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<p>Premature failures of carbamate ejector nozzle needle and motive nozzle in urea plants, operating under extreme pressure, temperature, and corrosive conditions, necessitated root cause analysis for enhanced reliability. Methodologies included visual inspection, dimensional measurements, optical emission spectrometry (OES), hardness testing, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). EDS, performed at 10&#xa0;keV, focused on elemental composition of surface deposits. Analysis revealed the nozzle needle suffered severe erosion–corrosion, evidenced by a 3&#xa0;cm length reduction and gray discoloration. Hardness profiles indicated localized strain hardening but also compromised toughness of Ferralium®255 due to abrasive fluid flow and material deviations (e.g., lower copper, no nitrogen). The motive nozzle exhibited catastrophic brittle fracture and significant bore expansion (from 21.77 to 23.15&#xa0;mm), with macroscopic cracks and microscopic quasi-cleavage features. Crucially, EDS of its inner surface deposits revealed a prominent sulfur peak, confirming sulfide presence. Microstructural examination further showed transgranular and discontinuous intergranular cracking, consistent with hydrogen embrittlement. Chemical analysis of the reaction chamber fluid indicated 7.2&#xa0;mg/L sulfate and 69.6&#xa0;mg/L ammonium ions at pH 6.7, providing the environmental context. These findings confirm nozzle needle erosion–corrosion from material limitations. For the motive nozzle, confirmed sulfur in deposits and microstructural evidence unequivocally identify sulfide stress cracking (SSC) as the dominant mechanism, driven by H<sub>2</sub>S-induced hydrogen ingress exacerbated by design flaws. Rectification involves material upgrades to high-nickel alloys, optimized designs, protective coatings, and enhanced operational controls for improved durability against erosion–corrosion and SSC.</p>

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Failure Analysis of Motive Nozzle and Nozzle Needle in a Carbamate Ejector: A Case Study from a Fertilizer Plant

  • 期刊论文

  • 发表日期：

    2025年11月26日

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  • Shaiful Rizam Shamsudin,
  • Mohd Fitri Mohamad Wahid,
  • Mokhtar Che Ismail,
  • Nur Farhana Hayazi,
  • Hafizal Yazid,
  • Chidambaram Subramanian

摘要

Premature failures of carbamate ejector nozzle needle and motive nozzle in urea plants, operating under extreme pressure, temperature, and corrosive conditions, necessitated root cause analysis for enhanced reliability. Methodologies included visual inspection, dimensional measurements, optical emission spectrometry (OES), hardness testing, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). EDS, performed at 10 keV, focused on elemental composition of surface deposits. Analysis revealed the nozzle needle suffered severe erosion–corrosion, evidenced by a 3 cm length reduction and gray discoloration. Hardness profiles indicated localized strain hardening but also compromised toughness of Ferralium®255 due to abrasive fluid flow and material deviations (e.g., lower copper, no nitrogen). The motive nozzle exhibited catastrophic brittle fracture and significant bore expansion (from 21.77 to 23.15 mm), with macroscopic cracks and microscopic quasi-cleavage features. Crucially, EDS of its inner surface deposits revealed a prominent sulfur peak, confirming sulfide presence. Microstructural examination further showed transgranular and discontinuous intergranular cracking, consistent with hydrogen embrittlement. Chemical analysis of the reaction chamber fluid indicated 7.2 mg/L sulfate and 69.6 mg/L ammonium ions at pH 6.7, providing the environmental context. These findings confirm nozzle needle erosion–corrosion from material limitations. For the motive nozzle, confirmed sulfur in deposits and microstructural evidence unequivocally identify sulfide stress cracking (SSC) as the dominant mechanism, driven by H2S-induced hydrogen ingress exacerbated by design flaws. Rectification involves material upgrades to high-nickel alloys, optimized designs, protective coatings, and enhanced operational controls for improved durability against erosion–corrosion and SSC.