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| Director, Office of Nuclear and Facility Safety |
U.S. Department of Energy |
Washington, DC 20585 |
| DOE/EH-0389 | Issue No. 94-01 | July 1994 |
Contamination of Emergency Diesel Generator Fuel Supplies
Content
This notice is one in a series of publications issued by the Office of
Nuclear and Facility Safety to share nuclear safety information throughout the
Department of Energy complex. For more information, contact Dick Trevillian,
Office of Operating Experience Analysis and Feedback, Office of Nuclear and
Facility Safety, U.S. Department of Energy, Washington, DC 20585, telephone
(301) 903-3074. No specific action or responses are required solely as a
result of this notice.
Safety Notices are distributed to U.S. Department of Energy Program Offices,
Field Offices, and contractors who have responsibility for the operation and
maintenance of nuclear and related facilities, and to other organizations
involved in nuclear safety. Written requests to be added to or deleted from
the distribution of Safety Notices should be sent to: BR Richard L.
Trevillian, EH-33, Room E-460 GTN, U.S. Department of Energy, Washington, DC
20585.
The ESH Office of Information Management maintains a file of Safety Notices and supporting
information. Copies can be obtained by contacting the Office of Information Management at (301)
903-0449 or by writing to the Office of Information Management, U.S. Department of Energy,
EH-72/Suite 100, CXXI/3, Washington, DC 20585.
This notice presents lessons learned from condition monitoring and
specifications for diesel fuel used in diesel generators. Some Department of
Energy facilities have experienced contamination or degradation of diesel fuel
resulting from inadequate storage and sampling, improper handling, and failure
to exclude foreign material during maintenance. Following are some of these
events plus some from commercial nuclear power plants. This notice also
contains information on how to maintain and sample stored diesel fuel to
improve reliability of emergency diesel generator fuel systems.
This notice applies to all DOE facilities that use diesel generators,
especially to provide emergency or backup power. The Office of Nuclear
and Facility Safety
advises facility operators to be aware of the requirements for diesel fuel
storage and sampling and to be familiar with the various Codes and Standards
relating to such systems. No specific action or response is required by this
notice.
This notice describes nine recent events involving degradation of diesel
generator fuel supplies that have been reported by DOE facility personnel and
seven similar occurrences at U.S. commercial nuclear power plants.
In May 1993, at Argonne National Laboratory-West, water-
contaminated diesel fuel oil caused a diesel-driven service water pump to be
shut down.1 The root cause of this event was
personnel error by maintenance workers who failed to inspect the interior of a
55-gallon drum before using it to transfer fuel oil to the fuel oil tank for
the pump. A crack had developed in top of the drum when it was exposed to
severe weather several weeks preceding the event. In November 1992, at Rocky Flats, a sample of diesel fuel from
underground storage tanks was found to have a high level of impurities.2 Site personnel determined that diesel fuel in the
underground storage tanks was not within the operational safety requirement
that impurities be less than 2 milligrams/100 milliliters. Analysts measured
impurities of 3.1 mg/100 ml. Engineers determined that stagnation from lack of
circulation caused the fuel impurity. Savannah River Site personnel reported seven occurrences that involved
fuel supplies for diesel generators.
In April 1994, analysts found sediment in excess of specifications in
a sample of fuel oil from an H-Tank Farm diesel generator.3
The sediment consisted of corrosion products consistent with degradation of
the internal surface of the fuel oil tank. In addition, the fuel oil filters
for the engine contained a mud-like substance that may have been fine corrosion
products. Site personnel installed a temporary day tank until they could
determine if the original tank could be refurbished or needed to be replaced.
In January 1994, the 754-1A diesel generator at the Laboratory
Technical Area failed to start during a monthly load test because fuel oil
located between the piston and cylinder head caused a hydraulic lock.4 Engineering personnel determined that foreign
material on the main seat of the fuel supply solenoid valve was a contributing
cause of this occurrence. The material held the valve off its seat causing
fuel to flow into the engine crankcase and cylinders. The foreign material
consisted of Teflon tape, rag fiber, silicone sealant, and, possibly, sand.
Site personnel determined that the material was introduced into the fuel oil
system during diesel renovation in November 1993.
