机械设计与制造-外文翻译.docVIP

12港口集装箱起重机的未来第一作者 凯瑟琳莫里斯S.E. Liftech顾问公司 第二作者 西摩霍伊特C.E. Liftech顾问公司导言 全球集装箱运输量大约以每年百分之八的速度持续增长，为了跟上这种增长，集装箱船是越来越大。现在的标准是拥有16集装箱对开4600标箱的后巴拿马型集装箱船舶。现在使用的新船拥有17集装箱对开和6000标箱。而拥有近7000标准箱的船舶预计于1998年投入使用。对于最大的船舶，为它们服务的终端的效率是尤为重要的。这是今天的终端运营商面临的挑战。前线终端是其集装箱装卸码头起重机。新的集装箱起重机必须将集装箱吊得比以往任何时候都要更高，移动得也更远、更快，更准确。该篇文章就是着眼于重机设计者和码头运营商面临的一些问题的。新的起重机有四个主要的设计关注点：大小：起重机必须足够大，并具备必要的强度和刚度，从而为船舶提供服务，并为当今的先进机械和电子系统提供有效的平台。因为体积的关系，这些起重机的设计必须使它们能够承受更大的风力和惯性力。增加的体积增加了起重机的总负荷。 速度：起重机必须足够快，以在更远的距离和更短的时间内处理更多的 集装箱。标准的要求是每小时最少运作40次。 耐用性：为了对得起花在自己身上的大量投资成本，起重机必须能够连续工作，没有停机时间。今天的起重机的设计必须达到可以升降二百万个来回或更多，相当于在20年时间里每年升降100000个来回。一台设计和维护良好的起重机应该会持续更长的一段时间，并且不需要大修。 车轮荷载和稳定性：起重机车轮荷载必须符合码头实力。起重机应能在风暴中保持稳定，从而避免使用那种安装繁琐并有可能干扰码头交通的铁斯。尺寸 自第一台集装箱起重机于20世纪50年代末诞生后，集装箱起重机的大小已增加了一倍以上。由Paceco于1959年设计的拥有23.8米的外展的马特森集装箱起重机可将22.7吨的箱子升降到轨道外15.6米处。最新的集装箱起重机拥有56米的外展，可将50.8吨的箱子升降到轨道外36米处。新的起重机的高度比之前任何的起重机都高，重量也都重高75米，重1300吨。在许多地方，热带风暴风荷载条件控制了起重机腿和窗台梁的设计。需要额外的钢材，但它不是必须的操作条件。出于这个原因，用模型做风洞试验往往是值得的。合理进行的风洞试验可以确切地确定不同风速的力量以及找出潜在的由风导致的振动问题。没有风洞试验数据，设计人员必须依靠那些可根据它们的一般性质保守估计的风荷载的标准守则。科罗拉多州立大学为三菱商事的新超级起重机进行的风洞试验允许设计风荷载已得到证实，收集的数据也可为未来起重机服务。吊臂长 鉴于在船舶的起重机和速度提升方面所花的的成本，新起重机的设计应处理至少有一个排的集装箱，其中超出预期的最大的船只除外。即使额外的能力并不需要，但额外的外展可以改进生产，因为热潮过后小车将不必在放慢区工作。小车 出于对结构、车轮荷载以及进行维护的考虑，一个起重机小车系统类型的选择具有重要意义。小车可以是靠绳子牵引的或是机械类型的。用绳子牵引的无轨小车系统，其小车驱动器、主提升机、臂起重机都设在机器内部的框架上。车和主提升机绳索从机器内部到达电车梁尾部，再通过小车，到达机臂的末梢。这种安排让小车浅且重量轻，从而实现更大的提升高度和结构上较小的负荷。葫芦小车上的机械有小车和主提升机。由于大多数的机械都在小车上，所以机械内部的框架要小得多，仅包含臂起重机。无绳索小车是需要的，主提升机绳索短于由绳子牵引的小车。结构 在结构设计上，重量是两种类型小车的主要区别。由绳索牵引的小车的重量不到机械小车的三分之一。最戏剧性的是，和由绳索牵引的小车相比，重机械小车对起重机造成的损伤程度要高出3到5倍。表2给出了一个例子说明这种影响。机械小车起重机的车轮负荷比绳牵引小车高出15 左右。小车的选择也将影响到臂的设计。一般来说，绳索牵引小车的起重机上需要使用双梯形梁，因为它使绳牵引相对简单。用较少的绳索的机械电车一般使用长方形或梯形单梁臂.不管是在绳牵小车还是在机械小车上，一个设计合理的单梁臂起重机重量都比一个设计合理的双梁臂起重机小车起重机轻。对于双梁起重机，偏心凸轮负载升降机在其中一个梁上采用额外的竖向荷载，从而增加了重量。对于单梁臂起重机，同样的装备只导致扭转，一般不予控制。因此，较大的部分是不需要的。维修 从服务的角度来看，机械小车的配置具有几个方面的优势。吊臂末梢均衡平台、陆转向滑轮、接触网手推车、绳索张紧、导流层和记耳光区块的维修是消除的。小车驱动绳索的消除和主提升机钢丝绳的缩短降低了储存和更换钢丝绳的成本。由绳索导致的石油泄漏污染也减少到最低限度。在操作上，因为起重机绳索要短得多，加之没有伸展的小车拖绳，机械小车提供了更好的负荷控制。车轮荷载 机械小车起重机的主要缺点是增加了机身重量和对码头的车轮负荷。有些码头没有强大到足以支持最新的由机械小车驱动的超级起重机。哥德堡港最近针对两个机械小车驱动的超级起重机进行了一次投标。最终哥德堡港选中了绳牵小车起重机，因为较低的起重机车轮负荷更符合现今实力有限的码头结构。一个有趣的说明：德国诺尔公司用绳驱动小车系统赢得了哥德堡港的合同，即使机器小车系统是指定的。他们还用机械小车起重机获得了美国总统轮船的大量订单。对ALP的投标，绳牵小车起重机已被指定，但诺尔提议机械小车起重机。ALP的起重机将被设在一个新的工厂设计，以适应新的和更大的起重机。对于有较高负荷的码头，机械小车起重机是首选系统。小车的选择应根据特定场所的需求，以及所有者和经营者的喜好。设计自动化 新的集装箱起重机提高了自动化的程度，从而增加了起重机生产力。要使自动化操作正确，所有系统元件的位置必须了解。对于固定的物体，这是一项容易的任务。对于移动的物体，如随运动小车伸缩的起重机结构，工作变得更加困难。 一种办法是要求有严格挠度限制的刚性结构。刚性结构有助于负荷控制，并方便操作者乘坐。这也是加重的。一个详细的结构设计过程，需要尽量减少重量和优化几何形状和构造。另一种方法是考虑到起重机运动负荷控制系统的设计和不指定挠度限制。这就需要更复杂的软件，但将导致一个更轻的起重机结构。如果采用严格挠度限制的做法，吊臂垂直偏转的一个重要原因是由于曲率和支撑物间存在联系。这是因为forestay的自重造成它沿其长度凹陷和沿其连杆旋转。这种效应实际上在没有负载的情况下稍稍提升了吊臂。一个为三菱最新的超级起重机设计的协助链接（正在申请专利）已经被发明了，它可以消除链接挠度和减少挠度曲率。这个链接的作用是将forestay保持在下滑的位置。高速新的起重机面临的挑战，不仅是更高的吞吐率，而且还包括从比以往任何时候都更深、更高的地方升降箱子以及跨域更长的船舶长度而增加的吞吐量。力量为了迎接大型起重机的挑战，小车和主要绞车驱动器正变得越来越强大，以提供更大的速度和加速度。增加驱动器和制动器电源并不困难，问题在于提供一个完整和平衡的系统。更高的运行速度的其中一个受害者就是操作者。剧烈的加速或减速会让他们感觉不舒服，很累。许多新的起重机指定在吊臂上提供额外的轨道，以及在一个独立的驾驶室内提供可脱离小车运动的轨梁。为小车提供动力以及通信的花彩系统是更快的小车驱动器所带来的一个问题。高小车加速度和速度可能会使花彩系统失去控制，变得混乱，并瘫痪。能适应更快小车的机动花彩系统已经被发明了。这些系统可以做一些高维修项目。新的系统，如感应电力和波导通讯系统，正在被开发和使用到的工业中。联系吊具并为它们提供电能的电缆也是高提升速度带来的一个问题，它往往会失去控制。供电电缆卷筒胡扯正在被应用于一些起重机。嵌入 当吊具被夹在正在全速提升的船舶上时就会发生嵌入。这一传递给起重机的巨大能量可以对起重机系统造成严重损害。随着吊车变得更大和更有力，嵌入负荷也会变得更严重，这需要一个精心设计的解决方案。 一种选择是，通过设计使整个构造和所有组成部分都能承受嵌入负荷。另一种方法是提供一个嵌入系统。嵌入系统是一种机械的解决方案，它能源消散绳索嵌入的力量，通常是通过液压系统来避免损害的起重机的。 