Design Solutions for Ice-Induced CNG Filling Failures: Field Issue Resolution through Filter Geometry and Seal Material Reengineering

Compressed Natural Gas (CNG) systems in automotive applications are highly sensitive to fuel quality, especially with respect to moisture content. Field issues were observed where high moisture levels in the CNG led to the formation of ice inside the receptacle during refueling operations. This ice formation obstructed the CNG filling process and adversely impacted the sealing performance of the O-ring, particularly under low-temperature conditions induced by pressure differentials between the storage tank and the filling station. Investigation revealed that the existing tablet-type filter design contributed to moisture entrapment within its wire mesh, exacerbating ice formation within the receptacle. To address this, the filter design was modified from a tablet-type to a cup-type filter, significantly reducing the likelihood of moisture retention and subsequent ice formation. Additionally, the O-ring material was upgraded to a formulation with improved sealing properties at lower temperatures, ensuring consistent performance even under adverse thermal conditions. These design modifications were validated through field trials and demonstrated a marked improvement in system reliability and refueling consistency. The changes effectively mitigated the operational challenges posed by poor fuel quality and ensured better performance of the CNG receptacle system in real-world conditions. This paper presents the root cause analysis, design interventions, material selection criteria, and the validation methodology adopted to resolve this critical issue.