When opening or closing compressor service and line isolation valves on a typical refrigeration system that is fitted with packed valves, what must you do?

Correct Answer: Option A — you must first remove the stem seal cap

Marine refrigeration packed valves utilize stem packing glands to prevent refrigerant leakage around the valve stem. The protective stem seal cap must be removed first to access the operating stem and prevent damaging the threads or secondary sealing surfaces during valve manipulation.