Guide for Safe Storage and Handling of Heated Petroleum Derived Asphalt Products and Crude Oil Residua API RECOMMENDED PRACTICE 2023 THIRD EDITION, AUGUST 2001 Copyright American Petroleum Institute P[.]
Purpose
This article offers guidance on the safe storage and handling of heated petroleum-based asphalt products and crude oil residua By understanding the potential hazards associated with these materials, individuals can effectively reduce the likelihood and impact of incidents.
Scope
This publication outlines the potential hazards and necessary precautions for the storage and handling of asphalt products and petroleum residua, particularly in heated tanks at refineries and bulk storage facilities, as well as during transportation in tank vehicles It emphasizes the importance of managing storage temperatures, which may vary above or below the boiling point of water The precautions are relevant for various petroleum materials requiring heating, including performance grade asphalt cement (bitumen), road oils, cutback asphalts, asphalt emulsions, fillers, industrial asphalts for roofing and waterproofing, blowing fluxes, crude-oil residua, heavy low-volatility crude oils, and asphalts containing polymers.
This document does not cover customer end-use applications, but such information can be sourced from various organizations listed in Appendix H However, it does include certain storage and handling practices for industrial and marine residual (bunker) fuels and low gravity heavy crude oils, which may be applicable at the discretion of facility management.
Retroactivity
This publication offers design guidelines for new facilities and significant revisions or expansions, without retroactive application to existing structures It serves as a valuable resource for reviewing programs or facilities when necessary.
Concept of Hazard vs Risk
Hazards are characteristics of materials that can lead to harm, including flammability, toxicity, and corrosivity These risks are only present when there is potential exposure; for instance, a hot material can cause thermal burns, and a corrosive acid can result in chemical burns, but only upon contact with the skin Without the possibility of exposure, there is no associated risk.
Assessing risk requires estimating both the likelihood and potential impact of exposure that may cause harm This approach applies not only to risks affecting individuals but also to property risks For example, when hydrocarbon vapors mix with air, they can ignite upon contact with an ignition source, leading to fires that may cause significant property damage.
This publication references the latest editions of various standards, codes, and publications as valuable information sources Additional details may also be found on the cited websites.
API 1 Std 650 Welded Steel Tanks for Oil Storage
Std 2000 Venting Atmospheric and Low-Pressure
Storage Tanks: Nonrefrigerated and Refrigerated
RP 2001 Fire Protection in Refineries
RP 2003 Protection Against Ignitions Arising Out of
Static, Lightning, and Stray Currents
Publ 2015 Cleaning Petroleum Storage Tanks
Publ 2021 Management of Atmospheric Storage Tank
Publ 2021A Interim Study—Prevention and Suppres- sion of Fires in Large Aboveground Atmospheric Storage Tanks
Publ 2210 Flame Arresters for Vents of Tanks Storing
Publ 2216 Ignition Risk of Hydrocarbon Vapors by
Hot Surfaces in the Open Air
RP 2350 Overfill Protection for Petroleum Storage
Std 2610 Design, Construction, Operation, Mainte- nance and Inspection of Terminal and Tank Facilities
2000 Edition of TLV's ® and BEIs ® Based on Threshold
Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices
IS-180 Safe Storage and Handling of Hot Asphalt
B31.3 Chemical Plant and Petroleum Refinery
ACGIH guideline TLVs for year 2000—change to measure- ment basis for asphalt (bitumen) fumes
Flammable and Combustible Liquids Code Handbook
30 Flammable and Combustible Liquids Code
325 Fire Hazard Properties of Flammable Liq- uids, Gases, and Volatile Solids
385 Tank Vehicles for Flammable and Combus- tible Liquids
NIOSH Pocket Guide to Chemical Hazards
Literature Review of Health Effects Caused by Occupa- tional Exposure to Asphalt Fumes—
Interim Review Produced by NIOSH In Support of Nomination to the National Toxicology Program
1910.1000 (and following) Subpart Z, “Toxic and
Hazardous Substances”; see especially Section 1910.1002
Acute hazards are substances that can cause health effects after a brief exposure, typically lasting only a few minutes to hours Such exposure may lead to both immediate and long-term health consequences.
API gravity is calculated using the formula 141.5 divided by the specific gravity at 60° F (15.56°C) minus 131.5 Lower API gravity values indicate heavier and denser materials, with water having an API gravity of 10 Any substance with an API gravity lower than 10 is considered "heavier than water."
3.3 asphalt: Dark brown or black solid or semi-solid material obtained as residuals in refining petroleum (also called bitumen or petroleum asphalt).
3.4 asphalt cement: In Europe “asphalt” refers to
“asphalt mix” and “bitumen” refers to the U.S phrasing
“asphalt cement”; in the United States, performance grade asphalt cement is the binder used for paving asphalt mix.
Cut-back asphalt is a type of asphalt blended with petroleum distillates to ensure it remains liquid at lower temperatures, making it ideal for road surface coatings There are three types of cut-back asphalts—slow, medium, and rapid-curing—each containing petroleum distillates with progressively lower boiling points.
3.6 asphalt compounded with special hydrocar- bon diluents: May be used for roofing or adhesives; han- dling properties can be similar to cutbacks, depending on the hydrocarbon diluent used.
3.7 asphalt, emulsion: Low viscosity suspension or emulsion of asphalt in water; used for treating roadways, cement waterproofing and roofing compounds
3.8 asphalt mix: A mixture of asphalt cement and aggre- gate for use in paving; in Europe the term “asphalt” refers to
The autoignition temperature, defined as the lowest temperature at which a material can ignite spontaneously without an external ignition source, is influenced by factors such as the nature and duration of heating, the size of the specimen, and heat loss conditions.
2American Conference of Governmental Industrial Hygienists, 6500
Glenway Avenue, Building D-5, Cincinnati, Ohio 45211. www.acgih.org
3Asphalt Institute, Research Park Drive, P.O Box 14052, Lexington,
4American National Standards Institute, 25 West 43rd Street, New
York, New York 10036 www.ansi.org
5European Asphalt Paving Association, P.O Box 175, 3620 AD
Breukelen, The Netherlands www.eapa.org
6National Fire Protection Association, Batterymarch Park, Quincy,
7National Institute for Occupational Safety and Health (NIOSH)/
Centers for Disease Control and Prevention (CDC), NIOSH/CDC,
4676 Columbia Parkway, Cincinnati, Ohio 45226 www.cdc.gov/ niosh
8U.S Department of Labor, Occupational Safety and Health Admin- istration, 200 Constitution Avenue, N.W Washington, D.C 20210.www.osha.gov
This guide outlines the safe storage and handling practices for heated petroleum-derived asphalt products and crude oil residua, emphasizing the importance of considering conditions such as moisture content and contaminants A commonly utilized testing method for these materials is ASTM method E 659.
Standard Test Method for Autoignition Temperature of Liq- uid Chemicals
3.10 bitumen: Petroleum asphalt; a synonymous term often used outside the USA for “asphalt cement”.
3.11 blowing fluxes: Asphaltic materials used as an intermediate to produce blown asphalt.
3.12 blown asphalt: Asphalt produced by blowing air through hot asphalt to produce material with special proper- ties (especially raising the softening point).
Boilover occurs when a storage tank containing a mixture of light and viscous hydrocarbons experiences a sudden overflow or ejection of its contents during a full surface fire This phenomenon is triggered by a heat wave, which is a layer of hot, heavy oil that reaches the water or water-oil emulsion at the bottom of the tank.
3.14 bunker fuels: A name given to residual fuel oils derived from processing crude oil when used for marine applications (see Residual Fuels, and Fuel Oil, #5 & #6)
3.15 chronic health hazard: Capable of causing effects occurring from exposure over a long period of time (often at low-level concentrations).
