大口徑截止閥一般應(yīng)用在鍋爐出口、主分汽缸、蒸汽主管等位置，這些位置存在以下問題:

Large diameter globe valves are generally used in boiler outlets, main distribution cylinders, steam main pipes, and other positions, which have the following problems:

1)鍋爐出口一般壓差比較大，因此蒸汽流速也更大，對密封面的沖蝕破壞作用也較大。另外鍋爐燃燒效率不可能為100%，這樣將造成鍋爐出口處的蒸汽含水量較大，容易對閥門密封面產(chǎn)生空化和汽蝕的破壞作用。

1) The pressure difference at the outlet of the boiler is generally large, so the steam flow rate is also higher, which has a greater impact on the erosion and damage of the sealing surface. In addition, the combustion efficiency of the boiler cannot be 100%, which will cause a high water content in the steam at the outlet of the boiler, making it easy to cause cavitation and cavitation damage to the valve sealing surface.

2)對鍋爐出口及分汽缸附近的截止閥，因為剛從鍋爐出來的蒸汽，有間斷性過熱現(xiàn)象發(fā)生，在其飽和的過程中，若鍋爐水軟化處理不是太好的話，往往會析出部分酸堿物質(zhì)，對密封面會造成腐蝕和沖蝕;還有一些可結(jié)晶的物質(zhì)也可能附著在閥門密封面結(jié)晶，導(dǎo)致閥門無法嚴(yán)密密封。

2) For the shut-off valves near the boiler outlet and distribution cylinder, intermittent overheating occurs due to the steam just coming out of the boiler. During its saturation process, if the boiler water is not softened properly, some acidic and alkaline substances will often precipitate, causing corrosion and erosion to the sealing surface; Some crystalline substances may also adhere to the valve sealing surface and crystallize, causing the valve to fail to seal tightly.

3)分汽缸進(jìn)出口閥門，因閥后蒸汽用量因生產(chǎn)要求等原因而造成用汽量時大時小，在流速變化較大的情況下，很容易產(chǎn)生閃蒸、空化等現(xiàn)象，從而對閥門密封面造成沖蝕、汽蝕等破壞作用。

3) The inlet and outlet valves of the split cylinder are prone to phenomena such as flash evaporation and cavitation due to varying steam consumption due to production requirements and other factors. When the flow rate changes significantly, this can cause damage to the valve sealing surface, such as erosion and cavitation.

4)一般大管徑管線開啟時，都需要對管線進(jìn)行預(yù)熱，而預(yù)熱過程一般要求很小流量蒸汽通過，使管線緩慢均勻加熱到一定程度后，才能完全開啟截止閥，避免造成管線急速升溫而產(chǎn)生過度膨脹，損壞部分連接部位。但在這過程中，閥門開度往往非常小，從而造成沖蝕率遠(yuǎn)遠(yuǎn)大于正常使用效果，嚴(yán)重降低閥門密封面的使用壽命。

4) When a large diameter pipeline is opened, it is generally necessary to preheat the pipeline, and the preheating process generally requires a small flow of steam to pass through, so that the pipeline can be slowly and evenly heated to a certain degree before the shut-off valve can be fully opened to avoid excessive expansion caused by rapid heating of the pipeline, which may damage some connection parts. However, during this process, the valve opening is often very small, resulting in a much higher erosion rate than normal use, seriously reducing the service life of the valve sealing surface.

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