Hydrogen Energy Compression and storage

A: The HPSD feels like a catch‑all because it does trip the machine on sensed pressure, which aligns with option C and limits continued compression, so those sound protected. Option A also seems covered because the trip happens before sustained rod overload, assuming the pressure tap is live. Option D tempts people who’ve seen hot valves, but once the trip hits, the heat input stops quickly. The miss is downstream piping: with block valves shut and the PSV gagged, pressure can climb in that trapped volume without the HPSD seeing it. The safeguard doesn’t see or protect that segment.

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.