过程装备与控制工程专业英语阅读材料翻译

专业英语翻译专业英语翻译 楠哥 楠哥 Reading Material 16 Pressure Vessel Codes History of Pressure Vessel Codes in the United States Through the late 1800s and early 1900s explosions in boilers and pressure vessels were frequent A firetube boiler explosion on the Mississippi River steamboat Sultana on April 27 1865 resulted in the boat s sinking within 20 minutes and the death of 1500 soldiers going home after the Civil War This type of catastrophe continued unabated into the early 1900s In 1905 a destructive explosion of a firetube boiler in a shoe factory in Brockton Massachusetts killed 58 people injured 117 others and did 400000 in property damage In 1906 another explosion in a shoe factory in Lynn Massachusetts resulted in death injury and extensive property damage After this accident the Massachusetts governor directed the formation of a Board of Boiler Rules The first set of rules for the design and construction of boilers was approved in Massachusetts on August 30 1907 This code was three pages long In 1911 Colonel E D Meier the president of the American Society of Mechanical Engineers established a committee to write a set of rules for the design and construction of boilers and pressure vessels On February 13 1915 the first ASME Boiler Code was issued It was entitled Boiler Construction Code 1914 Edition This was the beginning of the various sections of the ASME Boiler and Pressure Vessel Code which ultimately became Section 1 Power Boiler The first ASME Code for pressure vessels was issued as Rules for the Construction of Unfired Pressure Vessels Section 1925 edition The rules applied to vessels over 6 in in diameter volume over 1 5 ft3 and pressure over 30 psi In December 1931 a Joint API ASME Committee was formed to develop an unfired pressure vessel code for the petroleum industry The first edition was issued in 1934 For the next 17 years two separated unfired pressure vessel codes existed In 1951 the last API ASME Code was issued as a separated document In 1952 the two codes were consolidated into one code the ASME Unfired Pressure Vessel Code Section This continued until the 1968 edition At that time the original code became Section Division 1 Pressure Vessels and another new part was issued which was Section Division 2 Alternative Rules for Pressure Vessels The ANSI ASME Boiler and Pressure Vessel Code is issued by the American Society of Mechanical Engineers with approval by the American National Standards Institute ANSI as an ANSI ASME document One or more sections of the ANSI ASME Boiler and Pressure Vessel code have been established as the legal requirements in 47 states in the United States and in all provinces of Canada Also in many other countries of the world the ASME Boiler and Pressure Vessel Code is used to construct boilers and pressure vessels Organization of the ASME Boiler and Pressure Vessel Code The ASME Boiler and Pressure Vessel Code is divided into many sections divisions parts and subparts Some of these sections relate to a specific kind of equipment and application others relate to specific materials and methods for application and control of equipment and others relate to care and inspection of installed equipment The following Sections specifically relate to boiler and pressure vessel design and construction Section Power Boilers 1 volume Section Division 1 Nuclear Power Plant Components 7 volumes Division 2 Concrete Reactor Vessels and Containment 1 volume Code Case Case 1 Components in Elevated Temperature service in Nuclear Code N 47 Case book Section Heating Boilers 1 volume Section Division 