Lesson12CentrifugalPumpsMaintenanceOperationalProblemsRemedies.doc

Lesson 12 Centrifugal Pumps-Maintenance Operational Problems & Remedies第12课 离心泵的维护操作问题 & 补救措施During the operation of the centrifugal pumps (see Fig.12-1), several problems are faced which have to be looked into during their operation in order to get trouble-free service from these pumps. The main problem, typical to centrifugal pumps, faced by these pumps is cavitation, which is caused by the fact that these pumps operate with suction pressure much below the atmospheric pressure. This occurs mainly in the pumps used for transferring water. Other problems faced by these pumps are mainly due to normal wear and tear of the materials over a period of time.在离心泵(见图12-1)运转期间，要了解离心泵运转期间会面临的若干问题以便使其无故障地工作。离心泵面临的典型的主要问题是气蚀，造成这一事实的原因是这些泵是在吸入压力大大低于大气压力下工作的。这主要发生在用于输送水的泵中。这些泵面临的其他问题主要是在一段时间内材料的正常磨损。Operational Problems操作问题During the pump operation, as the water mass passes from eye of the impeller towards its periphery, it creates vacuum at the eye of the impeller and inside the suction pipe. If the temperature of the water passing through the suction pipe and the eye of the impeller happens to be higher than the saturation temperature of the water at the prevailing vacuum, some of the water may evaporate to form tiny vapor bubbles, which travel through the impeller. As the water mass passes from eye of the impeller towards its periphery, its pressure rises and the vapor in the tiny bubbles becomes unstable and condenses back to liquid causing small implosions in these bubbles. These implosions in the tiny vapor bubbles in the water mass have enough energy to cause pitting in the adjoining material of the impeller as well as the pump casing. This process of impeller and the casing material wastage is called cavitation.在泵操作过程中，当聚集的水从叶轮中心向外围传递时，在叶轮中心和吸入管内产生了真空。如果通过吸人管和叶轮孔的水温高于在当前的真空下水的饱和温度，一些水可能会蒸发形成微小的水蒸气泡，流过叶轮。当聚集的水从叶轮中心向外围传递时，其压力增加，而且在小气泡中的蒸汽变得不稳定并凝结为液体，导致在小气泡中内爆。这些水中小气泡的内爆具有足够的能量而造成叶轮毗邻的材料以及泵壳的凹陷。叶轮和泵壳材料损耗的过程被称为气蚀。As the pump operates at a particular available net positive suction head, the cavitation is found occurring at a particular location on the pump impeller and its casing. The location may vary from pump to pump as different pumps operate at different net positive suction heads. After several years of use, the pitting causes the wastage in the impeller and the casing material sufficient to make it weak requiring replacement.随着泵在一个特定可用的净压头下运行，气蚀是在泵叶轮及其外壳的特定位置发生的。发生的位置可能因泵的净压头不同而不同。经过数年的使用，点状腐蚀引起的叶轮和套管材料的消耗足以使它性能弱化从而需要更换。The only remedy to prevent cavitation in any pump is to ensure that the temperature of the water passing through the suction pipe and the eye of the impeller is maintained below the saturation temperature a t the prevailing vacuum. Apart from that, the inner surface of the casing may be coated with hard epoxy layer t o minimize the effect of cavitation.防止泵气蚀的唯一补救措施是确保通过吸人管和叶轮中心的水温保持低于在一般真空下的饱和温度。此外，泵壳的内表面可以涂硬的环氧树脂层将气蚀的影响减到最小。Other problems related to the centrifugal pump operation are mainly due to wear and tear in the moving parts due to friction. This will result in其他关于离心泵操作的问题主要是由于运动部件摩擦而造成的磨损。这将导致:Increase in the clearance between the impeller neck and the wear rings resulting in reduction in volumetric efficiency. Replacement of wear rings is the only remedy for this.1. 增加叶轮轴颈和耐磨环之间的间隙来减少容积效率的损失。更换耐磨环是唯一的解决办法。