閥門選購的質量檢查需兼顧外觀、材質、性能等維度，通過細致觀察與簡易測試，判斷是否符合使用需求。

　　The quality inspection of valve selection should take into account dimensions such as appearance, material, and performance. Through careful observation and simple testing, it is determined whether it meets the usage requirements.

　　外觀檢查直觀反映質量。鑄鐵閥門表面應無直徑超 2mm 的砂眼、氣孔，涂層均勻無剝落；不銹鋼閥門需有均勻金屬光澤，無氧化斑與劃痕，拋光面紋路一致。連接部位加工精度關鍵：法蘭密封面用直尺貼合，縫隙不超 0.1mm；螺紋接口牙型完整，無斷牙滑牙，如 DN50 閥門螺紋長度不小于 10mm。閥體標識需清晰，標注公稱直徑（如 DN100）、公稱壓力（如 PN16）、材質代號（如 WCB）等，標識模糊產品需謹慎。

　　Visual inspection provides a clear reflection of quality. The surface of cast iron valves should have no sand holes or air holes with a diameter exceeding 2mm, and the coating should be uniform without peeling off; Stainless steel valves should have a uniform metallic luster, no oxidation spots or scratches, and a consistent polished surface pattern. The key to the machining accuracy of the connecting parts is to use a ruler to fit the flange sealing surface, with a gap of no more than 0.1mm; the thread interface has a complete tooth shape without broken or sliding teeth, such as DN50 valves with a thread length of no less than 10mm. The valve body identification should be clear, indicating the nominal diameter (such as DN100), nominal pressure (such as PN16), material code (such as WCB), etc. If the identification is unclear, caution should be taken.

　　材質驗證要與標稱一致。碳鋼閥門可被磁鐵吸附，不銹鋼（如 304）通常不吸或弱吸附，必要時核對材質證明書（304 不銹鋼鉻≥18%、鎳≥8%）。塑料閥門（PVC、PPR）按壓無明顯變形，彎折閥桿有彈性不易斷。腐蝕性介質用閥需確認過流部件耐腐性，如襯氟閥門的氟塑料層應均勻無氣泡，厚度不小于 2mm。

　　The material verification should be consistent with the nominal value. Carbon steel valves can be magnetically adsorbed, while stainless steel (such as 304) usually does not or weakly adsorb. If necessary, check the material certificate (304 stainless steel chromium ≥ 18%, nickel ≥ 8%). Plastic valves (PVC, PPR) have no obvious deformation when pressed, and the bent valve stem has elasticity and is not easily broken. Valves used for corrosive media require confirmation of the corrosion resistance of the overcurrent components. For example, the fluoroplastic layer of fluorine lined valves should be uniform and free of bubbles, with a thickness of not less than 2mm.

　　密封性能是核心檢查項。手動測試關閉密封性：關閉閥門時閥桿轉動順暢，無卡滯過松（球閥 90° 靈活轉動，閘閥升降平穩）；小型閥門關閉后向進口吹氣，出口應無泄漏，大型閥門可要求提供打壓數據（1.5 倍公稱壓力下保壓 30 分鐘無滲漏）。填料函需密封良好，反復轉動閥桿無明顯滲漏（允許微量濕潤，不滴漏）。法蘭連接閥門的墊片要與密封面匹配（橡膠墊適用于低壓，金屬纏繞墊適用于高壓），且無破損褶皺。

　　Sealing performance is the core inspection item. Manual testing of sealing performance: When closing the valve, the valve stem rotates smoothly without any jamming or looseness (the ball valve rotates flexibly at 90 °, and the gate valve rises and falls smoothly); After the small valve is closed, blow air into the inlet, and there should be no leakage at the outlet. For large valves, pressure data can be requested (maintain pressure for 30 minutes at 1.5 times the nominal pressure without leakage). The packing box needs to be well sealed, and there should be no obvious leakage when the valve stem is repeatedly rotated (allowing for slight wetting without dripping). The gasket of the flange connected valve should match the sealing surface (rubber gasket is suitable for low pressure, metal wrap gasket is suitable for high pressure), and there should be no damage or wrinkles.

　　操作機構需靈活耐用。手柄或手輪安裝牢固，轉動時與閥桿無松動，如 DN200 閥門手柄長度不小于 200mm，轉動省力不打滑。電動或氣動閥門接通電源（氣源）后，啟閉應到位平穩，無異常噪音，限位裝置準確。軸承、導向套等部件需潤滑良好，轉動閥桿無卡澀。

　　The operating mechanism needs to be flexible and durable. The handle or handwheel is securely installed and does not loosen with the valve stem during rotation. For example, the length of the DN200 valve handle should not be less than 200mm, and it should be easy to rotate without slipping. After the electric or pneumatic valve is connected to the power (gas source), it should open and close smoothly, without any abnormal noise, and the limit device should be accurate. The components such as bearings and guide sleeves need to be well lubricated, and the rotating valve stem should not be stuck.

　　性能參數要適配使用場景。高溫管道用閥公稱壓力不低于工作壓力 1.25 倍，碳鋼閥門耐溫≤425℃，不銹鋼可達 600℃。輸送粘稠介質的閥門需流道通暢，閥芯結構防堵，如球閥通徑與管道一致。頻繁操作的閥門（如水處理系統），閥桿表面硬化處理（鍍鉻層≥0.05mm），避免頻繁使用導致磨損。

　　The performance parameters should be adapted to the usage scenario. The nominal pressure of valves used in high-temperature pipelines shall not be less than 1.25 times the working pressure, carbon steel valves shall have a temperature resistance of ≤ 425 ℃, and stainless steel valves shall have a temperature resistance of up to 600 ℃. Valves that transport viscous media require unobstructed flow channels and anti clogging valve core structures, such as ball valves with the same diameter as the pipeline. Valves that are frequently operated (such as water treatment systems) should have their valve stem surface hardened (chrome plating ≥ 0.05mm) to avoid wear and tear caused by frequent use.

　　總之，閥門選購需從外觀、材質、密封、操作多維度檢查，結合使用場景要求，必要時參考專業檢測數據，才能選到可靠產品，減少后期隱患。

　　In short, valve selection needs to be checked from multiple dimensions such as appearance, material, sealing, and operation, combined with the requirements of the usage scenario. If necessary, professional testing data should be referred to in order to select reliable products and reduce potential hazards in the later stage.

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