外文文獻 Failure analysis of centrifugal pump Abstract Cause defects in process system of centrifugal pump failure according to their causes can be divided into mechanical fault pump and pipeline pump is composed of pump abnormal vibration noise fault Causes of failure after class is relatively hidden not easy to find Through some examples encountered in the work the fault of centrifugal pump leads to the design process and pipeline system is analyzed and puts forward the corresponding countermeasures Keywords vacuum degree analysis of mechanical faults of centrifugal pump 1 centrifugal pump suction inlet Because of the gas density is far less than the liquid gas through the impeller head head can be far less than the liquid through the impeller In the different positions of the impeller of the pressure distribution different when the liquid is mixed with gas bubbles in the pressure the uneven after the first expansion compression produced a similar impact of cavitation the last may be crushed or broken The impellers are exciting force will be severe vibration and noise pump outlet pressure in the closed system along with the liquid circulation flow unable to discharge system if the gas entrained in quantity is more the pump will appear abnormal vibration The closed system of gas sources are mainly in two aspects 1 system design is not reasonable to exhaust the dead angle each to the system into the liquid of these dead area has a large number of residual air and in the cycle of these air may be brought into the pump 2 the working fluid system in the long process cycle of non condensable gas due to lack of gas liquid separation system emissions of non condensable gas ac cumulation in the system If the heating system of heat medium and other organic matter in the long time use will produce gaseous substances due to oxidation and other reasons The above two kinds of circumstances in the closed system the gas first as soon as possible to discharge system secondly to accurately determine the source of gas to gas in the system existence not stop to a gas liquid separation device in the system increases and regularly discharge Obviously for the closed cycle system in the appropriate part of the system installed gas collection storage system pressure and low or discharge device such as pipeline s highest point strengthen inspection regularly on exhaust system is essential A drying drum heating system Fig L in the 1 B41 5 H M 0506 satellite shielding pump found that volatility pump severe vibration noise outlet pressure test Exclusion of mechanical and electrical fault pump itself after study of the heat medium system find that the system of Jin wheel drum L without exhaust system filling heat medium drum heating jacket in the air does not come out When driving air is sucked into the failure of shielding pump So in the Jin wheel stalled on the exhaust valve exhaust gas of high restart shielding pump in the normal functioning of the system when the heating medium For the open cycle system gas produced in the system can be directly discharged into the atmosphere will not accumulate in the system So into the gas pump is mainly