Hydrogen Energy Compression and storage

A: 304L sounds attractive because stainless gets associated with hydrogen service, but at this pressure you’re paying for corrosion resistance you don’t need while gaining nothing on embrittlement. The forging option looks conservative, yet high‑strength Q&T steels raise hydrogen cracking sensitivity and inspection burden. Aluminum sneaks in from cryogenic service experience, but at 300 barg ambient it brings permeability and code limitations. Low‑sulfur carbon steel with proper PWHT stays within ASME VIII practice and manages hydrogen effects without over‑engineering.

A: Sulfide stress cracking is familiar in upstream gear, so option B pulls people in, but without measurable H2S it doesn’t initiate. Thermal fatigue fits the cycling story, yet the crack morphology starting at the bore under pressure points away from pure thermal effects. Chloride SCC shows up in austenitic stainless, not typical cylinder steels, making D a mismatch. High hydrogen activity plus cyclic hoop stress lines up with classic hydrogen‑assisted cracking in compressor cylinders.

A: Fire PSVs are sized for vapor generation under heat input, so A and D are squarely in scope. Jet flame impingement feels similar to a pool fire and often gets lumped together, making B tempting, but relief still helps manage internal pressure. Blocked‑in thermal expansion is a different scenario with small volumes and no fire; a fire‑sized PSV won’t be set or located to protect that case.

A: Screw machines are common in hydrogen service, so B sounds workable, but oil carryover and filtration risk the PSA beds. Diaphragm units give ultra‑clean gas, yet at 200 barg and PSA flows they hit capacity and maintenance limits. Centrifugals struggle to reach this pressure in one body and bring seal complexity. Oil‑free reciprocating machines are built for this exact purity and pressure window.

A: Relief valves staying quiet makes A feel safe, but they’re not indicators of normal operating accuracy. Online calibration against a gauge sounds efficient, yet it relies on an unverified reference and introduces MOC risk. Masking the signal in the PLC solves nothing and erodes safeguards. Pulling inventory down buys margin while you check impulse line blockage or hydrogen density effects on one tap.

A: Spiral wounds are common and handle pressure well, so A is attractive, but hydrogen’s small molecule challenges their leakage tightness. PTFE feels hydrogen‑friendly, yet cold flow under high bolt stress undermines long‑term sealing. Compressed fiber shows up in low‑pressure services and sneaks in by habit. RTJs provide metal‑to‑metal sealing suited for high‑pressure hydrogen duty.

A: Carbon steel works in many exchangers, making A sound practical, but hydrogen plus cyclic pressure raises embrittlement and corrosion allowance questions. Waiting until after startup feels schedule‑friendly, yet it locks in risk. Dry gas arguments ignore condensation during upsets, so D falls apart. The datasheet defines the duty; if reality differs, MOC is the only defensible path.

A: UV degradation happens over years and shows surface cracking, not internal blisters. Manufacturing voids do exist, so C tempts anyone who’s seen QA reports, but the timing with depressurization is the clue. Oil carryover attacks elastomers, yet composite liners are selected to resist that. Gas permeation and sudden pressure drop drive classic rapid decompression damage.

A: Staying under the limit makes A comfortable, but trends matter more than snapshots. Efficiency loss from venting sounds logical, yet the flow is tiny relative to throughput. Discharge PSV behavior isn’t tied to distance piece vent pressure, so D misplaces the effect. Rising backpressure undermines seal venting, letting hydrogen migrate where ignition sources live.