甲板运输船动力装置设计外文翻译资料

 2022-01-02 10:01

Chapter 7—AUXILIARY MACHINERY

Improper Venting of Evaporator Tube Nests

Improper venting of the evaporator tube nests causes either an accumulation of air in the tubes, with a loss of capacity, or an excessive loss of tube nest steam to the distilling condenser, with loss of economy. Troubles of this type usually result from improper operation rather than from material failures.

Scale Deposits on Evaporator Tubes

Until 1958, scale deposits on evaporator tubes had been one of the more serious causes of operating difficulties. In 1958, a new compound was authorized for treatment of evaporator feedwater. The new compound PD-8 evaporator treatment is far superior to the cornstarch-boiler compound formerly used. For details on PD-8 and its use, refer to the applicable chapter in

Last-Effect Shell Vacuum

Most manuafacturersrsquo; technical manuals indicate that a vacuum of approximately 26 inches of mercury should be obtained in the last-effect shell when the temperature of the seawater is 85 °F, and that the vacuum should be higher when the seawater is colder. Failure to obtain a vacuum of 26 inches of mercury, or more, can generally be traced to one of the following factors: air leaks, improper operation of air ejectors, insufficient flow of seawater, and ineffective use of heat transfer surface in the distilling condenser.

Testing for Air Leaks

The importance of eliminating air leaks can-not be overemphasized. Many distilling plant troubles are direct results of air leaks. Air leaks in the shells of distilling plants cause a loss of vacuum and capacity. Extreme care must be taken in making up joints and in keeping them tight. Joints should be periodically tested under pressure for leaks.

There are several methods by which tests can be made for air leaks in tube nests, heat exchangers, shells, and the piping systems of the distilling plant. When the plant is in operation, a candleflame can be used to test all joints and parts under vacuum. With the plant secured, air pressure tests or a soapsuds test can be used on the various component parts of the distilling plant. The manufacturerrsquo;s technical manual describes how the various parts of the plant can be isolated and placed under air pressure.

Air leakage may also be detected by hydrostatically testing the various parts of the plant. When performing air tests or hydrostatic tests, precautions should be taken not to exceed the maximum limit of the test pressures specified by the manufacturer.

Testing for Saltwater Leaks

If a leak is detected in a heat exchanger, the defective tube(s) should be located by means of

an air test or a hydrostatic test, in accordance with the recommended procedure in the manufacturerrsquo;s instructions. Blueprints should also be used to study the construction details of the individual heat exchanger.

As soon as a leaky tube has been located, it should be plugged at both ends. Special composition plugs are provided in the allowance repair parts and should be used.

Since plugging the tubes reduces the amount of heating surface, the heat exchanger will fail to give satisfactory performance after a number of tubes have been plugged. It will then become necessary to retube the heat exchanger. Under normal conditions, this work should be accomplished by a naval shipyard or tender. However, repair parts and a number of special tools are included in the Shiprsquo;s Allowance List to permit emergency repairs to the heat exchangers and to other parts of the distilling plant.

To find which of the tubes within a REMOVABLE TUBE BUNDLE is leaking, it is necessary to test the individual bundles hydrostatically. If the leak is in a removable bundle (vapor feed heaters when within an evaporator shell, evaporator tube nests, distilling condensers on Solo-shell end-pull plants), the bundle must be withdrawn and a hydrostatic test at full pressure (50 psi) must be applied on the tube side.

If a leak occurs in a NONREMOVABLE TUBE BUNDLE (distillate coolers, air ejectors condenser, external vapor feed heaters), the tube nest covers must be removed, and the full test pressure (50 psi) applied on the shell side of the unit.

If a nonremovable distillate condenser bundle is within an evaporator shell, the tube nest covers must be removed and a full test pressure of 30 psi should be applied to the evaporator shell.

