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Hazard Information Bulletins - Work Practices by the Electric Utilities Industry for Sulphur Hexaflouride Gas-Insulated Circuit Breakers.
Work Practices by the Electric Utilities Industry for Sulphur Hexaflouride Gas-Insulated Circuit Breakers.
- INFORMATION DATE : 19890130
- RECORD TYPE : Hazard Information Bulletin
- SUBJECT : Work Practices by the Electric Utilities Industry for Sulphur Hexaflouride Gas-Insulated Circuit Breakers.
U.S. Department of Labor Occupational Safety and Health Administration
Washington, DC 20210
Reply to the Attention of:
JAN 30 1989
MEMORANDUM FOR: REGIONAL-ADMINISTRATORS
THRU: LEO CAREY
Director
Office of Field Programs
FROM: EDWARD J. BAIER
Director
Directorate of Technical Support
SUBJECT: Safety Hazard Information Bulletin on Work Practices
Employed by the Electric Utilities Industry Regarding
Sulphur Hexaflouride Gas-Insulated Circuit Breakers
An inquiry was forwarded to this office by the OSHA New York Regional
Office regarding a possible safety hazard associated with sulphur
hexaflouride (SF(6)) circuit breakers used by electric utilities in
high-voltage transmission and distribution applications. The Edison
Electric Institute (EEI) was most helpful in providing information
necessary for this bulletin.
In response to the above inquiry, we conducted a series of investigations
including discussions with utility industry representatives and an on-site
visit to a utility substation to determine any potential existing hazards.
According to the EEI, member companies have been using SF(6) gas-insulated
circuit breakers for 20 years with associated maintenance hazards being
well-known within the industry. The chief safety hazard is the potential
exposure of maintenance employees to residual toxic by-products of SF(6)
breakdowns that occur after the gas is exposed to a series of arcings. In
most cases, the by-products (when present) may total a few grams. EEI
estimates that SF(6) equipment is used in general about 80 percent outdoors
and above ground, 15 percent indoors and 5 percent below ground. Attached
is one company's substation maintenance bulletin containing work practices
for SF(6) gas-insulated equipment.
During the on-site local substation visit, Virginia Power Company personnel
demonstrated maintenance procedures for a 230 kilovolt Westinghouse circuit
breaker which was undergoing door seal replacement due to a leak. The
observed Westinghouse unit consists of three interrupters and housings
sharing a common gas system. (See attached photograph.) Low pressure, 45
psig SF(6) surrounds the interrupter and acts as an insulator. High
pressure (approximately 270 psi) SF(6) is used to extinguish arcing during
an interruption cycle. After the gas was evacuated from the breakers and
deposited in a gas reclaiming system, and prior to replacing the door
seals, Virginia Power personnel demonstrated what they would do if the
presence of SF(6) by-products had been found. The Virginia Power personnel
wore protective clothing with air purifying respirators and used vacuum
cleaners with high-efficiency particulate air (HEPA) filters to demonstrate
the manner in which toxic residue would be removed if it were present.
Also attached is a response prepared by EEI to OSHA questions regarding
SF(6) equipment. The attachment provides, among other things, information
on the design and potential failure of equipment and detection of gas
leaks. It also addresses precautions that must be taken if equipment is
located in a confined space.
Please distribute this bulletin to Area Offices, State Plan States and
Consultation Projects.
Attachments
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