Oct 16, 2020

When the stock properties of a non-fully-speciated stock are being entered, BREEZE TankESP provides four options for users to input the necessary data which will be used to calculate the true vapor pressure. In this TankESP Tip, we will introduce each option below.

Option 1: Vapor Pressure Constants A and B

You can provide constant A and constant B into the Antoine's A column and Antoine's B column, respectively, in the Stocks and Composition form. When data is provided in Antoine's A column and Antoine's B column for a stock record while Antoine's C column is blank, TankESP uses Equation 1-25 in AP-42 Chapter 7 (June 2020) to calculate the true vapor pressure of the stock at the stored liquid surface temperature. Please see the equation below. Please note that the unit of constant B is degR in this equation.

Constants A and B

Option 2: Antoine's Constants A, B, and C

You can provide Antoine's constants A, B, and C into the Antoine's A, Antoine's B, and Antoine's C columns, respectively, in the Stocks and Composition form. When data is provided in these three columns for a stock record, TankESP uses Equation 1-26 in AP-42 Chapter 7 (June 2020) to calculate the true vapor pressure of the stock at the stored liquid surface temperature. Please see the equation below. Please note that the units of constant B and constant C are degC in this equation.

Antoine's A B C

Option 3: Reid Vapor Pressure (RVP) for Crude Oils

For crude oils for which the Reid vapor pressure is known, in the Stocks and Composition form you can enter the Reid vapor pressure into the RVP column and enter “Y” in the “Is Crude?” column (which confirms that the stocks are crude oils). When data is provided in the RVP column (please see *Note below) and “Y” is entered in the “Is Crude?” column, TankESP uses the following equation in Figure 7.1-13b in AP-42 Chapter 7 (June 2020) to calculate the true vapor pressure of the stock at the stock temperature.

RVP_Crude Oil

Option 4: Reid Vapor Pressure (RVP) and Distillation Slope (S) for Light Refined Stocks

For light refined stocks (gasolines and naphthas) for which the Reid vapor pressure and distillation slope are known, you can enter the Reid vapor pressure and distillation slope into the RVP column and S column, respectively, in the Stocks and Composition form. When data is provided in the RVP column  (please see *Note below) and S column, TankESP uses the following equation in Figure 7.1-14b in AP-42 Chapter 7 (June 2020) to calculate the true vapor pressure of the stock at the stock temperature.

RVP and S

 

*Note: The RVP data is not necessarily entered in the Stocks and Composition form for Option 3 and Option 4. You can also enter the RVP data in the Stock RVP column in the Edit Service Information form. If the RVP data is entered in both the Stocks and Composition form and the Edit Service Information form, the value in the Edit Service Information form will override the given RVP in the Stocks and Composition form. If the Stock RVP column is left blank in the Edit Service Information form, TankESP will use the values in the Stocks and Composition form. This RVP overriding function may be used, for example, when there is a seasonal RVP change for gasoline. Rather than create Summer and Winter grade gasolines as separate Stocks, you may show the same gasoline as the Stock for the whole year, and enter seasonal or monthly values for the Stock RVP in Stocks and Composition form.

Stock Examples

 

If you have questions about these four options, please contact the BREEZE Support Team via email at support@trinityconsultants.com or by phone at +1 (972) 661-8881 ext. 4, and it will be our pleasure to assist you.