Endress+Hauser NXA820 - Page 54

Calculations Tankvision
54 Endress+Hauser
The complexity starts with inconsistencies between the CTSh calculation as specified in
various International standards.
In IP PMP No. 11 (paragraph C.2, page 20) the above equation (1) is simplified to:
L00-NXA82xxx-16-00-00-xx-005
In order to be able to combine both equations, we have rewritten the equations to:
L00-NXA82xxx-16-00-00-xx-007
Where:
• α
1
= Linear thermal expansion coefficient
• α
S
= Area or suface thermal expansion coefficient
• δT = T
shell
- T
calib
Spherical tanks
Temperature correction for Spherical Tanks is calculated using the following equation:
L00-NXA82xxx-16-00-00-xx-008
Where:
• f’ = non-dimension factor representing change in partial volume, corresponding with h/2
The factor f’ can be calculated with:
L00-NXA82xxx-16-00-00-xx-009
Where:
• h = liquid depth
• r = vessel radius
Observe the following information!
• This calculation is conform to IP PMP No. 11
• Refer to Appendix A3 for values of f’
Horizontal cylindrical tanks (bullets)
Temperature correction for Horizontal Cylindrical Tanks is calculated using the following
equation:
L00-NXA82xxx-16-00-00-xx-010
Where:
• f’’ = non-dimension factor representing change in partial volume, corresponding with h/r2
The factor f’’ can be calculated with:
CTSh 1 + 2 **Tad=
CTSh 1 + 2 **T +*ad
1S
adT
2
=
CTSh 1 +*T * f‘ad
1
=
f‘ (h * r) / (h * r - (h / 3))
223
=
CTSh 1 +*T * f‘‘ad
1
=