3.16 coal tar pitch: A dark brown residue left after coal tar is redistilled; solid at ambient temperature Not a petro- leum process product.
3.17 cracking: Cleavage of molecules caused by high, localized temperatures; can lower flash point and cause flam- mable gas evolution.
3.18 crude-oil residua: Heavy hydrocarbon materials that are the “residue” after light hydrocarbons are separated by distilling; further processed to produce asphalt.
3.19 crude oils of low volatility: “Heavy” crude oils with gravity below 20 degrees API that may need to be trans- ported and stored at elevated temperatures.
3.20 frothover: The overflowing of a tank when water (or volatile hydrocarbon) boils under (but near) the surface of a viscous hot oil
3.21 fuel oil, #5 & #6: (See Residual Fuels, Bunker
Fuels) #6 fuel oil is also called Bunker “C” Oil.
3.22 fume: Small diameter particulate matter formed by condensation from the gaseous state of vaporized high molec- ular weight materials Although solids, fumes are small enough to behave like gases
3.23 hazard: An inherent chemical or physical property with the potential to do harm (flammability, toxicity, corrosiv- ity, stored chemical or mechanical energy)
3.24 heavy crude oil: Crude oil under 20 degrees API gravity is generally considered “heavy”.
The NIOSH defines the IDLH (Immediately Dangerous to Life or Health) level as the highest concentration of an air contaminant that allows for escape within 30 minutes without a respirator, while avoiding any health effects that could impair escape or cause irreversible harm.
3.26 natural asphalt: Naturally occurring petroleum materials which posses physical characteristics similar to asphalt derived by processing crude oil Found in nature as lake (pit) or rock asphalt
3.27 particulate: Inhalable materials considered by ACGIH to be hazardous when deposited anywhere in the res- piratory tract (see Appendix J).
The penetration test evaluates the hardness of asphalt cement by measuring how deep a weighted standard blunt needle penetrates the sample, expressed in units of 1/10 millimeter, at a specified temperature.
3.29 petroleum asphalt: Asphalt obtained by refining petroleum crude oil.
3.30 PCA: A polycyclic aromatic hydrocarbon (frequently used synonymously with PNA).
3.31 petroleum pitch: A product of petroleum process- ing (frequently used as a refinery intermediate).
3.32 PNA: A polynuclear aromatic hydrocarbon (fre- quently used synonymously with PCA).
3.33 pyrophoric: Iron sulfide or carbonaceous materials which, when exposed to air, can oxidize and heat, providing a source of ignition if a flammable vapor/air mixture is present.
Residual fuels are derived from the leftover components of crude oil and are often mixed with lighter hydrocarbons to attain the desired viscosity These fuels typically necessitate specialized pre-heating burners, along with appropriate handling and storage facilities, similar to bunker fuels.
3.35 risk: The probability of exposure to a hazard which results in harm
3.36 risk assessment: The identification and analysis, either qualitative or quantitative, of the likelihood and out- come of specific events or scenarios with judgements of prob- ability and consequences
3.37 risk-based analysis: A review of potential needs based on a risk assessment.
3.38 road oils: Asphalt for treating road surfaces which has been diluted with a petroleum thinner to a liquid consis- tency at lower temperature (see cutback asphalts).
3.39 self-ignition temperature: See autoignition tem- perature.
A 3.40 slopover occurs when hydrocarbon material spills from a tank due to the application of a water stream on the hot surface of boiling oil This phenomenon is more likely to happen if the oil is viscous and its temperature surpasses the boiling point of water.
3.41 slurry oils: (Catalyst bottoms) are highly aromatic bottom fractions Their high aromaticity gives them inherent solvency which makes them useful components to improve the stability of marine fuel blends
3.42 tar is a dark bituminous substance, either liquid or semi-liquid at room temperature, derived from the destructive distillation of coal, wood, peat, or other carbonaceous and vegetable materials, and is not a product of petroleum processing.
Vapor refers to the gaseous state of materials, which necessitates elevated temperatures for substances that are liquid or solid at room temperature For combustion to occur, materials must be in their vapor state.
Associated With Heated Storage and
OVERVIEW
Heavy hydrocarbon hazards relate to the need to store and handle them at elevated temperature and from the basic com- position of the materials.
Several inherent hazards relate to elevated temperature a Thermal burns. b Increased release of hydrogen sulfide. c Increased vapor release and fume formation. d Increased release of flammable vapors.
Heavy hydrocarbons, including asphalt and residua, pose significant hazards even at ambient temperatures due to their chemical composition Notably, hydrogen sulfide (H₂S) is highly toxic, while chronic exposure to heavy aromatic hydrocarbons containing polycyclic aromatic compounds (PCA/PNA) may lead to skin cancer Additionally, repeated exposure to these hydrocarbons can cause skin irritation.
Risk reduction involves recognizing these inherent haz- ards, controlling exposure and using good personal hygiene.
The MSDS for the material should provide help in identifying composition and potential hazards.
Certain issues associated with management of tanks and storage at high temperatures are addressed separately in Sec- tions 5 and 6.
When reviewing hazard information, it's crucial to understand that commonly used terms may refer to different materials For instance, while "asphalt" and "tar" may appear similar and have overlapping applications, they are distinct substances; asphalt is a petroleum product, whereas tar is a byproduct of wood or coal processing Both materials pose burn risks when handled hot, but their chemical compositions differ significantly This distinction is acknowledged by OSHA, which exempted asphalt from the "coal tar pitch volatiles" standard due to its lower potential chronic hazards.
THERMAL BURN HAZARDS TO PERSONNEL & RISK REDUCTION
Many asphalt, undiluted heavy crude oil and heavy resid- ual fuel products are normally maintained at elevated temper- atures to facilitate blending, transfer and transportation.
Appendix E outlines typical storage and handling temperatures, emphasizing that exposure to high temperatures can lead to severe burns The risk is heightened with heavy hydrocarbons, which possess a high specific heat capacity, act as effective insulators, and may adhere to the skin.
Personnel handling heated asphalt or heavy oil products must take necessary precautions to prevent contact and exposure It is essential to protect exposed skin with suitable clothing, footwear, and gloves, while eyes should be safeguarded with safety glasses, goggles, or a face shield Additionally, workers in the refining industry should be well-versed in measures to prevent thermal burns.
Rapid cooling is crucial for treating asphalt burns Following immediate cooling, specific first aid measures for burns caused by asphalt and similar substances should be taken into account, as detailed in Appendix C.
The removal of asphalt or similar substances from the skin necessitates specialized procedures and should be conducted under medical supervision It is crucial to seek professional medical treatment, as highlighted in the first aid guidance provided in Appendix C.
ACUTE HEALTH HAZARDS & RISK REDUCTION
Acute health hazards affect people during or shortly after exposure The effects may be transient or longer lasting
Hydrogen sulfide (H₂S) is a colorless, highly toxic gas that is flammable and heavier than air It can be found in asphalt, heavy crude oil, and storage vessels for residual fuel, as well as in transport vehicles Due to its density, H₂S can accumulate in vapor spaces, with flammable limits ranging from 4% to 44% by volume in air.
Measurements taken at a distance of a foot or more from hatch openings or domes typically indicate non-hazardous levels of H₂S However, there is a significant risk of dangerous exposure to high concentrations of H₂S in close proximity to open tank vessels, as well as tank truck, tank car, or barge hatches and domes.
Very brief high (under 1000 ppm) H 2 S exposures can cause severe respiratory difficulty, pulmonary edema, unconscious- ness, and death Relatively low concentration levels (under
100 ppm) can cause irritation of the eyes, nose, and throat.
