Abstract
Anti-corrosive thermosetting resins are commonly used in chemical plants to prevent corrosion failure of chemical equipment. As they are often used in contact with corrosive liquid for a long time, liquid penetration into the resins causes problems. On-line sensing to detect the penetrating liquid into the resins is useful to prevent accidents caused by the liquid reaching to the crucial parts of the chemical equipment and to estimate the life-time of the equipment. Penetration behavior of the liquid in an anti-corrosive resin can be described by Fick’s second law, which includes the diffusion coefficient. The method proposed in this study estimates the diffusion coefficient using optical fiber sensor modules embedded in the different depths of the anti-corrosive resin while the surface of the anti-corrosive resin is immersed in the liquid. The optical fiber sensor modules contain pH indicators on the light path of the fiber and the spectrum of the transmitted light is monitored. The diffusion coefficient is estimated from the difference between the time instants where the two sensor modules detect the liquid penetration. Nevertheless the diffusion coefficient estimated by the proposed method in an experiment was about 40% smaller than that estimated by a conventional off-line measurement, the study reveals that the proposed method is able to estimate the diffusion coefficient by on-line manner.
Highlights
Anti-corrosive thermosetting resins are commonly used for coating the surface of chemical plants to protect metallic equipment from corrosion and as a matrix resin in fiberreinforced plastics (FRPs) for corrosive process fluid
This paper proposes a sensing method to estimate the diffusion coefficient of Fick’s second law(9) to describe the liquid penetration in an anticorrosive thermosetting resin using an on-line measurement with two optical fiber sensors
The absorbance at the wavelength 640 nm, the color of orange, decreases when the hydrochloride aqueous solution reached to the sensor after penetration in the unsaturated polyester resin (Fig. 5)
Summary
Anti-corrosive thermosetting resins are commonly used for coating the surface of chemical plants to protect metallic equipment from corrosion and as a matrix resin in fiberreinforced plastics (FRPs) for corrosive process fluid. One of the causes of the degradation of anti-corrosive resins is the penetration of the liquid into resins. Sensing technologies to detect liquid penetration before it reaches to the critical parts of the equipment are important to prevent serious accidents caused by the degradation of resins. A variety of off-line measurements such as gravimetric liquid uptake evaluation(3), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) analysis(4), and penetration depth evaluation with Energy Dispersive X-ray Spectroscopy (EDS)(5) have been used to estimate the diffusion coefficients in resins.
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