ABSTRACT

Nickel-based alloy have an excellent corrosion resistance and good mechanical properties. The nickel-copper alloys (UNS(1) N04400) are used for broad of applications in an equally broad range of industries including chemical and petrochemical processing and oil and gas extraction. This paper present a comprehensive corrosion investigation of benzene condenser pipeline made of UNS N04400 at one of Saudi Basic Industries Corporation affiliates. Samples of the failed pipeline were obtained for analytical investigation. Metallographic examination was performed to evaluate microstructure of the failed pipe. The chemistry of a deposit collected from the pipe was analyzed by X-ray fluorescence (XRF) and carbon/ sulfur (C/S) analyzer. Scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy was used to study the corrosion damage morphology and the chemical composition of the deposit at the leak points. The study concludes that the pipe failure attributed to acidic corrosion that form inside the pipeline.

INTRODUCTION

Nickel-copper alloys are widely used as corrosion resistant materials in a wide range of industrial applications. On account of its high strength and excellent corrosion resistance, UNS N04400 is extensively utilized to a range of media including seawater, dilute hydrofluoric and sulfuric acids, and alkalies1. The alloy has been used extensively in many applications such as chemical processing equipment, gasoline and fresh water tanks, crude petroleum stills, valves and pumps, propeller shafts, marine fixtures and fasteners, electrical and electronic components, deaerating heaters, process vessels and piping, boiler feed water heaters and other heat exchangers1,2.

This paper describes tube failure investigation that took a place in benzene condenser pipeline. The material of construction of the tube is UNS N04400. Table 1 shows the chemical composition and mechanical properties of the tube material according to ASTM(2) B163 specification3. The operating temperature and pressure are around 45°C and 45 kg/cm2g respectively. The tube diameter is 4 inches SCH40. The as-received failed tube sample is presented in Figure 1.

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