caused by the inlet pipeline pump suction from the outside This fault and therefore should be focused on checking the suction pipe If a chilled water circulation system is an open system circulating pump as shown in Figure 2 the model 15150 a 125 a 400 head for the 45m flow rate of 190m3 h is the 1 single stage single suction centrifugal pump Found in operation began to pump start there is no abnormal starting about Z min after the periodic oscillation outlet pressure gauge pointer large radial swing serious when systematic pipe rack will shake Experiments were repeated the same phenomenon After inspection of the pump running parts no problem And frozen water level higher than the pump suction pipe on the pump body hydraulic loss is very small the pump cavitation does not occur Exclude factors consideration might be inhaled the gas pump and the pump suction line on inspection check the water tank that return water tank DN250 pipe located just above the pump suction pipe water tank liquid level from 0 3m LM from the mouth of the suction pipe High speed into the backwater pool of liquid entrainment from a large amount of air into the pump The suction the pump inhalation of air resulting in pump body vibration Therefore the pump suction pipe extending 1 Sm to the pool avoid water backwater port the failure to eliminate 2 centrifugal pump export pipeline gas block In the circulation system aggregation is higher or larger process upper valve is easy to produce gas pipeline Centrifugal pump operation in these areas will form the air bag liquid flows through the region of the flow resistance increases the partial pressure increases the compressed gas gas volume is reduced and the local pressure drop go round and begin again causing shock induced vibration system pipeline pump body water volatile liquid pressure This kind of fault appears in the system just started running when the system is not fully exhaust The rational design of the pipeline system can reduce the gas block Change 3 parameters and pump cavitation Common causes of pump cavitation are resistance loss of pump installation Fu is not reasonable the suction pipe is too large or pump selection can be properly work not reasonable etc But a selection of centrifugal pump was correct in the process of a complex system of stable work will change because of the extreme jump process parameters of cavitation 3 1 suction pressure changes caused by cavitation From the inhalation of liquid into the impeller region of low pressure column Bernoulli equation of pump can be seen when the surface pressure suction decreases the impeller entrance pressure is reduced whereas the rise That is to say the pump cavitation ability as the liquid pressure increases decreases as the surface pressure decreases From table 1 can be premise of CQ trans critical cycle system in the refrigeration coefficient heat coefficient is low CQ air conditioning and water coupling system scheme and the traditional medium air conditioning system electric water heater compared to total power consumption reduced by 32 1 comprehensive an efficient of performance increased by 47 4 4 Conclusion L CQ trans