API MPMS Chapter 19.2 · Standing Storage Loss & Working Loss Calculator
API 19.2 / EPA AP-42
Tank Geometry & Operating Conditions
Project Information
Tank Dimensions
Roof & Seal Type
Liquid & Vapor Properties
True vapor pressure at mean liq. surface temp
Throughput
Auto-calculated if blank
Fitting Counts
Methodology Overview
This calculator implements API MPMS Chapter 19.2 (2012) methodology for estimating volatile organic compound (VOC) emissions from floating roof tanks.
Total emissions are the sum of:
LS — Standing Storage Loss From seal gaps, roof fittings, roof drains, guide poles. Proportional to vapor pressure and roof area.
LW — Working Loss From liquid level changes during filling/emptying cycles. Proportional to throughput and vapor-space saturation.
LR — Rim Seal Loss Component Dominant term in LS. Varies significantly with seal design.
Note: Vapor pressure (P*) should be the true vapor pressure at the mean liquid surface temperature. Use the Reference Data tab for common liquid VP values.
Emission Results
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▸ Calculation Breakdown
Vapor Pressure Reference — Common Liquids
Liquid
Temp (°F)
TVP (psia)
MW (lb/lb-mol)
Density (lb/gal)
Gasoline RVP 10
60
10.0
87
5.83
Gasoline RVP 7
60
7.0
87
5.97
Gasoline RVP 5
60
5.0
90
6.10
Crude Oil — Light (50° API)
60
5.0
130
6.50
Crude Oil — Medium (35° API)
60
3.0
200
7.18
Crude Oil — Heavy (20° API)
60
1.0
280
7.83
Jet A / Kerosene
60
0.05
155
6.70
Diesel No. 2
60
0.02
190
7.08
Ethanol
60
1.0
46
6.59
Xylene
77
0.98
106
7.24
Toluene
77
1.53
92
7.26
Benzene
77
1.81
78
7.36
Seal Loss Factors (KRa, KRb, n) — API 19.2 Table 1
Primary Seal Type
KRa
KRb
n
Mechanical Shoe Seal
1.2
0.4
2.1
Liquid-Mounted Foam Seal
0.7
0.3
1.6
Vapor-Mounted Foam Seal
1.2
0.6
1.6
Resilient Filled Seal
0.3
0.1
2.0
Secondary Seal Loss Factor (KS) — API 19.2
Secondary Seal Type
KS (fraction of primary)
None
1.0 (no reduction)
Shoe-Mounted Secondary
0.15 (85% reduction)
Rim-Mounted Secondary
0.25 (75% reduction)
Fitting Loss Factors — API 19.2 Table 3 (lb-mol/yr per fitting)