaning out an underground
storage tank. After the tank was
scrubbed and prior to being filled with sand, the workman used a ladder to
climb down into the tank carrying an electric lamp and an electric saw
connected to a power supply with an extension cord. Vapors in the tank ignited causing the worker
to suffer second and third degree burns to 86 percent of his body.
Review
1.
Electrical equipment (light and saw) not designed for use in a hazardous
atmosphere was used in an area where flammable vapors could accumulate or
otherwise be present.
2. Confined
space regulations require three persons to be present when the confined space
contains (or could contain) a hazardous atmosphere.
3.
Confined space regulations require a reliable means of communication be
available for contacting emergency services.
4.
Monitoring of the confined space for oxygen, flammability and toxicity
must be performed prior to entry.
5.
Entry personnel are required to wear a harness attached to a lifeline
for retrieval (non-entry rescue) purposes.
The lifeline must be attached to a fixed point outside of the confined
space, or, when the depth of the confined space is 5 feet or greater, to a
mechanical retrieval device (hoist and tripod).
6.
Respirators must be selected and used to protect workers from
atmospheric contaminants.
7.
Permit-required (those containing or potentially containing hazardous
atmospheres) confined spaces must be ventilated prior to entry and continuously
throughout entry.
There was no information available about the
victim's condition. However, it is
extremely rare for someone suffering this level of burning to survive.
Accident #12
A plumber was attempting to warm a confined
space in which he intended to work. He
placed his lighted cutting torch in the vaulted area and closed the
opening. When he returned to the vault,
he noticed that the torch was no longer lit and, after entering the vault,
attempted to relight the torch. The
torch had used up the available oxygen in the space, causing it to extinguish,
and filled the space with acetylene.
When the plumber reopened the space, oxygen was again introduced and the
ignition caused the acetylene vapors to ignite.
The plumber was blown out the opening and burned over 65% of his
body. He died about a week later.
Review
1.
Tools are only to be used for their intended purpose.
2.
Cutting and welding are hot work operations that require a fire watch to
be present.
3.
Cutting and welding operations can emit toxic vapors into the air and
require exhaust ventilation, at minimum.
4. The
vault was a confined space and all of the requirements of a confined space
program should have been implemented (monitoring, ventilation, personnel,
training, etc.).