GOST 12.1.004–91

Random Section of GOST 12.1.004–91

3.1.14. Probability (Qi (e3)) during continuous work of electric appliances shall be unity for all facilities if electric equipment does not correspond to the combustible medium category and group or 10-8 if it corresponds to the appropriate category and group. In case of periodic operation of electric equipment and its failure to correspond to the combustible medium category and group, probability (Qi (e3)) shall be calculated analogous to probability (Qi (an)) in accordance with (42). If electric spark is formed only at start / stop of electric equipment that does not correspond to the combustible medium category and group in the case of n starts / stops, probability (Qi (e3)) shall be calculated analogous to probability (Qi (t2)) in accordance with (49). If electric equipment is in compliance with combustible medium, probability (Qi (e3)) calculated from (49) shall be multiplied by 10-8.

3.1.15. Probability (Qi (e4)) of the static electricity spark formation in the ith facility element shall be calculated as

(Qi (e4) = (Qi (X1) · (Qi (X2),                                                                                                (57)

where Qi (X1) is the probability of gaining static electricity in the ith facility element during a year;

Qi (X2) is the probability of failure, absence, or inefficiency of protection from static electricity during a year;

3.1.16. Probability (Qi (X1)) shall be assumed equal to unity if substances with specific volume electric resistance exceeding 105 Ohm·m are used in the ith facility element. In other cases, (Qi (X1)) is assumed to be zero.

3.1.17. Probability (Qi (X2)) shall be assumed equal to unity in the case of absence or inefficiency of static electricity protections. Probability (Qi (X2)) of protection means failure in operating elements shall be calculated based on of statistical data analogously to probability (Qi (an)) in accordance with (42).

Probability (Qi (X2)) in the designed facility elements shall be calculated analogously to probability (Qi (an)) in accordance with (43) based on the data on reliability of design means of protection from static electricity (for example, ionization, air dampening, etc.).

3.1.18. Frictional sparks (shock and friction sparks) result in the facility element under study (event HSn) from using intrinsically unsafe tools (event f1), destruction of moving units and components (event f2), using footwear with metal elements and nails (event f3), ingress of foreign items into moving mechanisms (event f4), etc., metal hatch impact (event f5). Probability (Qi (HSn)) shall be calculated as

Qi (HSn)  = 1 —  [1 — Qi (fn)],                                                                                        (58)

where

Qi (fn) is the probability of realization of any of fn causes shown below;

Qi (f1) is the probability of metal, grinding, or other intrinsically unsafe tool use in the ith facility element during a year;