Chemical Engineering December 2014 - 54

Solids Processing
Environmental Manager
Fire-Water Pumps
for CPI Facilities
Follow this guidance to improve the selection, design
and operation of pumps handling water for firefighting
and related systems
Amin Almasi
Consultant
F
ire-water pumps are critical
machines that save lives
and prevent chemical process
industries (CPI) facilities
from damage more so than
any other plant components. Firewater
pumps are nearly always centrifugal
pumps with capacity from
around 20-3,000 m3/h. Specific requirements
for fire-water pumps
are briefly noted in fire codes (such
as NFPA 20 [1]), but this may not
be sufficient for specifying highperformance
fire-water pumps in
a way that ensures good reliability
and operation as well as optimum
price. This article provides practical
notes on fire-water pumps to expand
upon the information that can
be found in existing fire codes.
Various styles and configurations
of fire-water pumps are available
at different prices. In addition to
proper selection, fire-water pumps
must be properly integrated into
the overall fire-water system, as an
integral part of the CPI facility.
Figure 1 shows an example of
a skid-mounted, diesel-enginedriven
fire-water pump package.
The performance and reliability of
a fire-water pumping system is an
important issue, and details of the
fire-water pumping system are usually
a part of risk studies, HAZOP
and inspection activities.
Fire-water pumps are important
to different stakeholders, including
clients, investors in the CPI plant,
and insurance providers. Usually
around 20-35% of the insurancedeficiency
rating points for a CPI
plant are related to inadequate firewater
pumping systems. On average,
5-10% of all fire-water pumping
systems in CPI plants have failed to
provide satisfactory services at the
time required (as evidenced during
actual fire cases or drill-type exercises).
Thus, it is critical to design,
implement, operate and maintain
these critical systems - beyond the
minimum requirements set forth in
published fire codes.
Fire-water system
Fire-protection efforts are categorized
as passive or active. The primary
passive measures for fire protection
include efforts to ensure sufficient
clearances, install protective barriers,
limit and protect fuel sources,
and other steps designed to reduce
fire risks (such as the use of less
hazardous materials, processes and
equipment). By comparison, active
fire-protection systems are designed
to detect and apply fire-protection
measures, which usually rely on some
effort to actually extinguish the fire.
Commonly used system components
include fire hydrants, monitors, hose
reels, water-spray systems, delugetype
fire-protection systems or waterexposure
cooling systems. The fire-water
pump plays an important role in
most active fire-protection systems.
System design and sizing
There have been different sets of
rules to define the required flow
and head of fire-water pumps. In
other words, a variety of differFIGURE
1 Fire-water pump assemblies
are typically skid-mounted to ease
installation and operation. Shown here
is an example of a skid-mounted, dieselengine-driven,
fire-water pump package
ent guidelines have been used to
estimate the ideal water volume
and flow requirements for CPI fire
cases, depending on plant specifics,
applicable codes, regulations and
fire-fighting methods. As a result,
these specifications will vary based
on whether the plant is using fire
control, fire suppression, exposure
cooling and so on.
Fire-water demands are usually
calculated based on the maximum
rate of water that will be required for
a worst-case scenario - typically a
potential scenario involving a large,
single-fire incident. The most remote
unit(s) from the fire-water pumps, or
the largest unit(s), are typically examined
to identify the worse possible fire
scenario(s). The potential scenario of
a vast fire in the largest unit should
be used to define the capacity of firewater
system. The most-remote fire
unit(s) should be used to define maximum
rated pressure of the fire-water
pump.
CPI fire cases can be very different,
considering the different types
of materials handled and the types
of operations carried out at different
facilities. Today, computerized
simulations play a critical role in
identifying and modeling potential
fire scenarios, validating fire-fighting
methodologies, and estimating
the required water capacity.
When evaluating a potential
fire-fighting scenario, additional
pressure (a safety margin to the
calculated head) should be added
to maintain the fire-water pressure
in all remote units and critical
fire-fighting systems; this is necessary
to ensure that a fire-water
stream with adequate pressure can
be maintained to support all appliChemiCal
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Chemical Engineering December 2014

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