Tank Gauging System

Tank Gauging

TGS (stands for Tank Gauging System) is package consist of several parts to measure liquid level and generate bellow parameters in the highest possible certainty so makes client sure everything is under control and nothing will fail. The most important goal of having a Tank Gauging System is control tanks and prevent any damage to a vessel contains valuable fluids such as hydrocarbons, crude oil and liquid gases.

Measured parameters

Bellow parameters were measured on a tank to provide users a wide range of technical information.

• Liquid level

Main liquid level is the most important parameter should be measured by a high precision level transmitter. Different type devices are available to measure main level but the most famous methods are radar and servo type level transmitters.

• Interface level

We faced to other liquids in most cases so located in bottom or top of main liquid does not have any value but makes uncertainty in control procedure. Fluid interface should be measured to calculated exact volume of main liquid in tank.

• Average temperature

Temperature is affective parameters on fluid density. Since we faced to hydrocarbons in most cases also temperature may be different from bottom to top then calculate an average value for compensations.

• Density

Density is main parameter for volume to mass conversion. Two main methods of density measurement are hydrostatic by sing a pressure transmitter and buoyancy by a displacer.

System components

Tank Gauging System contains some devices to measure parameters as follows:

1- Radar or Servo level transmitter measures main liquid level and volume.

2- Multipoint average temperature transmitter measures average temperature of liquid and liquid in bottom of tank.

3- Local indicator shows measured or compensated values and installed in bottom of tank to help operator see tank status easily.

4- Pressure transmitter was used for density measurement.

5- Compensator collects all devices data and calculated mass or compensated volume depends on fluid and ambient temperature or other process conditions. This task will be done by master device provides output in different digital field bus formats. Local indicator or servo level transmitter can play as master device on a tank.

6- Data concentrator receives digital buses from field and transmits to control or monitoring system. This part is able to log all received data too.

Calculated parameters

Tank Gauging System package can provide several parameters to client some of them are mentioned bellows:

Main liquid level
Correction Level
Average Temperature
Temperature of each point
Fluid density
Water (liquid) bottom Level
Water (liquid) bottom density
Bottom Pressure
Middle Pressure
Top Pressure
Compensated volume of liquid
Mass of main liquid
Low and Low-Low alarms
High and High-High alarms
Tank filled Percentage
Gas phase
Air Temperature
Flow Rate (Rate of change of level)
Volumetric Flow Rate
Leakage detection

System output

Tank Gauging System generates big volume of data and needs a good path to transmit data to control system also provide a digital filed bus. Most of the field buses designed based on Modbus protocol and modify to transmit signals in six kilometers. Since we faced a digital bus, should take care about junction boxes location arrangements.