Transcript Slide 1

Accident Prevention Manual
for Business & Industry:
Engineering & Technology
13th edition
National Safety Council
Compiled by
Dr. S.D. Allen Iske, Associate Professor
University of Central Missouri
CHAPTER 12
FLAMMABLE AND
COMBUSTIBLE LIQUIDS
Definitions
As defined by NFPA 30, Flammable and Combustible
Liquid Code:
• Flammable Liquid is any liquid having a closed–cup flash
point below 100°F, and having a vapor pressure not
exceeding 40 psia at 100°F.
• Combustible Liquids are those with flash points at or
above 100°F but below 200°F.
Definitions (Cont.)
• Flammable liquids—three classifications
• Class I liquids include those with flash points below 100°F.
• Class IA includes those with flash points below 73°F and having a boiling
point below 100°F.
• Class IB includes those with flash points below 73°F and having a boiling
point above 100°F.
• Class IC includes those having flash points at or above 73°F and below
100°F.
• Combustible liquids—four classifications
• Combustible liquids are those with flash points at or above 100°F.
• Class II includes those having flash points at or above 100°F and below 140°F.
• Class III includes those having flash points of or above 140°F and are subdivided
as follows:
• Class IIIA includes those with flash points at or above 140°F and below 200°F.
• Class IIIB includes those with flash points at or above 200°F.
Definitions (Cont.)
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Auto-ignition temperature: The minimum temperature at which a
flammable gas-air or vapor-air mixture will ignite from its own heat
source or a contacted heated source without the presence of an
open spark or flame.
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Flammable limits: The minimum concentration below which
propagation of flame does not occur on contact with a source of
ignition is the lower flammable limit (LFL). The maximum proportion
of vapor or gas in air above which propagation of flame does not
occur is the upper flammable limit (UFL).
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Flammable range: Lies between the LFL and UFL, expressed as
the percentage of vapor or gas in air by volume.
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Volatility: The tendency or ability of a liquid to vaporize.
Definitions (Cont.)
• Flash point: The minimum temperature at which a liquid gives
off vapor concentrated enough to form an ignitable mixture with
air near the surface of the liquid within a vessel. It is specified
by the appropriate testing procedure and apparatus.
• Oxygen deficiency: An atmosphere having less than the
percentage of oxygen found in normal air.
• Oxygen limits: For an explosion to occur, enough oxygen must
be present along with a vapor concentration in the flammable
range.
Definitions (Cont.)
• Propagation of flame: The spread of flame through the entire
volume of the flammable vapor-air mixture from a single
source of ignition.
• Rate of diffusion: The tendency of gas or vapor to disperse
into or mix with another gas or vapor, including air.
• Vapor pressure: The pressure exerted by a volatile liquid
under any of the equilibrium conditions that may exist between
the liquid and the vapor.
General Safety Measures
• Prevent dangerous mixtures
• Avoid unintentionally mixing flammable and combustible
liquids. Mixing flammable or combustible liquids can lower the
flash point of that liquid making it highly flammable.
• No smoking
• In a building or area where flammable liquids
are stored, handled, or used, forbid
personnel to smoke or carry matches, lighters
or other spark-producing devices.
• Static electricity
• Static electricity is generated by the contact and separation of
dissimilar materials. The principle hazards of static electricity
are fire and explosion caused by spark discharges that contain
enough energy to ignite flammable or explosive vapors,
gasses, or dust particles.
General Safety Measures (Cont.)
• Bonding and Grounding
• The purpose of bonding is to eliminate a difference in the staticelectrical-charge potential between two or more objects.
• The purpose of grounding is to eliminate a potential difference
between an object and the ground.
• When flammable liquids are
transferred from one container to
another, provide a means of
bonding between the two containers
before pouring.
• An adequate ground will continuously
discharge a charged, conductive
body. As a safety measure, use a
ground when any doubt exists
concerning a situation.
General Safety Measures (Cont.)
• Electrical equipment
• When flammable vapors exist, electricity becomes an ignition
source if the proper type of electrical equipment for these
atmospheres either has not been installed or has not been
maintained. Consult NFPA (National Fire Protection Association)
and NEC (National Electrical Codes) .
• Spark-resistant tools
• The hazard of flammable vapors or gasses igniting from sparks
must be recognized. Use special tools to minimize the danger of
sparks in hazardous locations.
Health Hazards
• Flammable and combustible liquids create a health
hazard when inhaled or when they come in contact
with the skin. Intoxication and other acute or chronic
conditions may result from breathing vapors or
flammable liquids.
Combustible-Gas Indicators
• Unless tests prove otherwise, assume that flammable
vapors and toxic mixtures are present in all tanks that have
contained or have been exposed at any time to flammable
and combustible liquids.