防摇 防摇负荷控制系统也得到发展。现在国际最先进的是电子防摇。如果起重机的操作者并不是熟练工，这些系统可以大大提高起重机生产率。尽管许多熟练的操作者更倾向于在没有防摇的情况下生产和工作。THE FUTURE OF QUAYSIDE CONTAINER CRANESCatherine A. Morris, S.E PrincipalLiftech Consultants Inc. Simo Hoite, C.E. AssociateLiftech Consultants IncINTRODUCTIONContainer traffic continues to grow worldwide at about eight percent a year. To keep up with this growth, container ships are getting bigger and bigger. Post-Panamax ships with 16 containers abeam and 4600 TEU are now standard. New ships are operating with 17 containers abeam and 6000 TEU. Ships with close to 7000 TEU are expected to enter service in 1998.For the largest ships, the efficiency of the terminals that serve them is especially critical. This is todays challenge to terminal operators. The front line of a terminal is its container handling quay cranes. New container cranes must move containers higher, further, faster, and more accurately than ever before.This paper looks at some of the issues this presents to crane designers and terminal operators.There are four major design concerns with the new cranes: Size: The cranes must be large enough and have the required strength and stiffness to service the ships and provide an effective platform for todays advanced mechanical and electronic systems. These cranes must be designed for greater wind and inertia forces because of their size. The increased outreach increases the overall loading on the crane. Speed: The cranes must be fast enough to handle more containers over greater distances in less time. A minimum rate of 40 moves per hour is the standard requirement. Durability: To justify the cost of their substantial investment, the cranes must be able to work continuously, without downtime. Todays cranes are designed for two million lift cycles or more, equivalent to 100,000 moves per year for 20 years. A properly designed and maintained crane should last longer without major overhaul.Wheel Loads and Stability: The crane wheel loads must be compatible with the quay strength. The cranes should be stable in storm winds to eliminate the need for tie-downs that are cumbersome to install and can interfere with wharf traffic.SIZEThe size of container cranes has more than doubled since the first container cranes were built in the late 1950s. The Matson container cranes built by Paceco in 1959 were designed to lift 22.7t boxes 15.6m over the rails with an outreach of 23.8m. The latest container cranes lift 50.8t boxes 36m over the rails with an outreach of 56m. The new cranes are taller and heavier than any before一up to 75m high and weighing 1300t.Typical size characteristics of state-of-the-art conventional single trolley post-Panamax container cranes are shown in Table 1. Wind LoadIn many locations, the storm wind load condition controls the design of the crane legs and sill beams. Extra steel is required, though it is not needed for operating conditions. For this reason, it is often worthwhile to do wind tunnel testing of a scale model. A properly conducted wind tunnel test can determine the exact forces for different wind speeds as well as identify potential wind induced vibration problems. Without wind tunnel test data, the designer must rely on standard codes for wind loads which can be conservative because of their general nature.Wind tunnel testing conducted at Colorado State University for Mitsubishis new