Lesson-11-Type-and-Construction-of-Marine-Pumps.doc

Lesson 11 Type and Construction of Marine Pumps第11课 船用泵的类型和结构1. A pump is a machine used to raise liquids from a low point to a high point. Alternatively it may simply provide the liquid with an increase in energy enabling it to flow or build up a pressure. The pumping action can be achieved in various ways according to the type of pump employed. The arrangement of pipe work, the liquid to be pumped and its purpose will result in certain system requirements or characteristics that must be met by the pump.泵是用来把液体从低处提升到高处的机械。或者可以简单地说, 泵是给液体提供能量从而使液体能够流动或者建立一定的压力。泵液体的过程依照所用泵的型号不同, 可以通过不同的途径来实现。管路布置、需要泵送的液体, 以及其目的将产生特定的系统需要或特性, 这些都要由泵来满足。2. The pumps, which are used on board ship, can be divided into two main groups: displacement pumps and centrifugal pumps. They can be broken down into three classes: (1) reciprocating, (2) rotary, and (3) centrifugal. Under reciprocating are the direct acting, power, and crank-fly wheel types. Under rotary are the gear, vane, screw and piston types. Under centrifugal are the volute, diffuser, mixed-flow, axial flow and turbine or regenerative types2.船用泵可分成两大类型:容积泵和离心泵。它们还可细分成3种:(1)往复泵，(2)回转泵，(3)离心泵。往复泵又分为直接作用式、动力驱动式、曲轴飞轮驱动式等;回转泵可分为齿轮式、叶片式、螺杆柱塞式等。离心泵可分为蜗壳式、导轮式、混流式、轴流式、旋涡式及再生式。displacement pumping容积泵3. The displacement pumping action is achieved by the reduction or increase in volume of a space causing the liquid (or gas) to be physically moved. The method employed is either a piston in a cylinder using a reciprocating motion, or a rotating unit using vanes, gears or screws容积泵的泵作用是通过增加或减少液体被实际移动的腔室容积。所采用的方式或者是套筒内做往复运动的柱塞或者是使用叶片、齿轮或螺杆的旋转装置。4. A reciprocating displacement pump is shown diagrammatically in Fig. 11-1, to demonstrate the operating principle. The pump is double-acting, that is, liquid is admitted to either side of the piston where it is alternately drawn in and discharged. As the piston moves upwards, suction takes place below the piston and liquid is drawn in, the valve arrangement ensuring that the discharge valve cannot open on the suction stroke. Above the piston, liquid is discharged and the suction valve remains closed. As the piston travels down, the operations of suction and discharge occur now on opposite sides.图11-1为往复容积泵的工作原理示意图。该泵是双作用泵，液体可以进入柱塞的两侧交替吸排。当柱塞上移时，液体从柱塞下吸入，阀的布置确保了吸液时排放阀不会打开。柱塞上部空间的液体被排出，此时吸入阀保持关闭。当柱塞下移时，吸排动作相反。5. A relief valve is always fitted between the pump suction and discharge chambers to protect the pump should it be operated with a valve closed in the discharge line.如果泵工作时排出管路阀门关闭，需要在吸入腔和排出腔之间设置安全阀以保护泵。6. Reciprocating displacement pumps are self-priming, will accept high suction lifts, produce the discharge pressure required by the system and can handle large amounts of vapor or entrained gases. They are, however, complicated in construction with a number of moving parts requiring attention and maintenance往复容积泵具有自吸能力，能产生较大的吸入高度，达到系统所要求的排出压力，能够输送大量蒸汽或者夹带的气体。然而它们结构复杂，有许多运动部件需要维护和保养。7. When starting the pumps the suction and discharge valves must be opened. It is important that no valves in the discharge line are closed, otherwise either the relief valve will lift or damage may occur to the pumps when it is started.当启动泵时，必须打开吸入阀和排出阀。排出管路中的所有阀均应开启，这点很重要，否则安全阀会开启或者启动时可能会对泵造成损害。8. Screw, vane and gear pumps are examples of rotary displacement pumps. All types of rotary pumps continue to force liquid into the system regardless of the opposition to the transfer. Due to this, reason, additional protection to these pumps is required or else the pump will continue to build up pressure and finally lead to rupture or damage to the pump. To avoid this, relief valves are fitted in the pumps. These relief valves are capable of bypassing entire throughput of the pump. Rotary pumps are highly sensitive pumps and therefore special care is needed in order to prevent any abrasive material from entering the pump which can damage the helices and clearances in the pump. The starting procedure of rotary displacement pumps is similar to that for the reciprocating displacement pump.