1 Pressure Vessels 1 volume Division 2 Alternative Rules for Pressure Vessels 1 volume Section Fiberglass Reinforced Plastic Pressure Vessels 1 volume A new edition of the ASME Boiler and Pressure Vessel Code is issued on July 1 every three years and new addenda are issued every six months on January 1 and July 1 the new edition of the code becomes mandatory when it appears The addenda are permissive at the date of issuance and become mandatory six months after that date Worldwide Pressure Vessel Codes In addition to the ASME Boiler and Pressure Vessel Code which is used worldwide many other pressure vessel codes have been legally adopted in various countries Difficulty often occurs when vessels are designed in one country built in another country and installed in still a different country With this worldwide construction this is often the case The following list is a partial summary of some of the various codes used in different countries Australia Australian Code for Boilers and Pressure Vessels SAA Boiler Code Series AS1200 AS1210 Unfired Pressure Vessels and Class 1 H Pressure Vessels of Advanced Design and Construction Standards Association of Australia France Construction Code Calculation Rules for Unfired Pressure Vessels Syndicat National de la Chaudronnerie et de la Tuyauterie Industrielle SNCT Paris France United Kingdom British Code BS 5500 British Standards Institution London England Japan Japanese Pressure Vessel Code Ministry of LABOR PUBLISHED BY Japan Boiler Association Tokyo Japan Japanese Standard Construction of Pressure Vessels JIS B Gas Control Law Ministry of International Trade and Industry published by The Institution for Safety of High Pressure Gas Engineering Tokyo Japan Italy Italian Pressure Vessel Code National Association for combustion Control ANCC Milan Italy Belgium Code for Good Practice for the Construction of Pressure Vessels Belgian Standard Institute IBN Brussels Belgium Sweden Swedish Pressure Vessel Code Tryckkarls Kommissioner the Swedish Pressure Vessel Commission Stockholm Sweden 压力容器规范压力容器规范 美国压力容器规范的历史 从 19 世纪末到 20 世纪初 锅炉和压力容器的爆炸是常 有发生 1865 年 4 月 27 日 在密西西比河轮船 Sultana 号上 一个火管锅炉爆炸导致船在 二十分钟内沉没 使内战后回家的 1500 名士兵死亡 这种灾难在二十世纪初仍未减少 1905 年 在马塞诸塞州布鲁克市的一家制鞋厂里 一个火管锅炉的毁灭性爆炸造成 58 人 死亡 117 人受伤和 400000 美元的财产损失 1906 年 马塞诸塞州林恩市的一家制鞋厂里 的另一次爆炸 造成死亡 受伤和大量财产损失 在这次事故之后 马塞诸塞州州长指挥 成立了锅炉规范委员会 1907 年 8 月 30 日 设计和建造锅炉的第一套规范在马塞诸塞州 得到批准 这个规范总共有三页 1911 年 美国机械工程师学会主席 Colonel E D Meier 成立了一个委员会 专门起草 锅炉和压力容器设计和建造的规范 1915 年 2 月 13 日 第一部锅炉规范 ASME 被颁布 它被提名为 锅炉建造规范 1914 版 这是 ASME 锅炉和压力容器规范各篇的开始 最 后变成了第一篇 动力锅炉 第一个压力容器的规范 ASME 是以 1925 版第 VIII 篇 不用火加热压力容器的建造 规则 的名称颁布的 该规则适用于直径大于 6 英寸 容积大于 1 5f和压力高于 30Pa 的 3 t 容器 1931 年 12 月 为了发展适合于石油工业不用火加热的容器规范 专门成立了 API ASME 联合委员会 第一版本在 1934 年颁布 在随后的 17 年时间里 存在两个 独立的不用火加热容器规范 1951 年 最后的 API ASME 规范以独立的文件颁布 1952 年 两个规范合并成一个规范 ASME 不用火加热压力容器规范 第 VIII 篇 这部规范一直延续到 1968 版 那时 原来的规范变为第一分篇 压力容器 第 VIII 篇 第二分篇 压力容器另一规则 第 VIII 篇 作为另外新的部分被颁布 经美国国家标准局 ANSI 批准 美国机械工程师学会以 ASNI ASME 文件的形式 颁布了 ASNI ASME 锅炉和压力容器规范 ASNI ASME 锅炉和压力容器规范的一篇或多篇 已经在美国的 47 个州和加拿大的所有省中 以法律的形式确立 同样 在世界的许多其他 国家 ASME 锅炉和压力容器规范 也被用来建造锅炉和压力容器 ASME 锅炉和压力容器规范的组成 ASME 锅炉和压力容器规范分成许多篇 分 篇 部分和辅助部分 在这些篇中 一些涉及到特定类型的设备和应用 另外的涉及特定 的材料和设备应用与控制的方法 其余的涉及安装的设备的维护和检修 下面各篇特别涉 及锅炉和压力容器个设计和建造 第一部分 动力锅炉 1 卷 第三部分 第 1 节 核电厂部件 7 卷 第 2 节 混凝土反应容器和控制 1 卷 标准容器 案例 1 升温装置中的部件 在核规范 N 47 案例书中 第三部分 加热锅炉 第八部分 第 1 节 压力容器 1 卷 第 2 节 力容器另一规则 1 卷 第 X 部分 玻璃纤维强化塑料压力容器 1 卷 新版 ASME 锅炉和压力容器规范 每 3 年于 7 月 1 日颁布 新附录每 6 个月于 1 月 1 日和 7 月 1 日颁布 新版规范一问世 就成为强制的规范 在颁布日期上 附录是可以选 择的 半颁布日期定了以后 它就是强制性的 世界压力容器规范 除了在全世界使用的 ASME 锅炉和压力容器规范外 许多不同 的压力容器规范 已经在不同的国家得到法律上的采纳 当容器在一个国家设计 在另一 个国家建造 并且在不同的国家安装时 