POWER April 2014 - 81

PLANT SAFETY
1. Penetrating the penstock. A 4-foot by 6-foot opening was cut into the penstock for
contract worker access. Two wooden bulkheads were constructed to contain and remove sandblasting
and grinding debris and to provide work area ventilation via flexible ducts. The result
was a confined space with only a single means of egress. Source: U.S. Chemical Safety Board
Upper intake
(Mushroom)
Flame-cut
access door
Lower outlet
(powerhouse)
potential to contain a hazardous atmosphere,
contains material that has the potential for
engulfing an entrant, has an internal configuration
such that an entrant could be trapped or
asphyxiated by inwardly converging walls or
by a floor that slopes downward and tapers to
a smaller cross section, or contains any other
recognized serious safety or health hazard.
Neither the painting contractor nor the
Elevation:
11,065 ft
11,000 ft
20 ft at 90°
Temporary
west bulkhead
10,200 ft
10,056 ft
10,000 ft
Paint sprayer at
time of incident
2. Inside the penstock. Five workers were trapped between the west bulkhead and
fire that began with the solvents and epoxy compounds. Properly equipped and trained rescue
workers were about 75 minutes away. Source: U.S. Chemical Safety Board
Epoxy components
Temporary
west bulkhead
Solvent
1,560 ft at 2°
Temporary
east bulkhead
Turbines
plant owner treated the penstock as a permitrequired
confined space, and neither evaluated
the hazards of a confined space when
flammable solvents were introduced in the
vicinity of where hot work and abrasive blasting
were part of the recoating of the penstock
interior walls.
Also, the plant owner did not have policies
and procedures in place that addressed
a confined space monitoring plan or continuous
monitoring of the workspace where
flammables were to be used. OSHA has
identified a hazardous atmosphere as " flammable
gas, vapor or mist in excess of 10%
of its lower flammable limit (LFL) " [29 CFR
1910.146(b)]. The National Fire Protection
Association (NFPA) defines LFL as " that
concentration of combustible material in air
below which ignition will not occur, " in its
Recommended Practice for Handling Releases
of Flammable and Combustible Liquids
and Gases, NFPA 329 (2005).
The documentation obtained by CSB confirmed
that the owner and contractor recognized
that there was only a single point of
egress within the penstock before the work
began but failed to address the problem in
the work plan. On the day of the incident,
the contractor took only a single flammable
atmosphere reading-at the entrance to the
penstock, 1,450 feet from the work area.
The owner's contracting process was also
Spray wands
Static mixing
block
15-ft-diameter
concrete penstock
12 ft diameter
steel-lined
penstock
ent or created by the work activity were not
eliminated or controlled. " Specifically, the
MEK circulating through nonconductive
hose was a likely source of a static spark that
ignited the MEK. The other possible ignition
source was halogen lamps used to illuminate
the penstock, none of which were of explosion-proof
construction (Figure 2).
There were also a number of administrative
causes of the fire. First, the facility management
knew about the epoxy application
and the intended use of MEK for cleaning
the paint guns but failed to " perform a hazard
April 2014 | POWER
MEK solvent
pump
evaluation of the epoxy recoating work " and
thereby failed to identify the hazard of using
flammable liquids within the penstock. In addition,
there was no pre-job safety planning
or option of using a nonflammable solvent.
Next, although the penstock is very long,
it is still classified as a permit-required confined
space. OSHA defines a confined space
as one that is: large enough to enter and perform
work, limited access and egress, and
not designed for continuous occupancy.
Further, OSHA defines a permit-required
confined space as one that contains or has the
www.powermag.com
Two-part
epoxy paint
sprayer
found to be inadequate. The owner's contractor
selection process was to rank contractor
proposals based on specific performance factors,
such as past performance, work quality,
and safety record. In the evaluation process,
this contractor received a " zero " in the safety
category, which according to the owner's selection
process should have disqualified the
contractor. However, the contractor was not
eliminated by management but was selected
primarily based on low price.
As the project proceeded, the owner was
aware of ongoing contractor safety problems,
including a recordable injury, evacuation of
the penstock due to high carbon monoxide
readings, and electrical problems caused by
the contractor. The owner took no action subsequent
to these incidents.
Finally, the plant's emergency response
plan for the penstock recoating project was
to call 911. " No emergency responders with
confined space technical rescue certifications
81
1,020 ft at 55°
1,563 ft at 10°

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POWER April 2014

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