API RP 581 - 3rd Ed.2016 - Add.2-2020 - Risk-Based Inspection Methodology

RISK-BASED INSPECTION METHODOLOGY, PART 3—CONSEQUENCE OF FAILURE METHODOLOGY 3-59
Table 4.10—Adjustments to Flammable Consequence for Mitigation Systems
Mitigation System
Consequence Area Adjustment
Consequence Area
Reduction Factor,
fact
mit
Inventory blowdown, coupled with
isolation system classification B or higher
Reduce consequence area by 25 % 0.25
Fire water deluge system and monitors Reduce consequence area by 20 % 0.20
Fire water monitors only Reduce consequence area by 5 % 0.05
Foam spray system Reduce consequence area by 15 % 0.15
Table 4.11—Gas Release Toxic Consequence Equation Constants for HF Acid and H2S
Continuous Releases Duration
(minutes)
HF Acid
H2S
c d c d
5 1.1401 3.5683 1.2411 3.9686
10 1.1031 3.8431 1.2410 4.0948
20 1.0816 4.1040 1.2370 4.238
40 1.0942 4.3295 1.2297 4.3626
60 1.1031 4.4576 1.2266 4.4365
Instantaneous Releases 1.4056 0.33606 0.9674 2.7840
Table 4.12—Gas Release Toxic Consequence Equation Constants for Ammonia and Chlorine
Continuous Releases Duration
(minutes)
Ammonia
Chlorine
e f e f
5 2,690 1.183 15,150 1.097
10 3,581 1.181 15,934 1.095
15 4,459 1.180 17,242 1.092
20 5,326 1.178 19,074 1.089
25 6,180 1.176 21,430 1.085
30 7,022 1.174 24,309 1.082
35 7,852 1.172 27,712 1.077
40 8,669 1.169 31,640 1.072
45 9,475 1.166 36,090 1.066
50 10,268 1.161 41,065 1.057
55 11,049 1.155 46,564 1.046
60 11,817 1.145 52,586 1.026
Instantaneous Releases 14.171 0.9011 14.976 1.177