super-cranes allowed design wind loads to be verified and data to be collected for future cranes.Boom LengthGiven the cost of the cranes and the rapid growth in ships, new cranes should be designed to handle at least one row of containers beyond the expected largest ships. Even if the extra capacity is not needed, the extra outreach allows for improved production because the trolley will not have to work in the slow down zone at the end of the boom.TrolleyThe selection of a cranes trolley system type is significant for the structure, for wheel loads, and for maintenance considerations. The trolley can be rope towed or machinery type.With a rope towed trolley system, the trolley drive, main hoist, and boom hoist are located in the machinery house on the frame. Trolley and main hoist ropes run from the machinery house to the end of the trolley girder, through the trolley, and to the tip of the boom. This arrangement allows the trolley to be shallow and lightweight, allowing greater lift height and smaller loads on the crane structure.A machinery on hoist trolley has the trolley and main hoist drives on board. With most of the machinery on the trolley, the machinery house on the frame is much smaller, containing only the boom hoist. No trolley drive ropes are required, and the main hoist ropes are shorter than for a rope towed trolley. StructuralFor the structural design, weight is the main difference between the two types of trolleys. The weight of the rope towed trolley is less than a third of a machinery trolley. Most dramatically, the heavier machinery trolley increases fatigue damage on a similar crane with rope towed trolley by a factor of 3 to 5. Table 2 gives an example of the effect on the structure. The wheel loads for a machinery trolley crane are about 15 % higher than for rope towed. The choice of trolley will also affect the boom design. Generally, twintrapezoidal girders are used on cranes with rope towed trolleys because it makes rope reeving relatively simple. For machinery trolleys, with fewer ropes, rectangular or trapezoidal mono-girder booms are generally used.A properly designed mono-girder boom crane weighs less than a properly designed twin girder boom crane for both rope trolley cranes and machinery trolley cranes. The eccentric lifted load applies additional vertical load on one of the two girders on the twin girder crane, which results in heavier sections. On a mono-girder boom, this same loading results in torsion only, which generally does not control. Therefore a larger section is not required.MaintenanceThe configuration of the machinery trolley has several advantages from a service standpoint. The maintenance of the boom tip equalizer platform, landside turning sheaves, catenary trolleys, rope tensioners, deflector sheaves, and slap blocks is eliminated. The elimination of the trolley drive ropes and shorter main hoist ropes reduces costs for stocking and replacing wire rope. Pollution from oil spilling from the ropes is also minimized.Operationally, because hoist ropes are much shorter and there is no stretch of trolley tow ropes, the machinery trolley provides better load control.Wheel LoadsThe main disadvantage of the machinery trolley is the increase in crane weight and wheel loads on the quay. Some quays are not strong enough to support the latest super-cranes with a