螺杆泵、叶片泵和齿轮泵都是回转泵。所有类型的回转泵都能够把液体压进系统，无论输退的管路中遇到多大的阻力。由于这个原因，这些泵被要求有附加保护，否则泵会持续产生很大的压力，最后导致泵破裂或损坏。为了避免这种损坏，这种泵必须安装溢流阀。这些溢流阀有能力旁通泵的整个流量。回转泵是高精密泵，因此要特别小心以避免磨粒进入泵体，损坏泵的螺旋线和间隙。回转容积泵的启动程序和往复容积泵有点相似。 Centrifugal Pump离心泵9. Centrifugal pumps are those where an impeller rotating at high speed throws the liquid by centrifugal force from the center to the periphery of the impeller where the liquid is discharged through the delivery outlet.离心泵泵内的叶轮高速旋转，并利用离心力将液体从叶轮的中心甩向四周，然后液体从排出口排出。10. A vertical, single stage, single entry, centrifugal pump for general marine duties is shown in Fig. 11-2. The pumping element is made up of a top cover, a pump shaft, an impeller, a bearing bush and a sealing arrangement around the shaft. The sealing arrangement may be a packed gland or a mechanical seal and the bearing lubrication system will vary according to the type of seal. Replaceable wear rings are fitted to the impeller and the casing. Centrifugal pumps, while being suitable for most general marine duties, are not self-priming and require some means of removing air from the suction pipeline and filling it with liquid.图11-2为普通船用单级、单侧吸入直立式离心泵。泵送部件由端盖(顶盖)、泵轴、叶轮、轴承套和环绕着轴的密封装置组成。密封装置可以是填料压盖或者是机械轴封，轴承润滑系统的类型由密封装置的类型决定。可以更换的密封环分别安装在叶轮和泵壳上。尽管离心泵适用于船上的大多数一般用途，但是不具备自吸能力，需要利用一些方法排除吸入管路的空气，注满液体。11. When starting a centrifugal pump the suction valve is opened and the discharge valve left shut: then the motor is started and the priming unit will prime the suction line. Once the pump is primed the delivery valve can be slowly opened and opening or closing the delivery valve can regulate the quantity of liquid. When stopping the pump the delivery valve is closed.启动离心泵时，打开吸入阀，关闭排出阀，然后开启马达，引水装置就会为吸入管引水。引水后即可慢慢开启排出阀，开大或关小排出阀以调节液体的排出量。停止用泵时，先关闭排出阀，然后再关闭马达。12. Regular maintenance on the machine will involve attention to lubrication of the shaft bearing ensuring that the shaft seal or gland is not leaking liquid. Unsatisfactory operation or loss of performance may require minor or major overhauls. Common faults, such as no discharge, may be a result of valves in the system being shut, suction strainers blocked or other faults occurring in the priming system. Air leaks in the suction piping, a choked impeller or too tight a shaft gland can all lead to poor performance.离心泵的常规保养需要注意检查轴承的润滑，确保轴封或密封压盖无漏液现象。如有运转不良或性能下降，可能需要进行小修或大修。常见的故障，比如没有排液，可能是由于系统的阀被关闭，吸入滤器堵塞或是引液系统的其他故障。吸入管路漏气、叶轮阻塞或轴封太紧都会导致性能差。13. Reciprocating pumps and rotary pumps are positive displacement type because they discharge a near constant amount of liquid regardless of pressure. If the discharge valve is closed, they build up a bursting pressure or stall their motor. Centrifugal pumps are nonpositive and fairly low pressure units. Here a closed discharge valve will not cause excessive pressure to build up.往复泵和回转泵是正容积泵，因为它们能输出几乎定量的液体而与压力无关。若排出阀关闭，它们将产生破坏性压力或使电动机堵转。离心泵是负容积泵，压力相对较低。即使关闭排出阀，它也不会产生过高的压力。14. In general, reciprocating pumps are suitable for delivering small quantities at high pressure, rotary pumps are used for moderate quantities at moderate pressure, and centrifugal pumps are more suitable for large quantities at low pressure. Centrifugal pumps, however, can be designed with a number of impellers in series to attain a high final delivery pressure. They are popular because they are very simple in construction, and can produce smooth, constant, nonpulsating discharge.通常，往复泵适于高压下输送少量液体，回转泵适于中等压力下输送中等数量的液体。离心泵则更适合于低压下输送大量液体。然而离心泵可设计成若干叶轮串联的形式，以获得较高的最终输出压力。它们因构造简单，并能产生平稳、连续、无脉动的流量而被普遍使用。B. Multiple Choice选择题Questions 1-5 are based on paragraphs 1-2. 根据课文第1-2段回答问题1-5。1. A pump may simply provide the liquid with an increase in energy enabling it to flow or build up a pressure. What does “it” in the sentence above refer to?简单地说，泵给它提供能量从而使它能够流动或者建立一定的压力。这里的“它”指的是什么液体?答案:BA. A pump. 泵B. The liquid. 液体C. Energy. 能量D. An increase. 增量2. A vane pump belongs to according to its working principle.