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DEPARTMENT OF TRANSPORTATION
Federal Railroad Administration
[Safety Advisory 2012-01]
Odorant Fade in Railroad Tank Cars
AGENCY: Federal Railroad
Administration (FRA), Department of
Transportation (DOT).
ACTION: Notice of Safety Advisory.
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SUMMARY: FRA is issuing Safety
Advisory 2012-01 to remind shippers
and consignees of railroad tank cars
containing odorized liquefied petroleum
gas (LPG), of the importance of taking
actions to ensure that a sufficient level
of odorant remains in the LPG
throughout the entire transportation
cycle. FRA is issuing this notice to raise
awareness within the hazardous
materials community, of the potential
consequences of having LPG reach endusers
as under-odorized or essentially
non-odorized material due to the
diminishment of the added odorant
during the transportation cycle
(commonly known as ‘‘odorant fade'').
This safety advisory recommends that
shippers and consignees of bulk
quantities of odorized LPG review their
existing LPG odorization standards and
procedures, and take appropriate
actions to guard against odorant fade in
their shipments.
FOR FURTHER INFORMATION CONTACT:
Kevin R. Blackwell, Railroad Safety
Specialist, Hazardous Materials
Division, Office of Safety Assurance and
Compliance, FRA, 1200 New Jersey
Avenue SE., Washington, DC 20590
(telephone: (202) 493-6315; email:
Kevin.Blackwell@dot.gov); or Kurt
Eichenlaub, Railroad Safety Specialist,
Hazardous Materials Division, Office of
Safety Assurance and Compliance, FRA,
1200 New Jersey Avenue SE.,
Washington, DC 20590 (telephone: (202)
493-6050; email:
Kurt.Eichenlaub@dot.gov).
SUPPLEMENTARY INFORMATION: DOT's
Hazardous Materials Regulations
(HMR), Title 49 Code of Federal
Regulations (CFR) Parts 171-180, allow
use of the proper shipping name,
‘‘liquefied petroleum gas'' (or LPG), for
a number of petroleum gases with
properties similar to propane. Much of
the LPG loaded and shipped in the
United States by railroad tank car is
from bulk suppliers to either industrial
end-users or to ‘‘midstream'' suppliers
who then sell and redistribute the LPG
to commercial, retail, and general public
end-users. In 2010, LPG represented less
than 9 percent of all loaded hazardous
materials tank car shipments originating
in the United States. Because LPG is a
colorless and odorless gas, odorants are
normally added to the material (with the
exception of LPG being shipped to
industrial end-users) in the liquid phase
to enable human detection when its
vaporized gases are released in the
atmosphere. The majority of LPG
produced for non-industrial uses is
odorized by bulk providers of the
material. The presence of LPG in the
consumer supply chain, with either diminished levels of odorant or no
odorant present, represents significant
safety risks. Absent sufficient
odorization of the commodity, LPG
leaks can go undetected and ignite.
Diminished or absent levels of LPG
odorant has been determined to have
been a contributing factor in incidents
that have resulted in injuries and
fatalities. For example, a July 30, 2010,
incident occurred at a condominium
construction site in Norfolk, MA, when
a release of LPG from a leaking
connection in the basement of a
building under construction resulted in
an explosion and fire. This incident
resulted in one fatality and seven
injuries. An investigation conducted by
the Massachusetts Department of Fire
Services, Division of Fire Safety,
revealed that the LPG in the storage
tanks at the construction site had
virtually no odorant present, explaining
why no one at the construction site
reported smelling the LPG leak prior to
the explosion. While the LPG involved
in the Norfolk accident did not originate
from a rail shipment, the investigation
into the accident revealed that a large
quantity of LPG—shipped via railroad
tank car as odorized—had been
delivered to commercial and retail endusers
with either a diminished level of
odorization or no odorization at all.