In September 1993, a fuel truck driver dispensed gasoline into the
diesel fuel tanks of seven pieces of portable equipment.5
The driver was on loan but had previously operated the fuel truck. However,
she normally drove a truck with hoses on opposite sides of the vehicle, and the
labeling and color coding on the truck in use was poor. The color coding on
the hose reel was reversed so that when one approached the gasoline door, a
green label (indicating diesel fuel) was visible. The driver engaged both the
gasoline and diesel power take-offs, making the two fuels available at the rear
of the truck. The procedure did not tell the driver to operate only one power
take-off pump and open only one valve at a time. In May 1993, technicians found water and sediment in excess of
specifications in a sample of fuel oil from the 247-1F diesel generator day
tank. However, they found no micro-organisms in the fuel oil.6 About a gallon of fuel was drained from the tank low
point to remove accumulated water.
In March 1993, an analyst at the HB-Line facility found an
unacceptable level of micro-organisms in diesel fuel for an emergency diesel
generator which caused a degradation of Class A equipment.7
Investigators determined that the direct cause of the occurrence was
micro-organism contamination in the diesel fuel day tank. They believed that
the contamination in the fuel could have originated from the diesel refueling
truck, or it could have formed from an accumulation of water and other
contaminants. Diesel fuel taken from the P and L Areas was circulated to other
areas at the site toward the end of 1992 and could have contained
micro-organisms, but, there was no evidence that fuel from P or L Areas was
contaminated. Except for the Replacement Tritium Facility, which reported a
high water content in its diesel fuel tank, other areas reported no diesel fuel
problems. After investigators discovered the micro-organisms, workers
drained and flushed the diesel tank, refueled it, and introduced biocide and
stability additives. In February 1993, analysts at the Tritium Facility found that sediment
levels and water content in the standby diesel generator fuel oil exceeded the
volume percent allowed by the technical safety requirements.8 Workers drained the contaminated fuel and replaced
it with fuel that supposedly met the surveillance requirements, but samples of
the new fuel also exceeded the limits for sediment. Maintenance personnel
drained several gallons of fuel from the tank and re-sampled it. About two
weeks later, they received the sample results, which indicated that the water
content was still high and the flash point for the fuel was only about 70 F.
The specified flash point is greater than 125 F. The facility changed their
fuel supplier to Central Services to assure fuel of a more consistent quality. In November 1992, chemists found 45 percent water in a sample of fuel
for the HB-Line emergency diesel generator.9
The surveillance requirement was 0.05 percent or less by volume. Investigators
determined that the root cause was either an inadequate sampling technique or
lack of procedures for taking samples from the HB-Line diesel fuel tank.
Technicians took samples from the low point of the fuel tank where
contaminants and water collect. The ORPS report stated that the samples should
have been taken at the level of the fuel suction lines to the diesel engine,
which would have provided a more accurate representation of the diesel fuel
quality. Personnel at several commercial nuclear power plants
reported a number of diesel fuel contamination events under the Licensee Event
Report system. In November 1991, at the St. Lucie plant in Florida, analysts found
high particulate levels in fuel oil from three of four storage tanks.10 They traced the contamination to a transfer pump
and hose on a fuel oil tank truck that had delivered fuel to the site a month
earlier. In April 1990, at the Perry station in Ohio, one emergency diesel
generator fuel oil sample showed high sediment levels because of the wrong
biocide additive.11 The sample analysis also
indicated degradation of the internal coating in the fuel oil storage tank.
Maintenance personnel re-coated the tank and changed the biocides to the
correct formula. In November 1989, at the Calvert Cliffs plant in Maryland, personnel
found high particulate levels and biological growth in emergency diesel
generator fuel samples from both fuel oil storage tanks.12
Technicians had drawn the samples from the lower third of the fuel oil tanks.
After the tanks were cleaned and new fuel obtained, they added appropriate
biocides to prevent growth of organisms. In August 1989, at the Sequoyah plant in Tennessee, chemistry
technicians found water and sludge in fuel oil samples because the procedures
did not comply with American Society for Testing Materials requirements for
sampling fuel oil.13 After workers removed
water, sludge, and sediment from the tanks, technicians obtained samples in
accordance with requirements and the samples were acceptable.
In January 1989, at the Perry plant in Ohio, analysts found high
concentration of insolubles in emergency diesel generator fuel that was the
result of aging fuel oil.14 Workers were
adding new fuel oil to the storage tank, which stirred up the bottom sediment
and caused particulates to be drawn into the sampling device. In December 1988, at the Dresden plant in Illinois, a fouled fuel
filter caused the emergency diesel generator speed and frequency to fall below
the plant protection system setpoint and initiated an isolation signal to
several plant systems.15 In September 1988, at the Turkey Point plant in Florida, a gradual
buildup of particulates in the diesel generator fuel filters caused high filter
back pressure, which degraded diesel engine performance.16
Investigators found that the filter replacement interval was too long. In May 1988, at Diablo Canyon in California, workers found the
emergency diesel generator day tank contained a fungus that clogged the primary
fuel filter.17 They also found fungus spores
in other tanks at the site.
