🔍 Key Concepts

• 46 CFR requirements for tank sounding tubes on cargo vessels • Difference between a valve (can isolate/stop flow) and a mechanical closure used only when sounding is not in progress • Safety purpose: preventing vapor escape and ignition sources from entering cargo tanks through sounding tubes

💭 Think About

• Ask yourself: Is a tank sounding tube normally kept OPEN to the atmosphere for measuring depth, or is it meant to be used as a flow/transfer line that needs throttling? • Which of these devices would allow quick, simple removal for taking a sounding, and then positive resealing without leaving a valve partly open? • Which options, if left in the wrong position, could accidentally block pressure relief or be used improperly as a cargo handling valve?

✅ Before You Answer

• Verify in 46 CFR that the termination above the weather deck is required to have a tight mechanical closure, not a flow‑control valve, to avoid misuse as a cargo valve. • Check which fittings are typically used on sounding pipes so that a sounding tape or bob can pass through easily. • Confirm that the correct fitting can be fully removed and resecured and does not function as an in-line throttling or stop valve.