Odorization
The proper odorization of LPG is
addressed by a combination of Federal
and State laws and regulations, as well
as by accepted industry standards and
practices. In accordance with the
applicable laws and regulations, LPG
intended for use by non-industrial
entities (e.g., commercial and retail
entities, and the general public) is
generally required to be odorized (or
‘‘stenched'') to enable the detection of
any unintended release or leak of the
gas. In the context of the rail
transportation of LPG, the HMR require
the odorization of LPG transported in
cargo tanks and portable tanks, but not
railroad tank cars. Specifically, 49 CFR
173.315(b)(1) provides that odorizing
LPG shipments in cargo and portable
tanks with 1.0 pound of ethyl mercaptan
per 10,000 gallons of LPG, or the
equivalent, is an acceptable form of
odorization.1 That section also provides
an exception from the odorization
requirement if odorization would be
‘‘harmful in the use or further
processing of the [LPG], or if odorization
will serve no useful purpose as a warning agent in such use or further
processing.'' Essentially, this exception
applies to LPG being transported to
industrial end-users.
The Occupational Safety and Health
Administration's requirements
regarding the storage and handling of
LPG found at 29 CFR 1910.110(b)(1)
essentially mirror DOT's odorization
requirements at 49 CFR 173.315(b)(1). In
addition to these Federal regulations,
the National Fire Protection Association
(NFPA) has also established odorization
standards that largely mirror the Federal
requirements. See NFPA Standard 58,
paragraph 1-4.1. In addition, most
States have adopted laws, regulations,
or codes that incorporate this NFPA
standard. Further, it is standard
industry practice to exceed the
established regulatory minimums and
add 1.5 pounds of ethyl mercaptan per
10,000 gallons of LPG in order to
combat the effects of odorant fade
should a release of material occur.
Odorant Fade
Under-odorization of railroad tank
cars containing LPG is sometimes
caused by the phenomenon commonly
known as odorant fade. While LPG may
be satisfactorily odorized in accordance
with the above requirements at the
source, there are circumstances that may
cause the odorant added to the LPG to
‘‘fade'' and render it virtually
undetectable by a person's sense of
smell. Typically, there are three
different potential causes of odorant
fade: oxidation, container condition,
and gas quality.
This safety advisory focuses on
recommendations to prevent odorant
fade caused by oxidation and/or the
condition of the LPG container. First,
oxidation can cause odorant fade when
the presence of rust in a tank car, or the
subsequent formation of rust over time,
as a result of the presence of oxygen and
moisture, decreases the amount of
odorant that is in the LPG in the tank
due to a chemical reaction between the
odorant and the oxidized (rusted)
surface. The presence of rust causes
mercaptans to oxidize into other
compounds that have a different odor
and lower intensity. Residual oxygen
from air and moisture that may be in the
container can increase the oxidation rate
of rust or even cause new rust to form
where previously none existed,
exasperating the rate at which the
odorant fades.
Next, the condition of the LPG
container itself can also potentially
cause odorant fade. An odorant can
adsorb onto the metal surface of the
container or even potentially be
absorbed into the metal surface itself.
This process is most likely to occur
when the container is new and has not
previously contained odorized LPG. It
can also occur when the inside of the
container has been left open to the air
while the container is out of service or
after the container has been cleaned and
purged (e.g., when a railroad tank car is
cleaned and purged for repair or service
at a tank car facility and then later
placed back into LPG service).
There are existing industry
procedures that can passivate (or treat)
the interior surface of an LPG container
in order to render the surface inactive so
that the odorant will not be diminished
through oxidation or adsorption/
absorption. Also, there are several
methods available to detect whether
there are adequate amounts of odorant
in LPG at any given point. The simplest,
and most often used method, is a ‘‘sniff
test'' where a person uses their sense of
smell to detect the presence of odorant.
The person performing a sniff test
should have a normal sense of smell,
uncompromised by such factors as
olfactory fatigue, sinus congestion,
allergies, head colds, smoking, or the
recent use of alcohol or drugs.
Colorimetric tube testing and the gas
chromatography test method provide
more quantitative methods to measure
the concentration of the odorant in LPG.
