OSHA Hazard Information Bulletins
November 19, 1993
| MEMORANDUM FOR: |
REGIONAL ADMINISTRATORS |
| THROUGH: |
LEO CAREY
Director
Office of Field Programs |
| FROM: |
PATRICIA K. CLARK
Director
Directorate of Technical Support |
| SUBJECT: |
Hazard Information Bulletin(1): Use of Hydrofluoric Acid in the Petroleum Refining Alkylation Process |
__________
FOOTNOTE(1) The Directorate of Technical Support issues Hazard Information
Bulletins (HIB) in accordance with OSHA Instruction CPL 2.65 to provide
relevant information regarding unrecognized or misunderstood health hazards,
inadequacies of materials, devices techniques, and safety engineering
controls. HIBs are initiated based on information provided by the field
staff, studies, reports and concerns expressed by safety and health
professionals, employers, and the public. Information is compiled based on a
thorough evaluation of available facts and in coordination with appropriate
parties.
The purpose of this bulletin is to alert field personnel to the potential
safety and health risks posed by hydrofluoric acid (HF) used in HF alkylation
units and to present the control measures implemented by industry to reduce
workers' exposure, and pertinent OSHA requirements.
In recent years the petroleum refining industry has placed an increasing
emphasis on the safety of the use of HF in petroleum refineries. Refineries
use the acid in a manufacturing process called "alkylation," which is
increasingly important in producing a high-quality gasoline. Hydrofluoric
acid is hazardous and corrosive and, if accidently released, can form a vapor
cloud. If the vapor cloud is concentrated enough it can be toxic until
sufficiently dispersed. In the past five years, there have been a number of
accidental releases of this acid from alkylation units at major petroleum
refineries in the United States.
Pure hydrogen fluoride is a clear, colorless, corrosive liquid that has
roughly the same weight as water (comparing equal volumes). It boils at 67
degrees Fahrenheit and, depending on the release conditions, can form a vapor
cloud if released to the atmosphere. It has a sharp, penetrating odor that
human beings can detect at very low concentrations (0.04-0.13 ppm(1), in the
air. It is completely soluble in water, in which it forms HF, which, in
concentrated solutions, vaporizes in air to form a noticeable cloud.
To protect against adverse effects from exposure to hydrofluoric acid in the
workplace, the Occupational Safety and Health Administration has established
a permissible exposure limit (PEL) of 3 ppm averaged over an eight-hour
workshift. The National Institute for Occupational Safety and Health
immediately dangerous to life or health (IDLH) concentration for HF is 30
ppm(2).
___________
FOOTNOTE(1) American Industrial Hygiene Association, Emergency Response Planning
Guidelines, AIHA Emergency Response Planning Guideline committee, Akron,
Ohio, 1988.
FOOTNOTE(2) U.S. Department of Health and Human Services, NIOSH Pocket Guide to
Chemical Hazards, Publication No. 90-117, Cincinnati, Ohio, June 1990.
Any contact with HF liquid or vapor can produce serious, painful chemical
burns, sometimes with delayed onset and hypocalcemia. The vapor can be
extremely irritating to the eyes, skin and respiratory tract. Short-term
exposure at high concentrations can cause serious health effects or death due
to extensive respiratory damage.
Because of the chemical burn hazard present with HF, refineries have
incorporated many or all of the following engineering controls at HF
alkylation units:
- Construction of concrete containment curbs around reactor and
HF storage vessels.
- Installation of segregated sewer systems designed to contain
spills and runoff from HF acid areas. Effluent is treated for HF
neutralization and removal before release to refinery main sewers.
- Routing all vents from the unit to a soda ash scrubber to
neutralize HF.
- Installation of soda ash solution vats for neutralizing
equipment that is to be removed from the unit for maintenance or
disposal.
- Installation of feed drying and HF acid regeneration systems to
keep moisture content of acid less than 4 percent to prevent corrosion of
equipment.
- Potassium hydroxide scrubbing of light products leaving unit to
neutralize trace amounts of HF that may present.
- Incineration of HF acid sludge in process heaters.
The above controls are designed to contain HF inside the unit area, thereby
minimizing exposure potential to workers outside the alkylation unit.
In addition, several OSHA regulations provide for the safe handling of
hazardous chemicals. Refineries that handle HF must meet many requirements.
For example, they must do the following:
- Develop and implement a process safety management program in
accordance with OSHA standard 29 CFR 1910.119, if they meet threshold
quantities.
- Monitor the site to determine the appropriate level of employee
respiratory protection (29 CFR (1910.134).
- Provide information and training, including first-aid training,
to employees about the hazardous chemicals to which they are exposed by
implementing a hazard communication program, (29 CFR 1910.1200).
- Implement a program of engineering controls, work practices and
personal protective equipment to control exposure (29 CFR 1910.134(b)(6), 29
CFR 1910.1000)
- Develop and implement an emergency response plan, including
emergency procedures and training of personnel (29 CFR 1910.120, 29 CFR
1910.38)
As with most refinery processes, the primary exposure control method used in
HF alkylation units is the containment of all process substances within the
unit equipment (i.e, vessels, piping, and pumps). Greatest exposure
potential occurs:
- During process stream sampling;
- During unloading of HF from trucks;
- Due to process leaks (fugitive emissions);
- Due to equipment failures (e.g., pump seals); and
- During equipment maintenance.
In June 1992, the American Petroleum Institute issued Recommended Practice
751, Safe Operation of Hydrofluoric Acid Alkylation Units. Due to the
severe hazard potential of HF, compliance officers should familiarize
themselves with this document prior to making an inspection involving HF.
Please disseminate this bulletin to all Area Offices, State Plan States,
Consultation Project Officers and appropriate local labor and trade
organizations.
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