These events illustrate conditions that could significantly compromise the
safety of facility operations and personnel because of loss of emergency or
backup diesel generator power caused by degraded fuel supplies. Proper storage
and handling of diesel fuel, especially fuel used for emergency diesel
generators, is necessary to assure the reliability of key systems. Facility
technical specifications or operational safety requirements should include
requirements for assuring that diesel fuel supplied by vendors is fresh and
meets specifications. When the fuel is delivered to facility storage tanks, it
must be sampled periodically to provide continued assurance of fuel quality.
A review of modern, large, industrial diesel fuel tank designs indicated
that tanks generally accommodate a certain amount of sediment and water in the
bottom. The outlet of the fuel tank for the diesel engine should be located at
some distance above the tank bottom to prevent the normal accumulation of water
and sediment from being drawn into the supply line. This practice is common in
commercial diesel fuel storage tanks and nuclear power plant emergency diesel
generator fuel tanks.
ASTM D 4057-88 18 recommends sampling
procedures of diesel fuel storage tanks that will detect sediment and water
from both outlet samples and bottom (or drain) samples.
Most diesel fuel problems result from low usage rates, which allow fuel to
degrade over time. The rate of degradation depends on storage temperature and
quality of the fuel. Heat may accelerate degradation and may cause condensate
to form on tank walls during the daily thermal cycle. Fuel oil degrades in two
ways during extended storage: (1) oxidation and polymerization, which yield
soluble and insoluble gums; and (2) chemical processes of bacteria, fungi, or
yeasts at the fuel/water interface, which produce solids and additional water.
The gums, water, microbiological growth, and bacterial solids are collectively
called particulate contamination and tend to settle at the tank bottom creating
a medium for further organic growth at the fuel/water interface. Removing
water and contaminants from the tank bottom and limiting the amount of water
and contaminants introduced with new fuel is extremely important.
Although the presence of sediment or water in commercial or industrial
diesel fuel tanks is accommodated by design, such contamination in an emergency
diesel generator fuel tank could adversely impact safety. If, for example, the
tank contents were agitated by addition of fuel while the emergency diesel
generator or fuel transfer pumps were in operation, sediment or water present
in the tank could be drawn into the fuel supply. Such contamination could
quickly clog fuel system strainers and cause fuel starvation of the emergency
diesel generator. Diagnosis and recovery of a diesel engine from fuel
starvation can be time consuming because the fuel injection pump, fuel lines,
and injectors may have to be cleaned and cleared of air before restart and
proper operation.
Another potential problem not always addressed in technical or operational
safety requirements is aging of diesel fuel. Since fuel usage is relatively
low and facilities may have relatively large quantities of fuel on hand, age
degradation of the diesel fuel is possible. Untreated diesel fuel begins to
degrade in 60 to 90 days. This degradation (by oxidation) can cause a high
concentration of fine particulates which in turn, can clog filters and damage
fuel injection components. ASTM D2276-9119
provides test methods for measuring fuel oil degradation.
In commercial applications, diesel fuel aging is limited by additives that
prevent degradation. Additives are vailable under a number of brand names.
Facility managers should consult with their fuel vendor and the diesel engine
manufacturer before choosing one. NS recommends that facilities consider the
use of additives to assure that the quality of diesel generator fuel is
maintained.
NS recommends that facilities consider the following good practices related
to fuel oil deliveries. Prior to adding new fuel oil to storage and supply
tanks, a sample of the fuel oil should be taken from the bottom of the
transport tank or truck. As a minimum, before adding the new fuel to existing
supplies, the sample should be visually checked for clarity and brightness, as
defined by ASTM D417620, and tested in
accordance with ASTM D975-9121 for API
gravity, kinematic viscosity, water, sediment, and flash point. One
fossil-fueled power plant initiated such sampling after mistakenly introducing
maple syrup into their fuel oil supply.
Analysis of the other properties of new fuel oil in accordance with ASTM
D975-91 should be completed within two weeks of the addition.
Periodic sampling should be performed in accordance with either ASTM
D4057-88 or ASTM D270-65 (re-approved in 1980)22.