machinery on hoist trolley. The Port of Goteborg recently put out a tender for two super-cranes with machinery hoist trolleys. The Port eventually selected rope towed trolley cranes because the lower crane wheel loads were more compatible with the limited strength of the existing quay structure.An interesting note: Noell Inc. of Germany won the Goteborg contract with a rope driven trolley system, even though a machinery trolley system was specified. They also won a large order from American President Lines for machinery trolley cranes. For the APL tender, a rope towed trolley was specified, but Noell proposed the machinery hoist trolley. The APL cranes were to be located at a new facility designed to accommodate the new and larger cranes. With the higher allowable wheel loads on the wharf, the machinery trolley crane was the preferred system.The trolley selection should be based on the needs at a particular location, as well as the preference of the owner and operators.Design for AutomationThe new container cranes have increasing degrees of automation that increase crane productivity. For automation to operate correctly, the location of all system components must be known. For fixed objects, this is an easy task. For moving objects, such as the crane structure flexing with the movement of the trolley, the task becomes more difficult.One approach is to require a very stiff structure with strict deflection limits. A stiff structure helps with load control and provides an easier ride for the operator. It is also heavier. A detailed structural design process is required to minimize the weight and optimize the geometry and sections.The alternative is to account for crane movement in the load control system design and not specify deflection limits. This requires more complex software, but will result in a lighter crane structure.If the strict deflection limit approach is taken, a significant source of vertical deflection of the boom is due to curvature and the presence of links in the stays. This is because the self-weight of the forestay causes it to sag along its length and rotate at the link. This effect actually raises the boom by a small amount when there is no load on it.An assist link (patent pending) has been developed for Mitsubishi s latest super- cranes that eliminates the link deflection and reduces the curvature. The link works by holding the forestay in the sagged position. See Figure 2.SPEEDThe challenge of the new cranes is not only an increased throughput, but an increased throughput while lifting boxes from deeper, higher, and over greater lengths in the ships than ever before.Typical speed characteristics of the state-of-the-art conventional single trolley post-Panamax container cranes are shown in Table 3.PowerTo meet the mega crane challenge, the trolley and main hoist drives are becoming increasingly powerful to provide greater speeds and accelerations. Increasing drive and brake power is not difficult. The problem is to provide a complete and balanced system.One casualty of the higher operating speeds is the operator. Severe accelerations and decelerations can be uncomfortable and tiring. Many new cranes are specified to provide an additional rail on the boom and trolley girder for a separate operator cab that moves independently from the trolley.The festoon systems that power the trolleys a