• Use approved chemical analytical methods to test for toxic
substances.
• Allow only experienced operators to use a combustible-gas
indicator.
Loading and Unloading Tank Cars
• Safety procedures are required for tank cars and tank
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trucks used to transport flammable and combustible liquids.
Refer to Association of American Railroads (AAR) and U.S.
Department of Transportation (DOT) standards and codes.
Only trained workers should load or unload tank cars
containing flammable or combustible liquids.
Do not load or unload cars before ensuring that no exposed
lights, fires, or other sources of ignition are in the area.
Closely check invoices and shipping papers on incoming
tank cars to make certain they match the actual numbers
on the tank car.
Loading and Unloading Tank Cars (Cont.)
• Fire safety:
• Ensure that no exposed lights, fires, or other sources of ignition are
in the area prior to loading or unloading cars.
• Stop loading and unloading during electrical storms.
• Know and execute safety procedures for handling fires.
• Personnel safety:
• Only trained employees should load or unload cars.
• Understand danger of fires, explosion, asphyxiation, and toxic
effects from exposure to vapors. Fall protection as required.
• Set operational procedures for safety.
Loading and Unloading Tank Cars (Cont.)
• Environmental Protection
• Use approved containers under any leaks to prevent contamination
and product loss.
• Limit quantities of flammable liquids exposed to atmosphere and
released to ground.
• Prepare for spills and emergency responses and compliance to
regulations.
• Avoid spills and overflows.
• Drivers must protect traffic and property.
Loading and Unloading Tank Cars (Cont.)
• Electrical considerations
• Provide approved electrical equipment on tank cars.
• Bound, ground, and insulate a tank car’s siding from the main rail
line for protection from stray electrical currents.
• Spotting cars
• Use a car mover when it is necessary to spot a car by hand.
• Inspection
• The company receiving or shipping a tank car should make a
general visual inspection of the unit and report any obvious defects
to the carrier.
Loading and Unloading Tank Cars (Cont.)
• Relieving pressure
• Relieve the tank car of interior pressure before removing the
domed manhole cover or the outlet valve cap. Raise the safety
valves and open the air valve a small amount at a time.
• Removing covers
• Loosen a screw-type dome cover by using a bar placed between
the lug and the knob on the cover’s top. Make two complete turns
to expose the ½ in. vent holes in the threaded portion of the dome
cover. Keep clear of vapors by standing upwind, out of vapor
accumulation.
• Chemical and physical layout of the unloading area may
require appropriate respiratory protection—SCBA or AirSupplied Respirator.
Loading and Unloading Tank Cars (Cont.)
• Connections
• Ensure integrity of the outlet valves
• Examine the outlet chamber for cracks before unloading.
• Use safe procedures to modify for temperature changes at valves.
• Worker should be in attendance during the entire loading or
unloading process.
• Use proper venting and vapor recovery units.
• Placards and shipping papers
• Follow proper U.S. DOT or counterpart regulatory guidelines for
using placards and shipping papers.
Loading and Unloading Tank Trucks
• Inspection
• See that trucks are kept in good repair and inspected daily. Place
special emphasis on the condition of lights, brakes, horns,
rearview mirrors, bonding straps, tires, steering, and motors.
• Smoking
• Prohibit smoking by truck drivers and anyone who helps driving,
loading or unloading, or attending to their unit.
• Provide each tank vehicle with at least one fire extinguisher,
each having at least a 10 B, C rating.
• Spotting trucks
• When a tank truck is being loaded or unloaded, see that the
brakes are set, the engine stopped, the lights are turned off, and
the bonding connection is made before the dome cover is
opened for inspection.
Loading and Unloading Tank Trucks (Cont.)
• Unloading and loading connections
• Trucks with motor-driven pumps should be shut off before loading
lines are connected or disconnected.
• Drivers must remain at the tank controls (within 25 ft).
• Leaks
• Avoid spills or overflows. If they do occur, immediately stop
loading, shut off the valves, and clean up the overflow before
resuming loading. Trap the liquid in containers, in an earthen or
sand-diked area, or in depression or pit, if possible.
• Fires
• In the event of a tank-truck fire during loading or unloading, shut
off the fuel supply to or from the truck if possible. Remove the
spout from the tank truck. To put out the fire use CO2, foam, or dry
chemical extinguishers.
Nonbulk Storage
• Keep or store Class I and Class II liquids within approved
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containers in buildings used for public assembly, such as
schools, churches, or theaters.
Keep the containers in a storage cabinet or a storage
room that does not open to a public portion of the building.
Limit the quantities stored in such locations (NFPA 30).
Do not store containers where they will obstruct exits,
stairways, or other areas used to safely leave the building.
Never store containers near stoves or heated pipes or
expose them to sunlight or other sources of heat.
