When performing maintenance work on the site connected to the vacuum system, detailed isolation measures should be taken to prevent leakage of vacuum and speed up the inspection and restore the original system as soon as possible. Leakage caused by the heater not only reduces the vacuum, but also the heater itself condensate without temperature rise or temperature rise below the design value, this heater can be used alone as the focus of vacuum management. In addition, the closed drain of the condenser drain groove is not strict, and the water in the shaft seal cooler water-free pipe belongs to such a leakage point.
When vacuum rapid drop fault occurs, spare jet pump and jet air extractor should be added to adjust the steam supply of shaft seal to normal. Use vacuum leak detection equipment to quickly find the closing door, safety door, flange, and water level in vacuum state. Meters, manholes, open water sealed doors, etc. Slow-down of the vacuum In the long-term operation of the unit, aging, wear, and loosening of the relevant components in the vacuum system can cause the vacuum to slowly decline.
Leakage points formed by wear: For example, the air seal sheet wears to cause vacuum leakage, and the ejector pump or ejector pump throat wear causes a drop in output force. Such failures need to be repaired and overhauled during overhaul. Leakage points formed by loosening: Such leakage points occur in frequently vibrating areas, such as condensation pumps, low inlet pumps with low hydrophobic pumps, etc. Special Leakage Point The special leak point is the position where the leak point is located and the leak situation is special. For example, the secondary bypass is suspended in midair and can only be checked by irrigation.
Some units of the last stage and the second stage of the last steam extraction are flanged at the outlet of the low pressure cylinder. In the lower part of the steam turbine, the leakage generated is not easy to find and requires special tools for leak detection. The condensate water supply system is not large enough to make up water. The leak will also occur in the case of. Special leaks are more difficult to find. If the vacuum system still leaks after all the conventional leaks have been eliminated, the leaks at special locations under vacuum should be considered.
Vacuum leak detection equipment and leak detection methods The existing vacuum leak detection equipment performance indicators are shown in the table! As shown, the helium mass spectrometer leak detection method has high sensitivity and good localization and is more suitable for vacuum leak detection in power plants. Helium mass spectrometer leak detection media is helium, helium density is less than the density of air, leak detection should be checked one by one from top to bottom, blocking one by one, in order to avoid detection of the lower part of the vacuum system when the helium floats near the upper leakage point Caused false positives. With the continuous development and improvement of steam turbine manufacturing technology and the application of modern electronic technology, the safety and reliability of the unit have been greatly improved. Maintaining a high condenser vacuum value and improving vacuum tightness are both simple and direct energy-saving measures, which can effectively improve the economic efficiency of the unit and play a role in the economic operation of the power plant.
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