Condensate should be removed from storage tanks on a quarterly basis or on a
monthly basis when it is known or suspected that the ground-water table is
equal to or higher than the bottom of buried storage tanks. Day tanks and
integral tanks should be checked monthly for water as a minimum. Accumulated
water should be removed immediately. If it is suspected that water has entered
suction piping, the entire fuel oil system between the tank and injectors
should be flushed.
As a minimum, stored fuel oil should be replaced, the accumulated sediment
removed, and the tank cleaned at ten-year intervals. Cleaning should be done
with sodium hypo-chlorite solutions or equivalent, rather than soap or
detergents, to preclude introduction of surfactants in the fuel system. Fuel
oil system components should be inspected for general corrosion and refurbished
or replaced to ensure that corrosion products do not contaminate fuel oil.
U.S. Nuclear Regulatory Commission Regulatory Guide 1.137, Fuel-Oil Systems
for Standby Diesel Generators; and American Nuclear Standards Institute N195,
Fuel Oil Systems for Standby Diesels provide guidance and good practices for
such systems.23,24 The
Department of Energy is preparing a standard for backup power sources for DOE
facilities.
ORPS Final Report CH-AA-ANLW-ANLW-1993-0004, "Loss
of 1000 gpm Diesel Water Pump," May 26, 1993. ORPS Ten-Day Update Report RFO--EGGR-PUFAB-1992-0343, "Diesel
Fuel Fails to Meet Quarterly Fuel Quality Surveillance," February 2,
1993. ORPS Notification Report SR--WSRC-HTANK-1994-0053, "Sediment
in 254-H Standby Diesel Generator Fuel Oil," April 18, 1994. ORPS Final Report SR--WSRC-LTA-1994-0004, "Failure
of 754-1A Diesel Generator During Load Test," March 18, 1994. ORPS Final Report SR--WSRC-TD-1993-0003, "Dispensing
of Gasoline Into Equipment Diesel Fuel Tanks," November 15, 1993. ORPS Ten-Day Report SR--WSRC-S247-1993-0013, "High
Water Content of Diesel Fuel," May 26, 1993 ORPS Final Report SR--WSRC-HBLINE-1993-0006, "Micro-Organisms
in Diesel Fuel," May 4, 1993. ORPS Final Report SR--WSRC-TRIT-1993-0013, "Diesel
Fuel Low Flash-point," June 2, 1993. ORPS Final Report SR--WSRC-HBLINE-1992-0023, "High
Water Content in HB-Line Diesel Generator Fuel," January 11, 1993. Licensee Event Report 335/91-007, St. Lucie Unit 1,
November 4, 1991, Nuclear Regulatory Commission Public Document Room,
Washington, D.C. 20555. Licensee Event Report 440/90-005, Perry Unit 1, April
5, 1990, Nuclear Regulatory Commission Public Document Room, Washington, D.C.
20555. Licensee Event Report 317/89-026, Calvert Cliffs Unit
1, November 28, 1989, Nuclear Regulatory Commission Public Document Room,
Washington, D.C. 20555. Licensee Event Report 327/89-025, Sequoyah Unit 1,
August 15, 1989, Nuclear Regulatory Commission Public Document Room,
Washington, D.C. 20555. Licensee Event Report 440/89-001, Perry Unit 1,
January 11, 1989, Nuclear Regulatory Commission Public Document Room,
Washington, D.C. 20555. Licensee Event Report 237/88-020, Dresden Unit 2,
December 24, 1988, Nuclear Regulatory Commission Public Document Room,
Washington, D.C. 20555. Licensee Event Report 250/88-022, Turkey Point Unit 3,
September 20, 1988, Nuclear Regulatory Commission Public Document Room,
Washington, D.C. 20555. Licensee Event Report 275/88-014, Diablo Canyon Unit
1, May 5, 1988, Nuclear Regulatory Commission Public Document Room, Washington,
D.C. 20555. ASTM D4057-88, Practice for Manual Sampling of
Petroleum and Petroleum Products. ASTM D2276-91, Test Method for Particulate Contaminant
in Aviation Fuel by Line Sampling. ASTM D4176-88, Test Method for Free Water and
Particulate Contaminant in Distillate Fuels (Clear and Bright Pass Fail
Proceedings). ASTM D975-91, Specification for Diesel Fuel Oils. ASTM D270-75, re-approved in 1980, Sampling Petroleum
and Petroleum Products. U.S. Nuclear Regulatory Commission Regulatory Guide
1.137, Fuel-Oil Systems for Standby Diesel Generators. ANSI N195-1976, Fuel Oil Systems for Standby Diesels.
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