Do not store flammable or combustible liquids in open
containers.
Nonbulk Storage (Cont.)
• Inside storage and mixing rooms
• Flammable or combustible liquids in approved, sealed containers
. present a potential, rather than an active, hazard.
• Isolate inside storage rooms as much as possible.
• Locate at or above grade along an exterior wall.
• NFPA 30 specifies architectural and mechanical requirements.
• Inside storage cabinets
• Codes most stringent for Class 1A liquids; some limit operations to 10
gallons stored outside cabinets per control area.
• Cabinets should be made of metal or wood and conform to ANSI
standards and NFPA 30.
• According to NFPA 30, no more than 120 gallons of Class I, Class II,
and Class IIIA liquids may be stored in an approved storage cabinet for
flammable liquids.
• Of this total, not more than 60 gallons may be of Class I and Class II liquids.
• No more than 3 cabinets may be in a single control area.
• Label required: FLAMMABLE – KEEP FIRE AWAY!
Non-bulk Storage (Cont.)
• Outside storage lockers
• If space permits, construct storage areas for flammable liquids as
separate buildings set aside from main facility.
• Construct similar to inside storage rooms.
• Approved pre-fabricated lockers may be used.
• Consult local regulations for location and use of outdoor storage
lockers.
Cleaning Small Tanks
• Work on a container that held flammable or combustible
liquids should be supervised by trained individual.
• Take special precautions for containers that held reactive
compounds (perchlorates, peroxides, nitrates, etc.)
• Note that container may have sufficient oxygen level for
combustion.
• See SDS for cleaning procedures.
• Clean in an approved area with ample ventilation.
• When possible, clean outdoors and away from ignition
source.
• Steaming, hot chemical washes, water filling, and use of
inert gas are common methods for cleaning and vapor
removal.
Disposal of Flammable Liquids
• Return unused, uncontaminated flammable liquids to the
vendor, salvage them for resale, or use them in some
other approved way.
• Mixture of clean flammable liquids sometimes need to be
separated before they are usable.
• If recycling or recovery of flammable liquids is not
feasible, give them to a licensed disposal contractor.
Regulatory Issues
• Receiving, storing, handling, and using flammable and
combustible liquids requires precautions and safe
practices. Be sure to consult:
• Regulations
• Local codes
• Fire underwriters
• NFPA
• DOT
• OSHA standards
• Trade associations
• Specific handbooks
Bulk Storage: Installation and Maintenance
• Tank construction
• All aspects of tanks should conform to NFPA 30A.
• Store bulk quantities of Class I in underground tanks or outside buildings.
• Vents
• Provide storage tanks with vents per NFPA 30.
• They should also be higher than the fill pipe opening and not less than 12 ft above
the adjacent ground level.
• Discharge vertically and so no vapors can enter building. Flame arrestors.
• Dikes
• Flow of flammable /combustible liquid can have serious
consequences because of topography or neighboring property.
• In these cases, install a curb, dike, or wall around a tank or group the tanks.
• Pumps
• Locate flammable liquid transfer pumps outside the buildings and
diked areas whenever possible.
• Use fire resistant construction in buildings that house equipment for transferring
flammable liquids.
• Good Housekeeping is essential for good safety practices.
Bulk Storage
• Gauging
• Allows operators to keep track of liquid levels in tanks.
• If a tank requires manual gauging and a walkway is not provided, arrange
a way for employees to measure the contents of storage tanks so that they
need not walk across the tank roof.
• Protect employees and provide early detection of releases.
• Underground Tanks
• When an underground tank is subject to heavy traffic over it, protect the
tank with at least 3 ft. of earth cover, 18 in. of tamped earth plus 6 in. of
reinforced concrete, or 18 in. of tamped earth plus 8 in. of asphalt
concrete.
• Specific design and installation requirements, firm foundations,
surrounding “jackets” of non-corrosive, inert materials to protect from
leaks.
• Aboveground tanks
• Refer to NFPA 30, when storing aboveground tanks. NFPA sets minimum
distances from property lines, public ways, and nearby buildings.
• For different types of flammable and combustible liquids there are different
boundaries set. See Tables 12-A, 12-B and 12-C.
Bulk Storage
• Spill control
• Release of flammable or combustible liquids may have serious
consequences due to topography and property.
• Use curb, wall or dike around a tank or group of tanks.
• Structure should have capacity of the single largest container.
• Equip areas with drain systems and control valves to prevent
leakage into water supplies, public sewers or storm drains.
• Tank fires and their control
• Prevention is the best way to reduce the risk of fires in storage
tanks.
• Provide tanks containing flammable liquids with a roof that floats
upon the surface of the liquid—an internal or external open-top
floating roof.