·Damage to the impeller shaft in the way of gland packing which may be rectified by replacement of the shaft or, if the shaft is fitted with a sleeve, by replacing sleeve.2. 压盖填料处的叶轮轴的损坏，可以通过更换轴来矫正，或者如果轴配备了套筒，可以通过替换套筒来矫正。·Wearing off damage to the bearings leading to increased power consumed by the pump. This may be rectified by replacement of the bearings.减弱轴承损坏将会增加泵的功率消耗。这可通过更换轴承来矫正。Removal of Pump for Inspection and Maintenance泵的拆卸检查和维护1. Isolate pump electrical circuit breaker on main switch board and attach a warning notice. (Do Not Operate-Men at Work.)1.断开主配电板上泵的电流接触器，挂上警示牌。(有人作业，勿动。)2. Switch off and lock pump supply at its local supply panel. Attach a warning notice to pump local supply panel.2 切断并锁上泵的配电板，在配电板上贴警示牌。3. Close suction and discharge valves, chain and lock hand wheels.3 关闭泵的吸排阀，用链条锁上手轮。4. Open pump suction and discharge pipe drain valves to bilge and when water ceases to flow; crack open the pipes/pump flange joints carefully to ensure that pump has drained off and is safe for opening.4.打开吸排管路上的放残阀，并排向舱底，当没有水流出时，小心地分开泵和管路的法兰接头，确保泵已排空，可以安全打开。5. Fix a shackle to lifting pad eye above pump and hang chain block; ensuring SWL (safe working load) of block, slings and shackles are satisfactory.5.将钩环挂在泵上部的提升孔中，悬挂链动滑轮，确保安全工作载荷，吊索和钩环都令人满意。6. Use a center-punch to match/mark coupling and casing, then remove the coupling bolts.6.用冲子标记联轴器和外壳，拆下联轴器螺栓。7. Remove motor supply cables; taping over bare ends with insulating tape.7 拆下电动机接线;裸端用绝缘胶布包上。8. Connect shackle and sling to motor eyebolt and lift motor clear of pump using overhead chain block. Lay motor on its side out of harms way, protecting machined surfaces on both pump and motor coupling halves against damage. (Cardboard and masking tape is a quick and efficient method.)8 将卸扣和吊索连接在电机的有眼螺栓上，提起电机。将电机放置在安全地带，保护泵和电机的联结面受到损坏。（纸板和胶带是快速和有效的方法）9. Disconnect all external fittings from pump casing e. g. cooling pipe, pressure gauge, oil reservoirs and air cock.9 拆下泵壳上所有的外部配件，如冷气管，压力表，油箱和空气阀。10. Remove bolting from top cover and remove cover. Scrape off old gasket and check mating surfaces, and renew gasket on assembly. (Light smear of grease on gasket/faces.)10 拆除上盖板的螺栓并取下盖板，刮去旧垫片，并检查配合面，成对更换垫片。 （光的油脂涂抹在垫片/面）11. The pump shaft with impeller can be lifted out of casing. 11泵轴与叶轮可以从里面抽出。12. Dismantle the impeller, and remove the wear ring.12拆卸叶轮，取下承磨环。13. Remove the gland packing; replacing it when reassembling. Remember to cut ends of packing at 45° and stagger joints when repacking gland.13 取下填料盘根，重新组装时换新。记住，换新时盘根末端斜切45度，错开接头。Inspection Procedure for Pump and Motor泵和电机的检查步骤Pump泵1. Impeller, pump shaft and internal volute/casing can now be inspected for erosion, pitting and wear.1 现在可以进行检查叶轮，泵轴和内部蜗壳/泵体有无腐蚀，麻点和磨损。2. If required rectify pitting or erosion in the impeller and casing with two-part alloy epoxy putty.2 如有必要修复叶轮或泵体的腐蚀或麻点，用合金补焊。3. Check main drive shaft bearings and thrust bearings for wear and replace if required.3 检查主轴承和推力轴承是否磨损，必要时更换。4. Check wear ring clearance using feeler gauges.4 用塞尺检查承磨环间隙。5. Check impeller/shaft key and keyways for damage and undue wear, unscrew impeller shaft securing nut and check threads are in satisfactory condition ; retighten to manufacturers torque settings.5 检查叶轮/轴键和键槽的损坏和过度磨损，拧下叶轮轴固定螺母和检查螺栓是否处于满意的状态，根据制造商扭矩设置重新拧紧。6. Give all parts a good clean removing any dirt/medium residue before re-assembly using new parts as required.6 重新组装前的要求，所有零件进行清洁，消除任何污垢/杂质，按要求使用新部件。