Moderate exposure to hydrogen sulfide can lead to symptoms such as headache, dizziness, nausea, vomiting, cough, and difficulty breathing The intensity of these effects is influenced by the concentration of the gas and the length of exposure Workers in environments with hydrogen sulfide must recognize these symptoms as potential indicators of more severe exposure, prompting the need for an investigation and the use of proper protective equipment Notably, the NIOSH IDLH level was reduced from 300 PPM to 100 PPM in the mid-1990s.
ACGIH TLV in 2000 was 10 ppm with an STEL/C of 15 ppm ACGIH have published a “Notice of Intended Change” to lower their TLV to 5 ppm.
Hydrogen sulfide (H₂S) has a potent odor reminiscent of rotten eggs; however, relying on smell as a warning sign is dangerous Short exposure to high levels of H₂S can quickly impair the sense of smell, while prolonged exposure to lower concentrations can also lead to a similar desensitization of the olfactory nerves Additionally, the strong scent of heated petroleum-based asphalt products and crude oil residues can further complicate detection.
“mask” the odor of H 2 S when present in these products and residua
Personnel at risk of hydrogen sulfide (H₂S) exposure must receive training on the associated hazards and potential exposure locations Appropriate respiratory protection is essential in relevant situations Activities that may involve H₂S exposure include tank gauging, maintenance, and the filling of barges, tank trucks, or rail cars, particularly during open transfers.
The Agency for Toxic Substances and Disease Registry includes information on hydrogen sulfide in their publication
“ATSDR Medical Management Guidelines for Acute Chemi- cal Exposures: Chemical Protocols” posted on their web site at: www.atsdr.cdc.gov/mmg15.html.
Inert atmospheres, like nitrogen or flue gas, are utilized to blanket liquids in tanks to minimize fire risks, but they can lead to the accumulation of pyrophoric materials The absence of oxygen in these environments poses serious hazards to personnel, as prolonged exposure can result in collapse or even death Brief encounters with oxygen-deficient atmospheres, such as during tank gauging or venting, may cause dizziness, especially if hydrocarbon vapors are present While these effects typically resolve upon returning to normal air, there remains a risk of accidents, such as falls or burns from hot surfaces For further details on pyrophoric materials, refer to sections 6.2 and 6.3.
Inhalation of vapors and fumes from heated asphalt can lead to short-term effects, including eye and respiratory irritation "Cut-back" asphalt, which is a blend of residual fuel and lighter distillate hydrocarbons, may emit vapors that cause symptoms such as irritation, light-headedness, and headaches Fortunately, these short-term effects are generally reversible upon removal from exposure.
Threshold Limit Values and Permissible Exposure Limits are intended to address longer term repeated exposure The
2000 edition of the ACGIH ® publication TLVs ® and BEIs ®
The Threshold Limit Values (TLVs) for chemical substances have set a new limit for "Asphalt (Petroleum; Bitumen) Fume" at 0.5 mg/m³, a significant reduction from the previous TLV of 5.0 mg/m³, primarily due to concerns about irritation of the mucous membranes in the eyes and respiratory tract Notably, there is no OSHA Permissible Exposure Limit (PEL) for asphalt fume, as OSHA has clarified that the limits for coal tar pitch volatiles do not apply to asphalt from any source To promote good industrial hygiene, it is essential to educate employees on the risks of fume exposure and provide appropriate protective equipment Additional information on TLVs, PELs, and related health studies can be found in Appendix J.
POTENTIAL CHRONIC HEALTH HAZARDS & RISK REDUCTION
Chronic health hazards typically arise from prolonged exposure and may not show effects immediately However, hydrogen sulfide is not classified as a chronic health hazard When working with asphalt and heavy hydrocarbon residual materials, it is important to consider the risks associated with repeated exposure According to the 2000 ACGIH TLVs ®, "Asphalt (Petroleum; Bitumen) Fume" is categorized with a carcinogenicity notation of A4, indicating it is "Not Classifiable as a Human Carcinogenic Agent." This classification was supported by the IARC in 1987 and reaffirmed by a 1997 NIOSH review of scientific studies on asphalt fume.
Petroleum-derived asphalts and residua differ in composition due to various factors, including the source of crude oil, processing methods, storage and handling temperatures, and the addition of components like clarified slurry oil or middle distillates These elements significantly influence the potential hazards linked to each specific product.
Certain heavy petroleum materials pose potential carcinogenic and health risks, including skin and respiratory effects, due to their varied composition Research primarily targets polycyclic and polynuclear hydrocarbons, with some identified as carcinogens, particularly for skin, while others are not The concentration of polycyclic aromatic compounds (PCAs) tends to rise with the aromatic content in heavy hydrocarbons Therefore, it is crucial to prioritize good hygiene, proper use of personal protective equipment (PPE), and minimize contact when higher aromatic materials are incorporated into products for enhanced performance.
Appendix J.4 presents NIOSH's brief summary of their litera- ture review of health effects and occupational exposure to asphalt fumes.
COMPATIBILITY OF MATERIALS AND AVOIDING FROTHOVERS
When transitioning a storage or transport vessel to asphalt or residual product service, it is crucial to implement precautions to prevent the mixing of incompatible materials, as this could lead to hazardous frothover situations.
When a tank has been out of service for a long time, it is crucial to thoroughly purge incompatible materials, particularly water and light hydrocarbons like distillate Discharging hot products into the tank can lead to boiling water, resulting in rapid expansion and potential overpressure Additionally, light hydrocarbons can release vapors that may create a flammable mixture in the tank's vapor space, with significant vapor release posing further overpressure risks Key areas to focus on during the purging process include the internal tank structure, piping, inlet chambers, and tank-bottom sumps This purging principle also applies to transport trucks, rail cars, and vessels to eliminate any retained water or light hydrocarbons.
4.5.1 CONTAMINATION BY WATER OR LIGHT
Accidental injection of water or light hydrocarbons into heated asphalt or crude oil residues can lead to a rapid and violent release of froth, steam, or vapor when temperatures exceed the boiling point of these substances This pressure buildup poses a risk of failure at the roof-to-shell seam in tanks constructed according to API standards.
650 The resulting potential frothover could affect a large area surrounding the tank.
Water and light hydrocarbons can enter a heated tank containing slop oil through various sources, including interconnecting lines, leaking coolers, or hot-oil heater coils, as well as from steam leaks or during unit start-ups and upsets Additionally, water may accumulate from condensate that forms on the underside of the tank's roof and upper shell when the tank's contents are below 212°F (100°C) or when the tank is out of service This condensate can sometimes flow down the inside of the tank shell to the bottom.
4.5.3.1 Removing Water (Bottoms) Prior to Input
If streams entering a heated asphalt or residua product tank operating at temperatures above 212°F (100°C) are not free from water, significant problems can occur as described above.
To prevent water or hydrocarbons from entering tanks, it is essential to use a roll-out spool or double block valves with a bleeder Water coolers connected to these tanks must maintain product pressures that exceed water pressure to avoid leaks Additionally, implementing external heat tracing and insulation, or electrical heat tracing for the lines, is advisable Tanks that have been inactive for long durations should be inspected to confirm that water bottoms have not built up.
It is important to avoid using steam-jacketed or steam-gutted hot-oil lines between process units and asphalt or residua storage and loading facilities, as leaks can occur, leading to product frothing.
4.5.3.2 Monitoring Of Rundown Temperatures And
Monitoring and control of temperature of materials being
Hot rundown into tanks can mitigate issues related to the unintended vaporization of light hydrocarbons When a tank holds light materials and the vapor space is lean, introducing hot rundown can elevate the vapor space into the flammable range Although a lean vapor space should not contain pyrophoric iron sulfide, higher temperatures and flammable vapors could ignite carbonaceous deposits Additionally, if hot rundown is added to a solvent-containing product, it may lead to rapid solvent vaporization, risking tank overpressure Concerns about water or solvent may arise if the tank has been previously empty or out of service.