• Such a roof greatly reduces the opportunity for vapors to accumulate within
the flammable range
Cleaning Tanks
• General precautions
• Confined-space entry procedures, appropriate training
• Clean tanks and vessels that have contained flammable and combustible
liquids before inspections, repairs, entry by personnel, or changes of product.
• An industrial plant lacking proper equipment and should consult supplier of
flammable or combustible liquids.
• Protective equipment
• Workers who are cleaning tanks should wear proper and appropriate PPE.
• A worker entering a tank and spending an extended time inside must wear a
supplied-air, full-face mask and a safety harness with a lifeline for rescue.
• Proper procedures
• A tank should be free of hazardous vapors and toxic materials before any
work is performed.
• Be sure that employees engaged in tank cleaning know appropriate first aid
and CPR.
• Have an attendant to monitor the worker’s behavior and know when to order
an evacuation.
Cleaning Storage Tanks
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Empty tank.
Purge the tank of all flammable vapors using ventilation, displacement, and other means.
Check atmosphere in tank to determine oxygen and flammable vapor levels.
Remove from the vicinity of the tank all sources of ignition.
Obtain appropriate confined-space entry and hot-work permits.
Disconnect and blank all products, steam, foam and similar lines.
Lock out all electrical equipment and use only lighting approved for specific atmosphere.
Undo all but four bolts on one manway and slowly open the remaining bolts.
After all available product has been removed, the tank is ready for ventilation.
Consult your supplier or refer to the appropriate manuals for advice on ventilating and
cleaning tanks.
Bond steam lines and water wash nozzles to the tank.
Ventilate or steam the tank.
Do gas-hazard test to see if the tank has adequate oxygen and is free of any flammable
or toxic vapors.
Have all personal protective equipment available.
Test for oxygen and flammable content with a calibrated and adjusted oxygen monitor.
When entering the tank, wear a fresh-air hose mask, air-supply tanks, and safety belts.
Continue ventilation for the duration of the work in the tank.
If inert gas has been used for freeing gas, check for oxygen deficiency.
Abandonment of Tanks
• Authorities require removal of tanks at the end of their
useful life and generally will not accept abandoning tanks
in place.
• Thoroughly clean obsolete tanks to remove flammable
vapors.
• Dismantle and remove them from the premises according
to the U.S. EPA underground storage tank regulations.
• If temporarily out of service, cap and secure fill lines,
gauge openings, and pump suction lines to reduce
tampering and accidental filling. Leave vent lines open.
Common Uses of Flammable
and Combustible Liquids
• Dip tanks
• Present a severe fire and explosion hazard—large exposed surface of flammable and
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combustible liquids leads to increased risk of fire.
Conduct dipping operations above grade in a detached, one-story building of noncombustible construction, or in separate one-story section.
Use room as large as possible to allow vapor dilution and reduced vapor accumulation.
Use mechanical ventilation that directs fresh air over vapor area, past point of
operation, and then to safe outside location.
Fire codes require interlock in case of ventilation failure.
• Japanning and drying ovens
• Ovens used for evaporating varnish, Japan enamel, and other flammable and
combustible liquids can present serious fire and explosion hazards.
• Provide ample ventilation and explosion venting for these ovens.
• Provide ovens with proper fire-extinguishing equipment and interlocks to shut down
process in case of fire.
Common Uses of Flammable
and Combustible Liquids
• Oil burners
• Oil and diesel can be used as fuel in heating applications.
• Use oil burners that are approved by a recognized testing
laboratory.
• To prevent faulty ignition or accumulation of soot, use the correct
type of fuel oil, as recommended by the manufacturer.
• Locate an industrial fuel oil supply tank outdoors and above
ground. Protect tank and piping to contain leaks and spills.
• Cleaning metal parts
• Refined petroleum solvents are used for cleaning grease and oil
from metal parts where ordinary ventilation is provided and the area
is clear of sources of ignition.
Common Uses of Flammable
and Combustible Liquids
• Internal-combustion engines
• To prevent the accumulation of rubbish, oil or fuel, and rags around
industrial internal-combustion engines, practice good housekeeping.
• Spray booths
• Conduct paint-spraying operations in detached buildings or away from
other operations, when possible.
• Use approved spray rooms or booths with adequate ventilation.
• Provide large spraying operation with automatic fire controls.
Automatic sprinklers or inert agents (CO2 ) systems are most effective.
• Liquefied petroleum gasses
• Gasses that liquefy under moderate pressure but convert to a gaseous
state upon relief of the pressure. (e.g., propane, butane, propylene,
and butylenes)
• LPG vapors presents similar hazard to any flammable gas. LPG vapor
is heavier than air; collects in low areas and requires ventilation.
• Use only experienced and reliable manufacturers and installers.