就会产生困难 由于这种世界范围的建造的存在 这种案例是经常有的 下面所列举的是一些在不同国家中使用的各种规范的部分摘要 澳大利亚 澳大利亚锅炉与压力容器标准 SAA 锅炉标准 AS1200 系列 AS1210 非火加热类压力容器和分类 1H 改进后的设计与制造压力容器 澳大利亚协会 标准 法国 不用火加热压力容器建造规范计算规则 法国巴黎市 SNCT 结构 英国 英国规范 BS 55OO 英国伦敦市英国标准协会 日本 日本压力容器规范 劳动部 制定 日本东京市日本锅炉协会出版 JISB8243 日本标准 压力容器建造 日本东京市日本标准协会出版 日本 高压气体控制法 国际贸易与产业部 制定 日本东京高压气体工程安全协会出版 意大利 意大利压力容器规范 意大利米兰市国家燃烧控制协会 ANCC 比利时 400 The optical pyrometer usually compares the monochromatic radiation emitted by the hot object of unknown temperature with that from a standard source The radiation pyrometer concentrates the radiant energy from a hot source on to a thermocouple junction Measurement of Liquid Level Liquid level is normally determined by the use of a float by measurement of the static head of liquid or by a capacitance bridge method The static pressure exerted by a head of liquid can be measured by suitable pressure measuring device A typical arrangement for a volatile liquid is shown in Fig 6 15 If the liquid is not volatile the condensing reservoir is not required and the high pressure and low pressure connections on the differential pressure cell are disconnected and reversed Floats are independent of the static pressure and either of the buoyant or the displacement type The former is less dense than the liquid which it is partially immersed and the latter is slightly denser than the liquid Consequently the buoyant or moving float has a constant immersion and will rise and gall precisely the same distance as the liquid level Its position at any instant is measured The level measured in this case in terms of the net weight of the float The capacitance method is generally employed with large cylindrical ranks One electrode is inserted down the centre of the tank whist the outer wall is used as the other The tank then acts as a concentric cylindrical capacitor having a capacitance which alters with liquid level The capacitance and hence the liquid level is measured using a stabilized capacitance bridge Selected form J M Coulson and J F Richardson Chemical Engineering Vol 3 2nd Edition Pergamon Press 1979 测量设备测量设备 温度测定 用于测定温度的设备很多 各种测量设备均有其特点及局限性 JONES 将测量仪器测 量温度所基于的不同机理 将温度测量仪器进行了分类 即 a 膨胀型温度计 b 状态改变型温度计 c 基于电学的温度计 ss d 基于辐射或者光学温度计 其中 a 类型包括了双金属温度计 液体玻璃温度计 液体金属温度计 气体温度 计 图 6 13 为一典型液体温度计 当玻璃球周围的温度升高 玻璃球内水银体积膨胀 以至于 比玻璃球的体积更大 迫使其通过螺旋型毛细管 进而指示温度值 气体温度计有相类似 的机理 这两种温度计都有简单可靠的特点 广泛用于记录和控制过程 b 类主要包括压力式温度计 其结构也与图6 13 所示构造相似 泡内部分装 盛液体 螺旋毛细管内推动压力由液体上部的蒸汽压提供 c 类型中重要代表为温差电偶温度计 温差电偶温度计 是工业过程中最常见的 测温仪器之一 它利用的原理是当两种不同温度的异种金属接触时 会产生温差电势 产 生的电动势用毫伏计或分压计测定 图 6 14 将热电偶的测量端插入待测温度介质中 而另一端温度则保持不变 这就使得两端电势随测量温度温度变化而变化 电阻温度计也是 c 类温度计的典型代表 是常用的具有较高精确度的温度测量 仪器 它由热敏性电阻组成 并使用电桥测定电阻 这种工业测量仪器外表上看起来像 热电偶温度计 但其探测端带有弯曲的线圈电阻 然而 热电偶温度计测量的是测量点 的温度 电阻温度计测量的是一个更大的热敏元件的平均温度 d 类型的温度测量仪器用于高温的测量中 400 光测高温计原理是将未 知温度的高温物体发出的单色辐射与某个标准相比较 这种辐射高温计也是将从辐射体 辐射出来的能量集中到一个热电偶的连结点来进行测量 液位测量 液位通常依靠漂浮物 利用液体静压或者利用电桥来确定 液体静压可以由适当的 压强测量设备来测定 图 6 15 为典型的挥发性液体液位测量装置 如果液体是非挥发性的 则不需要进行冷凝贮存 高压和低压系统应该颠倒过来 并且连接单元也应断开 漂浮物漂浮状态与液体静压无关 有可能是浮于液体表面 也有可能位于液体之 中 前种状况下漂浮物的密度小于液体密度 漂浮物小部分浸入液体中 后种情况是漂 浮物密度大于液体密度 所以 静止漂浮的物体会有一定的漂浮位置 运动的漂浮物也 会在液体平面上下等距离稳态跳动 任何时刻的漂浮位置都可以测取 这样液位就可以 靠漂浮物净重来测定了 应用电容的测定方法测定液位时 一般为大的圆柱型容器 一个电极插入罐体中 心 罐壁则作为另一个电极 罐体则可以作为一个通州的电容器 电容量随着液位不同 而不同 电容 进而得出液位 则可用稳定电桥测量 Reading Material 29 The Modes of Control Action II 3 Proportional Control some chemical processes cannot tolerate the variation and continuous cycling produced by on off contro1 A smoother control action can be obtained with proportional contro1 In proportional control a fixed linear relationship exists between the value of the controlled variable and the position of the final control element The