{ "background": "Process-control systems are critical for industrial operations in developing economies, yet their reliability is often poorly quantified. In Nigeria, a lack of structured field data on system performance hinders evidence-based maintenance and investment decisions within the engineering sector.", "purpose and objectives": "This case study evaluates a methodological framework for conducting a randomised field trial to assess the reliability of industrial process-control systems. The primary objective was to test the feasibility and rigour of the trial design in a real-world, resource-constrained setting.", "methodology": "A randomised field trial was implemented across multiple industrial sites. System reliability was measured as time-to-failure, analysed using a Weibull proportional hazards model: $h(t|X) = \\frac{\\beta}{\\eta} \\left(\\frac{t}{\\eta}\\right)^{\\beta-1} \\exp(\\theta X)$, where $X$ represents treatment covariates. Inference was based on robust standard errors clustered by site.", "findings": "The methodological evaluation revealed that the randomised trial design was feasible but encountered significant logistical challenges. A key finding was that systems subjected to the new diagnostic protocol showed a reliability improvement, with the hazard rate estimated to be 0.65 times that of the control group (95% CI: 0.52 to 0.81). Data collection on environmental stressors proved particularly valuable for the model.", "conclusion": "The randomised field trial provides a viable, though demanding, methodological approach for generating high-quality reliability data on process-control systems in challenging operational environments.", "recommendations": "Future applications should incorporate longer lead-in periods for site engagement and utilise ruggedised, automated data loggers to improve data completeness. The trial protocol should be adapted for phased implementation.", "key words": "reliability engineering, field trial, process control, maintenance strategy, industrial engineering, randomised experiment", "contribution statement": "This study presents a novel application of a randomised field trial methodology to the structural assessment of engineering system reliability in