If the distilling condenser is fitted with a diaphragm-type (Goubert) expansion joint, a test ring will be required to replace the tube nest cover for testing.

designed (stamped on the nameplate). Pressures at the air ejector nozzle may be 10 to 15 psig higher than the minimum specified by the manufacturer.

2. The primary causes of air ejector trouble are low steam pressure, wet steam, obstructed nozzle, or a clogged steam strainer. Such trouble is indicated by failure to obtain or to maintain the required vacuum. If the trouble is due to low steam pressure or to wet steam, it will be necessary either to increase the steam pressure or to pro-vide suitable drainage by installing a trap or by using manual means. If the nozzle or steam strainer is clogged, it must be removed and cleaned. Most plants are provided with two sets of air ejectors; this permits the use of the plant on one unit while the second is being cleaned or repaired. However, some of the latest plants have only one set of air ejectors.

When it becomes necessary to clean air ejector nozzles, they should be cleaned with the special nozzle reamers furnished to each ship for this purpose. Sharp-edged tools should never be used for cleaning nozzles because the nozzle surfaces will be damaged and the efficiency of the air ejectors will be impaired.

Procedures for testing air ejectors can be found in the manufacturerrsquo;s technical manual. In general, the same maintenance procedures should be followed for distilling plant air ejectors a

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Chapter 7—AUXILIARY MACHINERY

第七章 辅机

Improper Venting of Evaporator Tube Nests

蒸发器管排风不当

Improper venting of the evaporator tube nests causes either an accumulation of air in the tubes, with a loss of capacity, or an excessive loss of tube nest steam to the distilling condenser, with loss of economy. Troubles of this type usually result from improper operation rather than from material failures.

蒸发器管巢排气不当会导致管内空气积聚,导致容量损失,或管巢蒸汽过度损失至蒸馏冷凝器,造成经济损失。这种类型的故障通常是由于操作不当而不是材料故障造成的。

Scale Deposits on Evaporator Tubes

蒸发器管上的积垢

Until 1958, scale deposits on evaporator tubes had been one of the more serious causes of operating difficulties. In 1958, a new compound was authorized for treatment of evaporator feedwater. The new compound PD-8 evaporator treatment is far superior to the cornstarch-boiler compound formerly used. For details on PD-8 and its use, refer to the applicable chapter in

直到1958年,蒸发器管上的积垢一直是操作困难的更严重的原因之一。1958年,一种新的化合物被批准用于处理蒸发器给水。新型复合物PD-8蒸发器处理远远优于原玉米淀粉锅炉复合物。有关PD-8及其使用的详细信息,请参阅中的适用章节。

Most manuafacturersrsquo; technical manuals indicate that a vacuum of approximately 26 inches of mercury should be obtained in the last-effect shell when the temperature of the seawater is 85 °F, and that the vacuum should be higher when the seawater is colder. Failure to obtain a vacuum of 26 inches of mercury, or more, can generally be traced to one of the following factors: air leaks, improper operation of air ejectors, insufficient flow of seawater, and ineffective use of heat transfer surface in the distilling condenser.

大多数制造商的技术手册表明,当海水温度为85°F时,应在最后一个效果壳中获得约26英寸汞的真空,当海水温度较低时,真空应较高。如果不能获得26英寸汞或更高的真空度,通常可归结为以下因素之一:空气泄漏、空气喷射器操作不当、海水流量不足以及蒸馏冷凝器中传热面使用不当。

Testing for Air Leaks

空气泄漏试验

The importance of eliminating air leaks can-not be overemphasized. Many distilling plant troubles are direct results of air leaks. Air leaks in the shells of distilling plants cause a loss of vacuum and capacity. Extreme care must be taken in making up joints and in keeping them tight. .

消除漏气的重要性不能过分强调。许多蒸馏厂的故障都是空气泄漏的直接结果。蒸馏设备外壳中的空气泄漏会导致真空度和容量损失。在连接和保持紧密时必须格外小心

There are several methods by which tests can be made for air leaks in tube nests, heat exchangers, shells, and the piping systems of the distilling plant. When the plant is in operation, a candleflame can be used to test all joints and parts under vacuum. With the plant secured, air pressure tests or a soapsuds test can be used on the various component parts of the distilling plant. The manufacturerrsquo;s technical manual describes how the various parts of the plant can be isolated and placed under air pressure.

