Design and construction of a prototype gamma-ray densitometer for petroleum products monitoring applications

Gamma-ray densitometry is one of the most precise techniques used in on-line process monitoring and measurement which is applied in many industrial fields including petroleum industry. By means of this measurement, petroleum products interface in transmission line can be distinguished. It can also be used to determine mass flow rate being combined with a volume flow meter. The use of gamma-rays provides an important non-destructive and on-line technique for this purpose. Density measurement by gamma-rays can be carried out based on two principles: Transmission and Scattering. In the current work, MCNP4C Monte Carlo code was used for simulation of different configurations of density measurement tools based on the mentioned principles. Monte Carlo simulation showed that regarding to higher attenuation slope and also counting rate, the transmission-based technique is more sensitive to density change than the scattering modality. A laboratory setup was implemented for benchmarking of the simulation results. A disc source of 137Cs with 50 μCi activity, a 3-in. NaI (Tl) Scintillator detector and a 4-in. (in diameter) polyethylene pipe with 0.2 cm wall thickness was used in this experiment. Experimental results showed that in practical conditions, petroleum products such as gasoil, gasoline and also some other liquids, such as water with the density in the same range, can be distinguished from each other with the accuracy of 0.1 g/cm3.The experimental data were in good agreement with the simulated results with the maximum difference of less than 2%. Based on this validation using MCNP code, we can proceed to design an improved fluid densitometer device for industrial applications.

► Our work presents industrial application of radioisotopes especially gamma-rays.
► Density measurement by gamma-ray is based on Transmission and Scattering principles.
► We used MCNP code for simulation of configurations based on these principles.
► A laboratory setup was implemented for benchmarking of the simulation results.
► Using this setup, petroleum product can be distinguished with accuracy of 0.1 g/cm3.