The colorimetric tube, or stain tube, test
method measures the concentration of
odorant by pulling a measured amount
of LPG through a hermetically sealed
glass tube containing a detecting
reagent. The odorant causes a chemical
reaction resulting in a color change of
the tube material. The quantity of
odorant can be measured by reading the
concentration of the odorant from the
calibration scale that is marked on the
tube. The gas chromatography test
method is the most accurate method
because it separates the various
components of the LPG and odorant for
identification. However, this method is
costly and requires sending LPG
samples to a location that has the proper
equipment and trained personnel to
perform these tests.
Railroad Tank Cars
At present, while DOT's regulation
discussed above contains an odorization
requirement for LPG transported in
cargo and portable tank containers,
there is no comparable DOT regulation
regarding the transportation of LPG
transported in railroad tank cars. FRA is
currently reviewing this situation to
determine if further action is warranted.
During routine inspections at facilities
that receive railroad tank cars loaded
with LPG, FRA is obtaining data on the
LPG odorization testing procedures being used by industry. FRA is also
collecting data on the number of LPG
shipments that are received yearly, the
number of these shipments that are
shipped as odorized versus nonodorized,
and the number of odorized
shipments received that failed
odorization testing or were identified as
having insufficient odorant.
As noted above, there are currently
Federal regulations, State laws, and
accepted industry standards and testing
methods in place to ensure proper LPG
odorization. FRA encourages industry
members to comply with all applicable
requirements and standards. In order to
help prevent odorant fade incidents
involving LPG transported by railroad
tank car, and to facilitate compliance
with existing requirements and
standards, this safety advisory makes
several recommendations below.
Recommended Action: In an effort to
encourage industry members to take
actions to ensure that a sufficient level
of odorant remains in odorized LPG
shipped via railroad tank car throughout
the entire transportation cycle, FRA
recommends that:
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Facilities that load, offer, receive, or
offload railroad tank cars containing
LPG review their procedures to ensure
they are adequate to address the issue of
‘‘odorant fade'' and its various potential
causes, and that those procedures
ensure that tank car shipments of
odorized LPG are odorized to meet
applicable regulatory and industry
requirements and maintain sufficient
levels of odorant throughout the entire
transportation cycle. Such procedures
should ensure quantitative testing
methods are used to measure the
amount of odorant in LPG.
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Facilities that load odorized LPG
into railroad tank cars have adequate
procedures in place to identify if a tank
car received for loading of odorized LPG
has been out of LPG product service for
any extended length of time, is coming
from a tank car repair or cleaning
facility, or has been subjected to any
condition that could lead to corrosion of
the tank.
-
Facilities that load odorized LPG
into railroad tank cars inspect, to the
degree possible, railcars they receive for
signs of oxidation or corrosion, which
can lead to the loss of odorant.
-
Facilities that load odorized LPG
into tank cars take any other corrective
actions needed to ensure sufficient
levels of odorization remain in the
shipment throughout the entire
transportation cycle, such as increasing
the amount of odorant injected into the
LPG, if necessary.
FRA encourages industry members to
take actions consistent with the preceding recommendations, and to take
other complementary actions to help
ensure the safety of the Nation's citizens
and railroads. FRA may modify this
Safety Advisory 2012-01, issue
additional safety advisories, or take
other appropriate actions necessary to
ensure the highest level of safety on the
Nation's railroads, including pursuing
other corrective measures under its
regulatory authority.
1 Ethyl mercaptan is a colorless organic liquid
with a low odor threshold of 0.4 parts per billion,
thus making it easily detectable by persons with a
normal sense of smell when injected at standard
industry rates.
Issued in Washington, DC, on April 9, 2012.
Robert C. Lauby,
Acting Associate Administrator for Railroad
Safety/Chief Safety Officer.
[FR Doc. 2012-8970 Filed 4-12-12; 8:45 am]
BILLING CODE 4910-06-P
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