Advanced Failure Analysis of Hydraulic Systems in Volvo Articulated Haulers at Coal Mining Sites: Investigating Steering Cylinder Seal Failure and Brake Accumulator Degradation

Abstract

The condition of hydraulic systems is critical to the productivity and safety of heavy equipment in coal mining operations. This study analyzes Hydraulic Systems in Volvo Articulated Haulers at coal mining sites in South Sumatra, Indonesia. Progressive failure of the steering cylinder seal on a Volvo ART A40F, manifested as hydraulic oil leakage and a drop in measured steering pressure from the standard 250 bar to 203 bar; and degradation of the brake accumulator unit on a Volvo ART A40G, causing a low brake pressure warning and a drop in pressure from the normal range of 145-245 bar to 118 bar. Both failures were caused by wear-induced mechanisms exacerbated by the harsh mining environment fine particle contamination, high thermal cycling, and continuous duty cycles. For the A40F, post-repair inspection revealed that the scraper / dust seal had thinned from 7.8 mm (new) to 6.1 mm, allowing the ingress of particles that accelerated piston rod seal wear. For the A40G, three of the seven accumulators had lost their hydraulic oil connections, reducing nitrogen precharge and eliminating pressure reserve capacity. Corrective interventions of seal kit replacement on the A40F and accumulator replacement on the A40G restored operating pressures to 250 bar and 247 bar, respectively. Maintenance records from 2024-2026 revealed that accumulator failures occurred repeatedly each year per unit, indicating inadequate inspection intervals. These findings support a transition to a condition-based maintenance strategy for both system types.