Design of an Automatic Filling Unit for LPG Cylinders with Valve

Abstract

This paper addresses the chronic underperformance of a manual liquefied petroleum gas (LPG) cylinder filling line at an industrial plant (Plant X). We present the complete design of a novel, fully automatic filling system specifically engineered for LPG cylinders equipped with a tap-type safety valve, a prevalent standard in the regional market for which existing automation solutions are inadequate. Our methodological contribution is a structured engineering approach that begins with a root-cause analysis using functional analysis tools (Ishikawa, Octopus, and FAST diagrams) to diagnose systemic failures. This analysis directly informs the technical design phase, where we provide detailed sizing calculations for the core subsystems: a double-drive chain conveyor (capacity: 7500 m³/h) and a 12-station rotating carousel framework (throughput: ≥500 cylinders/hour). The system’s automation logic, formalized using GRAFCETs and implemented for a Schneider M340 PLC, ensures sequential control for filling, weight verification, leak testing, and sealing without manual intervention. The proposed design offers a fivefold increase in hourly production rate (from ~300 to 500-1500 cylinders/hour) and reduces the required operators from sixteen to five. Projected performance indicates the system would enable the plant to meet its daily target of 5,000 cylinders, generating a return on investment within 2 years and 7 months.