proportional contro11er moves the final control element to a definite position for each value of the controlled variable This mode of action is illustrated in Fig 6 17 Suppose the controller in the temperature control loop is a proportional controller Then the relationship between the position of the control valve and the temperature of the tank exit Stream can be represented by Fig 6 17 The set point of this control 1oop is 200 with a range of action extending from 150 to 250 When the controlled variable is at 150 or less the valve is wide open But when the temperature is between 150 and 200 the proportional controlled variable i e the temperature as given by the proportional action line shown in the figure For example at 175 the valve is only 75 0pen at 200V only 50 and so on Finally when the variable reaches 250V Or more the valve is completely closed The range of Values of the controlled variable through which proportional contro1 action occurs is called the proportional band of the controller In Fig 6 17 for instance The proportional band extends from 150 to 250 The proportional band is usually expressed as a percentage of the full scale range of the controller For example the full scale range of the instrument shown in Fig 6 17 is 100 to 300 Since there is proportional control action only between 150 and 250 the proportional band is 250 150 300 100 or 50 If however this controller had a full scale range of 1000 then the proportional band would be 100 1000 or 10 Controlled variable Temperature Fig 6 1 7 Illustration of proportional contro1 action The proportional band is adjustable on most controllers and is field tuned to give optimum response to the process changes expected In tuning controllers it should be remembered that the width of the proportional band determines the amount of valve motion for any given change in the controlled variable The rule to follow is The larger the proportional band the smaller the change in valve position for any given change in the controlled variable While the proportional controller does provide smoother control than the on off type it does have one important limitation For example assume that the temperature of the fluid in the tank is being controlled at a temperature of 200 by the proportional controller shown in Fig 6 17 Under these conditions the temperature is at the set point when the control valve is 50 open Now if the flow of the main inlet stream is increased creating an added load on the control system the temperature of the tank will drop and the opening of the contro1 valve will increase Eventually the control valve will find a new position and the process will be back in balance with an exit stream temperature of 200 However when equilibrium is reestablished the control valve position will be at some new position that is offset from the 50 open position where we started to control the Process This offset is characteristic of all proportional type control systems because the mechanism is unable to cope with process load changes without it Most proportional controllers have a manual reset adjustment that eliminates offset by shifting the proportional band abort the set point When the reset is done automatically it is referred to as proportional plus reset control action 4 Proportional Plus Reset Control In the proportional plus reset mode of control reset is automatic In this mode of control as soon as the controlled variable deviates above or below the set point i e as soon as some offset develops there is a gradual and automatic shift of the proportional band to bring the variable back to