Line washes can pose significant risks, especially when cool flushes containing water are introduced into materials stored above 212°F (100°C), as this can lead to boiling water issues Additionally, introducing a light hydrocarbon flush into a hot tank may result in over-pressure and could shift the lean tank vapor space into a flammable range.
FIRE PREVENTION
To prevent storage tank fires and explosions, it is essential to ensure that a flammable mixture is not present in the tank Effective measures include ventilating the tank to eliminate vapors and maintain a safe vapor space in heated storage tanks.
“lean” range (for tanks with low volatility materials stored at least 50°F below their open cup flash point). b Venting limited to a single vent that is properly sized [see
To ensure safe operations, it is crucial to prevent restrictions from condensed deposits in vents and to keep gauge hatches closed during normal functioning Regulating storage temperatures is essential to maintain evolved vapors outside the flammable range, while careful control is necessary when blowing lines with air or using air for mixing Additionally, inert blanketing of the vapor space can help reduce oxygen content, and temporarily inerting the vapor space with flue gas or another suitable medium is recommended when tanks are emptied at significantly higher rates than usual.
Ignition of hydrocarbon vapors can occur at oxygen levels of 11% or higher, but SOLAS mandates a maximum of 8% oxygen in inert blanketed tanks on crude oil tankers for safety This is achieved by using inert gas systems that maintain oxygen levels below 5% Inert gas, being lighter than hydrocarbon/air mixtures, can create stratification in the tank if introduced from the top, leaving heavier air/fuel mixtures near the surface This stratification can be advantageous when venting hydrocarbon vapors from the bottom while introducing inert gas at the top, effectively displacing the heavier mixture However, potential personnel exposure and environmental concerns must be considered, and special procedures may be necessary when decommissioning inert blanketed tanks due to the risk of pyrophoric iron sulfide buildup.
It is crucial to emphasize and adhere to precautions against exposure to ignition sources, as an internal explosion within a tank can lead to catastrophic consequences Such an explosion may create overpressure, resulting in the tank's roof detaching from the shell and potentially causing a full or partially obstructed tank fire For more information on suppression methods, refer to section 4.7, Appendix K, and API RP 2021, while Appendix A offers additional handling suggestions.
For hydrocarbons to ignite, they must exist in the vapor phase and fall within their flammable range Effective temperature control and an understanding of the materials stored in tanks are crucial, especially when transitioning a tank from one service to another This is particularly important when mixing hot heavy products with cooler products that contain lighter fractions, such as cutbacks.
Higher tank temperatures lead to increased vapor generation, and if temperatures exceed approximately 450°F or if localized overheating occurs, light vapors may form due to cracking This release of light components can elevate fire hazards.
Tanks may contain flammable mixtures in several scenarios, including when they are nearly empty and hold a product with significant vapor pressure, as air enters the tank during product withdrawal Additionally, filling tanks from a low level with air in the headspace and a product that has considerable vapor pressure can create hazards Elevated temperatures in tanks for low vapor pressure products, non-functioning inert gas blankets, air-blowing asphalts, mixing with light solvents, heating materials above their flash point, and inadequate ventilation can also contribute to the risk of flammability.
Small amounts of absorbed gases and low molecular weight components can build up in the vapor space of tanks, often exceeding expected concentrations Notably, hydrogen sulfide, which is heavier than air and highly flammable (with a flammability range of 4% to 44%), poses a significant fire risk as it can accumulate in these spaces.
4.6.2 POTENTIAL IGNITION SOURCES 4.6.2.1 Electrostatic Ignition
Asphalts are effective conductors of electricity, preventing the accumulation of electrostatic charges and significantly reducing the risk of electrostatic ignition However, when handling distillates during the mixing of asphalt-solvent blends, it is crucial to implement safety measures such as bonding and grounding, as outlined in API 2003 Additionally, introducing steam into the vapor space of asphalt tanks can create electrostatic charges that may ignite flammable vapors, necessitating careful adherence to bonding and grounding protocols when using steam hoses in potentially hazardous environments.
Pyrophoric materials in petroleum storage tanks include iron sulfide and carbonaceous deposits, each forming under different conditions Iron sulfide develops in oxygen-deprived environments and poses an ignition risk when exposed to air; thus, maintaining a low oxygen inert blanket (around 5%) is crucial to prevent its formation Conversely, carbonaceous deposits, often found in asphalt tanks, arise from the condensation of heavy vapors on tank surfaces At elevated temperatures (approximately 350°F to 375°F) and in the presence of oxygen, these deposits can ignite flammable mixtures.
Hot surface ignition is closely linked to the autoignition temperature of the materials involved Finding accurate autoignition temperatures can be challenging, as they are often variable and typically presented as estimates Generally, most straight asphalts have estimated autoignition temperatures ranging from 700°F to 900°F, while Material Safety Data Sheets (MSDSs) for certain cutbacks and specially formulated blends may indicate autoignition temperatures as low as 400°F.
Hot surface ignition is possible whenever a glow of color is visible from a hot metal surface (minimum of approximately
At temperatures reaching 750°F, such as those produced by a torch applied to the exterior of a tank's vapor space, there is a risk of smoldering carbon deposits in the insulation potentially causing heating API 2216 specifically addresses the issue of hot surface ignition Below are some autoignition temperatures pertinent to asphalt, as indicated in Material Safety Data Sheets (MSDSs).
Welding or other “open flame” ignition sources should be subject to normal controls used for hot work (see API 2009).
Hot work can inadvertently heat heavy materials, like waxy deposits in tanks, leading to the release of vapors into areas that were previously non-flammable.
Lightning can ignite fixed-roof tanks only if a flammable vapor mixture exists in the tank's headspace When pumping product from a tank without an inert blanket, air is typically drawn in, which can convert a previously too-rich headspace into a flammable mixture Therefore, it is advisable to halt pumping during lightning-prone weather conditions The API 2003 guidelines discuss the importance of addressing electrostatic phenomena, including lightning protection for tanks.
Flame arresters are typically not utilized on the vents of asphalt or heavy hot-oil tanks, as they are ineffective in preventing lightning from igniting these materials Additionally, their use is not advised for petroleum tanks that are equipped with pressure/vacuum (P/V) valves.
FIRE SUPPRESSION
Fire suppression for heavy oil products presents unique challenges due to several factors Firstly, the heat retained in hot products complicates fire suppression efforts, as effective extinguishing relies on cooling the burning material to reduce vapor release Additionally, the elevated temperatures hinder the maintenance of a foam blanket, which is crucial for preventing vapor release Lastly, the surfaces of hot heavy oil can lead to a phenomenon known as "frothover," further complicating suppression efforts.
When water is introduced, heavy-oil materials containing lighter fractions, such as crude oil, cut-backs, and blended residual fuels, can potentially lead to boilover conditions This occurs if water accumulates at the bottom of the tank, provided that the bulk storage temperature is significantly below 212°F (100°C).
The frothover, slopover and boilover phenomena are dis- cussed in Appendix E.7 and API RP 2021 Although API
In 2021, the coverage of heated tanks was explicitly excluded from the tank fire suppression scope; however, the methodologies for emergency response planning and tank fire suppression remain relevant, particularly regarding heavy oil phenomena For a more in-depth discussion on fire suppression techniques for heated heavy-oil tanks, refer to Appendix K.
Evacuate all non-involved personnel from areas at risk of fire where suppression efforts may lead to frothover, slopover, or boilover This precaution is crucial to implement before initiating any fire suppression activities.
NFPA 11 advises against using portable foam streams on high viscosity materials heated above 200°F (93.3°C), emphasizing the need for good judgment when applying foam to tanks with hot oils, burning asphalts, or liquids that have a boiling point higher than water While the low water content in foams can help cool these fuels gradually, it may also lead to violent frothing and slopover of the tank's contents.