7. Enter date of overhaul and parts renewed in the pump maintenance record card.7 在泵的维修记录卡上记下检修和更换零件的日期。Drive motor驱动马达1. Grip motor drive shaft/coupling firmly and check for excess axial and longitudinal movement. Rotate shaft at speed by hand, allowing it to run to a stop whilst listening for excess noise from bearings. The bearings should be replaced if necessary.1 紧固电机驱动器轴/耦合，检查是否有多余的轴向和纵向移动。手动旋转轴，允许它运行停了下来，听有无多余的轴承杂音。如有必要，应更换轴承。2. Megger check motor windings to ensure no dampness is present and windings are in good condition. Any suspect readings indicate a full motor strip to check condition of rotor and stator.2 兆欧表检查电机绕组，以确保没有潮湿，绕组都处于良好状态。任何可疑的读数意味着对电机转子和定子进行全面的拆检。3. If these checks are satisfactory, grease bearings as required. Some bearings are now sealed for life and will not require greasing.3 如果这些检查是令人满意的，按要求润滑脂轴承。有些轴承密封不需要润滑。Procedure to Start the Pump泵的启动程序1. Unlock and remove chains from inlet/outlet valve wheels and open both valves full. 1 解锁除去入口/出口阀手轮的固定，两个阀门全部打开。2. Open air cock and expel air from line and pump while checking for any leaks.2 打开空气阀从管路及泵排出空气，同时检查是否有泄漏3. Turn the shaft coupling and ensure shaft is free to rotate.3 转动联轴器确保轴能自由转动。4. Reconnect motor.4 重新连接电机。5. Remove danger notices from pump power supplies and reinstate breakers.5 从泵的电源端和配电板取下警示牌6. Start and record current drawn by the motor under starting and running conditions. Check and record the discharge pressure.6 开始记录电动机起动和运行条件下的电流。检查并记录的排出压力B. Multiple Choice选择题Questions 1-4 are based on paragraphs on Operational Problems. 根据课文操作问题部分回答问题1-4.1. Cavitation of centrifugal pumps may be caused by .1.离心泵的气蚀可能是由_引起。答案.B A. high speed water passing over the impeller blade.水高速流经叶轮叶片B. tiny vapor bubbles travelling through the impeller. 微小气泡经过叶轮C. explosion inside the pump.泵内爆裂D. lower saturation temperature of the water passing through the pump饱和温度更低的水流经泵2. Reduced capacity accompanied by vibration and noise at the suction of a centrifugal pump results from the action of vapor pockets in the water being pumped caused by .2.离心泵吸人量减少并伴随有振动和噪声，这是由于_引起的被泵的水中发生的气蚀 的行为。答案.CA. fluid friction流体摩擦B. pump knocking泵敲C. cavitation气蚀D. water hammer水击3. What can be the remedy to prevent cavitation in centrifugal pumps?3.离心泵中的气蚀可采取哪种补救措施?答案A A. To ensure the temperature of the water passing through the suction pipe and the eye of the impeller is maintained below the saturation temperature at the prevailing vacuum.A.确保通过吸入管和叶轮中心的水的温度保持低于在当时真空下的饱和温度。B. To ensure the temperature of the water passing through the suction pipe and the eye of the impeller is maintained above the saturation temperature a t the prevailing vacuum. 确保通过吸人管和叶轮中心的水的温度保持高于在当时真空下的饱和温度。C. To ensure the temperature of the water passing through the suction pipe and the eye of the impeller is maintained as high as the saturation temperature at the prevailing vacuum. 确保通过吸人管和叶轮中心的水的温度保持与当时真空下的饱和温度相同。D. None of the above. 以上都不是。4. Wear and tear in the moving parts due to friction may result in由于摩擦导致的运动件的磨损会导致离心泵 答案:DA. increase in the clearance between the impeller neck and the wear rings叶轮颈部和耐磨环的间隙增加B. damage to the impeller shaft in the way of gland packing通过填料压盖损伤叶轮轴C. wearing off damage to the bearings leading to increased power轴承上的磨损减少可增加功率D. all of the above. 以上全部Questions 5-6 are based on paragraphs on Removal of Pump for Inspection and Maintenance. 