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1 Internal leakage of the valve: energy consumption calculation requires knowing this first. The device performs daily calculations of energy consumption. Compared to yesterday, with the same raw materials, if the yield decreases, and after ruling out process and instrumentation-related issues, I would initially suspect that internal leakage in the valves might be causing the increased energy consumption. 2 thermometers are “essential” for testing. If a valve leaks, the temperature of the adjacent pipelines will increase or decrease significantly as measured by a thermometer. The stethoscope follows closely behind. We identified internal leakage in the valve by using the first and second methods, but we couldn’t be completely sure; at this point, detection with a stethoscope becomes very important. A screwdriver can be used as a \"stethoscope\": place one end of the screwdriver’s head perpendicular to the pipeline, and hold the other end close to your ear to listen carefully for any abnormal \"buzzing\" sounds within the pipeline; if such sounds are present, it indicates that there is a leak in the valve at that location. 3. The method to determine internal leakage in a valve is as follows: 4–6 hours after the valve is closed, 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 be an “internal leak”. This method of judgment is applicable to most valves with internal leakage, but in practical work we have encountered some special cases: steam or drain valves connected in parallel to the main steam or drain pipes. When the last valve in this series is located close to the main pipe, if any valve in one of the branches of the pipeline leaks internally, the temperature of the other valves will rise to above 70°C, as is the case with boiler drain valves and superheated steam traps. 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. Criteria for determining internal leakage in valves (temperature): Medium temperature, temperature of the pipe wall behind the steam trap. Severe internal leakage: >500°C; >250°C with a temperature difference of less than 50°C compared to the pipe wall in front of the valve; >200°C with a temperature difference of less than 50°C compared to the pipe wall in front of the valve; >150°C with a temperature difference of less than 50°C compared to the pipe wall in front of the valve; >120°C with a temperature difference of less than 30°C compared to the pipe wall in front of the valve. Moderate internal leakage: >200°C with a temperature difference of less than 80°C compared to the pipe wall in front of the valve; >150°C with a temperature difference of less than 80°C compared to the pipe wall in front of the valve; >100°C with a temperature difference of less than 80°C compared to the pipe wall in front of the valve; >80°C with a temperature difference of less than 50°C compared to the pipe wall in front of the valve. Leakage: >200°C with a temperature difference greater than 50°C compared to the pipe wall in front of the valve; >150°C with a temperature difference greater than 50°C compared to the pipe wall in front of the valve; >100°C with a temperature difference greater than 50°C compared to the pipe wall in front of the valve; >80°C with a temperature difference greater than 50°C compared to the pipe wall in front of the valve. Temperatures: 400°C–500°C, 300°C–400°C, 150°C–300°C. 4. By changing the operating mode of the system, there may be high-temperature steam present upstream and downstream of some valves, such as in the primary bypass lines or the feed pump recirculation control valves. Even if these valves are airtight and do not leak, the temperature of their valve stems can still exceed 70°C. Therefore, the determination of internal leakage in these valves can alter the way the system operates. For example, the temperature after using the high-pressure bypass valve can be compared with the exhaust temperature from the turbine’s low-pressure cylinder; by isolating the water used for cooling the high-pressure bypass valve and observing any changes in temperature downstream of the valve, it is possible to determine whether there is internal leakage in that valve. Similarly, by shutting down the feedwater pump and observing whether there are changes in the flow rate of the feedwater pump before and after adjusting the isolation valves, it is possible to determine whether there is internal leakage in those adjustment valves. 5. Through other means, steam isolation valves or drain valves for the main steam pipes can be connected in parallel; when the last valves are all located near the main pipes, if there is a leak in any of the valves in the piping system, the temperatures of the other valves will rise to above 70°C, as is the case with the valves in a boiler’s drainage system. 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 in front of the primary valve is measured to determine whether there is internal leakage.