根据工作原理，叶片泵属于_。答案.CA. reciprocating pump往复泵B. centrifugal pump离心泵C. positive displacement pump正容积泵D. centripetal pump向心泵3. A screw pump belongs to according to its working principle.根据工作原理，螺杆泵属于_。答案.BA. reciprocating pump .往复泵B. positive displacement pump正容积泵C. centrifugal pump离心泵D. centripetal pump向心泵4. The pumps employed on board the ship can be divided into two main categories i. e. pumps and centrifugal pumps.船用泵可以分为两种主要类型，例如_泵和离心泵。答案.CA. gear齿轮B. non positive displacement负容积C. positive displacement正容积D. rotary回转5. Gear pumps are positive displacement type because they discharge a near constant amount of liquid pressure.5.齿轮泵是正容积泵，因为它与压力_，排出几乎恒定量的液体。答案;CA. depending upon依赖于(A项译为:因为它依赖于压力)B. in relative to有关C. regardless of无关D. axial-flow轴流Questions 6-9 are based on paragraphs 3-9. 根据课文第3-9段回答问题6 -9.6. The displacement pumping action is achieved by the reduction or increase in causing the liquid (or gas) to be physically moved.容积泵通过泵腔的增减实现液体(或气体)的移动(吸排)。答案DA. flow amount of a liquid 液体流量B. power of the pump泵功率C. area of a space工作面积D. volume of a space工作容积7. A relief valve is always fitted between the reciprocating pump suction and discharge chambers to protect the pump with a valve closed in the discharge line.安全阀通常装在往复泵的吸入腔和排出腔间，排出管上的阀关闭以保护泵。答案:AA. should it be operated泵工作时B. it should be operated泵被操作时C. if it will be operated 如果泵将被操作D. will it be operated泵将被操作时8. When staring the reciprocating displacement pumps, it is important that , otherwise either the relief valve will lift or damage may occur to the pumps when it is started.当启动往复容积泵时，很重要，否则安全阀会开启或者可能会对泵造成损害。答案:B A. a valve in the discharge line is closed排出管路上一个阀关闭B. no valves in the discharge line are closed排出管路上没有阀关闭C. some of the valves in the discharge line are opened排出管路上一些阀打开D. none of the valves in the discharge line are opened排出管路上的阀都关闭9. The starting procedure of is similar to that for the reciprocating displacement pump._的启动过程与往复容积泵的过程相似。答案;AA. rotary displacement pumps回转容积泵B. centrifugal pumps离心泵C. impeller pumps叶轮泵D. axial flow pumps轴流泵Questions 10-12 are based on paragraphs 10-12. 根据课文第10-12段回答问题10-12。10. The pumping element for a vertical, single stage, single entry, centrifugal pump consists of .单级、单侧吸入直立式离心泵泵送元件由一组成。答案AA. a top cover, a pump shaft, an impeller, bearing bush and a sealing arrangement.端盖(顶盖)、泵轴、叶轮、轴承套和密封装置B a casing, a pump shaft, a vane, a bearing bush and a sealing arrangement外壳、泵轴、叶片、轴承套和密封装置 C. a top cover, a screw, an impeller, bearing bush and a sealing arrangement端盖、螺杆、叶轮、轴承套和密封装置D. a casing, a rotor, a propeller, a bearing bush and a sealing arrangement外壳、转子、螺旋桨、轴承套和密封装置11. Common faults with centrifugal pumps, such as no discharge, may be a result of 离心泵的通常故障，如没有排放，可能是_的结果。答案.CA. valves in the system being shut系统阀被关闭B. suction strainers blocked吸入滤器堵塞C. either A or B A或BD. neither A nor B既不是A也不是B12. Which feature of a centrifugal pump reduces the need for renewing worn impellers and pump casings? 离心泵的哪个特点减少了更新磨损的叶轮和泵壳的必要?答案.DA. Close radial clearance between impeller hub and casing. 叶轮轮毂和壳体间径向间隙小。B. Low rotational speed of impeller. 叶轮转速低C. Removable end plate. 可移动端板。D. Replaceable impeller and casing wear rings. 可替换的叶轮和壳体承磨环。Questions 13-15 are based on paragraphs 13-14. 根据课文第13-14段回答问题13-15。13. Which of the following will be the advantage of a centrifugal pump as compared with a reciprocating pump? Its discharge is continuous;It has no internal valves; Upon accidental closing of discharge valve, excessive pressure will not build up与往复泵相比，下列哪些是离心泵的优点?答案;A它的排出是连续的;它没有内阀;排出阀意外关闭，不会形成过压A. B. C. D. only 14. In general, is suitable for delivering small quantities at high pressure. 通常来说，_更适合高压下输送少量液体。答案.AA. a reciprocating pump往复泵B. a gear pump齿轮泵C. a commingle pump混合泵 D. a vane pump叶片泵15. are more suitable for large quantities at low pressure._适合于低压下输送大量液体。答案:CA. Reciprocating pumps往复泵B. Rotary pumps回转泵C. Centrifugal pumps离心泵D. Gear pumps齿轮泵Task 2 Vocabulary and Structure任