Fire suppression experts recommend carefully cooling the burning surface with various methods before initiating a foam attack It is crucial to execute this step thoughtfully to prevent the negative effects of applying too much water too soon.
Some facilities advise against the use of fixed or semi-fixed systems that deliver foam directly to heated heavy-oil tanks This is particularly important when foam is applied beneath a partially obstructed roof, as it can lead to steam formation that may cause the roof to detach from the vessel in an uncontrolled manner.
In the event of a tank fire, utilizing mixers to "roll the tank" can effectively transport cooler product to the burning surface, thereby minimizing vapor release and disrupting the combustion process This method can be implemented alongside gentle water-cooling techniques for enhanced safety.
If there is a fire inside a tank and the roof is still intact then routing inert gas into the tank head space has been success- fully used for suppression
Early in the fire suppression process any external heating of material in the tank should be stopped.
For spill fires, if the fire does not go out after cooling with water spray, a dry chemical (followed by foam) or dual agent attack may be successful.
TANK ROOFS
Asphalt tanks should have a watertight, free-draining roof.
Tanks should receive regular internal inspections to detect accumulation of deposits on the underside of the roof.
Deposit formation can be caused by condensation of vapors
(especially near vents) or might be a result of over-filling.
Excessive accumulation of deposits can lead to roof overload When heavy deposits form due to overfilling and build-up beneath a cool roof surface, the roof's support relies on the excess tank inventory If the supporting asphalt inventory is removed, it may create an air space beneath the roof, potentially leading to structural failure.
Tank roofs must include frangible seams as specified by API 650 It is essential for maintenance and monitoring to acknowledge that the buildup of carbonaceous deposits can be pyrophoric, potentially heightening the risk of fire.
TANK VENTS
Asphalt and heavy hot-oil tanks typically feature a single, rainproof vent positioned at a high point on the roof to prevent low oxygen areas within the tank Regular inspections of these vents are essential to clear any coke-like deposits Facilities should ensure safe access for inspections, potentially by installing walkways to mitigate risks associated with roof corrosion Some facilities have opted for an alternative vent location just inboard of the roof/wall seam, which has reportedly reduced condensation buildup on the roof and allows for easier observation of tank venting from the ground.
To ensure safety, it is essential to keep gauging hatches and roof manways closed to prevent unintended cross venting, which can alter the flammability characteristics of the internal tank atmosphere Utilizing manways for gauging can lead to a flow rate that exceeds that of a standard gauge hatch, increasing the risk of hazardous conditions.
Pressure-vacuum vents are typically not utilized in asphalt storage services due to the risk of condensed asphalt vapors causing pallet sticking and potential tank collapse When inert blanketing with gases like carbon dioxide or nitrogen is employed, maintaining the inert blanket requires the use of pressure-vacuum vents To ensure these vents remain clean, inert gas should be injected Flame arresters are generally not used on asphalt or heavy hot-oil tanks, particularly those with pressure-vacuum valves For existing asphalt storage tanks equipped with these devices, a regular preventive maintenance program is essential for inspection and cleaning to ensure proper functionality The frequency of these inspections should be based on historical data and sound engineering judgment.
TANK TEMPERATURE MEASUREMENT
Routine temperature readings are essential for effectively managing the product temperature in the tank It is crucial to use a reliable temperature-measuring device that extends sufficiently into the tank to capture accurate product temperatures Avoid taking readings near the tank's shell, bottom, heating coils, or fired tubes to ensure representative data.
When the sensing element encounters vapor while the temperature control system is operational, it may generate an incorrect low temperature signal This can lead to the heat treating medium in the tank circulating at its maximum rate until the product reaches the temperature sensor, allowing for an accurate reading to be communicated to the control system.
When stored products come into contact with overheated heating coils or fired tubes, it can lead to the cracking of heavy hydrocarbons and the production of substantial amounts of light hydrocarbon vapors.
Certain facilities require the installation of temperature indicators on the product rundown line leading to the tank, as well as two additional indicators positioned 60 degrees on either side of the fill line within the tank This setup offers unit operators essential backup instrumentation and diagnostic tools to assess abnormal conditions, such as the presence of a "plume" of hot material entering the tank.
LIQUID COVERAGE OF TANK HEATING SOURCES
To prevent excessive localized heating and potential product cracking, it is crucial to maintain a liquid level in internal tanks that is several inches above the fired tubes or heat-exchange surfaces during heating Insufficient fluid coverage can lead to the generation of light ends and carbonaceous deposits, which may become pyrophoric under certain conditions Utilizing advanced technologies like radar, microwave, or ultrasonic gauging can enhance tank level monitoring, reducing the need for frequent maintenance associated with conventional gauges.
TANK HEATING COIL CONSIDERATIONS
For asphalt and residual product tanks, it is essential to utilize all-welded heating coils To reduce the risk of leaks, these heating coils must be tested while the tank is not in operation.
Positioning the coils at the bottom of the tank enhances heating and agitation of the lower layers while minimizing the risk of pumping the product level below the coils.
Regular inspections of tanks with steam coils or fired heaters are essential to identify steam leaks and hydraulic hammer issues that could harm the coils When the coils are not in use, it is important to open an atmospheric bleed near the tank and monitor it frequently for any signs of condensate or product leaks Additionally, routine checks of isolation spools and car seals on double-block valves are necessary to ensure effective separation.
EFFECTS OF TANK TEMPERATURE CYCLING
To prevent steam evolution from accumulated water, products like cutback asphalts, road oils, and emulsions must be stored at temperatures below 212°F (100°C) It is crucial to avoid operating tanks in temperature ranges that fluctuate around the boiling point of water, as these fluctuations can lead to water accumulation and rapid vaporization, often resulting in frothovers Maintaining tank contents consistently above this temperature is essential for optimal storage conditions.
At 212°F (100°C), the frequent cycle of filling and emptying minimizes water accumulation due to condensation However, exceeding the boiling point of water can lead to the separation of milled emulsions.
Temperature fluctuations in the range of 212°F – 265°F
(100°C – 130°C) should be avoided as they could result in condensation, breaking of emulsions and frothing.
HAZARDS OF INACTIVE TANKS
Inactive tanks can pose significant hazards when reactivated, necessitating careful management of the change The temperature at the shell or bottom of an inactive tank may not accurately reflect the bulk contents, leading to potential risks Even if the product is kept above water's boiling point, cooler layers can form at the bottom, allowing water or emulsion to accumulate Disturbances, such as mechanical agitation, can mix this water with heated asphalt, resulting in rapid steam generation This increase in volume can exceed the tank's capacity, risking ruptures at the roof-to-shell seam or causing violent frothovers.
To reduce water accumulation, it is essential to position tank connections and draw-offs close to the tank sump Special precautions are necessary when moving product in or out of an inactive tank Prior to any product movement, all water or emulsion accumulations must be drained Pumping should commence at a low rate, with careful monitoring for any abnormal conditions, especially when transferring materials at temperatures exceeding the boiling point of water.
Concerns arise when residual light hydrocarbons remain from previous storage, as the introduction of hot heavy materials can vaporize these lighter hydrocarbons This process may shift the tank's vapor space into a flammable zone, posing a significant fire hazard.
If large quantities of vapor are generated then the venting capacity of the tank may be exceeded with the potential to overpressure and rupture a tank seam.
Adding hot asphalt to a cool, inactive tank can lead to rapid air and vapor expansion in the tank's vapor space, potentially causing overpressure and damage Standard vent-sizing calculations typically account only for air and vapor displacement from the incoming fluid, but rapidly expanding vapor can produce much larger quantities To mitigate this risk, it is advisable to introduce a small amount of hot product initially, allowing the tank to gradually heat up before the main delivery Additionally, resizing vents to accommodate worst-case scenarios when adding hot product to a cool tank can serve as an effective engineering solution.