critical cycle air conditioner water coupling system has the advantages of compact structure but also to meet the refrigeration refrigeration and hot water hot water heating heating and hot water 5 kinds of conditions can effectively improve the system utilization 2 the exhaust heat of the coupling system can recover and utilize CQ trans critical cycle the overall performance of the higher system has the advantages and potentialities in energy use environmental safety and economic operation and so on has the broad application prospect 中文翻譯 離心泵的故障分析 摘要 離心泵故障按其產(chǎn)生的原因可以分成泵本身的機械故障 泵和管道組成的工藝 系統(tǒng)存在的缺陷導致的泵出現(xiàn)異常振動 噪聲等故障 后類故障原因比較隱蔽 不 易查明 通過工作中遇到的幾個實例 對工藝和管路系統(tǒng)設計問題導致的離心泵故 障進行了分析 并提出了相應的對策 關鍵詞 離心泵 機械故障 分析 真空度 由于氣體密度遠小于液體 氣體通過葉輪流道時 所能得到的壓頭遠小于液體 通過葉輪流道時所得到的壓頭 在葉輪流道中的不同位置 壓力分布不同 當液體 中混有氣體時 氣泡在這種不均勻的壓力作用下 先膨脹后壓縮 產(chǎn)生了類似汽蝕 的沖擊 最后有可能會被壓潰或破滅 葉輪受到激振力作用會劇烈振動并發(fā)出噪聲 泵出口壓在密閉系統(tǒng)中與液體一起循環(huán)流動 無法排出系統(tǒng) 如果系統(tǒng)中夾帶的氣 體的量比較多 泵就會出現(xiàn)異常振動 密閉系統(tǒng)中氣體來源主要有兩個方面 l 系統(tǒng)本身設計不合理存在難以排氣的死角 每次向系統(tǒng)中注入液體時這些死角區(qū) 域殘留有大量空氣 而在循環(huán)時這些空氣有可能被帶入泵中 2 系統(tǒng)工作液體在長期工藝循環(huán)中產(chǎn)生不凝性氣體由于系統(tǒng)缺少氣液分離 排放措 施不凝性氣體在系統(tǒng)中積聚 如加熱系統(tǒng)中的熱媒等有機物在長期循環(huán)使用中會因 氧化等原因產(chǎn)生氣態(tài)物質 在密閉系統(tǒng)中出現(xiàn)上述兩種情況時 首先要盡快想辦法排放系統(tǒng)中的氣體 其 次要準確判斷氣體的來源杜絕氣體在系統(tǒng)中的存在 不能杜絕的 要在系統(tǒng)中增加氣 液分離裝置并定期進行排放 顯然對于密閉循環(huán)系統(tǒng) 在系統(tǒng)的合適部位裝設氣體 收集 存系統(tǒng)壓力轉低點 和 或 排放裝置 如系統(tǒng)管路的最高點 加強巡檢對系統(tǒng) 進行定期排氣是必不可少的 某干燥轉鼓熱媒加熱系統(tǒng) 如圖 l 中的 1 臺 B41 5 H M 0506 衛(wèi)型屏蔽泵在試車 中發(fā)現(xiàn)泵體振動嚴重噪聲大出口壓力劇烈波動 排除泵本身有機械和電氣故障后對 整個熱媒系統(tǒng)進行研究 發(fā)現(xiàn)該系統(tǒng)中的錦輪轉鼓 設備 l 無排氣口系統(tǒng)充注熱媒 時 轉鼓加熱夾套中的空氣排不出來 開車時 空氣被吸入屏蔽泵中造成故障 于 是在錦輪轉鼓上加裝排氣閥 在系統(tǒng)補加熱媒時進行高位排氣再起動屏蔽泵泵運轉 正常 對于開放式循環(huán)系統(tǒng) 系統(tǒng)中產(chǎn)生的氣體可以直接排入大氣氣體在系統(tǒng)中不會 積聚 所以進入泵中的氣體主要是由泵的進口管路從外界吸入的 因此發(fā)生這類故 障時應著重對吸入管路進行檢查 如某冷凍水循環(huán)系統(tǒng)是一個開放系統(tǒng) 如圖 2 所示其中的循環(huán)泵 型號 151 50 一 125 一 400 揚程為 45m 流量為 190m3 h 是 1 臺單級單吸離心泵 運行中發(fā)現(xiàn) 泵剛起動時并無異常起動約 Zmin 后開始出現(xiàn)周期性振動 出口壓力表指針大輻擺動 嚴重時系統(tǒng)管架也隨之晃動 經(jīng)多次試驗 均重復出現(xiàn)同樣現(xiàn)象 經(jīng)檢查該泵運轉 部件沒有問題 而且該泵供水的冷凍水箱液位高于泵體 吸入管路上水力損失很小 泵不會發(fā)生氣蝕 排除諸因素后 考慮可能是泵運行中吸入了氣體 遂對泵吸入管 路進行重點檢查 檢查冷凍水箱時發(fā)現(xiàn)水箱 DN250 的回水管管口正好位于泵吸入管 管口上方 離水箱液面 0 3m 離吸入管管口 lm 高速沖入池中的回水從液面夾帶大 量空氣直沖泵 吸入口 使泵吸入大量空氣 造成泵體振動 為此采取將泵吸入管向池內(nèi)延伸 1 sm 避開水池回水口 結果消除了故障 2 離心泵出口管路存在的氣堵 在循環(huán)管路系統(tǒng)中 管路的較高處或較大的工藝閥門上部易產(chǎn)生氣體的聚集 離心泵運行時在這些部位會形成氣囊 液體流經(jīng)這些區(qū)域時流動阻力增大 局部壓 力升高 壓縮氣體 氣體體積減小 又使局部壓力下降 周而復始 造成液體壓力 劇烈波動形成系統(tǒng)管路水擊導致泵體振動 這類故障多出現(xiàn)于系統(tǒng)剛開始運行 系統(tǒng)排氣不充分的時候 合理地設計系統(tǒng) 管路可以減少產(chǎn)生氣堵 3 工藝參數(shù)變化與泵的汽蝕 常見的引起泵汽蝕的因素主要有泵的安裝福度不合理 吸入管路的阻力損失太 大或泵選型可適當 工作點不合理等 但在復雜的工藝系統(tǒng)中一臺原本選型正確 工作穩(wěn)定的離心泵也會因跳工藝參數(shù)的極端變化發(fā)生汽蝕 3 1 吸入壓力變化引發(fā)汽蝕 從泵的吸入液面到葉輪流道低壓區(qū)列伯努利方程 可以看到當吸入液面上的壓 力減小時 葉輪入口的壓力就降低 反之則上升 也就是說泵的抗汽蝕能力隨液面 壓力增大而提高 隨液面壓力減小而降低 由表 1 可以看出 cq 跨臨界循環(huán)系統(tǒng)在制冷系數(shù) 制熱系數(shù)均偏低的前提下 cq 空調(diào) 熱水禍合系統(tǒng)方案與傳統(tǒng)工質空調(diào)系統(tǒng) 電熱水器方案相比全年總耗電量減少 了 32 1 全年綜合性能系數(shù)提高了 47 4 4 結論 l cq 跨臨界循環(huán)空調(diào) 熱水禍合系統(tǒng)結構緊湊 而且能夠滿足制冷 制冷 熱 水 熱水 制熱 制熱 熱水 5 種工況需求 可以有效提高系統(tǒng)利用率 2 該禍合系統(tǒng)可以回收和利用 cq 跨臨界循環(huán)的排氣熱量 系統(tǒng)總體性能較高 在能源利用 環(huán)境安全和經(jīng)濟運行等方面都具有優(yōu)勢和潛力 具有廣闊的應用前景