Rheonics Support

What products are involved in this article?
This article is based on the use of RCP (Rheonics Control Panel) connected to the SME (Smart Module Electronics) operating SRD, DVP, and DVM. Hence it can be used for any of these Rheonics sensors.

What is the purpose of this article?
Explain the process to get temperature and pressure corrections specific to the hydrocarbon group, using API density referral. Generally used to compare densities of petroleum liquids like crude oil, refined products, or industrial petrochemicals.

1. Math model

Shown below is the mathematical formula for API Specific Gravity 

Equation 1. API Specific Gravity

The SRD sensor can measure inline density, viscosity, and temperature, in addition, we can use multiple mathematical models to calculate the concentration of a mix. To calculate the specific gravity of a fluid we can use Equation 1, where:

SGref temp: Specific gravity at the reference temperature.

ρcomp: Compensated density.

ρref: Reference density, is the density around which the sensor will compensate the readings. This is defined and should be specified by the user.

ρL: Inline density measured.

ρwater: Water density.

K0 and K1: Coefficients, specified by the user. These coefficients can be found in the API-ASTM tables.

TL: Inline temperature measured in °C

Tref: Reference temperature, is the temperature around which the sensor will compensate the readings. This is defined and should be specified by the user.

2. Checking the data

All density, viscosity compensation, and concentration models can be loaded into the sensor through the RCP software from Rheonics, in the “Calculation” tab. The API Specific Gravity model needs K1 and K0 coefficients, those values can be found in the API-ASTM-IP petroleum measurement tables, as shown below in Table 1. 

3. How to load models into the Sensor electronics?

Figure 1. Calculation tab for API Specific gravity

In the following steps, we will show how to load the model into the sensor electronics:

1. In the “Select Measurement to Apply Model” dropdown list select “Concentration”.

2. In the “Select Model from the list” dropdown list select “API Specific Gravity“. When you select the model, you will get more information about the specific equation used and the coefficients you will need.

3. The “Options” list shows a list of the most common K0 and K1 values for the hydrocarbon group. Also, you can choose the “Custom” option and input your own coefficients K0 and K1.

4. Input “K0” coefficient. For this example, it has a value of 613.97.

5. Input “K1” coefficient. For this example, it has a value of 0,0000.

6. Input “Reference temperature” for the water density, in this example, is 20 °C.

7. Input “Water density” in Kg/m3 at the reference temperature, in this example, is 998.23 Kg/m3.

8. Click “Upload Model” to load the model settings into sensor electronics. The button should turn GREEN for a couple of seconds if the action was successful or turn RED if the operation was unsuccessful. This action will refresh the “Calculated Value”.

9. Click “Load Configuration” to update the display and channel configurations in sensor electronics.

10. The “Calculation History” button allows you to open a file with the last uploaded models.

    
    

3.1. Handling Sensor Outputs

For the SME-TRD, the compensated viscosity values can be shown on the display. Select the line to display the parameter:

Figure 3. Selecting read line for LCD display.

Select the analog channel to send data, this can be verified in the “Service” Tab

Figure 4. Selecting analog output channel

Measurement can always be accessed at the register address that is displayed.

Figure 5. Modbus TCP/IP register

3.2 Demonstration Video

Video 1. Configuration API Specific gravity model in RPC Software.