STORING ASPHALT EMULSIONS
An asphalt emulsion is a nonflammable liquid mixture pro- duced by combining asphalt and water (as much as 20 to 30%) with an emulsifying agent such as soap or colloidal clays (from
Asphalt emulsions typically contain low-flash hydrocarbon components and water, and should be stored below the boiling point of the hydrocarbon to maintain stability These emulsions are designed to remain liquid at ambient temperatures and should not be heated above the boiling point of water to prevent breaking and frothing Additionally, exposure to freezing conditions can cause the emulsion to break, leading to the release of water and potential issues such as broken pipes.
STORING & HANDLING POLYMER MODIFIED ASPHALT
Polymer modified asphalt (bitumen) is a generic name for physical blends or chemical cross-linked blends of asphalt
Bitumen is often combined with various polymers and may include non-polymeric additives or fluxes In road construction, the polymer content typically remains below 10%, while roofing applications can utilize blends with polymer content ranging from 10% to 40%.
Polymers are used to change the temperature characteristics of the blends
Polymer modification of asphalt necessitates handling at elevated temperatures, as unmodified asphalt remains stable below its "cracking" temperatures However, the polymers in modified asphalt are prone to thermal degradation, which is influenced by both time and temperature Increased temperatures and prolonged exposure lead to greater degradation of the polymer blend Typically, first-generation polymer modified asphalts should be stored at temperatures not exceeding 380°F, although some specific polymers may tolerate higher temperatures according to manufacturer specifications Decomposition can result in harmful vapors and fumes, potentially compromising product quality and operational efficiency.
Extended personnel exposure to decomposition products resulting from excessive temperatures may lead to respiratory irritation, dizziness, nausea and/or headaches However, the
The European Asphalt Pavement Association (EAPA) highlights comparative studies showing that emissions from standard paving grades and SBS-modified bitumen do not significantly differ under proper working conditions This finding is supported by research conducted in Australia, indicating that exposure to fumes is unlikely in closed systems, although it serves as a caution for loading and unloading operations.
The EAPA emphasizes the importance of following specific supplier advice, such as that found in Material Safety Data Sheets (MSDSs), for safe product handling Key best practices for working with asphalt include operating at the lowest effective temperature, minimizing fume exposure through proper temperature control and ventilation, and utilizing appropriate personal protective equipment.
GENERAL HIGH TEMPERATURE OPERATING CONSIDERATIONS
To ensure safety in operational reviews, products stored in tanks without inert-gas blanketing should be kept at temperatures at least 15°F below their minimum closed cup flash points This practice helps maintain a vapor space that is fuel-lean, reducing the risk of ignition However, for asphalt cutbacks, it may be challenging to keep storage temperatures below the flash point, which is often lower than ambient temperatures Some companies intentionally maintain tank temperatures above 15°F over the closed cup flash point to create a "fuel-rich" vapor space, thereby minimizing flammability risks.
Proper storage of products at temperatures exceeding 350°F (177°C) is crucial due to the risk of deposits forming from condensation and oxidation in heated asphalt storage tanks These deposits can generate exothermic heat and may autoignite at temperatures above 375°F (190°C), leading to a smoldering condition that depletes oxygen levels inside the tank Maintaining a balanced oxygen-depleted atmosphere is essential to prevent autoignition of carbonaceous deposits Inerting storage tanks operating between 350°F and 450°F (177°C to 232°C) is a common industry practice, as inert-gas blanketing can inhibit deposit oxidation However, this method also creates conditions conducive to the formation of pyrophoric iron sulfides, introducing additional hazards.
To prevent thermal cracking and the formation of light products in heavy oils, it is crucial not to store the product above 450°F (232°C) without inert blanketing Prolonged exposure to temperatures nearing 500°F (260°C) can lead to these issues Therefore, it is advisable to initiate inert blanketing at least 50°F (28°C) below this critical temperature for optimal safety.
INERT-GAS BLANKETING
To prevent the tank vapor space from entering the flammable range, it is essential to inert the vapor space with flue gas, nitrogen, or another suitable medium when operating conditions such as temperature, product movement, or venting cannot be reliably controlled, especially if the product temperature exceeds 450°F (232°C) According to SOLAS regulations for tanker ships, inert gas must maintain a maximum oxygen concentration of 5%, ensuring that the tank vapor space does not exceed 8% oxygen While steam can be used as an inerting medium, it is less desirable due to its potential to generate static charges and its sensitivity to temperature.
(Cooling, such as from rain, will condense steam and could draw in much more air than the same temperature change would if using a non-condensable inert gas.)
Inerting tanks that store sulfur-containing materials is crucial to prevent the formation of pyrophoric iron sulfide deposits, which pose a fire risk Utilizing flue gas with approximately 5% oxygen for inerting can significantly reduce these deposits To effectively maintain the inert blanket and prevent damage to the tank or environmental releases, pressure-vacuum venting in accordance with API 2000 standards should be implemented, in coordination with experienced tank and venting specialists.
When utilizing an inert-gas blanket, several potential concerns must be addressed: the introduction of personnel hazards due to the use of inert gas, the risk of oxygen entering the vapor space when a gauge hatch is opened or during rapid product withdrawal that leads to pressure equalization with air, and the possibility of oxygen infiltrating the vapor space if the inerting system fails.
Additional concern arises when an inert blanketed tank is taken out of service, as discussed in 6.3.2.
PYROPHORIC DEPOSITS
Storage tanks can contain two types of pyrophoric deposits: iron sulfide and carbonaceous materials Iron sulfide forms when hydrogen sulfide reacts with iron in moist conditions, a process that is accelerated in an inert atmosphere Carbonaceous materials result from the condensation and oxidation of vapors in heated asphalt storage tanks, leading to solidified heavy hydrocarbons on tank surfaces and inside piping Maintaining around 5% oxygen in the inert-gas blanket has been shown to inhibit the formation of these pyrophoric substances.
Table 1—Temperatures for Consideration During Heated Tank Operating Condition Review
Situation Temperature Action Reason Reference
Straight residual Based on closed cup flash point
Maintain 15°F (9°C) below CC flash pt.
Seek to keep tank atmosphere fuel lean
Straight residual Based on open cup flash point
Maintain 50°F (28°C) below OC flash pt.
Seek to keep tank atmosphere fuel lean
Flash at ambient or below
Raise temperature or volatility of solvent
Seek to keep tank atmosphere fuel rich
Non-inert bulk storage 350°F (177°C) or higher Consider inert blanket Carbon deposit exothermic activity begins
350°F (177°C) or higher Minimize air flow High temperature oxidation of deposits
Non-inert bulk storage > 375°F (190°C) Consider inert blanket Carbon deposits may autoignite and smolder
Non-inert bulk storage > 450°F (232°C) Consider inert blanket Prevent thermal cracking of stored material
Inert blanketed storage All temperatures Keep O 2 at 5% to 8% Inhibit pyrophoric iron sulfide formation
Maximum tank temperature 500°F (260°C) Do not exceed— or use hi-temp tank
Tank thermal stress limit Section 6.5
API 650 pyrophoric deposits can ignite spontaneously when exposed to oxygen, leading to combustion that poses a significant ignition risk in the presence of flammable atmospheres To mitigate this hazard, it is crucial to prevent additional air from entering the tank, as actions like pumping product out or opening manways can introduce fresh air and enhance ventilation, potentially igniting smoldering deposits.
6.3.2 Taking Tanks Out of Service when Potentially
Special precautions should be followed when tanks poten- tially containing pyrophoric deposits are taken out of service
To mitigate the risks associated with pyrophoric deposits, it is crucial to maintain these deposits in a wet state until the surrounding atmosphere is rendered non-flammable, ensuring that the deposits are either oxidized or safely removed A comparable issue occurs on ships when the inert gas blanket in cargo tanks is substituted with atmospheric air.