根据课文泵的拆卸检查和维护部分回答问题5-6.5. When removing a centrifugal pump for inspection and maintenance, and pump electrical circuit breaker on main switch board.5.当进行泵的拆卸检查和维护时，并主配电板上的泵断路器。答案.D A. open/tip打开/翻转B. close/tag关闭/标示C. isolate/gap断开/成缝隙D. isolate/tag断开/标示6. Fix a shackle to lifting pad eye above pump and hang chain block; ensuring of block, slings and shackles are satisfactory.将钩环挂在泵上部的提升孔中，悬挂链动滑轮，确保.，吊索和钩环都令人满意。 答案:D A. materials材料B. pressures压力C. rated load额定载荷D. safe working load安全工作载荷Questions 7-9 are based on paragraphs on Inspection Procedure for Pump and Motor. 根据课文泵和电机的检查步骤部分回答问题7 -9.7. inspect impeller, pump shaft and internal volute/casing of the centrifugal pump for 检查离心泵的叶轮、泵轴和内部蜗壳/套管的_。答案.DA. erosionA.腐蚀情况B. pitting点蚀情况C. wear磨损状况D. all of the above以上全部8. Check clearance of wear ring of centrifugal pumps by means of .通过_检查离心泵的耐磨环间隙。答案.AA. feeler gauges塞尺B. bridge gauges轴差规(桥形规)C. micrometers微米D. lead wire铅丝9. Which of the following work should be done when inspecting the motor drive?当检查电机驱动的时候要做下面哪项工作?答案:DA. Check motor drive shaft/coupling for excess axial and longitudinal movement. 检查电机驱动轴/联轴器过量的轴向和纵向运动。B. Check motor windings with a megger. 用兆欧表检查电机绕组C. Rotate shaft at speed by hand, allowing it to run to a stop whilst listening for excess noise from bearings. 手动转动电机轴，允许转动时停下来以听来自轴承的噪声。D. All of the above. 以上全部。Task 2 Vocabulary and Structure任务2词汇与结构A. Technical Terms A.专业术语Translate the following into Chinese.1. atmospheric pressure大气压力2. saturation temperature. 饱和温度3. net positive suction head净正吸入压头4. wear ring耐磨环5. volumetric efficiency容积效率6. land packing压盖填料7. circuit breaker断路器8. chain block链动滑轮9. insulating tape绝缘胶带10. coupling bolt连接螺栓11. mating surface配合面12. gland packing压盖填料13. feeler gauge塞尺B. Active Words常用词Complete the following sentences by filling in the blanks with the words in the table. Change the form of the words if necessary. 从框中选词完成句子，如有必要改变词的形式。renewdismantleunscrewretightenswitch offdrain1. Separate band brakes are fitted to hold the cable lifter and the mooring drum when the power is switch off .安装了分开的带式制动器以在关掉电源的情况下来控制锚链齿轮和绞缆筒。2. The condenser sea water boxes are protected by sacrificial mild steel plates which must be renewed regularly. 冷凝器的海水箱由定期更换的牺牲软钢板保护。3. The bilge main is arranged to drain any watertight compartment other than ballast, oil or water tanks and to discharge the contents overboard. 舱底水总管用作除了压舱物、油或水柜的任何不透水的隔间的排水，并排到船外。4. The filter must be dismantle for cleaning at regular intervals. 滤器必须定时拆卸清洁。5. Close valve C. Open valve A, then open valve B 1. 2 turn, loosen hose at test cock# 4 to remove air. Retighten hose. 关闭阀C，打开阀A，然后依次打开阀B 1.2，在料检测口松开输水管来排出空气。重新固定输水管。6 unscrew the locks from the doors. 把门上的锁拧松。C. Handy Phrases常用短语Understand the phrases by studying the sentences below and translate the phrases into Chinese. 通过学习下面的句子理解短语，并将短语译成汉语。1. in the way of关于方面e. g. Cracks in the way of scavenging air port should be remedied by means of metalock. 例如:扫气口处的裂纹应用金属扣修补。2. as well as也 e. g. The watertight door must be arranged for local opening and closing as well as operation from a point above the bulkhead deck.例如:水密门必须为局部的打开和关闭安排作准备，也要为舱壁甲板上某一点的操作作淮备。3. apart from除.之外e. g. Apart from the advantages and disadvantages for each of the drive and control methods, all electric drives have difficulty with heavy continuous overloads. 例如:除了每一种驱动和控制方法的优缺点之外，所有的电驱都难以在连续重载情况下运行。第 18 页