Determine gauged pressure profile

Gauged pressure calculations allow you to calculate the probable pressure reading as if a pressure gauge were present. Accordingly, gauged pressures are calculated for each profile point in the line segment. "Profile points" are the configured linepost points in a pipe segment. The pipe segments represent intervals within a pipeline that receive upstream and downstream pressure information. No pressure information is recorded in between the upstream and downstream areas where pressure information is gathered. Your Administrator will have configured the required profile points and pipe segments along your pipeline using the Advanced Database Editor (ADE).

Gauged pressures for a pipe segment are determined as follows:

Hydraulic gradient calculation for each fragment in the pipe segment

The system performs the following calculations to gather hydraulic gradient information for each fragment in the pipe segment:

1. Calculate Darcy friction factor using Colebrook White’s flow resistance with Newton Raphson’s iterative method.

2. Calculate flow-induced pressure loss (that is, hydraulic gradient) using Darcy-Weisbach equation.

3. Calculate hydrostatic pressure change.

4. Calculate the fragment’s downstream pressure by subtracting the fragment upstream pressure with flow-induced pressure loss and hydrostatic pressure changes. The first fragment’s upstream pressure is the pipe segment’s upstream pressure telemetered value, and the downstream pressure becomes the upstream pressure for the next fragment, and so on.

5. Repeat steps 1–4 until the end of the pipe segment is reached.

6. The calculated fragment pressure at the end of the pipe segment is compared with the telemetered value and a correction factor is determined.

7. The vapor pressure is the pressure in height when the product evaporates and is calculated using the following formula:

   Height Equivalent = Base Pressure / (Density of Fluid x Constant)

8. Apply the correction factor to the hydraulic gradient of all the fragments inside the pipe segment.

Gauged pressure calculation for each linepost in the pipe segment

9. The flow induced pressure loss is calculated.

10. The hydrostatic pressure loss (or gain) is calculated.

11. The gauged pressure is calculated by subtracting the previous linepost pressure with flow induced pressure loss and hydrostatic pressure loss (or gain).