This situation arises frequently when unloading tank ships.
To prevent pyrophoric ignition, SOLAS advises purging the tank until the hydrocarbon vapor concentration is reduced to below 2% before introducing air This measure ensures that the tank's atmosphere remains fuel-lean, minimizing the risk of ignition from potential reactions between iron sulfide and air.
BLOWING LINES WITH AIR
To prevent rapid oxidation of hot asphalt at temperatures exceeding 350°F (177°C), it is crucial to minimize the amount of air used when blowing oxidizer rundown lines Establishing procedures for a controlled product release with minimal air displacement is essential Continuous monitoring of line temperatures during the air-blowing process is necessary, and the use of inert gases like nitrogen is recommended Additionally, high-pressure compressed air should be avoided for clearing obstructed lines.
TEMPERATURE STRESS LIMITATIONS OF TANKS
Storage tanks constructed to meet API 650 standards are limited to a maximum temperature of 500°F (260°C) due to stress constraints on the shell However, certain facilities manage industrial grades at elevated temperatures using specially designed tanks If there is a proposal to store materials above 500°F (260°C), it is essential to assess the tank's suitability for such conditions.
RESPONDING TO ABNORMAL SITUATIONS
Appendix A outlines various abnormal situations that may arise during the storage and handling of heated heavy-oil products, while Appendix D shares incidents that offer valuable lessons for managing these scenarios Employee knowledge and awareness, along with well-defined operating procedures for start-up, shutdown, and emergencies, are crucial for effectively addressing and resolving such conditions Implementing robust management systems that focus on procedures, training, and simulated drills is essential for a comprehensive preparedness program These programs can significantly enhance heat management, including heater control, mixer usage, external cooling, product movement, venting, and inert-blanketing.
MIXING—GENERAL
The asphalt manufacturing process includes mixing components to achieve specific physical characteristics, but this process can present inherent hazards During mixing, previously blended materials like cutbacks may emit light hydrocarbons, potentially allowing the vapor space in the tank to enter the flammable range if air is present Additionally, sources of ignition, such as pyrophoric deposits, pose a risk Furthermore, if hydrogen sulfide is present in the product, the agitation from mixing can accelerate its release.
MECHANICAL MIXING
To ensure safe handling of asphalts, facilities must incorporate controls that minimize excessive vapor release when adding diluents, particularly hot stocks Efficient mixing can be achieved through the use of in-line blenders or pump-around systems with mechanical mixers Additionally, large tanks may necessitate the use of multiple mixers to ensure adequate mixing.
AIR MIXING
Air mixing is an efficient method, but it poses hazards by potentially generating flammable vapors in the tank's vapor space and beyond if vented When using air for mixing, it is crucial to closely monitor the asphalt temperature and the amount of air injected, as increases in temperature in either the liquid or gas phase may indicate problems due to the exothermic nature of oxidation Additionally, tank pressure should be monitored, and equipment should be employed to control air quantity to prevent overpressure Precautions must also be taken to ensure that water is not introduced into the tank along with the air.
VENTING AND WATER-FREEING
Proper venting of vehicles transporting hot oils and asphalts is essential to prevent frothovers, as outlined in NFPA 385 A frothover can occur when water or volatile hydrocarbons boil beneath the surface of viscous hot oil, particularly if hot asphalt is loaded into a tank car containing water Initially, the asphalt may cool upon contact with the cold metal, but once the water boils, expanding steam can lead to overflow While froth suppressants can reduce the risk of frothovers during the loading of heated asphalt products, they must be approved by the user or purchaser prior to use It is crucial to prevent water from contacting hot products, and loading should cease if popping or cracking sounds are heard, indicating moisture presence.
FIRED HEATERS ON TANK VEHICLES
Fired heaters on tank trucks or rail cars should not be oper- ating while at a loading rack.
CLEANING TANK TRUCKS AND RAIL CARS
Cleaning tank trucks and rail cars involves the same con- cerns for personal hygiene discussed in 4.4 These tanks are normally permit-required confined spaces as regulated by
OSHA, and appropriate preparation and permitting is required Any cleaning of tanks involving the use of hydro- carbon solvents should ensure that:
1 Personal protective equipment needs have been evalu- ated and implemented.
2 That sources of ignition (such as truck heaters) are shut off.
3 That proper static ignition control is in place.
Improper spraying of solvents can lead to explosions and severe injuries To mitigate these risks, API 2003 offers guidelines on grounding and bonding Additionally, it is advisable to explore alternative cleaning methods that do not involve hydrocarbon solvents.
INSPECTING TANK TRUCKS AND RAIL CARS
When inspecting tank truck or rail car compartments, it is essential to adhere to permit-required confined space entry regulations Special attention must be given to the potential hazards related to the previous cargo and the presence of an inert atmosphere within the tank.
LOADING AND UNLOADING TANK TRUCKS AND RAIL CARS
Loading trucks or rail cars with hot asphalt products heightens the risk of personnel exposure to thermal burns and hydrogen sulfide emissions It is crucial to implement safety precautions when working near tank openings, such as loading hatches Additionally, handling loading equipment like hoses increases the likelihood of skin contact, making good personal hygiene essential Avoiding the use of contaminated clothing, including gloves, is also important for safety.
Heated asphalt products and crude-oil residua can be managed safely by adhering to established procedures This document, along with its references, provides essential information to create safe work practices that mitigate exposure to inherent hazards and lower associated risks.
Table A-1—Guide for Asphalt/Residua Handling
Potential Hazard Causes Potential Remedies or Precautions
Plan operator response action to reduce temperature. Frothing Water or volatile hydrocarbons in (or entering) a hot tank, truck, or tank car
Keep water out: hatches closed, roofs intact, steam coils, steam heaters, and coolers leak free; conduct tightness tests Avoid cycling tank temperatures (near the boiling point of water).
Keep blending components free from water and/or volatile hydrocarbons when blending with hot residuals.
To ensure optimal results, it is essential to minimize, accurately measure, and control temperatures Components should be thoroughly mixed as they are added to the tank, rather than adding them first and then mixing Additionally, allowing entrained water to gradually boil off is crucial to prevent rapid steam generation.
Vapor flashing (ignition) Presence of hydrocarbon vapors and air and ignition source; vapors evolve as a result of heating mixes or cracking
Minimize storage temperatures (preferably below 350°F). Avoid using air for blowing lines to tank if possible (con- sider inert gas instead) If air is used, minimize tank tem- peratures.
Recognize and control ignition sources.
Pyrophoric iron sulfide formation Oxygen-deficient atmosphere in the presence of H 2 S and iron
Blanket the tank with an inert gas.
Wet interior tank surfaces when tank is opened for repair or inspection.
Maintain 3 to 5% oxygen in tank head space.
Pyrophoric carbon Buildup of carbonaceous deposits Maintain 3 to 5% oxygen in tank head space if inert gas blanketed.
Minimize storage temperature (target below 350°F). Avoid deposit buildup in insulation on outside of tank near vents.
Autoignition Inherent property of hydrocarbons Inert blanket tanks (preferably w 5% oxygen).
Eliminate or minimize uncontrolled ingress of air. Avoid accumulation of carbonaceous tank deposits.
Damage to skin and eyes Burns and splashes Prevent spills, leaks & overfilling.
Wear proper personal protective equipment.
Hydrogen sulfide exposure (acute hazard; vapors can cause death)
Vapor accumulation during loading operations Provide training in materials hazards.
Avoid breathing vapors (stand upwind of open hatches and use appropriate respiratory protection as required)
Do not put face near tank openings or vents or put head inside enclosed spaces.
