Step 1: Understand differential pressure, pressure, temperature, and density inputs

There are up to four analog inputs read to calculate flow rates for volume and mass.

The differential pressure from the analog is read as a required input. This value will be used to calculate the volume and mass flow rates using API 14.3 calculations. With the volume and mass flow rates, and the time that has elapsed since the last calculations, the quantity of volume and mass that has accumulated over that duration can be calculated.

To perform these calculations, the following values are required at flowing conditions: Density, Viscosity and the Isentropic Exponent.

Density

• If the Accumulator is configured with a density analog, the value provided by the density analog will be used.

• If the Accumulator is not configured with a density analog, flowing density will be looked up using API 11.3.2.1 Table 6.6. To look up the value, the flowing temperature and pressure provided by the temperature and pressure analogs on the Accumulator will be used.

• For product types other than Ethylene, ensure that the accumulator is configured with a density analog to prevent the system from defaulting to Ethylene-specific lookup tables.

Dynamic Viscosity

• If the Product Type is configured with a viscosity table (as described in Configure the Product Type Row Edit Viscosity Table tab), the kinematic viscosity will be looked up using the Product Type Viscosity table. To look up the value, the flowing temperature provided by the temperature analog on the Accumulator will be used. After looking up the kinematic viscosity, the system will calculate a dynamic viscosity.

• If the Product Type is not configured with a viscosity table, dynamic viscosity will be looked up using API 11.3.2.1 Table 6.2. To look up the value, the flowing temperature and pressure provided by the temperature and pressure analogs on the Accumulator will be used.

• For product types other than Ethylene, ensure that the Product Type is configured with a viscosity table to prevent the system from defaulting to Ethylene-specific lookup tables.

Isentropic Exponent

• If the Product Type is configured with an Isentropic Exponent (as described in Configure the Product Type Row Edit Main tab), the value provided will be used.

• If the Product Type is not configured with an isentropic exponent, the isentropic exponent will be looked up using API 11.3.2.1 Table 6.3. To look up the value, the flowing temperature and pressure provided by the temperature and pressure analogs on the Accumulator will be used.

• For product types other than Ethylene, ensure that the Product Type is configured with an Isentropic Exponent to prevent the system from defaulting to Ethylene-specific lookup tables.