DL/T 639-1997 in English

1 Subject Content and Application Scope

1.1 This standard includes the safe application of SF6 gas, the safety and protection measures during the operation and disassembly of equipment, as well as the management and application of personal protective articles, and so on.
1.2 This standard is applicable to the safety and protection of operation, test and maintenance personnel of SF6 in electrical apparatus, and the other relevant using units of SF6 electrical apparatus still can make references from this standard.

2 Normative References

The following standards contain provisions which, through reference in this text, constitute provisions of this standard. At time of publication, the editions indicated were valid. All standards are subject to revision, and parties concerned are encouraged to discuss the possibility of applying the latest edition of the following standards.
GB 8905-1996 "The Guide for Processing and Measuring SF6 Gas in Power Apparatus"
GB 11651-89 "Selection Rules of Articles for Labor Protection Use"
GB 12022-89 "Sulphur Hexafluoride for Industrial Use"
DL/T 595-1996 "Rules for Supervising SF6 Gas in Electrical Apparatus"
DL/T 596-1996 "The Preventive Test Work for Electric Equipment Regulation"
SD 312-89 "Biotoxication Tests by Sulphur Hexafluoride"
IEC 376-1972 "Regulations for and Acceptance of New Sulphur Hexafluoride"
IEC 480-1974 "Guide to Checking Sulfur Hexafluoride Taken from Electrical Equipment"

3 Terms

3.1 Sulphur hexafluoride
Sulphur hexafluoride is of gas state, nontoxic, colorless, flavorless and with very stable chemical properties at normal temperature and pressure, its density is 6.16g/L and it is with outstanding insulation, arc extinguishing and electrical performances at 20℃ and 101325 Pa.
3.2 SF6 electrical apparatus
It is the electrical apparatus filled with sulphur hexafluoride as the isolation medium, such as sulphur hexafluoride circuit breaker, transformer, cable and Gas Insulated Switchgears (GIS), etc.
3.3 Toxic decomposition products
The production of SF6 gas is accompanied by various toxic gases which may be mixed into the gas product; SF6 gas in electrical apparatus still will produce various toxic and corrosive gases and solid decomposition products through the action of electrical corona, spark and arc discharge. These gases mainly are thionyl sulfide (SOF2), sulfuryl fluoride (SO2F2), sulfur tetrafluoride (SF4), sulphonyl tetrafluoride (SOF4), sulfur dioxide (SO2), disulfur decafluoride (S2F10) and disulfuryl decafluoride (S2F10O); the solid decomposition products mainly are copper fluoride (CuF2), dimethyl silicone difluoride [Si(CH3)2F2] and aluminum fluoride (AlF3) powder. See Appendix A for the permissible contents of toxic decomposition products in work place.
3.4 Purifying handle for SF6 gas
The toxic decomposition products in SF6 gas may be absorbed with adsorbent, or may be eliminated through chemical reaction with acid solution or alkali solution, and this process of eliminating the toxic decomposition products in SF6 gas with various methods is named as purifying handle for SF6 gas.

Foreword I
1 Subject Content and Application Scope
2 Normative References
3 Terms
4 Safe Application of Sulphur Hexafluoride
5 Management and application of Safety Protection Articles
6 Organization Management and Labor Hygiene
Appendix A (Normative) Permissible Contents of SF6 Gas and Its Toxic Decomposition Products in Work Place
Appendix B (Normative) Quality Standards of SF6 Gas