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Criteria for determining internal leakage in valves: 1. The method for detecting internal leakage in a valve is as follows: after the valve has been closed for 4–6 hours, use an infrared temperature meter to measure the temperature of the valve stem (near the valve body) or at a point 150 mm downstream of the valve body. If the temperature is above 70°C, it is considered to indicate “internal leakage”. This method of judgment is applicable to most internally leaking valves. However, in practical work, we have encountered the following special situations: (1) Due to the location where the pipes are installed, there is turbulent high-temperature steam in front of and behind some valves, such as the drain valves or sewage valves connected to pressurized drain or relief pipes; even if these valves are airtight, the temperature of their valve stems can still exceed 70°C. (2) Steam drain valves or blowdown valves connected side by side to the steam and water discharge mains; when the last valve in each line is located near the main, any internal leakage in a valve within that line will cause the temperatures of the other valves to rise above 70°C, as is the case with boiler blowdown valves and superheated steam drains. Therefore, other methods must be used to determine internal leakage in these valves; generally, the temperature of the pipe wall in front of the valve or the temperature of the valve stem just before the valve is measured to assess internal leakage. 2. If the operator confirms or suspects internal leakage in the valve, they must notify the maintenance personnel to arrive and conduct an inspection. Only after it is confirmed together with the maintenance personnel that there is indeed internal leakage can a defect be recorded, and the name of the maintenance technician who made the assessment should also be noted in the defect information. 3. When there is a disagreement between operators and maintenance personnel regarding whether the valve has internal leakage, the following table should be referred to for confirmation. If a disagreement persists, the equipment management department’s inspection staff should be notified to make a determination, with the decision of the head of the General Affairs Department being final.