Test Fluid Lifecycle Management in High-Pressure Injector Bench Operations

ISO 4113 calibration fluid is the hydraulic working medium of every high-pressure fuel injector test bench. Its degradation behavior and effect on measurement accuracy have never been quantified. This paper presents the first systematic lifecycle analysis of ISO 4113 fluid on a Hartridge AVM5 production bench. Section II reviews the fluid degradation mechanisms and related prior work. Section III describes the experimental setup and instrumentation. Empirical degradation models for kinematic viscosity, ISO 4406 contamination, and antioxidant depletion are developed in Section IV. Section V derives a transfer function linking viscosity drift to bench flow measurement error and presents increased false escape rate. The conventional fixed-interval fluid change schedule allows the bench to operate in a degraded state invisible to standard monitoring. This causes faulty injectors to pass inspection at a measurably higher rate. Section VI presents a condition-based change trigger implemented entirely within the existing AVM5 PLC and MES infrastructure. This eliminates the quality risk while reducing hazardous fluid disposal and lifecycle environmental impact. Section VII quantifies the environmental impact under current and optimized fluid management. Results, discussion, and cost savings are presented in Section VIII. The methodology is transferable to any facility operating under ISO 4113 or SAE J967 calibration fluid specifications.