Defines the ratio of the normal operating pressure to the design pressure. The value of Fp is used in Appendix R and Section 5.11 of the API 650 Code.
The minimum value of Fp is 0.4. Values lower than 0.4 are automatically set to 0.4.
The maximum value of Fp is 1.0. Values higher than 1 are automatically set to 1.
If your tank has zero internal design pressure, enter a value of 0.4 for Fp.