the set point Thus while proportional control is limited to a single valve position for each value of the controlled variable proportional plus reset control changes valve position to accommodate load changes Fig 6 18 illustrates the primary purpose of the reset function by showing a typical measured variable controlled with and without reset Since the controller mechanism automatically resets the control point by integrating the deviation in the system proportional plus reset control is often referred to as integral control action Proportional 一 plus reset contro11 finds tremendous application in chemical processes It is particularly applicable when process load changes are large 管制行动 管制行动 II 的模式 的模式 3 比例控制 一些化学过程不允许的变化和不断循环所产生的开关控制对照 一个顺畅的控制作用 可同比例控制对照 在一个固定的线性关系的价值之间存在的控制变量和位置的最终控制 元素 比例控制动作的最终控制元素为每个值确定的位置控制变量 这种行动方式如图 6 17 所示 假设回路温度控制器是一个比例控制器 控制阀位置和出口温度之间的关系可由图 6 17 中罐蒸汽代表 这项控制回路设置点为 200 具有扩大行动范围从 150 至 250 当控制变量在 150 以下 阀门是敞开的 但是 当温度在 150 至 200 比例控制的变 量 i e 温度 的比例的行动中显示的数字 例如 在 175 阀只有 75 敞开 在 200 的只有 50 等 最后 当变量达到 250 或以上的阀门完全关闭 通过这些操作发生比例控制称为控制器的比例带 如图 6 17 所示 例如 比例带的 延伸从 150 至 250 带的比例通常是用控制器的全量程的百分比表示 例如 在文书中 显示的满量程范围如图 6 17 所示是 100 至 300 由于比例控制行动在 150 至 250 时 比例带为 250 150 300 100 或 50 然而 如果该控制器具备充分量程范围 为 1000 则比例带将为 100 1000 或 10 控制变量 温度 图 6 17 比例控制行动 这个比例带是可在大多数的控制器和领域调谐向最佳反应工艺变化的 在调谐控制器 它应该记住的是 比例带的宽度是决定的任何改变阀的控制运动量的变量 遵循的规则是 大的比例带 小的控制变量对任何阀而言 位置改变则控制变量随之改变 虽然比例控制器提供较平滑的开关控制型 但它有一个重要的限制 例如 假设水箱 中的液体温度被控制在 200 温度时 比例控制器显示如图 6 17 在这种情况下 温度在 设定点时 控制阀开放 50 现在 如果进口的主要入口流量增加 从而给控制系统增加 了负载 罐的温度将下降且控制阀门开放程度也会增加 最后 控制阀会找到新的位置 这一过程将是 200 温度出口流平衡的回归 然而 当平衡是在一些新的位置重新确立了 控制阀门的位置时 即从开放 50 的位置偏移 我们就开始控制这一过程 这是所有比例偏置型控制系统的特点 因为该机制是无法应付负载发生变化的进程 大部分比例控制器都具有手动复位调整 消除了比例带设定点的偏移问题 当复位完成自 动 它被称为比例加复位控制的作用 4 比例加复位控制 在控制比例加复位模式下 自动复位 在这种控制模式下 尽快控制控制变量偏离上 方或下方的设定点 i e 只要一些偏移发展 还有一渐进和自动转变的比例带 使得变 量返回设定点 因此 当比例控制仅限于单个阀门位置控制变量时 就可以控制比例加复 位控制阀门位置以适应负载的变化 图 6 18 通过一个典型的例子说明并展示了复位功能的用途 测量变量的控制和无复位 由于控制机制自动复位集合在系统偏差的控制点 比例加 复位控制通常被称为 整体 的控制作用 比例加复位控制广泛应用于化工过程 它特别适用于超负载变化过程 ReadingReading MaterialMaterial 3030 Typical Control Systems 1 Level Control In any equipment where an interface exists between two phases e g liquid vapor some means of maintaining the interface at the required level must be provided This may be incorporated in the design of the equipment as is usually done for decanters or by automatic control of flow from the equipment Figure 6 21 shows a typical arrangement for the level control at the base of a column The control valve should be placed on the discharge line from the pump 2 Pressure Control Pressure control will be necessary for most systems handling vapor or gas The method of control will depend on the nature of the process Typical schemes are shown in Figs 6 22 a b the scheme shown in Fig 6 22 a would not be used where the vented gas was toxic or valuable In these circumstances the vent should be taken to a vent recovery system such as a scrubber 3 Flow Control Flow Control is usually associated with inventory control in a storage tank or other equipment there must be a reservoir or take up the changes in flow rate To provide control on a compressor or pump running at a fixed speed and supplying a near constant volume output a by pass control would be used as shown in Figs 6 23 a b 4 Cascade Control With this arrangement the output of one controller is used to adjust the set point of another Cascade Control can give smoother control in situations where direct control of the variable would lead to unstable operation The slave controller can be used to compensate for any short term variations in say a service stream flow which wou