Asphalt and residual product vapor or fume exposure
Vapor accumulation during loading operations Wear respiratory protection if appropriate.
Do not put face near tank openings or vents or put head inside enclosed spaces (e.g when gauging).
Roof collapse Accumulation of asphalt, residua or carbon deposits on underside of roof
Heat stress failure Tank overtemperature Include maximum temperature in procedures.
Keep tank temperature within heat-stress limits.
Avoid blowing air into tanks if possible.
Size vent properly; inspect and clean vent periodically. Use open vent with hat design
Bottom failure Steam from water under a hot tank Provide drainage for water.
Minimum Open Cup Flash Point Temperature*
Type and Grade Reference Specification Fahrenheit Celsius
PG asphalt binder (all grades) AASHTO MP1 446 min 230 min.
Rolling thin-film oven test
MP1 Performance Graded Asphalt Binder
M81 Cutback Asphalt (Rapid-Curing Type)
M82 Cutback Asphalt (Medium-Curing Type)
M115 Asphalt Used in Dampproofing and
M238 Asphalt for Undersealing Portland Cement
M239 Asphalt for Use in Waterproof Membrane
T48 Flash and Fire Points by Cleveland Open
D 41 Asphalt Primer Used in Roofing and
D 93 Standard Method of Test for Flash point by
D 323 Standard Method of Test for Vapor Pres- sure of Petroleum Products (Reid Method)
D 449 Asphalt Used in Dampproofing and
D 946 Penetration-Graded Asphalt Cement for
D 2026 Cutback Asphalt (Slow-Curing Type)
D 2027 Cutback Asphalt (Medium-Curing Type)
D 2028 Cutback Asphalt (Rapid-Curing Type)
D 2521 Asphalt Used in Canal, Ditch, and Pond
D 3141 Asphalt for Undersealing Portland Cement
D 3381 Viscosity-Graded Asphalt Cement for Use in Pavement Construction
Flash points are typically measured using the COC open cup methods ASTM D 92 and AASHTO T48 Due to the volatility of diluents in MC and RC cutback grades, the TAG open cup apparatus with a glass cup is preferred Some experts opt for closed cup procedures for all cutback products with volatile hydrocarbon diluents The International Safety Guide for Oil Tankers & Terminals favors closed cup values for flash points, noting that open cup values are approximately 6°C (10°F) higher and that closed cup results are more consistent According to the UN Dangerous Goods Regulations, a substance is considered flammable if it has a flash point of no more than 60.5ºC (140.9ºF) in a closed-cup test or 65.6ºC (150ºF) in an open-cup test The regulations acknowledge that results from open and closed cup tests are not directly comparable, and variations in regulations are permissible to accommodate these differences.
Minimum Open Cup Flash Point Temperature*
Type and Grade Reference Specification Fahrenheit Celsius
9American Association of State Highway and Transportation Offi- cials, 444 North Capitol Street, N.W., Washington, D.C 20001. www.aashto.org
10American Society for Testing and Materials, 100 Bar Harbor
Drive, West Conshohoken, PA 19428 www.astm.org
C.1 General First Aid for Burns
Severe burns require immediate and proper treatment to prevent shock and serious infections It is crucial for patients with significant burn injuries to be referred to a specialized burn center The American Burn Association has outlined specific criteria for these referrals to ensure optimal care.
American Burn Association (ABA) Central Office—Chicago www.ameriburn.org
625 N Michigan Ave., Ste 1530 Chicago, Illinois 60611 Telephone: 312.642.9260 [Member Toll-free: 800.548.2876]
Fax: 312.642.9130 email: info@ameriburn.org Most MSDS and other first aid advice stress:
1 Immediate cooling (noting that heavy hydrocarbons have high specific heat capacity and are good insulators so extended time may be needed).
2 Getting professional medical attention for significant burns
3 Not trying to wipe off or remove hot asphalt (so skin doesn't come with it) Allow solidified material to remain in place until cooled Natural separation should occur in
4 If removal of cooled asphalt is attempted, mineral oil may be effective if worked into the skin around the asphalt while allowing the asphalt to “float off”.
C.2 First Aid for Asphalt (Bitumen) Burns
The following first aid summary was extracted from www.concawe.be/Html/REPORT1-97/B/B43.htm:
Report no 1/97 petroleum products—first aid emergency and medical advice © CONCAWE, Brussels, March 1997
This material is used with permission of CONCAWE with acknowledgement and appreciation.
Prepared for CONCAWE's Health and Petroleum Products Management Groups by:
G.P Ebbon, U Fornari, J.-P Gennart, A.J Riley and B.J. Simpson
In the event of accidental skin contact with heated bitumen, do not attempt to remove it; instead, immediately immerse the affected area in cold running water If bitumen adheres completely around a limb or finger, carefully split the bitumen to avoid a tourniquet effect as it cools, and seek medical advice promptly.
In case of eye contact with hot bitumen, it is crucial to cool the eye immediately with plenty of cold running water and seek medical attention For cold bitumen exposure, irrigate the eye thoroughly with water, and if irritation persists, consult a medical professional If bitumen remains in the eye, refer the patient to an eye unit or hospital for further treatment.
Doctors should avoid attempting to remove firmly adhering bitumen from the skin, as it poses no further harm once cooled and acts as a sterile covering for burns If bitumen forms a tourniquet, it should be split to prevent blood flow restriction The bitumen plaque typically detaches on its own after a few days of healing If removal is necessary due to the contact site, warm medicinal paraffin can be applied, followed by washing with soap and water, and then using a proprietary refatting agent or skin cleansing cream.
Reference: CONCAWE (1992) Bitumens and bitumen derivatives Product Dossier No 92/104 Brussels: CON-CAWE
HEATED ASPHALT AND RESIDUAL PRODUCTS
D.1 Fire and Explosion in an Empty
From Safety Digest of Lessons Learned, Section 6, Safe
Operation of Storage Facilities (Page 24)
Ignition occurred shortly after work started on top of an
“empty” 140 ft diameter, 120,000 barrel bunker fuel tank.
Workers used a torch to cut an access hole, which led to a rapid internal fire spreading beneath the roof Within 5 to 7 minutes, vapor ignited inside the tank, causing the roof's frangible weld seam to split in three locations Fortunately, there were no reported injuries.
A torch can effectively heat deposits like residual wax and heavy oil on the interior surfaces of a tank, which can release vapors and create a flammable mixture Additionally, traditional gas testing only assesses conditions at the time of testing, and the introduction of heat from a torch can significantly alter these conditions.
Changes in conditions require careful review and management It may be necessary to conduct a physical inspection of both sides of a surface before allowing the use of a torch Additionally, cold cutting is often the preferred method for surfaces that have deposits.
A fire and explosion in an “empty” 140-ft diameter,
120,000 barrel bunker fuel tank damaged the roof and walls.
A fire ignited while a torch was being used to create an access hole in the roof, following several days of preparation that included purging the tank, obtaining entry permits, and beginning abrasive-blast cleaning Notably, sections of the floor had previously been cut with torches without any issues prior to the incident.
Investigators determined that a torch ignited a layer of residual wax and heavy oil on the roof's underside, causing vapor to flash due to the fire's heat and leading to significant damage The fire was contained within about 10 minutes.
A month prior to the explosion, the tank was decommissioned for repairs due to a floor leak During this time, furnace oil was introduced into the tank, heated, and mixed to eliminate heavy waxy hydrocarbons settled at the bottom Subsequently, the tank was emptied of the furnace oil flushings, blinded, and prepared for maintenance by being turned over and gas-freed.
In the days leading up to the incident, the tank underwent purging, entry permits were secured, and abrasive-blast cleaning commenced Additionally, sections of the floor were cut using torches without any prior issues before the fire occurred.