Chemical Engineering December 2010 - 32

Cover Story
Fire prevention &
Fighting teChniqueS
Breaking the fire triangle
Three necessary components make up
the fire triangle (Figure 5) for an HTF
system: oxygen, an ignition source and
fuel (DP:DPO). How do we address
each of these successfully to avoid
their fiery combination?
Oxygen. Within process vessels, provide
blanketing with dry, inert gas. Nitrogen
is typically used, and should be
a minimum of 99% purity.
Ignition sources. HCEs of CSP
plants are the previously identified
point of AIT concern, as the surfaces
can reach temperatures above the
DP:DPO AIT, particularly when leakage
reduces the flowrate of the HTF
through the HCE. To date there has
been no known provision made to avert
the potential drifting of a DP:DPO
cloud across the HCE. Upon the first
detection of leakage from piping components
in the proximity of potential
ignition sources, prompt maintenance
should be scheduled for repair or replacement.
Potential for open flames
(such as smoking, welding and cutting
torches) can be addressed by
strict compliance with adequate administrative
controls. Electrical area
classification design should be properly
addressed so that it conforms to
applicable code requirements. This
should establish a minimum radius
around each potential DP:DPO leak
point, and should be determined according
to specified standards for the
requirements of electrical enclosures,
switches, motors and so on.
Fuel (DP:DPO). Use of HTFs at very
high temperatures often requires an
organic heat-transfer fluid of highReferences
1.
" Therminol VP-1 Heat Transfer Fluid Vapor
Phase / Liquid Phase Heat Transfer Fluid " ,
Pub. No 7239115C, Solutia Inc.
2. Apanel, George J., " Process Economics Program
Report 247, Gas To Liquids Update " ,
SRI Consulting, 2002.
3. " Systems Design Data " , pp. 4.3 - 4.4, Pub.
No. 9239193, ver. C., Solutia Inc.
4. " Organic Heat Transfer Fluids and Equipment " ,
Ind. Risk Insurers, IM.7.1.5, p. 1,
June 1, 1975.
5. Pratt, Thomas H., " Electrostatic Ignitions of
Fires and Explosions " , Wiley-AIChE, Center
for Process Safety, July 15, 1997.
6. NFPA 77, " Recommended Practice on Static
Electricity " , National Fire Protection Assoc.,
2007.
7. NFPA Standard 30, " Flammable and Combustible
Liquids Code " , NFPA, 2008.
8. ASME B31.1 - " Power Piping " , American
Soc. of Mechanical Engineers, New York, NY,
2004.
9. ASME B31.3 - " Chemical Plant and Petroleum
Refinery Piping " , ASME, New York,
NY, 2004.
10. ASME Code - Sec. VIII - Div. I - " Pressure
Vessels " , ASME, New York, NY, 2004.
11. ASME Code - Sec. VIII - Div. II - " Pressure
Vessels-Alternative Rules " , ASME, New
York, NY, 2004.
12. Loss Prevention Data Sheets 7-99, " Organic
Heat Transfer Fluids " , Factory Mutual,
2009.
32 ChemiCal engineering www.Che.Com DeCember 2010
13. " National Board Inspection Code " , National
Board of Boiler and Pressure Vessel Inspectors,
Columbus, OH, 2007.
14. API 510, " Pressure Vessel Inspection Code " ,
Am. Petroleum Institute, Washington, D.C.,
2006.
15. " Systems Design Data " , Pub. No. 7239193
ver. C, Therminol Heat Transfer Fluids, Solutia
Inc.
16. Vincent, G. C., Nelson, R. C., Russell, W. W.,
Hydrocarbon Mist Explosions - Part II, Prevention
by Water Fog, Loss Prevention, (Vol.
10), American Institute of Chemical Engineers,
1976.
17. Britton, L. G. , Spontaneous Fire in Insulation
Plant/Operation Progress (Vol. 10, No.
1), pp. 33, Jan., 1991.
est thermal stability, which is
the DP:DPO eutectic fluid. The
proper approach to eliminating
the presence of DP:DPO outside
of its containment is by careful
design and installation of the
system and its components,
and incorporating a culture of
effective preventive maintenance
and inspections for the
system's proper operational
integrity. For the unexpected
leaks, designs incorporating
remote isolation capability can
help minimize DP:DPO release
and personnel exposure during
these events.
FUEL
Figure 5. Oxygen, an ignition source and fuel
(DP:DPO) are the three necessary components of
the fire triangle for an HTF fire scenario
Fire fighting response
For small or incipient-stage fires with
a limited and minimal source of fuel
(DP:DPO), the use of a handheld fire
extinguisher can be an effective and
appropriate selection to extinguish
a fire. Approach to the fire should
be from upwind to avoid breathing
partially combusted materials, with
standard sweeping discharge of drychemical
or carbon-dioxide media.
Consider placement of 20-30 lb (9-14
kg) dry-chemical fire extinguishers in
easily accessible locations at each level
of structure where the fire potential
exists in HTF handling areas [12].
Personnel must be properly trained in
the operation of selected extinguishers
and techniques for approaching and
extinguishing HTF fires.
Larger dry-chemical units are available
on trailers and can be quickly
transported to distant locations within
the expanse of a facility. It is recommended
that personnel intended to
operate such equipment receive specialized
training and certification
prior to being authorized to respond.
Onsite fire brigades can address fires
much more rapidly than offsite fire departments,
and can help to minimize
potential damage, system downtime
and repairs.
As mentioned earlier, fires involving
larger releases of HTF in non-congested
areas of a facility that are beyond
the capability of incipient-stage
response techniques are perhaps best
managed by remote isolation of the
DP:DPO source, and allowing the fire
to burn out without risk to employees.
Runoff of liquid should be directed
away from areas that might result in
costly damage, extensive downtime
and repairs. Water monitor stations
equipped with water fog nozzles may
provide needed protection and cooling
of equipment in certain areas, which
should be assessed in planning for a
fire-water management scheme.
Indoor areas may require sprinkler
protection when potential leak points
HEAT
OXYGEN
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Chemical Engineering December 2010

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