Repurposing high-pressure gas transmission pipelines for hydrogen transport in Germany is advancing from feasibility studies to structured on-site implementation. This field-based operator perspective demonstrates how certifications and verifications of operational readiness are translated into a predictable and auditable commissioning process, culminating in the initial hydrogen purging of repurposed sections within the emerging German hydrogen core network. The approach leverages material and integrity records, as well as vendor approvals for valves, seals, and instrumentation, condensing planning into a concise package: pipeline sectioning, safe blowdown routes, defined ramp rates and hold points, sampling locations, SCADA tags for trend monitoring, and explicit stop conditions. Execution prioritizes controlled hydrogen flow via a mobile control skid, straightforward field measurements, and SCADA trend analysis to monitor the mixing front. Endpoint gas quality is verified through stabilized pressure and composition checks, while displacement mixtures are safely managed using mobile venting and flaring systems. Acceptance is documented in streamlined standard documents – a purging plan, ramp/hold table, sampling protocol, and a concise checklist for alarms and detection – ensuring a transparent and efficient handover to operations without excessive paperwork. Context is provided through key facts: initial sections were scheduled for conversion in 2025, targeting approximately 400 km by year-end, including a major 56-inch corridor. Interfaces with existing pipeline routes are addressed as planning context rather than detailed case studies. The focus is on transferable execution steps and documentation that enabled predictable commissioning across multiple corridors: a one-page purging plan, essential ramp/hold points, endpoint sampling at defined boundaries, and a compact acceptance dossier. The objective is clarity over complexity – delivering an implementation-ready model that enables transmission system operators to convert “hydrogen-ready” assets into operational hydrogen service with transparent risk controls and standardized, repeatable documentation.