Question 38 TK02 - Tank Vessel Assistant - Liquefied Gas

The Correct Answer is B. --- ### Why Option B is Correct **Option B) closed, opened a half turn, and then closed again** This procedure is the standard operational practice taught for ensuring a tight, secure seal on most manual valves (especially globe and gate valves). When a valve is closed initially, a small piece of scale, dirt, or debris might become trapped between the valve seat and the disc/plug, preventing a perfect metal-to-metal or soft seal. By opening the valve a slight amount (e.g., a quarter or half turn) and then reclosing it, the flow pressure is used to "wash" or dislodge any trapped particles away from the seating surfaces, allowing the valve to achieve a proper, leak-free seat on the second closure. --- ### Why Other Options Are Incorrect **Option A) closed against the stop and the locking pin inserted** This procedure focuses on security and isolation (keeping the valve physically in the closed position), not the quality of the seal itself. If debris is preventing the initial closure from seating correctly, locking the valve ensures it stays closed—but still potentially leaking. **Option C) set up tight using a valve wrench** Using excessive force, especially with a tool like a wrench, can severely damage the valve components. It can score the seating surfaces, distort the stem, or ruin the packing gland, leading to permanent leaks and requiring immediate maintenance. Valves should be closed firmly by hand only. **Option D) set up as tight as possible by hand** While better than using a wrench, closing a valve "as tight as possible" is still excessive force (over-tightening). Overtightening rapidly wears down the seat and disc material, and it doesn't solve the core problem of debris being potentially lodged in the valve seat. If the valve feels exceptionally tight, it’s often because debris is blocking the closure, meaning forcing it shut will cause damage rather than guarantee a proper seal.