有几种方法可以用来测试蒸馏装置的管巢、热交换器、壳体和管道系统中的空气泄漏。当设备运行时,可以用烛光在真空下测试所有接头和零件。在设备安全的情况下,可以对蒸馏设备的各个部件进行气压试验或肥皂水试验。制造商的技术手册描述了如何在空气压力下隔离和放置设备的各个部分。

Air leakage may also be detected by hydrostatically testing the various parts of the plant. When performing air tests or hydrostatic tests, precautions should be taken not to exceed the maximum limit of the test pressures specified by the manufacturer.

空气泄漏也可以通过对工厂各个部分进行水压试验来检测。在进行空气试验或水压试验时,应采取预防措施,使其不超过制造商规定的试验压力最大限值。

Testing for Saltwater Leaks

盐水泄漏试验

If a leak is detected in a heat exchanger, the defective tube(s) should be located by means of an air test or a hydrostatic test, in accordance with the recommended procedure in the manufacturerrsquo;s instructions. Blueprints should also be used to study the construction details of the individual heat exchanger.

As soon as a leaky tube has been located, it should be plugged at both ends. Special composition plugs are provided in the allowance repair parts and should be used.

Since plugging the tubes reduces the amount of heating surface, the heat exchanger will fail to give satisfactory performance after a number of tubes have been plugged. It will then become necessary to retube the heat exchanger. Under normal conditions, this work should be accomplished by a naval shipyard or tender. However, Shiprsquo;s Allowance List to permit emergency

如果在热交换器中检测到泄漏,应通过以下方式定位有缺陷的管路,按照制造商说明中建议的程序进行空气试验或水压试验。还应使用设计图研究单个热交换器的结构细节。

一旦发现泄漏管,应在两端将其塞住。在允许维修的零件中提供特殊的组合塞,应使用。

由于堵管会减少受热面的数量,因此在堵管数根管子后,换热器将无法达到令人满意的性能。然后需要重新润滑热交换器。在正常情况下,这项工作应由海军造船厂或投标方完成。但是,维修零件和一些特殊工具包含在船舶的津贴清单中,以允许对热交换器和蒸馏厂的其它零件进行维修。

repairs to the heat exchangers and to other parts of the distilling plant

To find which of the tubes within a REMOVABLE TUBE BUNDLE is leaking, it is necessary to test the individual bundles hydrostatically. If the leak is in a removable bundle (vapor feed heaters when within an evaporator shell, evaporator tube nests, distilling condensers on Solo-shell end-pull plants), the bundle must be withdrawn and a hydrostatic test at full pressure (50 psi) must be applied on the tube side.

If a leak occurs in a NONREMOVABLE TUBE BUNDLE (distillate coolers, air ejectors condenser, external vapor feed heaters), the tube nest covers must be removed, and the full test pressure (50 psi) applied on the shell side of the unit.

If a nonremovable distillate condenser bundle is within an evaporator shell, the tube nest covers must be removed and a full test pressure of 30 psi should be applied to the evaporator shell.

If the distilling condenser is fitted with a diaphragm-type (Goubert) expansion joint, a test ring will be required to replace the tube nest cover for testing.

designed (stamped on the nameplate). Pressures at the air ejector nozzle may be 10 to 15 psig higher than the minimum specified by the manufacturer.

2. The primary causes of air ejector trouble are low steam pressure, wet steam, obstructed nozzle, or a clogged steam strainer. Such trouble is indicated by failure to obtain or to maintain the required vacuum. If the trouble is due to low steam pressure or to wet steam, it will be necessary either to increase the steam pressure or to pro-vide suitable drainage by installin

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