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

3-48 API RECOMMENDED PRACTICE 581
Liquid
Ideal Gas
NBP Ambient
Ideal Gas Ideal Gas
Fluid MW Density
Specific
(°F) State
Constant Constant
(lb/ft 3 )
Heat Eq.
A B
Cp
Ideal Gas Ideal Gas Ideal Gas
Constant Constant Constant
C D E
EEA 132 61 313 Liquid Note 2 1.06E+05 2.40E+05 6.59E+02 1.50E+05 1.97E+03 715
EE 90 58 275 Liquid Note 2 3.25E+04 3.00E+05 1.17E+03 2.08E+05 4.73E+02 455
EG 62 69 387 Liquid Note 2 6.30E+04 1.46E+05 1.67E+03 9.73E+04 7.74E+02 745
EO 44 55 51 Gas Note 2 3.35E+04 1.21E+05 1.61E+03 8.24E+04 7.37E+02 804
AIT
(°F)
NOTE 1
p
2 3
C = A + BT + CT + DT with T in K, units for C p are J/(kg-mol-K).
NOTE 2
2 2
⎛ C ⎞ ⎛ E ⎞
⎜ ⎟ ⎜ ⎟
C
T
T
p = A+ B⎜ ⎟ + D⎜ ⎟
⎜ ⎡C⎤⎟ ⎜ ⎡E⎤⎟
⎜sinh
cosh
⎝
⎢
T
⎥⎟ ⎠
⎜
⎝
⎢
T
⎥⎟
⎣ ⎦ ⎣ ⎦⎠
with T in K, units for C p are J/(kg-mol-K).
NOTE 3
p
2 3 4
C = A + BT + CT + DT + ET with T in K, units for C p are J/(kg-mol-K).
NOTE 4 Pyrophoric materials, by definition, autoignite and therefore a very low value for the AIT is assumed.
NOTE 5 Conversion factor for units of C p is 1 J/(kg-mol-K) = 5.27 × 10 -4 Btu/(kg-mol- o R).