entech. WKP Magazine Explosion Simulation – Gas Dispersal Study P a g e | 13 Table 4-4 looks at the period that each gas is hazardous as it exits the mine and compares this with the combined contaminant duration. The full contaminant duration is determined when the combined contaminants are above 0.5 ppm. The degree of hazard for each gas can be measured with the time that the contaminant stays above its TWA and STEL. Table 4-4 - Contaminant duration according to exposure standards. Figure 4-1 – Gas concentration in ppm over time, exhausting via Rise 1. With the primary fan drawing 390 mᶟ/s, the fuming event is over within 16 minutes. The second peak Vent Status Fan On 1. Fan Off Fan Off Winter Contaminant Exhaust Rise 2 Rise 1 Plant Portal Willows Portal Rise 1 Time Format M:S D:H:M:S D:H:M:S D:H:M:S D:H:M:S Start 01:29 00:03:22:50 00:09:33:40 00:06:39:50 00:15:07:30 End 17:11 00:16:40:50 01:05:41:20 01:02:51:40 03:12:18:40 Period 15:40 00:13:18:00 00:20:07:40 00:20:11:50 02:21:11:10 Period > TWA 01:27 00:05:37:50 00:04:51:10 00:04:36:10 00:06:26:40 Period > STEL 01:23 00:02:29:10 00:01:03:30 00:01:20:20 00:01:18:50 Period > TWA 00:43 00:00:00:00 00:00:00:00 00:15:52:20 00:00:00:00 Period > STEL 00:25 00:00:00:00 00:00:00:00 00:00:00:00 00:00:00:00 Period > TWA 01:57 00:13:02:00 00:16:07:00 00:15:52:20 01:00:24:40 Period > STEL 01:12 00:00:51:00 00:00:00:00 00:00:31:00 00:00:08:40 Period > TWA 00:00 00:01:51:00 00:00:00:00 00:00:00:00 00:00:00:00 Period > STEL 00:00 00:00:00:00 00:00:00:00 00:00:00:00 00:00:00:00 *NO2 duration for > 0.5 ppm is used when the combined gas duration is protracted, i.e., when fans are off, as all gases are already at safe levels. CO Duration of Dispersal NO NO2 NH3 Combined Gas Duration > 0.5ppm* 2. Fan Off
RkJQdWJsaXNoZXIy MjE2NDg3